Merge pull request 'CUB-32: Add usage logging service' (#11) from agent/dex/CUB-32-usage-logging-service into dev

Reviewed-on: #31
Reviewed-by: Joshua <joshua@cnjmail.com>

backend/API/Controllers/FilamentsController.cs

@@ -1,6 +1,7 @@
 using Extrudex.API.DTOs;
 using Extrudex.API.DTOs.Filaments;
 using Extrudex.Domain.Entities;
+using Extrudex.Domain.Interfaces;
 using Extrudex.Infrastructure.Data;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
@@ -17,16 +18,22 @@ namespace Extrudex.API.Controllers;
 public class FilamentsController : ControllerBase
 {
     private readonly ExtrudexDbContext _dbContext;
+    private readonly ILowStockDetector _lowStockDetector;
     private readonly ILogger<FilamentsController> _logger;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="FilamentsController"/> class.
     /// </summary>
     /// <param name="dbContext">The database context for data access.</param>
+    /// <param name="lowStockDetector">The low-stock detection service for filament alerts.</param>
     /// <param name="logger">The logger for diagnostic output.</param>
-    public FilamentsController(ExtrudexDbContext dbContext, ILogger<FilamentsController> logger)
+    public FilamentsController(
+        ExtrudexDbContext dbContext,
+        ILowStockDetector lowStockDetector,
+        ILogger<FilamentsController> logger)
     {
         _dbContext = dbContext;
+        _lowStockDetector = lowStockDetector;
         _logger = logger;
     }
 
@@ -95,7 +102,7 @@ public class FilamentsController : ControllerBase
             .OrderByDescending(s => s.CreatedAt)
             .Skip((pageNumber - 1) * pageSize)
             .Take(pageSize)
-            .Select(s => MapToFilamentResponse(s))
+            .Select(s => MapToFilamentResponse(s, _lowStockDetector))
             .ToListAsync();
 
         var response = new PagedResponse<FilamentResponse>
@@ -136,7 +143,7 @@ public class FilamentsController : ControllerBase
             return NotFound(new { error = $"Filament with ID '{id}' not found." });
         }
 
-        return Ok(MapToFilamentResponse(spool));
+        return Ok(MapToFilamentResponse(spool, _lowStockDetector));
     }
 
     /// <summary>
@@ -211,7 +218,7 @@ public class FilamentsController : ControllerBase
         if (entity.MaterialModifierId.HasValue)
             await _dbContext.Entry(entity).Reference(s => s.MaterialModifier).LoadAsync();
 
-        var response = MapToFilamentResponse(entity);
+        var response = MapToFilamentResponse(entity, _lowStockDetector);
         return CreatedAtAction(nameof(GetFilament), new { id = entity.Id }, response);
     }
 
@@ -292,7 +299,37 @@ public class FilamentsController : ControllerBase
         if (entity.MaterialModifierId.HasValue)
             await _dbContext.Entry(entity).Reference(s => s.MaterialModifier).LoadAsync();
 
-        return Ok(MapToFilamentResponse(entity));
+        return Ok(MapToFilamentResponse(entity, _lowStockDetector));
+    }
+
+    /// <summary>
+    /// Gets only the filament spools that are flagged as low stock.
+    /// A spool is considered low stock when its remaining weight percentage
+    /// is at or below the configured threshold.
+    /// </summary>
+    /// <returns>A list of low-stock filament spools with alert metadata.</returns>
+    /// <response code="200">Returns the list of low-stock filament spools.</response>
+    [HttpGet("low-stock")]
+    [ProducesResponseType(typeof(List<FilamentResponse>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<List<FilamentResponse>>> GetLowStockFilaments()
+    {
+        _logger.LogDebug("Getting low-stock filaments (threshold: {Threshold}%)",
+            _lowStockDetector.LowStockThresholdPercent);
+
+        var spools = await _dbContext.Spools
+            .Include(s => s.MaterialBase)
+            .Include(s => s.MaterialFinish)
+            .Include(s => s.MaterialModifier)
+            .Where(s => s.IsActive)
+            .OrderByDescending(s => s.CreatedAt)
+            .ToListAsync();
+
+        var lowStockItems = spools
+            .Where(s => _lowStockDetector.IsLowStock(s.WeightRemainingGrams, s.WeightTotalGrams))
+            .Select(s => MapToFilamentResponse(s, _lowStockDetector))
+            .ToList();
+
+        return Ok(lowStockItems);
     }
 
     /// <summary>
@@ -361,10 +398,12 @@ public class FilamentsController : ControllerBase
     /// Maps a Spool domain entity to a FilamentResponse DTO.
     /// Denormalizes material names for display convenience.
     /// Populates the QrCodeUrl for easy frontend access to the spool's QR code.
+    /// Calculates low-stock status and remaining weight percentage.
     /// </summary>
     /// <param name="s">The spool entity to map.</param>
-    /// <returns>A FilamentResponse DTO with denormalized material names and QR code URL.</returns>
+    /// <param name="lowStockDetector">The low-stock detection service for computing alert flags.</param>
-    private static FilamentResponse MapToFilamentResponse(Spool s) => new()
+    /// <returns>A FilamentResponse DTO with denormalized material names, QR code URL, and low-stock metadata.</returns>
+    private static FilamentResponse MapToFilamentResponse(Spool s, ILowStockDetector lowStockDetector) => new()
     {
         Id = s.Id,
         MaterialBaseId = s.MaterialBaseId,
@@ -387,6 +426,8 @@ public class FilamentsController : ControllerBase
         StorageLocation = s.StorageLocation,
         CreatedAt = s.CreatedAt,
         UpdatedAt = s.UpdatedAt,
-        QrCodeUrl = $"/api/qr/spool/{s.Id}"
+        QrCodeUrl = $"/api/qr/spool/{s.Id}",
+        IsLowStock = lowStockDetector.IsLowStock(s.WeightRemainingGrams, s.WeightTotalGrams),
+        RemainingWeightPercent = lowStockDetector.GetRemainingWeightPercent(s.WeightRemainingGrams, s.WeightTotalGrams)
     };
 }

