import { Inject, Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { DataSource, Repository } from 'typeorm';
import { CreateMenuActionsDto } from './dto/create.dto';
import { plainToInstance } from 'class-transformer';
import {
  getSkipOffset,
  paginate,
} from 'src/config/pagination/pagination.service';
import { SearchMenuActionsDto } from './dto/search-dto';
import { UpdateMenuActionsDto } from './dto/update.dto';
import { Response } from 'src/config/pagination/paginationDto';
import { CACHE_MANAGER } from '@nestjs/cache-manager';
import { Cache } from 'cache-manager';
import { MenuActionsEntity } from 'src/entities/MenuActions.entity';

/**
 * Menu Actions Service
 *
 * This service handles all business logic for managing menu actions within the application.
 * Menu actions represent individual operations or permissions that can be performed
 * within menu items (e.g., "create", "read", "update", "delete", "export").
 *
 * The service provides basic CRUD operations with pagination support but has several
 * limitations and missing features compared to other similar services in the codebase.
 *
 * @Injectable - Marks this class as a NestJS injectable service
 */
@Injectable()
export class MenuActionsService {
  constructor(
    private datasource: DataSource,
    @Inject(CACHE_MANAGER) private cacheManager: Cache,
    @InjectRepository(MenuActionsEntity)
    private readonly menuRepo: Repository<MenuActionsEntity>,
  ) {}

  /**
   * Search and retrieve menu actions with pagination.
   *
   * Builds a query with user joins for audit information but doesn't implement
   * the search functionality defined in SearchMenuActionsDto (q parameter).
   *
   * @param searchDto - Search criteria and pagination parameters
   * @returns Paginated response with menu actions
   *
   * @bug Does not implement the 'q' search parameter from SearchMenuActionsDto
   * @note CacheManager is injected but not used in this method
   * @performance Consider adding database indexes on frequently queried columns
   */
  async findAll(
    searchDto: SearchMenuActionsDto,
  ): Promise<Response<MenuActionsEntity>> {
    // Start building the query with joins for user information
    const query = this.menuRepo
      .createQueryBuilder('menu_action')
      // .leftJoin('menu_action.group', 'group') // Commented out - maybe future feature
      // .addSelect(['group.id', 'group.name']) // Commented out
      .leftJoin('menu_action.user', 'user') // Join creator user
      .addSelect(['user.fname', 'user.lname', 'user.employeeCode'])
      .leftJoin('menu_action.modified_by', 'modified_by') // Join last modifier user
      .addSelect([
        'modified_by.fname',
        'modified_by.lname',
        'modified_by.employeeCode',
      ])
      .orderBy('menu_action.order_no', 'ASC'); // Order by display order

    // BUG: Missing implementation of search parameter 'q'
    // The SearchMenuActionsDto has a 'q' parameter for text search,
    // but it's not being used in the query
    // if (searchDto.q) {
    //   query.andWhere('menu_action.name LIKE :search', {
    //     search: `%${searchDto.q}%`,
    //   });
    // }

    // Apply pagination
    const [skip, limit] = getSkipOffset(searchDto);
    const [data, total] = await query.skip(skip).take(limit).getManyAndCount();

    // Calculate pagination metadata
    const pagination = paginate(total, searchDto.per_page, searchDto.page);
    return { list: data, pagination };
  }

  /**
   * Find a single menu action by ID with full relations.
   *
   * @param id - Numeric ID of the menu action
   * @returns Single menu action entity with all relations or null
   *
   * @performance Loading all relations may be heavy. Consider selective loading.
   */
  findOne(id: number) {
    return this.menuRepo.findOne({
      where: { id },
      relations: ['menu', 'group', 'user', 'modified_by'], // Load all relations
    });
  }

  /**
   * Create a new menu action.
   *
   * @param userId - ID of the user creating the menu action
   * @param createDto - Menu action data
   * @returns Newly created menu action entity
   *
   * @note No duplicate checking - could create multiple actions with same name
   * @note No validation beyond DTO validation
   * @note Should potentially clear relevant caches after creation
   */
  create(userId: number, createDto: CreateMenuActionsDto) {
    // Convert DTO to entity with creator information
    const menuEntity = plainToInstance(MenuActionsEntity, {
      ...createDto,
      by_user: userId, // Set creator from parameter (not from DTO)
    });

    // Save to database
    return this.menuRepo.save(menuEntity);
  }

  /**
   * Update an existing menu action.
   *
   * @param id - Numeric ID of the menu action to update
   * @param updateDto - Updated menu action data
   * @returns Update result
   *
   * @note No validation that the ID exists before update
   * @note No duplicate checking for name conflicts
   * @note Should potentially clear relevant caches after update
   */
  update(id: number, updateDto: UpdateMenuActionsDto) {
    // Convert DTO to entity
    const menuEntity = plainToInstance(MenuActionsEntity, {
      ...updateDto,
      // Missing: modified_by should be set to current user
    });

    // Execute update
    return this.menuRepo.update(id, menuEntity);
  }

  /**
   * Delete a menu action.
   *
   * @param id - Numeric ID of the menu action to delete
   * @returns Delete result
   *
   * @warning Hard delete - permanently removes record
   * @note No validation of dependencies (e.g., if action is used elsewhere)
   * @note Should potentially clear relevant caches after deletion
   * @note Consider soft delete with is_deleted flag for audit trail
   */
  delete(id: number) {
    return this.menuRepo.delete(id);
  }
}
