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src/common/base/base.service.ts

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+import { NotFoundException, Logger } from '@nestjs/common';
+import { PrismaService } from '../../database/prisma.service';
+import { PaginationDto } from '../dto/pagination.dto';
+import { PaginationMeta } from '../types/api-response.type';
+
+/**
+ * Generic base service with common CRUD operations
+ * Extend this class for entity-specific services
+ */
+export abstract class BaseService<T, CreateDto, UpdateDto> {
+  protected readonly logger: Logger;
+
+  constructor(
+    protected readonly prisma: PrismaService,
+    protected readonly modelName: string,
+  ) {
+    this.logger = new Logger(`${modelName}Service`);
+  }
+
+  /**
+   * Get the Prisma model delegate
+   */
+  protected get model() {
+    return (this.prisma as any)[this.modelName.toLowerCase()];
+  }
+
+  /**
+   * Find all records with pagination
+   */
+  async findAll(
+    pagination: PaginationDto,
+    where?: any,
+  ): Promise<{ items: T[]; meta: PaginationMeta }> {
+    const { skip, take, orderBy } = pagination;
+
+    const [items, total] = await Promise.all([
+      this.model.findMany({
+        where,
+        skip,
+        take,
+        orderBy,
+      }),
+      this.model.count({ where }),
+    ]);
+
+    const totalPages = Math.ceil(total / take);
+
+    return {
+      items,
+      meta: {
+        total,
+        page: pagination.page || 1,
+        limit: pagination.limit || 10,
+        totalPages,
+        hasNextPage: (pagination.page || 1) < totalPages,
+        hasPreviousPage: (pagination.page || 1) > 1,
+      },
+    };
+  }
+
+  /**
+   * Find a single record by ID
+   */
+  async findOne(id: string, include?: any): Promise<T> {
+    const record = await this.model.findUnique({
+      where: { id },
+      include,
+    });
+
+    if (!record) {
+      throw new NotFoundException(`${this.modelName} not found`);
+    }
+
+    return record;
+  }
+
+  /**
+   * Find a single record by custom criteria
+   */
+  findOneBy(where: any, include?: any): Promise<T | null> {
+    return this.model.findFirst({
+      where,
+      include,
+    });
+  }
+
+  /**
+   * Create a new record
+   */
+  create(data: CreateDto, include?: any): Promise<T> {
+    return this.model.create({
+      data,
+      include,
+    });
+  }
+
+  /**
+   * Update an existing record
+   */
+  async update(id: string, data: UpdateDto, include?: any): Promise<T> {
+    // Check if record exists
+    await this.findOne(id);
+
+    return this.model.update({
+      where: { id },
+      data,
+      include,
+    });
+  }
+
+  /**
+   * Soft delete a record (sets deletedAt)
+   */
+  async delete(id: string): Promise<T> {
+    // Check if record exists
+    await this.findOne(id);
+
+    return this.model.delete({
+      where: { id },
+    });
+  }
+
+  /**
+   * Hard delete a record (permanently removes)
+   */
+  async hardDelete(id: string): Promise<T> {
+    // Check if record exists
+    await this.findOne(id);
+
+    return this.prisma.hardDelete(this.modelName, { id });
+  }
+
+  /**
+   * Restore a soft-deleted record
+   */
+  async restore(id: string): Promise<T> {
+    return this.prisma.restore(this.modelName, { id });
+  }
+
+  /**
+   * Check if a record exists
+   */
+  async exists(id: string): Promise<boolean> {
+    const count = await this.model.count({
+      where: { id },
+    });
+    return count > 0;
+  }
+
+  /**
+   * Count records matching criteria
+   */
+  count(where?: any): Promise<number> {
+    return this.model.count({ where });
+  }
+
+  /**
+   * Execute a transaction
+   */
+  transaction<R>(fn: (prisma: PrismaService) => Promise<R>): Promise<R> {
+    return this.prisma.$transaction(async (tx) => {
+      return fn(tx as unknown as PrismaService);
+    });
+  }
+}