backend/API/Controllers/UsageLogsController.cs

@@ -0,0 +1,117 @@
+using Extrudex.API.DTOs.UsageLogs;
+using Extrudex.Domain.Enums;
+using Extrudex.Domain.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Extrudex.API.Controllers;
+
+/// <summary>
+/// API controller for recording and querying filament usage logs.
+/// Usage logs provide a fine-grained audit trail of filament consumption
+/// from printer integrations or manual input.
+/// </summary>
+[ApiController]
+[Route("api/[controller]")]
+[Produces("application/json")]
+public class UsageLogsController : ControllerBase
+{
+    private readonly IUsageLogService _usageLogService;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="UsageLogsController"/> class.
+    /// </summary>
+    /// <param name="usageLogService">The usage log service for recording and querying usage.</param>
+    public UsageLogsController(IUsageLogService usageLogService)
+    {
+        _usageLogService = usageLogService;
+    }
+
+    /// <summary>
+    /// Records a new filament usage entry.
+    /// </summary>
+    /// <param name="request">The usage entry details.</param>
+    /// <returns>The created usage log entry.</returns>
+    [HttpPost]
+    [ProducesResponseType(typeof(UsageLogResponse), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    public async Task<ActionResult<UsageLogResponse>> Create([FromBody] CreateUsageLogRequest request)
+    {
+        if (!Enum.TryParse<DataSource>(request.DataSource, ignoreCase: true, out var dataSource))
+        {
+            return BadRequest($"Invalid data source: '{request.DataSource}'. Valid values: Mqtt, Moonraker, Manual.");
+        }
+
+        var entry = await _usageLogService.RecordUsageAsync(
+            spoolId: request.SpoolId,
+            gramsUsed: request.GramsUsed,
+            dataSource: dataSource,
+            printerId: request.PrinterId,
+            printJobId: request.PrintJobId,
+            mmExtruded: request.MmExtruded,
+            usageTimestamp: request.UsageTimestamp,
+            notes: request.Notes
+        );
+
+        return CreatedAtAction(
+            nameof(GetBySpool),
+            new { spoolId = entry.SpoolId },
+            MapToResponse(entry));
+    }
+
+    /// <summary>
+    /// Gets usage logs for a specific spool, ordered by most recent first.
+    /// </summary>
+    /// <param name="spoolId">The spool ID to filter by.</param>
+    /// <returns>A collection of usage log entries for the spool.</returns>
+    [HttpGet("spool/{spoolId:guid}")]
+    [ProducesResponseType(typeof(IEnumerable<UsageLogResponse>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IEnumerable<UsageLogResponse>>> GetBySpool(Guid spoolId)
+    {
+        var logs = await _usageLogService.GetBySpoolAsync(spoolId);
+        return Ok(logs.Select(MapToResponse));
+    }
+
+    /// <summary>
+    /// Gets usage logs for a specific printer, ordered by most recent first.
+    /// </summary>
+    /// <param name="printerId">The printer ID to filter by.</param>
+    /// <returns>A collection of usage log entries for the printer.</returns>
+    [HttpGet("printer/{printerId:guid}")]
+    [ProducesResponseType(typeof(IEnumerable<UsageLogResponse>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IEnumerable<UsageLogResponse>>> GetByPrinter(Guid printerId)
+    {
+        var logs = await _usageLogService.GetByPrinterAsync(printerId);
+        return Ok(logs.Select(MapToResponse));
+    }
+
+    /// <summary>
+    /// Gets usage logs for a specific print job, ordered by most recent first.
+    /// </summary>
+    /// <param name="printJobId">The print job ID to filter by.</param>
+    /// <returns>A collection of usage log entries for the print job.</returns>
+    [HttpGet("print-job/{printJobId:guid}")]
+    [ProducesResponseType(typeof(IEnumerable<UsageLogResponse>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IEnumerable<UsageLogResponse>>> GetByPrintJob(Guid printJobId)
+    {
+        var logs = await _usageLogService.GetByPrintJobAsync(printJobId);
+        return Ok(logs.Select(MapToResponse));
+    }
+
+    /// <summary>
+    /// Maps a UsageLog domain entity to a UsageLogResponse DTO.
+    /// </summary>
+    private static UsageLogResponse MapToResponse(Domain.Entities.UsageLog log) => new()
+    {
+        Id = log.Id,
+        SpoolId = log.SpoolId,
+        PrinterId = log.PrinterId,
+        PrintJobId = log.PrintJobId,
+        GramsUsed = log.GramsUsed,
+        MmExtruded = log.MmExtruded,
+        UsageTimestamp = log.UsageTimestamp,
+        DataSource = log.DataSource.ToString(),
+        Notes = log.Notes,
+        CreatedAt = log.CreatedAt,
+        UpdatedAt = log.UpdatedAt
+    };
+}

backend/API/DTOs/Filaments/FilamentDtos.cs

@@ -76,6 +76,19 @@ public class FilamentResponse
     /// Encodes a deep link to the spool's detail page.
     /// </summary>
     public string QrCodeUrl { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Whether this spool is flagged as low stock — remaining weight is at or
+    /// below the configured low-stock threshold percentage.
+    /// Useful for UI alerts and inventory dashboards.
+    /// </summary>
+    public bool IsLowStock { get; set; }
+
+    /// <summary>
+    /// Remaining filament weight as a percentage of total weight (0–100).
+    /// Rounded to one decimal place. Returns 0 if total weight is zero.
+    /// </summary>
+    public decimal RemainingWeightPercent { get; set; }
 }
 
 /// <summary>

backend/API/DTOs/UsageLogs/UsageLogDtos.cs

@@ -0,0 +1,115 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Extrudex.API.DTOs.UsageLogs;
+
+/// <summary>
+/// Request DTO for recording a filament usage entry.
+/// </summary>
+public class CreateUsageLogRequest
+{
+    /// <summary>
+    /// The ID of the spool that provided the filament.
+    /// </summary>
+    [Required]
+    public Guid SpoolId { get; set; }
+
+    /// <summary>
+    /// The number of grams of filament consumed.
+    /// </summary>
+    [Required]
+    [Range(0.01, double.MaxValue, ErrorMessage = "GramsUsed must be a positive value.")]
+    public decimal GramsUsed { get; set; }
+
+    /// <summary>
+    /// The source of the usage data (Mqtt, Moonraker, Manual).
+    /// </summary>
+    [Required]
+    public string DataSource { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The ID of the printer that consumed the filament. Optional.
+    /// </summary>
+    public Guid? PrinterId { get; set; }
+
+    /// <summary>
+    /// The ID of the print job associated with this usage. Optional.
+    /// </summary>
+    public Guid? PrintJobId { get; set; }
+
+    /// <summary>
+    /// The number of millimeters of filament extruded. Optional.
+    /// </summary>
+    public decimal? MmExtruded { get; set; }
+
+    /// <summary>
+    /// When the usage occurred (UTC). Defaults to now if not specified.
+    /// </summary>
+    public DateTime? UsageTimestamp { get; set; }
+
+    /// <summary>
+    /// Optional notes about this usage entry.
+    /// </summary>
+    [MaxLength(2000)]
+    public string? Notes { get; set; }
+}
+
+/// <summary>
+/// Response DTO for a usage log entry.
+/// </summary>
+public class UsageLogResponse
+{
+    /// <summary>
+    /// Unique identifier for the usage log entry.
+    /// </summary>
+    public Guid Id { get; set; }
+
+    /// <summary>
+    /// The spool that provided the filament.
+    /// </summary>
+    public Guid SpoolId { get; set; }
+
+    /// <summary>
+    /// The printer that consumed the filament, if applicable.
+    /// </summary>
+    public Guid? PrinterId { get; set; }
+
+    /// <summary>
+    /// The print job associated with this usage, if applicable.
+    /// </summary>
+    public Guid? PrintJobId { get; set; }
+
+    /// <summary>
+    /// Grams of filament consumed.
+    /// </summary>
+    public decimal GramsUsed { get; set; }
+
+    /// <summary>
+    /// Millimeters of filament extruded, if available.
+    /// </summary>
+    public decimal? MmExtruded { get; set; }
+
+    /// <summary>
+    /// When the usage occurred (UTC).
+    /// </summary>
+    public DateTime UsageTimestamp { get; set; }
+
+    /// <summary>
+    /// Source of the usage data (Mqtt, Moonraker, Manual).
+    /// </summary>
+    public string DataSource { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Optional notes about this usage entry.
+    /// </summary>
+    public string? Notes { get; set; }
+
+    /// <summary>
+    /// When the record was created (UTC).
+    /// </summary>
+    public DateTime CreatedAt { get; set; }
+
+    /// <summary>
+    /// When the record was last updated (UTC).
+    /// </summary>
+    public DateTime UpdatedAt { get; set; }
+}

