add yard distances management to rule engine

- Introduced new yard distances resource with CRUD operations.
- Created migration for yard distances table with necessary constraints.
- Implemented service and repository for yard distances handling.
- Added controller for API endpoints to manage yard distances.
- Updated rule engine configuration to include yard distances.
- Enhanced rule engine resource page to support yard distance selection.
- Updated contracts and train builder pages to handle new yard distance logic.
- Added error handling utility for better error message extraction.

apps/edr-freight-api/src/modules/rule-engine/services/yard-distances.service.ts

@@ -0,0 +1,119 @@
+import { PaginatedResponse } from '@edr/types';
+import {
+  BadRequestException,
+  ConflictException,
+  Inject,
+  Injectable,
+  NotFoundException,
+} from '@nestjs/common';
+import { CreateYardDistanceDto } from '../dto/create-yard-distance.dto';
+import { ListYardDistancesQueryDto } from '../dto/list-rule-engine-query.dto';
+import { UpdateYardDistanceDto } from '../dto/update-yard-distance.dto';
+import { YardDistance } from '../entities/yard-distance.entity';
+import {
+  IYardDistancesRepository,
+  YARD_DISTANCES_REPOSITORY,
+} from '../interfaces/yard-distances.repository.interface';
+import { IYardsRepository, YARDS_REPOSITORY } from '../interfaces/yards.repository.interface';
+
+/**
+ * Flat row shape for the backoffice config table: the yard relations stay for
+ * API consumers, plus label fields the generic rule-engine grid can render.
+ */
+export type YardDistanceRow = YardDistance & {
+  fromYardLabel: string;
+  toYardLabel: string;
+};
+
+const yardDisplay = (yard?: { label?: string; code?: string } | null): string =>
+  yard?.label ?? yard?.code ?? '—';
+
+const toRow = (entity: YardDistance): YardDistanceRow =>
+  Object.assign(entity, {
+    fromYardLabel: yardDisplay(entity.fromYard),
+    toYardLabel: yardDisplay(entity.toYard),
+  });
+
+@Injectable()
+export class YardDistancesService {
+  constructor(
+    @Inject(YARD_DISTANCES_REPOSITORY)
+    private readonly repository: IYardDistancesRepository,
+    @Inject(YARDS_REPOSITORY)
+    private readonly yardsRepository: IYardsRepository,
+  ) {}
+
+  async findAll(query: ListYardDistancesQueryDto): Promise<PaginatedResponse<YardDistanceRow>> {
+    const page = await this.repository.findPaged(query);
+    return { ...page, items: page.items.map(toRow) };
+  }
+
+  async findById(id: string): Promise<YardDistanceRow> {
+    const entity = await this.repository.findById(id);
+    if (!entity) throw new NotFoundException(`Yard distance ${id} not found`);
+    return toRow(entity);
+  }
+
+  async create(dto: CreateYardDistanceDto): Promise<YardDistanceRow> {
+    await this.assertValidPair(dto.fromYardId, dto.toYardId);
+
+    const created = await this.repository.create({
+      fromYardId: dto.fromYardId,
+      toYardId: dto.toYardId,
+      distanceKm: dto.distanceKm.toFixed(2),
+    });
+    return toRow(created);
+  }
+
+  async update(id: string, dto: UpdateYardDistanceDto): Promise<YardDistanceRow> {
+    const existing = await this.findById(id);
+
+    const fromYardId = dto.fromYardId ?? existing.fromYardId;
+    const toYardId = dto.toYardId ?? existing.toYardId;
+    if (fromYardId !== existing.fromYardId || toYardId !== existing.toYardId) {
+      await this.assertValidPair(fromYardId, toYardId, id);
+    }
+
+    const updated = await this.repository.update(id, {
+      fromYardId,
+      toYardId,
+      ...(dto.distanceKm != null ? { distanceKm: dto.distanceKm.toFixed(2) } : {}),
+    });
+    if (!updated) throw new NotFoundException(`Yard distance ${id} not found`);
+    return toRow(updated);
+  }
+
+  async remove(id: string): Promise<void> {
+    await this.findById(id);
+    await this.repository.softDelete(id);
+  }
+
+  /**
+   * Both yards must exist and differ, and the pair must not already be
+   * configured in either direction — distances are symmetric, so an A→B row
+   * already covers B→A.
+   */
+  private async assertValidPair(
+    fromYardId: string,
+    toYardId: string,
+    ignoreId?: string,
+  ): Promise<void> {
+    if (fromYardId === toYardId) {
+      throw new BadRequestException('From and to yards must be different');
+    }
+
+    const [fromYard, toYard] = await Promise.all([
+      this.yardsRepository.findById(fromYardId),
+      this.yardsRepository.findById(toYardId),
+    ]);
+    if (!fromYard) throw new BadRequestException(`Yard ${fromYardId} does not exist`);
+    if (!toYard) throw new BadRequestException(`Yard ${toYardId} does not exist`);
+
+    const existing = await this.repository.findBetween(fromYardId, toYardId);
+    if (existing && existing.id !== ignoreId) {
+      throw new ConflictException(
+        `A distance between ${fromYard.label} and ${toYard.label} is already configured`,
+      );
+    }
+  }
+}