feat: enhance locomotive creation and management with optional code generation and default max pull weight

apps/edr-freight-api/src/modules/locomotives/dto/create-locomotive.dto.ts

@@ -8,10 +8,13 @@ import {
 } from '../entities/locomotive.entity';
 
 export class CreateLocomotiveDto {
-  @ApiProperty({ example: 'LOCO-001' })
+  // Optional on input — the service auto-generates a sequential LOCO-NNN code
+  // when none is supplied.
+  @ApiPropertyOptional({ example: 'LOCO-001' })
+  @IsOptional()
   @IsString()
   @MaxLength(32)
-  code!: string;
+  code?: string;
 
   @ApiPropertyOptional()
   @IsOptional()
@@ -32,11 +35,13 @@ export class CreateLocomotiveDto {
   @IsUUID()
   currentYardId?: string;
 
-  @ApiProperty({ example: 3500 })
-  @Transform(({ value }) => Number(value))
+  // Defaults to 2500 tons when omitted (see service).
+  @ApiPropertyOptional({ example: 2500, default: 2500 })
+  @IsOptional()
+  @Transform(({ value }) => (value === '' || value == null ? undefined : Number(value)))
   @IsNumber()
   @Min(0)
-  maxPullWeightTons!: number;
+  maxPullWeightTons?: number;
 
   @ApiProperty({ example: 760 })
   @Transform(({ value }) => Number(value))

apps/edr-freight-api/src/modules/locomotives/locomotives.service.ts

@@ -29,20 +29,40 @@ export class LocomotivesService {
     });
   }
 
-  async create(dto: CreateLocomotiveDto): Promise<Locomotive> {
-    const [existing] = await this.locomotivesRepository.findAll({ where: { code: dto.code } });
+  /** Default max pull weight (tons) applied when the caller omits it. */
+  private static readonly DEFAULT_MAX_PULL_WEIGHT_TONS = 2500;
 
+  /**
+   * Generate the next sequential locomotive code (LOCO-001, LOCO-002, …) by
+   * scanning the highest existing LOCO-NNN number. Used when the caller does not
+   * supply a code.
+   */
+  private async generateCode(): Promise<string> {
+    const all = await this.locomotivesRepository.findAll({});
+    let max = 0;
+    for (const loco of all) {
+      const match = /^LOCO-(\d+)$/.exec(loco.code ?? '');
+      if (match) max = Math.max(max, Number(match[1]));
+    }
+    return `LOCO-${String(max + 1).padStart(3, '0')}`;
+  }
+
+  async create(dto: CreateLocomotiveDto): Promise<Locomotive> {
+    const code = dto.code?.trim() || (await this.generateCode());
+
+    const [existing] = await this.locomotivesRepository.findAll({ where: { code } });
     if (existing) {
-      throw new ConflictException(`Locomotive code ${dto.code} already exists`);
+      throw new ConflictException(`Locomotive code ${code} already exists`);
     }
 
     return this.locomotivesRepository.create({
-      code: dto.code,
+      code,
       name: dto.name?.trim() || null,
       locomotiveType: dto.locomotiveType as LocomotiveType,
       status: dto.status as LocomotiveStatus,
       currentYardId: dto.currentYardId ?? null,
-      maxPullWeightTons: dto.maxPullWeightTons,
+      maxPullWeightTons:
+        dto.maxPullWeightTons ?? LocomotivesService.DEFAULT_MAX_PULL_WEIGHT_TONS,
       maxTrainLengthMeters: dto.maxTrainLengthMeters,
       powerKw: dto.powerKw ?? null,
       tractionForceKn: dto.tractionForceKn ?? null,

apps/edr-freight-api/src/modules/wagons/wagons.service.ts

@@ -77,7 +77,10 @@ export class WagonsService {
   async update(id: string, dto: UpdateWagonDto): Promise<Wagon> {
     const wagon = await this.findById(id);
     Object.assign(wagon, dto);
-    return this.wagonRepo.save(wagon);
+    await this.wagonRepo.save(wagon);
+    // Re-read with the relation so the response reflects the new yard label
+    // instead of the stale relation object loaded before the assign.
+    return this.findById(id);
   }
 
   async remove(id: string): Promise<void> {