backend/Domain/Entities/UsageLog.cs

@@ -0,0 +1,72 @@
+using Extrudex.Domain.Base;
+using Extrudex.Domain.Enums;
+
+namespace Extrudex.Domain.Entities;
+
+/// <summary>
+/// Represents a single filament usage log entry. Records how much filament
+/// was consumed, by which printer, at what time, and optionally linked to
+/// a print job. This provides a fine-grained audit trail of filament consumption
+/// independent of print job lifecycle.
+/// </summary>
+public class UsageLog : AuditableEntity
+{
+    /// <summary>
+    /// Foreign key to the spool that provided the filament.
+    /// </summary>
+    public Guid SpoolId { get; set; }
+
+    /// <summary>
+    /// Navigation to the spool that provided the filament.
+    /// </summary>
+    public Spool Spool { get; set; } = null!;
+
+    /// <summary>
+    /// Foreign key to the printer that consumed the filament.
+    /// Nullable to support manual entries without a specific printer.
+    /// </summary>
+    public Guid? PrinterId { get; set; }
+
+    /// <summary>
+    /// Navigation to the printer that consumed the filament.
+    /// </summary>
+    public Printer? Printer { get; set; }
+
+    /// <summary>
+    /// Foreign key to the print job associated with this usage entry.
+    /// Nullable because usage can be logged before or without a print job.
+    /// </summary>
+    public Guid? PrintJobId { get; set; }
+
+    /// <summary>
+    /// Navigation to the print job associated with this usage entry.
+    /// </summary>
+    public PrintJob? PrintJob { get; set; }
+
+    /// <summary>
+    /// The number of grams of filament consumed in this usage event.
+    /// </summary>
+    public decimal GramsUsed { get; set; }
+
+    /// <summary>
+    /// The number of millimeters of filament extruded in this usage event.
+    /// Optional — may not be available for all data sources.
+    /// </summary>
+    public decimal? MmExtruded { get; set; }
+
+    /// <summary>
+    /// Timestamp when the usage occurred (UTC). This is the actual time of
+    /// consumption, which may differ from CreatedAt if the entry was recorded later.
+    /// </summary>
+    public DateTime UsageTimestamp { get; set; } = DateTime.UtcNow;
+
+    /// <summary>
+    /// The source of the usage data (which integration path provided it).
+    /// </summary>
+    public DataSource DataSource { get; set; } = DataSource.Manual;
+
+    /// <summary>
+    /// Optional notes about this usage entry.
+    /// </summary>
+    public string? Notes { get; set; }
+}

backend/Domain/Interfaces/ILowStockDetector.cs

@@ -0,0 +1,39 @@
+namespace Extrudex.Domain.Interfaces;
+
+/// <summary>
+/// Detects low-stock filament spools based on configurable weight thresholds.
+/// Determines whether a spool's remaining filament falls below a critical level
+/// so that alerts and API flags can be surfaced to the user.
+/// </summary>
+public interface ILowStockDetector
+{
+    /// <summary>
+    /// Determines whether a spool is considered low stock based on its remaining
+    /// weight relative to its total weight and the configured threshold percentage.
+    /// </summary>
+    /// <param name="weightRemainingGrams">The current remaining weight in grams.</param>
+    /// <param name="weightTotalGrams">The total spool weight in grams when full.</param>
+    /// <returns>
+    /// <c>true</c> if the remaining weight percentage is at or below the configured
+    /// low-stock threshold; <c>false</c> otherwise. Returns <c>false</c> for spools
+    /// with zero total weight to avoid division-by-zero.
+    /// </returns>
+    bool IsLowStock(decimal weightRemainingGrams, decimal weightTotalGrams);
+
+    /// <summary>
+    /// Calculates the remaining weight as a percentage of total weight.
+    /// </summary>
+    /// <param name="weightRemainingGrams">The current remaining weight in grams.</param>
+    /// <param name="weightTotalGrams">The total spool weight in grams when full.</param>
+    /// <returns>
+    /// A value between 0 and 100 representing the percentage of filament remaining.
+    /// Returns 0 if total weight is zero to avoid division-by-zero.
+    /// </returns>
+    decimal GetRemainingWeightPercent(decimal weightRemainingGrams, decimal weightTotalGrams);
+
+    /// <summary>
+    /// Gets the currently configured low-stock threshold percentage.
+    /// Useful for API responses so clients know what threshold is in effect.
+    /// </summary>
+    decimal LowStockThresholdPercent { get; }
+}

backend/Domain/Interfaces/IUsageLogService.cs

@@ -0,0 +1,57 @@
+using Extrudex.Domain.Entities;
+using Extrudex.Domain.Enums;
+
+namespace Extrudex.Domain.Interfaces;
+
+/// <summary>
+/// Service for recording filament usage entries. Writes to the usage_logs table
+/// and provides query capabilities for usage history.
+/// </summary>
+public interface IUsageLogService
+{
+    /// <summary>
+    /// Records a filament usage entry.
+    /// </summary>
+    /// <param name="spoolId">The spool that provided the filament.</param>
+    /// <param name="gramsUsed">Grams of filament consumed.</param>
+    /// <param name="dataSource">Where the data came from.</param>
+    /// <param name="printerId">Optional printer ID.</param>
+    /// <param name="printJobId">Optional print job ID.</param>
+    /// <param name="mmExtruded">Optional mm extruded.</param>
+    /// <param name="usageTimestamp">When the usage occurred (defaults to UTC now).</param>
+    /// <param name="notes">Optional notes.</param>
+    /// <returns>The created UsageLog entity.</returns>
+    Task<UsageLog> RecordUsageAsync(
+        Guid spoolId,
+        decimal gramsUsed,
+        DataSource dataSource,
+        Guid? printerId = null,
+        Guid? printJobId = null,
+        decimal? mmExtruded = null,
+        DateTime? usageTimestamp = null,
+        string? notes = null);
+
+    /// <summary>
+    /// Retrieves usage logs for a specific spool, ordered by usage timestamp descending.
+    /// </summary>
+    /// <param name="spoolId">The spool ID to filter by.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A collection of usage logs for the spool.</returns>
+    Task<IEnumerable<UsageLog>> GetBySpoolAsync(Guid spoolId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Retrieves usage logs for a specific printer, ordered by usage timestamp descending.
+    /// </summary>
+    /// <param name="printerId">The printer ID to filter by.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A collection of usage logs for the printer.</returns>
+    Task<IEnumerable<UsageLog>> GetByPrinterAsync(Guid printerId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Retrieves usage logs for a specific print job, ordered by usage timestamp descending.
+    /// </summary>
+    /// <param name="printJobId">The print job ID to filter by.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A collection of usage logs for the print job.</returns>
+    Task<IEnumerable<UsageLog>> GetByPrintJobAsync(Guid printJobId, CancellationToken cancellationToken = default);
+}

