Merge remote-tracking branch 'origin/dev' into agent/dex/CUB-32-usage-logging-service

# Conflicts:
#	backend/Infrastructure/Data/ExtrudexDbContext.cs
#	backend/Infrastructure/Data/Migrations/ExtrudexDbContextModelSnapshot.cs

backend/API/Controllers/PrintJobsController.cs

@@ -413,6 +413,92 @@ public class PrintJobsController : ControllerBase
         return NoContent();
     }
 
+    // ── GET /api/printjobs/{id}/cost-summary ──────────────────────────
+
+    /// <summary>
+    /// Gets the material cost summary for a specific print job.
+    /// Calculates total material cost from filament usage (grams derived)
+    /// and the spool's purchase price. Returns warnings instead of errors
+    /// when cost data is unavailable.
+    /// </summary>
+    /// <param name="id">The unique identifier of the print job.</param>
+    /// <returns>A cost summary with breakdown and any warnings about missing data.</returns>
+    /// <response code="200">Returns the cost summary. Warnings field lists any missing data.</response>
+    /// <response code="404">If the print job with the given ID is not found.</response>
+    [HttpGet("{id:guid}/cost-summary")]
+    [ProducesResponseType(typeof(CostSummaryResponse), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<CostSummaryResponse>> GetCostSummary(Guid id)
+    {
+        _logger.LogDebug("Getting cost summary for print job {Id}", id);
+
+        var job = await _dbContext.PrintJobs
+            .Include(j => j.Spool)
+                .ThenInclude(s => s!.MaterialBase)
+            .FirstOrDefaultAsync(j => j.Id == id);
+
+        if (job is null)
+        {
+            _logger.LogWarning("Print job {Id} not found for cost summary", id);
+            return NotFound(new { error = $"Print job with ID '{id}' not found." });
+        }
+
+        var warnings = new List<string>();
+        var spool = job.Spool;
+
+        // Build response with what we have
+        var response = new CostSummaryResponse
+        {
+            PrintJobId = job.Id,
+            PrintName = job.PrintName,
+            SpoolId = job.SpoolId,
+            SpoolSerial = spool?.SpoolSerial ?? string.Empty,
+            SpoolBrand = spool?.Brand ?? string.Empty,
+            SpoolColorName = spool?.ColorName ?? string.Empty,
+            MmExtruded = job.MmExtruded,
+            GramsDerived = job.GramsDerived,
+            SpoolPurchasePrice = spool?.PurchasePrice,
+            SpoolWeightTotalGrams = spool?.WeightTotalGrams,
+            StoredCostPerPrint = job.CostPerPrint
+        };
+
+        // Validate spool data availability
+        if (spool is null)
+        {
+            warnings.Add("Spool data is not available for this print job. Cost cannot be calculated.");
+            response.Warnings = warnings;
+            return Ok(response);
+        }
+
+        // Check if we can calculate cost
+        if (!spool.PurchasePrice.HasValue)
+        {
+            warnings.Add("Spool purchase price is not set. Cost per gram and total material cost cannot be calculated.");
+        }
+
+        if (spool.WeightTotalGrams <= 0)
+        {
+            warnings.Add("Spool total weight is zero or invalid. Cost per gram and total material cost cannot be calculated.");
+        }
+
+        // If we have enough data, calculate the cost
+        if (spool.PurchasePrice.HasValue && spool.WeightTotalGrams > 0)
+        {
+            var pricePerGram = spool.PurchasePrice.Value / spool.WeightTotalGrams;
+            response.PricePerGram = Math.Round(pricePerGram, 4);
+            response.TotalMaterialCost = Math.Round(job.GramsDerived * pricePerGram, 4);
+        }
+
+        // Warn if grams derived is zero but mm extruded is non-zero
+        if (job.GramsDerived == 0 && job.MmExtruded > 0)
+        {
+            warnings.Add("GramsDerived is zero despite MmExtruded being non-zero. Cost may be inaccurate. Consider re-deriving grams from filament parameters.");
+        }
+
+        response.Warnings = warnings;
+        return Ok(response);
+    }
+
     // ── Gram Derivation Formula ────────────────────────────────────
 
