import { Injectable, UnauthorizedException, ConflictException, BadRequestException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { eq, and, isNull } from 'drizzle-orm';
import * as bcrypt from 'bcrypt';
import * as jwt from 'jsonwebtoken';
import { nanoid } from 'nanoid';
import { randomUUID } from 'crypto';
import { getDb } from '../db/connection';
import { users, passwords, sessions } from '../db/schema';
import { RegisterDto } from './dto/register.dto';
import { LoginDto } from './dto/login.dto';

export interface TokenPayload {
  sub: string;
  email: string;
  role: string;
  sessionId: string;
  deviceId?: string;
}

@Injectable()
export class AuthService {
  constructor(private configService: ConfigService) {}

  private getDb() {
    const databaseUrl = this.configService.get<string>('database.url');
    return getDb(databaseUrl!);
  }

  async register(registerDto: RegisterDto, ipAddress?: string, userAgent?: string) {
    const db = this.getDb();

    // Check if user already exists
    const existingUser = await db
      .select()
      .from(users)
      .where(eq(users.email, registerDto.email.toLowerCase()))
      .limit(1);

    if (existingUser.length > 0) {
      throw new ConflictException('User with this email already exists');
    }

    // Hash password
    const hashedPassword = await bcrypt.hash(registerDto.password, 12);

    // Create user
    const [newUser] = await db
      .insert(users)
      .values({
        email: registerDto.email.toLowerCase(),
        name: registerDto.name,
        role: 'user',
      })
      .returning();

    // Store password
    await db.insert(passwords).values({
      userId: newUser.id,
      hashedPassword,
    });

    // Initialize credit balance (done via trigger or separate service call)
    // This will be handled by the credits service

    return {
      id: newUser.id,
      email: newUser.email,
      name: newUser.name,
      createdAt: newUser.createdAt,
    };
  }

  async login(loginDto: LoginDto, ipAddress?: string, userAgent?: string) {
    const db = this.getDb();

    // Find user
    const [user] = await db
      .select()
      .from(users)
      .where(eq(users.email, loginDto.email.toLowerCase()))
      .limit(1);

    if (!user) {
      throw new UnauthorizedException('Invalid credentials');
    }

    // Check if user is soft-deleted
    if (user.deletedAt) {
      throw new UnauthorizedException('Account has been deleted');
    }

    // Get password
    const [passwordRecord] = await db
      .select()
      .from(passwords)
      .where(eq(passwords.userId, user.id))
      .limit(1);

    if (!passwordRecord) {
      throw new UnauthorizedException('Invalid credentials');
    }

    // Verify password
    const isPasswordValid = await bcrypt.compare(loginDto.password, passwordRecord.hashedPassword);

    if (!isPasswordValid) {
      throw new UnauthorizedException('Invalid credentials');
    }

    // Generate tokens
    const tokenData = await this.generateTokens(
      user.id,
      user.email,
      user.role,
      loginDto.deviceId,
      loginDto.deviceName,
      ipAddress,
      userAgent,
    );

    return {
      user: {
        id: user.id,
        email: user.email,
        name: user.name,
        role: user.role,
      },
      ...tokenData,
    };
  }

  async refreshToken(refreshToken: string, ipAddress?: string, userAgent?: string) {
    const db = this.getDb();

    // Find session by refresh token
    const [session] = await db
      .select()
      .from(sessions)
      .where(and(eq(sessions.refreshToken, refreshToken), isNull(sessions.revokedAt)))
      .limit(1);

    if (!session) {
      throw new UnauthorizedException('Invalid refresh token');
    }

    // Check if refresh token is expired
    if (new Date() > session.refreshTokenExpiresAt) {
      throw new UnauthorizedException('Refresh token expired');
    }

    // Get user
    const [user] = await db.select().from(users).where(eq(users.id, session.userId)).limit(1);

    if (!user || user.deletedAt) {
      throw new UnauthorizedException('User not found');
    }

    // Revoke old session (refresh token rotation)
    await db
      .update(sessions)
      .set({ revokedAt: new Date() })
      .where(eq(sessions.id, session.id));

    // Generate new tokens
    const tokenData = await this.generateTokens(
      user.id,
      user.email,
      user.role,
      session.deviceId ?? undefined,
      session.deviceName ?? undefined,
      ipAddress,
      userAgent,
    );

    return {
      user: {
        id: user.id,
        email: user.email,
        name: user.name,
        role: user.role,
      },
      ...tokenData,
    };
  }

  async logout(sessionId: string) {
    const db = this.getDb();

    await db
      .update(sessions)
      .set({ revokedAt: new Date() })
      .where(eq(sessions.id, sessionId));

    return { message: 'Logged out successfully' };
  }

  private async generateTokens(
    userId: string,
    email: string,
    role: string,
    deviceId?: string,
    deviceName?: string,
    ipAddress?: string,
    userAgent?: string,
  ) {
    const db = this.getDb();

    const privateKeyRaw = this.configService.get<string>('jwt.privateKey');
    if (!privateKeyRaw) {
      throw new Error('JWT private key not configured');
    }
    const privateKey: string = privateKeyRaw;
    const accessTokenExpiry = this.configService.get<string>('jwt.accessTokenExpiry') || '15m';
    const refreshTokenExpiry = this.configService.get<string>('jwt.refreshTokenExpiry') || '7d';
    const issuer = this.configService.get<string>('jwt.issuer');
    const audience = this.configService.get<string>('jwt.audience');

    // Generate session ID (must be UUID for database)
    const sessionId = randomUUID();

    // Create session record
    const refreshTokenString = nanoid(64);
    const refreshTokenExpiresAt = new Date(Date.now() + 7 * 24 * 60 * 60 * 1000); // 7 days
    const accessTokenExpiresAt = new Date(Date.now() + 15 * 60 * 1000); // 15 minutes

    await db.insert(sessions).values({
      id: sessionId,
      userId,
      token: sessionId,
      refreshToken: refreshTokenString,
      refreshTokenExpiresAt,
      ipAddress,
      userAgent,
      deviceId,
      deviceName,
      expiresAt: accessTokenExpiresAt,
    });

    // Generate JWT payload
    const tokenPayload: Record<string, unknown> = {
      sub: userId,
      email,
      role,
      sessionId,
      ...(deviceId && { deviceId }),
    };

    // Sign access token
    const accessToken = jwt.sign(tokenPayload, privateKey, {
      algorithm: 'RS256' as const,
      expiresIn: accessTokenExpiry as jwt.SignOptions['expiresIn'],
      ...(issuer && { issuer }),
      ...(audience && { audience }),
    });

    return {
      accessToken,
      refreshToken: refreshTokenString,
      expiresIn: 15 * 60, // 15 minutes in seconds
      tokenType: 'Bearer',
    };
  }

  async validateToken(token: string) {
    try {
      const publicKey = this.configService.get<string>('jwt.publicKey');
      if (!publicKey) {
        throw new Error('JWT public key not configured');
      }
      const audience = this.configService.get<string>('jwt.audience');
      const issuer = this.configService.get<string>('jwt.issuer');

      const payload = jwt.verify(token, publicKey, {
        algorithms: ['RS256'],
        audience,
        issuer,
      }) as TokenPayload;

      return {
        valid: true,
        payload,
      };
    } catch (error) {
      return {
        valid: false,
        error: error.message,
      };
    }
  }
}