backend/Infrastructure/Data/Configurations/UsageLogConfiguration.cs

@@ -0,0 +1,91 @@
+using Extrudex.Domain.Entities;
+using Extrudex.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Extrudex.Infrastructure.Data.Configurations;
+
+/// <summary>
+/// EF Core configuration for the UsageLog entity.
+/// Maps to the usage_logs table with snake_case columns and appropriate indexes.
+/// </summary>
+public class UsageLogConfiguration : BaseEntityConfiguration<UsageLog>
+{
+    /// <inheritdoc/>
+    public override void Configure(EntityTypeBuilder<UsageLog> builder)
+    {
+        base.Configure(builder);
+
+        builder.Property(e => e.SpoolId)
+            .HasColumnName("spool_id")
+            .IsRequired();
+
+        builder.Property(e => e.PrinterId)
+            .HasColumnName("printer_id");
+
+        builder.Property(e => e.PrintJobId)
+            .HasColumnName("print_job_id");
+
+        builder.Property(e => e.GramsUsed)
+            .HasColumnName("grams_used")
+            .HasPrecision(10, 2)
+            .IsRequired();
+
+        builder.Property(e => e.MmExtruded)
+            .HasColumnName("mm_extruded")
+            .HasPrecision(12, 2);
+
+        builder.Property(e => e.UsageTimestamp)
+            .HasColumnName("usage_timestamp")
+            .IsRequired();
+
+        builder.Property(e => e.DataSource)
+            .HasColumnName("data_source")
+            .HasConversion<string>()
+            .HasMaxLength(50)
+            .IsRequired();
+
+        builder.Property(e => e.Notes)
+            .HasColumnName("notes")
+            .HasMaxLength(2000);
+
+        // Index on spool_id for querying usage by spool
+        builder.HasIndex(e => e.SpoolId)
+            .HasDatabaseName("ix_usage_logs_spool_id");
+
+        // Index on printer_id for querying usage by printer
+        builder.HasIndex(e => e.PrinterId)
+            .HasDatabaseName("ix_usage_logs_printer_id");
+
+        // Index on print_job_id for querying usage by print job
+        builder.HasIndex(e => e.PrintJobId)
+            .HasDatabaseName("ix_usage_logs_print_job_id");
+
+        // Index on usage_timestamp for chronological queries
+        builder.HasIndex(e => e.UsageTimestamp)
+            .HasDatabaseName("ix_usage_logs_usage_timestamp");
+
+        // Index on data_source for filtering by integration path
+        builder.HasIndex(e => e.DataSource)
+            .HasDatabaseName("ix_usage_logs_data_source");
+
+        // Relationships
+        builder.HasOne(e => e.Spool)
+            .WithMany()
+            .HasForeignKey(e => e.SpoolId)
+            .HasConstraintName("fk_usage_logs_spool")
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasOne(e => e.Printer)
+            .WithMany()
+            .HasForeignKey(e => e.PrinterId)
+            .HasConstraintName("fk_usage_logs_printer")
+            .OnDelete(DeleteBehavior.SetNull);
+
+        builder.HasOne(e => e.PrintJob)
+            .WithMany()
+            .HasForeignKey(e => e.PrintJobId)
+            .HasConstraintName("fk_usage_logs_print_job")
+            .OnDelete(DeleteBehavior.SetNull);
+    }
+}

backend/Infrastructure/Data/ExtrudexDbContext.cs

@@ -24,6 +24,7 @@ public class ExtrudexDbContext : DbContext
     public DbSet<AmsSlot> AmsSlots => Set<AmsSlot>();
     public DbSet<PrintJob> PrintJobs => Set<PrintJob>();
     public DbSet<FilamentUsage> FilamentUsages => Set<FilamentUsage>();
+    public DbSet<UsageLog> UsageLogs => Set<UsageLog>();
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {

backend/Infrastructure/Data/Migrations/20260426184329_AddUsageLogTable.cs

@@ -0,0 +1,534 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Extrudex.Infrastructure.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddUsageLogTable : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "usage_logs",
+                columns: table => new
+                {
+                    id = table.Column<Guid>(type: "uuid", nullable: false),
+                    spool_id = table.Column<Guid>(type: "uuid", nullable: false),
+                    printer_id = table.Column<Guid>(type: "uuid", nullable: true),
+                    print_job_id = table.Column<Guid>(type: "uuid", nullable: true),
+                    grams_used = table.Column<decimal>(type: "numeric(10,2)", precision: 10, scale: 2, nullable: false),
+                    mm_extruded = table.Column<decimal>(type: "numeric(12,2)", precision: 12, scale: 2, nullable: true),
+                    usage_timestamp = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    data_source = table.Column<string>(type: "character varying(50)", maxLength: 50, nullable: false),
+                    notes = table.Column<string>(type: "character varying(2000)", maxLength: 2000, nullable: true),
+                    created_at = table.Column<DateTime>(type: "timestamp with time zone", nullable: false, defaultValueSql: "now() at time zone 'utc'"),
+                    updated_at = table.Column<DateTime>(type: "timestamp with time zone", nullable: false, defaultValueSql: "now() at time zone 'utc'")
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_usage_logs", x => x.id);
+                    table.ForeignKey(
+                        name: "fk_usage_logs_print_job",
+                        column: x => x.print_job_id,
+                        principalTable: "print_jobs",
+                        principalColumn: "id",
+                        onDelete: ReferentialAction.SetNull);
+                    table.ForeignKey(
+                        name: "fk_usage_logs_printer",
+                        column: x => x.printer_id,
+                        principalTable: "printers",
+                        principalColumn: "id",
+                        onDelete: ReferentialAction.SetNull);
+                    table.ForeignKey(
+                        name: "fk_usage_logs_spool",
+                        column: x => x.spool_id,
+                        principalTable: "spools",
+                        principalColumn: "id",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(6535), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(6535) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7016), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7016) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7027), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7028) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7034), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7035) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7042), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7042) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7049), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7049) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7291), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7292) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7453), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7453) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7461), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7461) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7468), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7468) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7474), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7474) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7480), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7481) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000007"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7487), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7487) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000008"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7493), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7493) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000009"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7500), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7500) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000010"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7507), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7507) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000011"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7513), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7513) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000012"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7519), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7520) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000013"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7526), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7526) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000014"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7532), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7532) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000015"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7538), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7539) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7690), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7690) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7838), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7838) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7846), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7846) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7853), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7853) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7859), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7859) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7865), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7866) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000007"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7872), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7872) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000008"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7878), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7879) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000009"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7885), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7885) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000010"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7891), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7891) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000011"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7898), new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7898) });
+
+            migrationBuilder.CreateIndex(
+                name: "ix_usage_logs_data_source",
+                table: "usage_logs",
+                column: "data_source");
+
+            migrationBuilder.CreateIndex(
+                name: "ix_usage_logs_print_job_id",
+                table: "usage_logs",
+                column: "print_job_id");
+
+            migrationBuilder.CreateIndex(
+                name: "ix_usage_logs_printer_id",
+                table: "usage_logs",
+                column: "printer_id");
+
+            migrationBuilder.CreateIndex(
+                name: "ix_usage_logs_spool_id",
+                table: "usage_logs",
+                column: "spool_id");
+
+            migrationBuilder.CreateIndex(
+                name: "ix_usage_logs_usage_timestamp",
+                table: "usage_logs",
+                column: "usage_timestamp");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "usage_logs");
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1096), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1096) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1620), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1620) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1630), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1630) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1638), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1638) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1645), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1645) });
+
+            migrationBuilder.UpdateData(
+                table: "material_bases",
+                keyColumn: "id",
+                keyValue: new Guid("10000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1651), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1652) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1850), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(1850) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2041), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2041) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2049), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2049) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2055), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2056) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2062), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2062) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2068), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2068) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000007"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2075), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2075) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000008"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2081), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2081) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000009"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2100), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2100) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000010"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2107), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2107) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000011"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2113), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2113) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000012"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2120), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2120) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000013"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2126), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2126) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000014"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2132), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2133) });
+
+            migrationBuilder.UpdateData(
+                table: "material_finishes",
+                keyColumn: "id",
+                keyValue: new Guid("20000000-0000-0000-0000-000000000015"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2139), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2139) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000001"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2304), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2304) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000002"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2463), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2463) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000003"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2471), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2471) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000004"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2477), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2478) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000005"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2484), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2484) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000006"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2490), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2491) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000007"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2497), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2497) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000008"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2503), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2503) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000009"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2510), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2510) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000010"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2516), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2516) });
+
+            migrationBuilder.UpdateData(
+                table: "material_modifiers",
+                keyColumn: "id",
+                keyValue: new Guid("30000000-0000-0000-0000-000000000011"),
+                columns: new[] { "created_at", "updated_at" },
+                values: new object[] { new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2522), new DateTime(2026, 4, 26, 13, 14, 18, 745, DateTimeKind.Utc).AddTicks(2523) });
+        }
+    }
+}

backend/Infrastructure/Data/Migrations/ExtrudexDbContextModelSnapshot.cs

@@ -104,77 +104,6 @@ namespace Extrudex.Infrastructure.Data.Migrations
                     b.ToTable("ams_units", (string)null);
                 });
 