     /// <summary>

backend/API/DTOs/PrintJobs/CostSummaryResponse.cs

@@ -0,0 +1,55 @@
+namespace Extrudex.API.DTOs.PrintJobs;
+
+/// <summary>
+/// Response DTO for the cost summary of a print job.
+/// Provides a breakdown of material cost based on filament usage
+/// and spool pricing data. If cost data is incomplete, warnings
+/// are returned instead of throwing an error.
+/// </summary>
+public class CostSummaryResponse
+{
+    /// <summary>Unique identifier of the print job.</summary>
+    public Guid PrintJobId { get; set; }
+
+    /// <summary>Human-readable name of the print job.</summary>
+    public string PrintName { get; set; } = string.Empty;
+
+    /// <summary>Foreign key to the spool used for this print job.</summary>
+    public Guid SpoolId { get; set; }
+
+    /// <summary>Serial number of the spool.</summary>
+    public string SpoolSerial { get; set; } = string.Empty;
+
+    /// <summary>Brand of the spool.</summary>
+    public string SpoolBrand { get; set; } = string.Empty;
+
+    /// <summary>Color name of the spool.</summary>
+    public string SpoolColorName { get; set; } = string.Empty;
+
+    /// <summary>Total millimeters of filament extruded during this print.</summary>
+    public decimal MmExtruded { get; set; }
+
+    /// <summary>Derived grams consumed for this print job.</summary>
+    public decimal GramsDerived { get; set; }
+
+    /// <summary>Purchase price of the full spool, if available.</summary>
+    public decimal? SpoolPurchasePrice { get; set; }
+
+    /// <summary>Total weight of the spool in grams when full.</summary>
+    public decimal? SpoolWeightTotalGrams { get; set; }
+
+    /// <summary>Calculated price per gram (purchase price / total weight), if available.</summary>
+    public decimal? PricePerGram { get; set; }
+
+    /// <summary>Calculated total material cost for this print job, if available.</summary>
+    public decimal? TotalMaterialCost { get; set; }
+
+    /// <summary>The CostPerPrint stored on the print job entity, if set.</summary>
+    public decimal? StoredCostPerPrint { get; set; }
+
+    /// <summary>
+    /// Warnings about missing data that prevent cost calculation.
+    /// Empty if all data is available and cost was calculated successfully.
+    /// </summary>
+    public List<string> Warnings { get; set; } = new();
+}

backend/API/Filters/FluentValidationFilter.cs

@@ -0,0 +1,69 @@
+using FluentValidation;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+
+namespace Extrudex.API.Filters;
+
+/// <summary>
+/// Action filter that automatically validates request DTOs using FluentValidation
+/// validators registered in DI. Runs before the controller action executes.
+/// Returns 400 Bad Request with validation errors if validation fails.
+/// </summary>
+public class FluentValidationFilter : IAsyncActionFilter
+{
+    private readonly IServiceProvider _serviceProvider;
+    private readonly ILogger<FluentValidationFilter> _logger;
+
+    public FluentValidationFilter(IServiceProvider serviceProvider, ILogger<FluentValidationFilter> logger)
+    {
+        _serviceProvider = serviceProvider;
+        _logger = logger;
+    }
+
+    public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
+    {
+        foreach (var argument in context.ActionArguments.Values)
+        {
+            if (argument is null) continue;
+
+            var argumentType = argument.GetType();
+            var validatorType = typeof(IValidator<>).MakeGenericType(argumentType);
+
+            // Try to resolve a validator for this argument type
+            var validator = _serviceProvider.GetService(validatorType) as IValidator;
+            if (validator is null) continue;
+
+            _logger.LogDebug("Validating {Type} with {Validator}", argumentType.Name, validator.GetType().Name);
+
+            var validationResult = await validator.ValidateAsync(
+                new ValidationContext<object>(argument), context.HttpContext.RequestAborted);
+
+            if (!validationResult.IsValid)
+            {
+                foreach (var error in validationResult.Errors)
+                {
+                    context.ModelState.AddModelError(error.PropertyName, error.ErrorMessage);
+                }
+            }
+        }
+
+        if (!context.ModelState.IsValid)
+        {
+            var errors = context.ModelState
+                .Where(kvp => kvp.Value?.Errors.Count > 0)
+                .ToDictionary(
+                    kvp => kvp.Key,
+                    kvp => kvp.Value!.Errors.Select(e => e.ErrorMessage).ToArray());
+
+            context.Result = new BadRequestObjectResult(new
+            {
+                title = "Validation failed",
+                status = 400,
+                errors
+            });
+            return;
+        }
+
+        await next();
+    }
+}

