cost center implementation module

backend/src/cost-centers/cost-center.entity.ts

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+import { Column, CreateDateColumn, Entity, OneToMany, PrimaryGeneratedColumn, UpdateDateColumn } from 'typeorm';
+import { Asset } from '../../assets/entities/asset.entity';
+import { Expense } from '../../expenses/entities/expense.entity';
+
+
+@Entity({ name: 'cost_centers' })
+export class CostCenter {
+@PrimaryGeneratedColumn('uuid')
+id: string;
+
+
+@Column({ type: 'varchar', length: 200, unique: true })
+name: string;
+
+
+@Column({ type: 'text', nullable: true })
+description?: string | null;
+
+
+// Optional reverse relations if you maintain assets/expenses in the same project
+@OneToMany(() => Asset, (asset) => asset.costCenter, { cascade: false })
+assets?: Asset[];
+
+
+@OneToMany(() => Expense, (expense) => expense.costCenter, { cascade: false })
+expenses?: Expense[];
+
+
+@CreateDateColumn({ name: 'created_at' })
+createdAt: Date;
+
+
+@UpdateDateColumn({ name: 'updated_at' })
+updatedAt: Date;
+}

backend/src/cost-centers/cost-centers.controller.ts

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+import { Body, Controller, Delete, Get, Param, Patch, Post } from '@nestjs/common';
+import { CostCentersService } from './cost-centers.service';
+import { CreateCostCenterDto } from './dto/create-cost-center.dto';
+import { UpdateCostCenterDto } from './dto/update-cost-center.dto';
+
+
+@Controller('cost-centers')
+export class CostCentersController {
+constructor(private readonly svc: CostCentersService) {}
+
+
+@Post()
+create(@Body() dto: CreateCostCenterDto) {
+return this.svc.create(dto);
+}
+
+
+@Get()
+findAll() {
+return this.svc.findAll();
+}
+
+
+@Get(':id')
+findOne(@Param('id') id: string) {
+return this.svc.findOne(id);
+}
+
+
+@Patch(':id')
+update(@Param('id') id: string, @Body() dto: UpdateCostCenterDto) {
+return this.svc.update(id, dto);
+}
+
+
+@Delete(':id')
+remove(@Param('id') id: string) {
+return this.svc.remove(id);
+}
+
+
+// Link existing asset to cost center
+@Post(':id/assets/:assetId')
+attachAsset(@Param('id') id: string, @Param('assetId') assetId: string) {
+return this.svc.attachAsset(id, assetId);
+}
+
+
+// Link existing expense to cost center
+@Post(':id/expenses/:expenseId')
+attachExpense(@Param('id') id: string, @Param('expenseId') expenseId: string) {
+return this.svc.attachExpense(id, expenseId);
+}
+}

backend/src/cost-centers/cost-centers.service.ts

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+import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
+}
+
+
+async remove(id: string) {
+const cc = await this.repo.findOne({ where: { id } });
+if (!cc) throw new NotFoundException('Cost center not found');
+// Optionally: check if assets/expenses exist and prevent deletion
+const hasChildren = await this.repo.manager
+.getRepository('Asset')
+.createQueryBuilder('a')
+.where('a.costCenterId = :id', { id })
+.getCount();
+
+
+if (hasChildren > 0) {
+throw new BadRequestException('Cannot delete cost center with linked assets');
+}
+
+
+await this.repo.remove(cc);
+return { deleted: true };
+}
+
+
+// Helper: attach existing asset/expense to cost center by id
+async attachAsset(costCenterId: string, assetId: string) {
+// This method uses query runner / repository to update asset's foreign key
+const cc = await this.repo.findOne({ where: { id: costCenterId } });
+if (!cc) throw new NotFoundException('Cost center not found');
+
+
+const assetRepo = this.repo.manager.getRepository('Asset');
+const asset = await assetRepo.findOne({ where: { id: assetId } });
+if (!asset) throw new NotFoundException('Asset not found');
+
+
+asset.costCenterId = costCenterId;
+await assetRepo.save(asset);
+return asset;
+}
+
+
+async attachExpense(costCenterId: string, expenseId: string) {
+const cc = await this.repo.findOne({ where: { id: costCenterId } });
+if (!cc) throw new NotFoundException('Cost center not found');
+
+
+const expenseRepo = this.repo.manager.getRepository('Expense');
+const expense = await expenseRepo.findOne({ where: { id: expenseId } });
+if (!expense) throw new NotFoundException('Expense not found');
+
+
+expense.costCenterId = costCenterId;
+await expenseRepo.save(expense);
+return expense;
+}
+}

backend/src/cost-centers/cost.module.ts

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+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { CostCenter } from './entities/cost-center.entity';
+import { CostCentersService } from './cost-centers.service';
+import { CostCentersController } from './cost-centers.controller';
+
+
+@Module({
+imports: [TypeOrmModule.forFeature([CostCenter])],
+providers: [CostCentersService],
+controllers: [CostCentersController],
+exports: [CostCentersService],
+})
+export class CostCentersModule {}

backend/src/cost-centers/create-cost-center.dto.ts

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+import { IsNotEmpty, IsOptional, IsString, MaxLength } from 'class-validator';
+
+
+export class CreateCostCenterDto {
+@IsString()
+@IsNotEmpty()
+@MaxLength(200)
+name: string;
+
+
+@IsOptional()
+@IsString()
+description?: string;
+}