-            modelBuilder.Entity("Extrudex.Domain.Entities.FilamentUsage", b =>
-                {
-                    b.Property<Guid>("Id")
-                        .HasColumnType("uuid")
-                        .HasColumnName("id");
-
-                    b.Property<DateTime>("CreatedAt")
-                        .ValueGeneratedOnAdd()
-                        .HasColumnType("timestamp with time zone")
-                        .HasColumnName("created_at")
-                        .HasDefaultValueSql("now() at time zone 'utc'");
-
-                    b.Property<decimal>("GramsUsed")
-                        .HasPrecision(10, 2)
-                        .HasColumnType("numeric(10,2)")
-                        .HasColumnName("grams_used");
-
-                    b.Property<decimal>("MmExtruded")
-                        .HasPrecision(12, 2)
-                        .HasColumnType("numeric(12,2)")
-                        .HasColumnName("mm_extruded");
-
-                    b.Property<string>("Notes")
-                        .HasMaxLength(2000)
-                        .HasColumnType("character varying(2000)")
-                        .HasColumnName("notes");
-
-                    b.Property<Guid>("PrintJobId")
-                        .HasColumnType("uuid")
-                        .HasColumnName("print_job_id");
-
-                    b.Property<Guid>("PrinterId")
-                        .HasColumnType("uuid")
-                        .HasColumnName("printer_id");
-
-                    b.Property<DateTime>("RecordedAt")
-                        .ValueGeneratedOnAdd()
-                        .HasColumnType("timestamp with time zone")
-                        .HasColumnName("recorded_at")
-                        .HasDefaultValueSql("now() at time zone 'utc'");
-
-                    b.Property<Guid>("SpoolId")
-                        .HasColumnType("uuid")
-                        .HasColumnName("spool_id");
-
-                    b.Property<DateTime>("UpdatedAt")
-                        .ValueGeneratedOnAdd()
-                        .HasColumnType("timestamp with time zone")
-                        .HasColumnName("updated_at")
-                        .HasDefaultValueSql("now() at time zone 'utc'");
-
-                    b.HasKey("Id");
-
-                    b.HasIndex("PrintJobId")
-                        .HasDatabaseName("ix_filament_usages_print_job_id");
-
-                    b.HasIndex("PrinterId")
-                        .HasDatabaseName("ix_filament_usages_printer_id");
-
-                    b.HasIndex("RecordedAt")
-                        .HasDatabaseName("ix_filament_usages_recorded_at");
-
-                    b.HasIndex("SpoolId")
-                        .HasDatabaseName("ix_filament_usages_spool_id");
-
-                    b.HasIndex("SpoolId", "RecordedAt")
-                        .HasDatabaseName("ix_filament_usages_spool_id_recorded_at");
-
-                    b.ToTable("filament_usages", (string)null);
-                });
-
             modelBuilder.Entity("Extrudex.Domain.Entities.MaterialBase", b =>
                 {
                     b.Property<Guid>("Id")
@@ -216,50 +145,50 @@ namespace Extrudex.Infrastructure.Data.Migrations
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000001"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9388),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(6535),
                             DensityGperCm3 = 1.24m,
                             Name = "PLA",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9388)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(6535)
                         },
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000002"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9871),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7016),
                             DensityGperCm3 = 1.27m,
                             Name = "PETG",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9871)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7016)
                         },
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000003"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9881),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7027),
                             DensityGperCm3 = 1.04m,
                             Name = "ABS",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9881)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7028)
                         },
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000004"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9888),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7034),
                             DensityGperCm3 = 1.07m,
                             Name = "ASA",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9888)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7035)
                         },
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000005"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9895),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7042),
                             DensityGperCm3 = 1.21m,
                             Name = "TPU",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9895)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7042)
                         },
                         new
                         {
                             Id = new Guid("10000000-0000-0000-0000-000000000006"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9901),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7049),
                             DensityGperCm3 = 1.14m,
                             Name = "Nylon",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 291, DateTimeKind.Utc).AddTicks(9902)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7049)
                         });
                 });
 
@@ -303,122 +232,122 @@ namespace Extrudex.Infrastructure.Data.Migrations
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000001"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(90),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7291),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(90)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7292)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000002"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(251),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7453),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Matte",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(251)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7453)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000003"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(259),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7461),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Silk",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(259)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7461)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000004"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(266),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7468),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Glitter",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(266)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7468)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000005"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(272),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7474),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Marble",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(272)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7474)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000006"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(278),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7480),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Sparkle",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(278)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7481)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000007"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(285),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7487),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000002"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(285)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7487)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000008"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(291),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7493),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000002"),
                             Name = "Matte",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(291)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7493)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000009"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(297),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7500),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000002"),
                             Name = "Silk",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(298)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7500)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000010"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(304),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7507),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000003"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(304)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7507)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000011"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(310),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7513),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000003"),
                             Name = "Matte",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(310)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7513)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000012"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(316),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7519),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000004"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(317)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7520)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000013"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(323),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7526),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000004"),
                             Name = "Matte",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(323)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7526)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000014"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(329),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7532),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000005"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(329)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7532)
                         },
                         new
                         {
                             Id = new Guid("20000000-0000-0000-0000-000000000015"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(336),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7538),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000006"),
                             Name = "Basic",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(336)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7539)
                         });
                 });
 
@@ -462,90 +391,90 @@ namespace Extrudex.Infrastructure.Data.Migrations
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000001"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(482),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7690),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Carbon Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(482)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7690)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000002"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(805),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7838),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Glass Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(806)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7838)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000003"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(815),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7846),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Wood Fill",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(815)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7846)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000004"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(821),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7853),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000001"),
                             Name = "Glow-in-the-Dark",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(821)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7853)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000005"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(828),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7859),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000002"),
                             Name = "Carbon Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(828)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7859)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000006"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(834),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7865),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000002"),
                             Name = "Glass Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(834)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7866)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000007"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(840),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7872),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000003"),
                             Name = "Carbon Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(840)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7872)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000008"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(847),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7878),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000003"),
                             Name = "Glass Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(847)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7879)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000009"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(853),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7885),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000004"),
                             Name = "Carbon Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(853)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7885)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000010"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(859),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7891),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000006"),
                             Name = "Carbon Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(860)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7891)
                         },
                         new
                         {
                             Id = new Guid("30000000-0000-0000-0000-000000000011"),
-                            CreatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(866),
+                            CreatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7898),
                             MaterialBaseId = new Guid("10000000-0000-0000-0000-000000000006"),
                             Name = "Glass Fiber",
-                            UpdatedAt = new DateTime(2026, 4, 26, 18, 34, 33, 292, DateTimeKind.Utc).AddTicks(866)
+                            UpdatedAt = new DateTime(2026, 4, 26, 18, 43, 28, 895, DateTimeKind.Utc).AddTicks(7898)
                         });
                 });
 
@@ -877,6 +806,81 @@ namespace Extrudex.Infrastructure.Data.Migrations
                     b.ToTable("spools", (string)null);
                 });
 
