feat(categories): implement category management with hierarchical structure and update product association

backend/src/app.module.ts

@@ -13,6 +13,7 @@ import { ReceiptAliasModule } from './receipt-alias/receipt-alias.module';
 import { AuthModule } from './auth/auth.module';
 import { UsersModule } from './users/users.module';
 import { UserProductsModule } from './user-products/user-products.module';
+import { CategoriesModule } from './categories/categories.module';
 import { JwtAuthGuard } from './auth/jwt-auth.guard';
 
 
@@ -31,6 +32,7 @@ import { JwtAuthGuard } from './auth/jwt-auth.guard';
     AuthModule,
     UsersModule,
     UserProductsModule,
+    CategoriesModule,
   ],
   providers: [
     {

backend/src/categories/categories.controller.ts

@@ -0,0 +1,20 @@
+import { Controller, Get } from '@nestjs/common';
+import { CategoriesService } from './categories.service';
+import { Public } from '../auth/decorators/public.decorator';
+
+@Controller('api/categories')
+export class CategoriesController {
+  constructor(private readonly categoriesService: CategoriesService) {}
+
+  @Public()
+  @Get()
+  findAll() {
+    return this.categoriesService.findAll();
+  }
+
+  @Public()
+  @Get('tree')
+  findTree() {
+    return this.categoriesService.findTree();
+  }
+}

backend/src/categories/categories.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { CategoriesService } from './categories.service';
+import { CategoriesController } from './categories.controller';
+import { PrismaModule } from '../prisma/prisma.module';
+
+@Module({
+  imports: [PrismaModule],
+  providers: [CategoriesService],
+  controllers: [CategoriesController],
+  exports: [CategoriesService],
+})
+export class CategoriesModule {}

backend/src/categories/categories.service.ts

@@ -0,0 +1,33 @@
+import { Injectable } from '@nestjs/common';
+import { PrismaService } from '../prisma/prisma.service';
+
+export type CategoryNode = {
+  id: number;
+  name: string;
+  parentId: number | null;
+  children: CategoryNode[];
+};
+
+@Injectable()
+export class CategoriesService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  async findAll() {
+    return this.prisma.category.findMany({ orderBy: { name: 'asc' } });
+  }
+
+  async findTree(): Promise<CategoryNode[]> {
+    const all = await this.prisma.category.findMany({ orderBy: { name: 'asc' } });
+    const map = new Map<number, CategoryNode>();
+    all.forEach((c) => map.set(c.id, { ...c, children: [] }));
+    const roots: CategoryNode[] = [];
+    map.forEach((node) => {
+      if (node.parentId === null) {
+        roots.push(node);
+      } else {
+        map.get(node.parentId)?.children.push(node);
+      }
+    });
+    return roots;
+  }
+}

backend/src/products/dto/update-product.dto.ts

@@ -1,4 +1,4 @@
-import { IsNotEmpty, IsOptional, IsString, MaxLength } from 'class-validator';
+import { IsNotEmpty, IsNumber, IsOptional, IsString, MaxLength } from 'class-validator';
 
 export class UpdateProductDto {
   @IsOptional()
@@ -26,4 +26,8 @@ export class UpdateProductDto {
   @IsString()
   @MaxLength(191)
   brand?: string;
+
+  @IsOptional()
+  @IsNumber()
+  categoryId?: number | null;
 }

backend/src/products/products.service.ts

@@ -21,6 +21,7 @@ export class ProductsService {
       include: {
         tags: { include: { tag: true } },
         nutrition: true,
+        categoryRef: { include: { parent: { include: { parent: true } } } },
       },
       orderBy: { name: 'asc' },
     });
@@ -114,6 +115,7 @@ export class ProductsService {
       category?: string | null;
       subcategory?: string | null;
       brand?: string | null;
+      categoryId?: number | null;
     } = {};
 
     if (typeof data.name === 'string') {
@@ -160,6 +162,10 @@ export class ProductsService {
       updateData.brand = data.brand.trim() || null;
     }
 
+    if ('categoryId' in data) {
+      updateData.categoryId = data.categoryId ?? null;
+    }
+
     return this.prisma.product.update({
       where: { id },
       data: updateData,