CUB-37: implement cost-per-print calculation service

backend/API/Controllers/PrintJobsController.cs

@@ -2,6 +2,7 @@ using Extrudex.API.DTOs;
 using Extrudex.API.DTOs.PrintJobs;
 using Extrudex.Domain.Entities;
 using Extrudex.Domain.Enums;
+using Extrudex.Domain.Interfaces;
 using Extrudex.Infrastructure.Data;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
@@ -19,16 +20,22 @@ namespace Extrudex.API.Controllers;
 public class PrintJobsController : ControllerBase
 {
     private readonly ExtrudexDbContext _dbContext;
+    private readonly ICostPerPrintService _costService;
     private readonly ILogger<PrintJobsController> _logger;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="PrintJobsController"/> class.
     /// </summary>
     /// <param name="dbContext">The database context for data access.</param>
+    /// <param name="costService">The cost-per-print calculation service.</param>
     /// <param name="logger">The logger for diagnostic output.</param>
-    public PrintJobsController(ExtrudexDbContext dbContext, ILogger<PrintJobsController> logger)
+    public PrintJobsController(
+        ExtrudexDbContext dbContext,
+        ICostPerPrintService costService,
+        ILogger<PrintJobsController> logger)
     {
         _dbContext = dbContext;
+        _costService = costService;
         _logger = logger;
     }
 
@@ -413,6 +420,34 @@ public class PrintJobsController : ControllerBase
         return NoContent();
     }
 
+    // ── POST /api/printjobs/{id}/cost ─────────────────────────────
+
+    /// <summary>
+    /// Calculates the cost of goods sold (COGS) for a specific print job.
+    /// Uses the spool’s purchase price and the print job’s derived grams consumed
+    /// to produce a cost breakdown. Returns warnings instead of errors when
+    /// cost data is missing or incomplete.
+    /// </summary>
+    /// <param name="id">The unique identifier of the print job.</param>
+    /// <returns>A cost breakdown with warnings if data is incomplete.</returns>
+    /// <response code="200">Returns the cost breakdown for the print job.</response>
+    /// <response code="404">If the print job with the given ID is not found.</response>
+    [HttpPost("{id:guid}/cost")]
+    [ProducesResponseType(typeof(CostPerPrintResponse), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<CostPerPrintResponse>> CalculateCost(Guid id)
+    {
+        _logger.LogDebug("Calculating cost for print job {Id}", id);
+
+        var result = await _costService.CalculateAsync(id);
+
+        // If the job was not found, return 404
+        if (result.Warnings.Any(w => w.Contains("not found")))
+            return NotFound(new { error = $"Print job with ID '{id}' not found." });
+
+        return Ok(MapCostToResponse(result));
+    }
+
     // ── Gram Derivation Formula ────────────────────────────────────
 
     /// <summary>
@@ -509,4 +544,22 @@ public class PrintJobsController : ControllerBase
         CreatedAt = j.CreatedAt,
         UpdatedAt = j.UpdatedAt
     };
+
+    /// <summary>
+    /// Maps a domain CostPerPrintResult to an API CostPerPrintResponse DTO.
+    /// </summary>
+    private static CostPerPrintResponse MapCostToResponse(CostPerPrintResult r) => new()
+    {
+        PrintJobId = r.PrintJobId,
+        PrintName = r.PrintName,
+        SpoolId = r.SpoolId,
+        SpoolSerial = r.SpoolSerial,
+        MmExtruded = r.MmExtruded,
+        GramsDerived = r.GramsDerived,
+        PurchasePrice = r.PurchasePrice,
+        WeightTotalGrams = r.WeightTotalGrams,
+        CostPerGram = r.CostPerGram,
+        CostPerPrint = r.CostPerPrint,
+        Warnings = r.Warnings
+    };
 }