+            modelBuilder.Entity("Extrudex.Domain.Entities.UsageLog", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at")
+                        .HasDefaultValueSql("now() at time zone 'utc'");
+
+                    b.Property<string>("DataSource")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)")
+                        .HasColumnName("data_source");
+
+                    b.Property<decimal>("GramsUsed")
+                        .HasPrecision(10, 2)
+                        .HasColumnType("numeric(10,2)")
+                        .HasColumnName("grams_used");
+
+                    b.Property<decimal?>("MmExtruded")
+                        .HasPrecision(12, 2)
+                        .HasColumnType("numeric(12,2)")
+                        .HasColumnName("mm_extruded");
+
+                    b.Property<string>("Notes")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)")
+                        .HasColumnName("notes");
+
+                    b.Property<Guid?>("PrintJobId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("print_job_id");
+
+                    b.Property<Guid?>("PrinterId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("printer_id");
+
+                    b.Property<Guid>("SpoolId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("spool_id");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated_at")
+                        .HasDefaultValueSql("now() at time zone 'utc'");
+
+                    b.Property<DateTime>("UsageTimestamp")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("usage_timestamp");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("DataSource")
+                        .HasDatabaseName("ix_usage_logs_data_source");
+
+                    b.HasIndex("PrintJobId")
+                        .HasDatabaseName("ix_usage_logs_print_job_id");
+
+                    b.HasIndex("PrinterId")
+                        .HasDatabaseName("ix_usage_logs_printer_id");
+
+                    b.HasIndex("SpoolId")
+                        .HasDatabaseName("ix_usage_logs_spool_id");
+
+                    b.HasIndex("UsageTimestamp")
+                        .HasDatabaseName("ix_usage_logs_usage_timestamp");
+
+                    b.ToTable("usage_logs", (string)null);
+                });
+
             modelBuilder.Entity("Extrudex.Domain.Entities.AmsSlot", b =>
                 {
                     b.HasOne("Extrudex.Domain.Entities.AmsUnit", "AmsUnit")
@@ -909,36 +913,6 @@ namespace Extrudex.Infrastructure.Data.Migrations
                     b.Navigation("Printer");
                 });
 
-            modelBuilder.Entity("Extrudex.Domain.Entities.FilamentUsage", b =>
-                {
-                    b.HasOne("Extrudex.Domain.Entities.PrintJob", "PrintJob")
-                        .WithMany("FilamentUsages")
-                        .HasForeignKey("PrintJobId")
-                        .OnDelete(DeleteBehavior.Cascade)
-                        .IsRequired()
-                        .HasConstraintName("fk_filament_usages_print_job");
-
-                    b.HasOne("Extrudex.Domain.Entities.Printer", "Printer")
-                        .WithMany("FilamentUsages")
-                        .HasForeignKey("PrinterId")
-                        .OnDelete(DeleteBehavior.Restrict)
-                        .IsRequired()
-                        .HasConstraintName("fk_filament_usages_printer");
-
-                    b.HasOne("Extrudex.Domain.Entities.Spool", "Spool")
-                        .WithMany("FilamentUsages")
-                        .HasForeignKey("SpoolId")
-                        .OnDelete(DeleteBehavior.Restrict)
-                        .IsRequired()
-                        .HasConstraintName("fk_filament_usages_spool");
-
-                    b.Navigation("PrintJob");
-
-                    b.Navigation("Printer");
-
-                    b.Navigation("Spool");
-                });
-
             modelBuilder.Entity("Extrudex.Domain.Entities.MaterialFinish", b =>
                 {
                     b.HasOne("Extrudex.Domain.Entities.MaterialBase", "MaterialBase")
@@ -1013,6 +987,34 @@ namespace Extrudex.Infrastructure.Data.Migrations
                     b.Navigation("MaterialModifier");
                 });
 
+            modelBuilder.Entity("Extrudex.Domain.Entities.UsageLog", b =>
+                {
+                    b.HasOne("Extrudex.Domain.Entities.PrintJob", "PrintJob")
+                        .WithMany()
+                        .HasForeignKey("PrintJobId")
+                        .OnDelete(DeleteBehavior.SetNull)
+                        .HasConstraintName("fk_usage_logs_print_job");
+
+                    b.HasOne("Extrudex.Domain.Entities.Printer", "Printer")
+                        .WithMany()
+                        .HasForeignKey("PrinterId")
+                        .OnDelete(DeleteBehavior.SetNull)
+                        .HasConstraintName("fk_usage_logs_printer");
+
+                    b.HasOne("Extrudex.Domain.Entities.Spool", "Spool")
+                        .WithMany()
+                        .HasForeignKey("SpoolId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired()
+                        .HasConstraintName("fk_usage_logs_spool");
+
+                    b.Navigation("PrintJob");
+
+                    b.Navigation("Printer");
+
+                    b.Navigation("Spool");
+                });
+
             modelBuilder.Entity("Extrudex.Domain.Entities.AmsUnit", b =>
                 {
                     b.Navigation("Slots");
@@ -1037,17 +1039,10 @@ namespace Extrudex.Infrastructure.Data.Migrations
                     b.Navigation("Spools");
                 });
 
-            modelBuilder.Entity("Extrudex.Domain.Entities.PrintJob", b =>
-                {
-                    b.Navigation("FilamentUsages");
-                });
-
             modelBuilder.Entity("Extrudex.Domain.Entities.Printer", b =>
                 {
                     b.Navigation("AmsUnits");
 
-                    b.Navigation("FilamentUsages");
-
                     b.Navigation("PrintJobs");
                 });
 
@@ -1055,8 +1050,6 @@ namespace Extrudex.Infrastructure.Data.Migrations
                 {
                     b.Navigation("AmsSlots");
 
-                    b.Navigation("FilamentUsages");
-
                     b.Navigation("PrintJobs");
                 });
 #pragma warning restore 612, 618

