import { Injectable, UnauthorizedException } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { ConfigService } from '@nestjs/config';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, IsNull, MoreThan } from 'typeorm';
import * as bcrypt from 'bcrypt';
import { User } from '../../entities/user.entity';
import { RefreshToken } from '../../entities/refresh-token.entity';

interface GoogleProfile {
  id: string;
  emails: Array<{ value: string; verified: boolean }>;
  displayName: string;
  photos: Array<{ value: string }>;
}

@Injectable()
export class AuthService {
  constructor(
    @InjectRepository(User)
    private readonly userRepository: Repository<User>,
    @InjectRepository(RefreshToken)
    private readonly refreshTokenRepository: Repository<RefreshToken>,
    private readonly jwtService: JwtService,
    private readonly configService: ConfigService,
  ) {}

  async validateOAuthUser(profile: GoogleProfile): Promise<User> {
    const email = profile.emails?.[0]?.value;
    const googleId = profile.id;
    const displayName = profile.displayName;
    const avatarUrl = profile.photos?.[0]?.value;

    if (!email || !googleId) {
      throw new UnauthorizedException('Invalid Google profile');
    }

    let user = await this.userRepository.findOne({
      where: { googleId },
    });

    if (user) {
      // Update last login and profile info
      user.lastLoginAt = new Date();
      user.displayName = displayName;
      user.avatarUrl = avatarUrl;
      await this.userRepository.save(user);
    } else {
      // Create new user
      user = this.userRepository.create({
        googleId,
        email,
        displayName,
        avatarUrl,
        lastLoginAt: new Date(),
      });
      await this.userRepository.save(user);
    }

    return user;
  }

  async generateTokens(
    user: User,
  ): Promise<{ accessToken: string; refreshToken: string }> {
    // Generate access token
    const payload = { sub: user.id, email: user.email };
    const accessToken = this.jwtService.sign(payload);

    // Generate refresh token
    const refreshTokenValue = this.generateRandomToken();
    const hashedToken = await bcrypt.hash(refreshTokenValue, 10);

    // Calculate expiration (7 days)
    const expiresAt = new Date();
    expiresAt.setDate(expiresAt.getDate() + 7);

    // Save refresh token to database
    const refreshTokenEntity = this.refreshTokenRepository.create({
      userId: user.id,
      token: hashedToken,
      expiresAt,
    });
    await this.refreshTokenRepository.save(refreshTokenEntity);

    return {
      accessToken,
      refreshToken: `${refreshTokenEntity.id}:${refreshTokenValue}`,
    };
  }

  async refreshTokens(
    token: string,
  ): Promise<{ accessToken: string; refreshToken: string; user: User }> {
    const [tokenId, tokenValue] = token.split(':');

    if (!tokenId || !tokenValue) {
      throw new UnauthorizedException('Invalid refresh token format');
    }

    const storedToken = await this.refreshTokenRepository.findOne({
      where: {
        id: tokenId,
        revokedAt: IsNull(),
        expiresAt: MoreThan(new Date()),
      },
      relations: ['user'],
    });

    if (!storedToken) {
      throw new UnauthorizedException('Invalid or expired refresh token');
    }

    const isValid = await bcrypt.compare(tokenValue, storedToken.token);
    if (!isValid) {
      throw new UnauthorizedException('Invalid refresh token');
    }

    // Revoke old token (rotation)
    await this.revokeRefreshToken(token);

    // Generate new tokens
    const { accessToken, refreshToken } = await this.generateTokens(
      storedToken.user,
    );

    return {
      accessToken,
      refreshToken,
      user: storedToken.user,
    };
  }

  async revokeRefreshToken(token: string): Promise<void> {
    const [tokenId] = token.split(':');

    if (tokenId) {
      await this.refreshTokenRepository.update(
        { id: tokenId },
        { revokedAt: new Date() },
      );
    }
  }

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

  private generateRandomToken(): string {
    const chars =
      'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    let result = '';
    for (let i = 0; i < 64; i++) {
      result += chars.charAt(Math.floor(Math.random() * chars.length));
    }
    return result;
  }
}