backend/API/Validators/FilamentValidators.cs

@@ -0,0 +1,108 @@
+using Extrudex.API.DTOs.Filaments;
+using FluentValidation;
+
+namespace Extrudex.API.Validators;
+
+/// <summary>
+/// Validation rules for creating a Filament (Spool) via the /filaments route.
+/// Mirrors the domain rules enforced in the controller and ensures consistent
+/// validation regardless of the request pipeline entry point.
+/// </summary>
+public class CreateFilamentRequestValidator : AbstractValidator<CreateFilamentRequest>
+{
+    public CreateFilamentRequestValidator()
+    {
+        RuleFor(x => x.MaterialBaseId)
+            .NotEmpty().WithMessage("MaterialBaseId is required.");
+
+        RuleFor(x => x.MaterialFinishId)
+            .NotEmpty().WithMessage("MaterialFinishId is required.");
+
+        RuleFor(x => x.Brand)
+            .NotEmpty().WithMessage("Brand is required.")
+            .MaximumLength(200).WithMessage("Brand must not exceed 200 characters.");
+
+        RuleFor(x => x.ColorName)
+            .NotEmpty().WithMessage("ColorName is required.")
+            .MaximumLength(200).WithMessage("ColorName must not exceed 200 characters.");
+
+        RuleFor(x => x.ColorHex)
+            .NotEmpty().WithMessage("ColorHex is required.")
+            .Matches(@"^#[0-9A-Fa-f]{6}$").WithMessage("ColorHex must be a valid hex color code (e.g., #FF0000).");
+
+        RuleFor(x => x.WeightTotalGrams)
+            .GreaterThan(0).WithMessage("Total weight must be greater than zero.");
+
+        RuleFor(x => x.WeightRemainingGrams)
+            .GreaterThanOrEqualTo(0).WithMessage("Remaining weight must be non-negative.");
+
+        RuleFor(x => x.WeightRemainingGrams)
+            .LessThanOrEqualTo(x => x.WeightTotalGrams)
+            .WithMessage("WeightRemainingGrams cannot exceed WeightTotalGrams.");
+
+        RuleFor(x => x.FilamentDiameterMm)
+            .GreaterThan(0).WithMessage("Filament diameter must be greater than zero.");
+
+        RuleFor(x => x.SpoolSerial)
+            .NotEmpty().WithMessage("SpoolSerial is required.")
+            .MaximumLength(200).WithMessage("SpoolSerial must not exceed 200 characters.");
+
+        When(x => x.PurchasePrice.HasValue, () =>
+        {
+            RuleFor(x => x.PurchasePrice!.Value)
+                .GreaterThanOrEqualTo(0).WithMessage("Purchase price must be non-negative.");
+        });
+    }
+}
+
+/// <summary>
+/// Validation rules for updating a Filament (Spool) via the /filaments route.
+/// Enforces the same domain rules as creation, plus ensures the updated
+/// WeightRemainingGrams does not exceed the updated WeightTotalGrams.
+/// </summary>
+public class UpdateFilamentRequestValidator : AbstractValidator<UpdateFilamentRequest>
+{
+    public UpdateFilamentRequestValidator()
+    {
+        RuleFor(x => x.MaterialBaseId)
+            .NotEmpty().WithMessage("MaterialBaseId is required.");
+
+        RuleFor(x => x.MaterialFinishId)
+            .NotEmpty().WithMessage("MaterialFinishId is required.");
+
+        RuleFor(x => x.Brand)
+            .NotEmpty().WithMessage("Brand is required.")
+            .MaximumLength(200).WithMessage("Brand must not exceed 200 characters.");
+
+        RuleFor(x => x.ColorName)
+            .NotEmpty().WithMessage("ColorName is required.")
+            .MaximumLength(200).WithMessage("ColorName must not exceed 200 characters.");
+
+        RuleFor(x => x.ColorHex)
+            .NotEmpty().WithMessage("ColorHex is required.")
+            .Matches(@"^#[0-9A-Fa-f]{6}$").WithMessage("ColorHex must be a valid hex color code (e.g., #FF0000).");
+
+        RuleFor(x => x.WeightTotalGrams)
+            .GreaterThan(0).WithMessage("Total weight must be greater than zero.");
+
+        RuleFor(x => x.WeightRemainingGrams)
+            .GreaterThanOrEqualTo(0).WithMessage("Remaining weight must be non-negative.");
+
+        RuleFor(x => x.WeightRemainingGrams)
+            .LessThanOrEqualTo(x => x.WeightTotalGrams)
+            .WithMessage("WeightRemainingGrams cannot exceed WeightTotalGrams.");
+
+        RuleFor(x => x.FilamentDiameterMm)
+            .GreaterThan(0).WithMessage("Filament diameter must be greater than zero.");
+
+        RuleFor(x => x.SpoolSerial)
+            .NotEmpty().WithMessage("SpoolSerial is required.")
+            .MaximumLength(200).WithMessage("SpoolSerial must not exceed 200 characters.");
+
+        When(x => x.PurchasePrice.HasValue, () =>
+        {
+            RuleFor(x => x.PurchasePrice!.Value)
+                .GreaterThanOrEqualTo(0).WithMessage("Purchase price must be non-negative.");
+        });
+    }
+}