backend/Infrastructure/Services/LowStockDetector.cs

@@ -0,0 +1,95 @@
+using Extrudex.Domain.Interfaces;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+
+namespace Extrudex.Infrastructure.Services;
+
+/// <summary>
+/// Detects low-stock filament spools by comparing the remaining weight percentage
+/// against a configurable threshold. The threshold can be set via:
+///   1. EXTRUDEX_LOW_STOCK_THRESHOLD env var (highest priority, e.g. "25")
+///   2. FilamentAlerts:LowStockThresholdPercent in appsettings.json
+///   3. Default: 20% (a standard spool is "low" when ≤20% remains)
+/// </summary>
+public class LowStockDetector : ILowStockDetector
+{
+    private readonly ILogger<LowStockDetector> _logger;
+
+    /// <summary>
+    /// The percentage threshold below which a spool is considered low stock.
+    /// For example, 20 means a spool is "low" when ≤20% of its filament remains.
+    /// </summary>
+    public decimal LowStockThresholdPercent { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="LowStockDetector"/> class.
+    /// Reads the low-stock threshold from configuration with env var override support.
+    /// </summary>
+    /// <param name="configuration">Application configuration for threshold settings.</param>
+    /// <param name="logger">Logger for diagnostic output.</param>
+    public LowStockDetector(IConfiguration configuration, ILogger<LowStockDetector> logger)
+    {
+        _logger = logger;
+
+        // Priority: env var > appsettings > default (20%)
+        var envThreshold = Environment.GetEnvironmentVariable("EXTRUDEX_LOW_STOCK_THRESHOLD");
+        var configThreshold = configuration.GetValue<decimal?>("FilamentAlerts:LowStockThresholdPercent");
+
+        if (!string.IsNullOrEmpty(envThreshold) && decimal.TryParse(envThreshold, out var parsedEnv))
+        {
+            LowStockThresholdPercent = Math.Clamp(parsedEnv, 0m, 100m);
+            _logger.LogInformation(
+                "Low-stock threshold set from env var EXTRUDEX_LOW_STOCK_THRESHOLD: {Threshold}%",
+                LowStockThresholdPercent);
+        }
+        else if (configThreshold.HasValue)
+        {
+            LowStockThresholdPercent = Math.Clamp(configThreshold.Value, 0m, 100m);
+            _logger.LogInformation(
+                "Low-stock threshold set from config FilamentAlerts:LowStockThresholdPercent: {Threshold}%",
+                LowStockThresholdPercent);
+        }
+        else
+        {
+            LowStockThresholdPercent = 20m;
+            _logger.LogInformation(
+                "Low-stock threshold using default: {Threshold}%", LowStockThresholdPercent);
+        }
+    }
+
+    /// <inheritdoc />
+    public bool IsLowStock(decimal weightRemainingGrams, decimal weightTotalGrams)
+    {
+        if (weightTotalGrams <= 0m)
+        {
+            _logger.LogDebug(
+                "Spool with total weight {Total}g cannot be evaluated for low stock — treating as not low",
+                weightTotalGrams);
+            return false;
+        }
+
+        var remainingPercent = GetRemainingWeightPercent(weightRemainingGrams, weightTotalGrams);
+        var isLow = remainingPercent <= LowStockThresholdPercent;
+
+        if (isLow)
+        {
+            _logger.LogDebug(
+                "Spool is LOW STOCK: {Remaining}g / {Total}g = {Percent:F1}% (threshold: {Threshold}%)",
+                weightRemainingGrams, weightTotalGrams, remainingPercent, LowStockThresholdPercent);
+        }
+
+        return isLow;
+    }
+
+    /// <inheritdoc />
+    public decimal GetRemainingWeightPercent(decimal weightRemainingGrams, decimal weightTotalGrams)
+    {
+        if (weightTotalGrams <= 0m)
+            return 0m;
+
+        return Math.Round(
+            (weightRemainingGrams / weightTotalGrams) * 100m,
+            1,
+            MidpointRounding.AwayFromZero);
+    }
+}

backend/Infrastructure/Services/UsageLogService.cs

@@ -0,0 +1,81 @@
+using Extrudex.Domain.Entities;
+using Extrudex.Domain.Enums;
+using Extrudex.Domain.Interfaces;
+using Extrudex.Infrastructure.Data;
+using Microsoft.EntityFrameworkCore;
+
+namespace Extrudex.Infrastructure.Services;
+
+/// <summary>
+/// Implementation of <see cref="IUsageLogService"/> that persists usage entries
+/// to the usage_logs table via EF Core.
+/// </summary>
+public class UsageLogService : IUsageLogService
+{
+    private readonly ExtrudexDbContext _dbContext;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="UsageLogService"/> class.
+    /// </summary>
+    /// <param name="dbContext">The EF Core database context for data persistence.</param>
+    public UsageLogService(ExtrudexDbContext dbContext)
+    {
+        _dbContext = dbContext;
+    }
+
+    /// <inheritdoc/>
+    public async Task<UsageLog> RecordUsageAsync(
+        Guid spoolId,
+        decimal gramsUsed,
+        DataSource dataSource,
+        Guid? printerId = null,
+        Guid? printJobId = null,
+        decimal? mmExtruded = null,
+        DateTime? usageTimestamp = null,
+        string? notes = null)
+    {
+        var entry = new UsageLog
+        {
+            SpoolId = spoolId,
+            GramsUsed = gramsUsed,
+            DataSource = dataSource,
+            PrinterId = printerId,
+            PrintJobId = printJobId,
+            MmExtruded = mmExtruded,
+            UsageTimestamp = usageTimestamp ?? DateTime.UtcNow,
+            Notes = notes
+        };
+
+        _dbContext.UsageLogs.Add(entry);
+        await _dbContext.SaveChangesAsync();
+
+        return entry;
+    }
+
+    /// <inheritdoc/>
+    public async Task<IEnumerable<UsageLog>> GetBySpoolAsync(Guid spoolId, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.UsageLogs
+            .Where(u => u.SpoolId == spoolId)
+            .OrderByDescending(u => u.UsageTimestamp)
+            .ToListAsync(cancellationToken);
+    }
+
+    /// <inheritdoc/>
+    public async Task<IEnumerable<UsageLog>> GetByPrinterAsync(Guid printerId, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.UsageLogs
+            .Where(u => u.PrinterId == printerId)
+            .OrderByDescending(u => u.UsageTimestamp)
+            .ToListAsync(cancellationToken);
+    }
+
+    /// <inheritdoc/>
+    public async Task<IEnumerable<UsageLog>> GetByPrintJobAsync(Guid printJobId, CancellationToken cancellationToken = default)
+    {
+        return await _dbContext.UsageLogs
+            .Where(u => u.PrintJobId == printJobId)
+            .OrderByDescending(u => u.UsageTimestamp)
+            .ToListAsync(cancellationToken);
+    }
+}

backend/Program.cs

@@ -55,6 +55,12 @@ builder.Services.AddSingleton<IQrCodeService, QrCodeService>();
 // ── Cost Per Print Calculation ─────────────────────────────
 builder.Services.AddScoped<ICostPerPrintService, CostPerPrintService>();
 
+// ── Low Stock Detection ────────────────────────────────────
+builder.Services.AddSingleton<ILowStockDetector, LowStockDetector>();
+
+// ── Usage Logging ───────────────────────────────────────────
+builder.Services.AddScoped<IUsageLogService, UsageLogService>();
+
 // ── FluentValidation ──────────────────────────────────────
 // Registers all validators from the API assembly into DI.
 builder.Services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly());

backend/appsettings.json

@@ -20,5 +20,8 @@
     "RequestTimeout": "00:00:15",
     "Enabled": true,
     "HistoryBatchSize": 25
+  },
+  "FilamentAlerts": {
+    "LowStockThresholdPercent": 20
   }
 }

frontend/src/app/components/filament-table/filament-table.component.html

@@ -83,6 +83,35 @@
       </td>
     </ng-container>
 
+    <!-- Cost Column -->
+    <ng-container matColumnDef="cost">
+      <th mat-header-cell *matHeaderCellDef mat-sort-header="cost">Cost</th>
+      <td mat-cell *matCellDef="let filament">
+        <div class="cost-cell">
+          @if (filament.purchasePrice !== null) {
+            <span class="cost-price">{{ formatCurrency(filament.purchasePrice) }}</span>
+            @let cpg = getCostPerGram(filament);
+            @if (cpg !== null) {
+              <span class="cost-per-gram">${{ cpg.toFixed(2) }}/g</span>
+            }
+          } @else {
+            <span class="cost-unknown">&mdash;</span>
+          }
+        </div>
+      </td>
+    </ng-container>
+
+    <!-- Usage Column -->
+    <ng-container matColumnDef="usage">
+      <th mat-header-cell *matHeaderCellDef mat-sort-header="usage">Usage</th>
+      <td mat-cell *matCellDef="let filament">
+        <div class="usage-cell">
+          <span class="usage-grams">{{ formatWeight(getGramsUsed(filament)) }} used</span>
+          <span class="usage-remaining">{{ formatWeight(filament.weightRemainingGrams) }} left</span>
+        </div>
+      </td>
+    </ng-container>
+
     <!-- Stock Level Indicator Column -->
     <ng-container matColumnDef="stockLevel">
       <th mat-header-cell *matHeaderCellDef mat-sort-header="stockLevel">Stock</th>

frontend/src/app/components/filament-table/filament-table.component.scss

@@ -55,7 +55,7 @@ $color-inactive: #94a3b8;  // Gray — inactive spool
 // Table styling
 .filament-table {
   width: 100%;
-  min-width: 700px;
+  min-width: 900px;
 
   th {
     font-weight: 600;
@@ -132,6 +132,48 @@ $color-inactive: #94a3b8;  // Gray — inactive spool
   letter-spacing: 0.02em;
 }
 
