import {
  Injectable,
  NotFoundException,
  ConflictException,
  BadRequestException,
} from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import * as bcrypt from 'bcrypt';
import { User, UserRole } from '../entities';
import {
  CreateUserDto,
  UpdateUserDto,
  UserResponseDto,
  ChangePasswordDto,
} from './user.dto';

@Injectable()
export class UserService {
  constructor(
    @InjectRepository(User)
    private userRepository: Repository<User>,
  ) {}

  async create(createUserDto: CreateUserDto): Promise<UserResponseDto> {
    // Check if email already exists
    const existingEmail = await this.userRepository.findOne({
      where: { email: createUserDto.email },
    });
    if (existingEmail) {
      throw new ConflictException('Email already exists');
    }

    // Check if username already exists
    const existingUsername = await this.userRepository.findOne({
      where: { username: createUserDto.username },
    });
    if (existingUsername) {
      throw new ConflictException('Username already exists');
    }

    // Hash password
    const saltRounds = 10;
    const passwordHash = await bcrypt.hash(createUserDto.password, saltRounds);

    // Create user
    const user = this.userRepository.create({
      ...createUserDto,
      passwordHash,
    });

    const savedUser = await this.userRepository.save(user);
    return new UserResponseDto(savedUser);
  }

  async findAll(): Promise<UserResponseDto[]> {
    const users = await this.userRepository.find({
      order: { createdAt: 'DESC' },
    });
    return users.map((user) => new UserResponseDto(user));
  }

  async findOne(id: string): Promise<UserResponseDto> {
    const user = await this.userRepository.findOne({ where: { id } });
    if (!user) {
      throw new NotFoundException('User not found');
    }
    return new UserResponseDto(user);
  }

  async findByUsername(username: string): Promise<User | null> {
    return this.userRepository.findOne({ where: { username } });
  }

  async findByEmail(email: string): Promise<User | null> {
    return this.userRepository.findOne({ where: { email } });
  }

  async update(
    id: string,
    updateUserDto: UpdateUserDto,
  ): Promise<UserResponseDto> {
    const user = await this.userRepository.findOne({ where: { id } });
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // Check if email is being changed and if it already exists
    if (updateUserDto.email && updateUserDto.email !== user.email) {
      const existingEmail = await this.userRepository.findOne({
        where: { email: updateUserDto.email },
      });
      if (existingEmail) {
        throw new ConflictException('Email already exists');
      }
    }

    // Check if username is being changed and if it already exists
    if (updateUserDto.username && updateUserDto.username !== user.username) {
      const existingUsername = await this.userRepository.findOne({
        where: { username: updateUserDto.username },
      });
      if (existingUsername) {
        throw new ConflictException('Username already exists');
      }
    }

    // Hash new password if provided
    if (updateUserDto.password) {
      const saltRounds = 10;
      updateUserDto.password = await bcrypt.hash(
        updateUserDto.password,
        saltRounds,
      );
    }

    // Update user
    Object.assign(user, updateUserDto);
    if (updateUserDto.password) {
      user.passwordHash = updateUserDto.password;
      delete updateUserDto.password;
    }

    const updatedUser = await this.userRepository.save(user);
    return new UserResponseDto(updatedUser);
  }

  async remove(id: string): Promise<void> {
    const user = await this.userRepository.findOne({ where: { id } });
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // Prevent deleting the last admin
    if (user.role === UserRole.ADMIN) {
      const adminCount = await this.userRepository.count({
        where: { role: UserRole.ADMIN },
      });
      if (adminCount <= 1) {
        throw new BadRequestException('Cannot delete the last admin user');
      }
    }

    await this.userRepository.remove(user);
  }

  async changePassword(
    id: string,
    changePasswordDto: ChangePasswordDto,
  ): Promise<void> {
    const user = await this.userRepository.findOne({ where: { id } });
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // Verify current password
    const isPasswordValid = await bcrypt.compare(
      changePasswordDto.currentPassword,
      user.passwordHash,
    );
    if (!isPasswordValid) {
      throw new BadRequestException('Current password is incorrect');
    }

    // Hash new password
    const saltRounds = 10;
    user.passwordHash = await bcrypt.hash(
      changePasswordDto.newPassword,
      saltRounds,
    );

    await this.userRepository.save(user);
  }

  async validateUser(username: string, password: string): Promise<User | null> {
    const user = await this.userRepository.findOne({
      where: { username, isActive: true },
    });
    if (!user) {
      return null;
    }

    const isPasswordValid = await bcrypt.compare(password, user.passwordHash);
    if (!isPasswordValid) {
      return null;
    }

    return user;
  }

  async createAdminIfNotExists(): Promise<void> {
    const adminExists = await this.userRepository.findOne({
      where: { role: UserRole.ADMIN },
    });

    if (!adminExists) {
      const saltRounds = 10;
      const passwordHash = await bcrypt.hash('admin123', saltRounds);

      const adminUser = this.userRepository.create({
        email: 'admin@placebo.mk',
        username: 'admin',
        passwordHash,
        role: UserRole.ADMIN,
        isActive: true,
      });

      await this.userRepository.save(adminUser);
      console.log('Default admin user created: admin / admin123');
    }
  }
}