+// Cost cell
+.cost-cell {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 80px;
+
+  .cost-price {
+    font-weight: 600;
+    color: var(--mat-sys-on-surface);
+  }
+
+  .cost-per-gram {
+    font-size: 11px;
+    color: var(--mat-sys-on-surface-variant);
+    letter-spacing: 0.02em;
+  }
+
+  .cost-unknown {
+    color: var(--mat-sys-on-surface-variant);
+    font-style: italic;
+  }
+}
+
+// Usage cell
+.usage-cell {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 100px;
+
+  .usage-grams {
+    font-weight: 500;
+    color: var(--mat-sys-on-surface);
+  }
+
+  .usage-remaining {
+    font-size: 12px;
+    color: var(--mat-sys-on-surface-variant);
+  }
+}
+
 // Remaining weight cell
 .remaining-cell {
   display: flex;

frontend/src/app/components/filament-table/filament-table.component.ts

@@ -30,6 +30,8 @@ export type FilamentColumn =
   | 'brand'
   | 'serial'
   | 'remaining'
+  | 'cost'
+  | 'usage'
   | 'stockLevel'
   | 'status';
 
@@ -70,6 +72,8 @@ export class FilamentTableComponent implements OnInit {
     'brand',
     'serial',
     'remaining',
+    'cost',
+    'usage',
     'stockLevel',
     'status',
   ]);
@@ -143,6 +147,18 @@ export class FilamentTableComponent implements OnInit {
             getRemainingPercent(b),
             isAsc
           );
+        case 'cost':
+          return compare(
+            a.purchasePrice ?? 0,
+            b.purchasePrice ?? 0,
+            isAsc
+          );
+        case 'usage':
+          return compare(
+            a.weightTotalGrams - a.weightRemainingGrams,
+            b.weightTotalGrams - b.weightRemainingGrams,
+            isAsc
+          );
         case 'stockLevel':
           return compare(
             stockLevelOrder(classifyStockLevel(a)),
@@ -243,6 +259,29 @@ export class FilamentTableComponent implements OnInit {
     }
     return `${Math.round(grams)}g`;
   }
+
+  /** Template helper: format currency */
+  formatCurrency(value: number): string {
+    return new Intl.NumberFormat('en-US', {
+      style: 'currency',
+      currency: 'USD',
+      minimumFractionDigits: 2,
+      maximumFractionDigits: 2,
+    }).format(value);
+  }
+
+  /** Template helper: compute cost per gram for a filament */
+  getCostPerGram(filament: Filament): number | null {
+    if (filament.purchasePrice === null || filament.purchasePrice === 0 || filament.weightTotalGrams <= 0) {
+      return null;
+    }
+    return filament.purchasePrice / filament.weightTotalGrams;
+  }
+
+  /** Template helper: compute grams used for a filament */
+  getGramsUsed(filament: Filament): number {
+    return filament.weightTotalGrams - filament.weightRemainingGrams;
+  }
 }
 
 /** Compare helper for sorting */

frontend/src/app/components/inventory-summary/inventory-summary.component.html

@@ -87,6 +87,43 @@
       </div>
     </div>
 
+    <!-- Average Cost per Gram -->
+    @if (avgCostPerGram() !== null) {
+      <div class="summary-item metric-card"
+           matTooltip="Average cost per gram across priced, active spools"
+           matTooltipPosition="below">
+        <mat-icon aria-hidden="true" class="metric-icon">scale</mat-icon>
+        <div class="metric-content">
+          <span class="metric-value">${{ avgCostPerGram()!.toFixed(2) }}/g</span>
+          <span class="metric-label">Avg Cost/g</span>
+        </div>
+      </div>
+    }
+
+    <!-- Total Usage -->
+    <div class="summary-item metric-card"
+         matTooltip="Total filament used across all spools"
+         matTooltipPosition="below">
+      <mat-icon aria-hidden="true" class="metric-icon">trending_down</mat-icon>
+      <div class="metric-content">
+        <span class="metric-value">{{ formatWeight(totalGramsUsed()) }}</span>
+        <span class="metric-label">Total Used</span>
+      </div>
+    </div>
+
+    <!-- Estimated Used Value -->
+    @if (estimatedUsedValue() !== null) {
+      <div class="summary-item metric-card"
+           matTooltip="Estimated value of filament consumed"
+           matTooltipPosition="below">
+        <mat-icon aria-hidden="true" class="metric-icon">receipt_long</mat-icon>
+        <div class="metric-content">
+          <span class="metric-value">{{ formatCurrency(estimatedUsedValue()!) }}</span>
+          <span class="metric-label">Used Value</span>
+        </div>
+      </div>
+    }
+
     <!-- Overall Remaining Stock Bar -->
     <div class="summary-item metric-card stock-bar-card"
          matTooltip="{{ formatWeight(totalRemainingGrams()) }} of {{ formatWeight(totalCapacityGrams()) }} remaining"

frontend/src/app/components/inventory-summary/inventory-summary.component.ts

@@ -88,6 +88,37 @@ export class InventorySummaryComponent implements OnInit, OnDestroy {
       .reduce((sum, f) => sum + (f.purchasePrice ?? 0), 0)
   );
 
+  /** Computed: average cost per gram across active spools with a price */
+  readonly avgCostPerGram = computed(() => {
+    const priced = this.filaments().filter(
+      (f) => f.isActive && f.purchasePrice !== null && f.purchasePrice! > 0 && f.weightTotalGrams > 0
+    );
+    if (priced.length === 0) return null;
+    const totalCost = priced.reduce((sum, f) => sum + f.purchasePrice!, 0);
+    const totalWeight = priced.reduce((sum, f) => sum + f.weightTotalGrams, 0);
+    return totalWeight > 0 ? totalCost / totalWeight : null;
+  });
+
+  /** Computed: total grams used across all spools */
+  readonly totalGramsUsed = computed(() =>
+    this.filaments().reduce(
+      (sum, f) => sum + (f.weightTotalGrams - f.weightRemainingGrams),
+      0
+    )
+  );
+
+  /** Computed: total estimated value of used filament */
+  readonly estimatedUsedValue = computed(() => {
+    const priced = this.filaments().filter(
+      (f) => f.isActive && f.purchasePrice !== null && f.purchasePrice! > 0 && f.weightTotalGrams > 0
+    );
+    if (priced.length === 0) return null;
+    return priced.reduce((sum, f) => {
+      const usedFraction = (f.weightTotalGrams - f.weightRemainingGrams) / f.weightTotalGrams;
+      return sum + f.purchasePrice! * usedFraction;
+    }, 0);
+  });
+
   /** Computed: total remaining weight across all spools in grams */
   readonly totalRemainingGrams = computed(() =>
     this.filaments().reduce((sum, f) => sum + f.weightRemainingGrams, 0)
@@ -169,8 +200,8 @@ export class InventorySummaryComponent implements OnInit, OnDestroy {
     return new Intl.NumberFormat('en-US', {
       style: 'currency',
       currency: 'USD',
-      minimumFractionDigits: 0,
+      minimumFractionDigits: 2,
-      maximumFractionDigits: 0,
+      maximumFractionDigits: 2,
     }).format(value);
   }
 }