import {
  Injectable,
  UnauthorizedException,
  ConflictException,
  BadRequestException,
} from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { ConfigService } from '@nestjs/config';
import * as bcrypt from 'bcrypt';
import { UsersService } from '../users/users.service';
import { VerificationService } from '../users/verification.service';
import { RegisterDto } from './dto/register.dto';
import { LoginDto } from './dto/login.dto';
import { User } from '../users/entities/user.entity';
import { normalizeIranMobile } from '../common/phone.util';
import { OtpMessageKind } from '../common/enums';

/** Returned when an action needs phone verification before tokens are issued. */
export interface VerificationRequired {
  requiresVerification: true;
  phone: string; // masked
}

@Injectable()
export class AuthService {
  constructor(
    private usersService: UsersService,
    private verificationService: VerificationService,
    private jwtService: JwtService,
    private configService: ConfigService,
  ) {}

  /**
   * Create an account from a mobile number. Email is optional contact info only.
   * The account starts unverified; a LOGIN OTP is sent and must be confirmed via
   * `verifyOtp` before tokens are issued.
   */
  async register(registerDto: RegisterDto): Promise<VerificationRequired> {
    const phone = normalizeIranMobile(registerDto.phone);
    if (!phone) {
      throw new BadRequestException('Invalid mobile number');
    }

    // An unverified account means a previous signup was never confirmed — let
    // the user resume it. Only a *verified* phone is a real duplicate.
    const existing = await this.usersService.findByPhone(phone);
    if (existing?.phoneVerified) {
      throw new ConflictException('Mobile number already registered');
    }

    const email = registerDto.email?.trim().toLowerCase() || null;
    if (email) {
      const emailOwner = await this.usersService.findByEmail(email);
      if (emailOwner && emailOwner.id !== existing?.id) {
        throw new ConflictException('Email already in use');
      }
    }

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

    // Resume the stale record (overwriting name/password/email) instead of
    // locking the number behind it, or create a fresh account.
    const user = existing
      ? await this.usersService.update(existing.id, {
          email,
          firstName: registerDto.firstName,
          lastName: registerDto.lastName,
          password: hashedPassword,
        })
      : await this.usersService.create({
          phone,
          email,
          firstName: registerDto.firstName,
          lastName: registerDto.lastName,
          password: hashedPassword,
          phoneVerified: false,
        });

    const { destination } = await this.verificationService.issueLoginOtp(
      user,
      OtpMessageKind.REGISTER,
    );
    return { requiresVerification: true, phone: destination };
  }

  /**
   * Password login by mobile. If the phone isn't verified yet, an OTP is sent and
   * verification is required to finish.
   */
  async login(loginDto: LoginDto) {
    const phone = normalizeIranMobile(loginDto.phone);
    if (!phone) {
      throw new UnauthorizedException('Invalid credentials');
    }

    const user = await this.usersService.findByPhone(phone);
    if (!user) {
      throw new UnauthorizedException('Invalid credentials');
    }

    const isPasswordValid = await bcrypt.compare(loginDto.password, user.password);
    if (!isPasswordValid) {
      throw new UnauthorizedException('Invalid credentials');
    }

    if (!user.isActive) {
      throw new UnauthorizedException('Account is deactivated');
    }

    if (!user.phoneVerified) {
      // Account exists but never finished signup verification — treat as
      // registration completion (welcome wording), not a passwordless login.
      const { destination } = await this.verificationService.issueLoginOtp(
        user,
        OtpMessageKind.REGISTER,
      );
      return { requiresVerification: true, phone: destination } as VerificationRequired;
    }

    const tokens = await this.generateTokens(user);
    return { user: this.publicUser(user), ...tokens };
  }

  /**
   * Passwordless login: send a one-time code to a registered phone. Returns a
   * generic response regardless of whether the phone exists (no enumeration).
   */
  async requestOtp(rawPhone: string) {
    const phone = normalizeIranMobile(rawPhone);
    if (phone) {
      const user = await this.usersService.findByPhone(phone);
      if (user && user.isActive) {
        await this.verificationService.issueLoginOtp(user);
      }
    }
    return { sent: true };
  }

  /** Verify a LOGIN OTP (registration completion or passwordless login). */
  async verifyOtp(rawPhone: string, code: string) {
    const phone = normalizeIranMobile(rawPhone);
    if (!phone) {
      throw new BadRequestException('Invalid mobile number');
    }
    const user = await this.usersService.findByPhone(phone);
    if (!user || !user.isActive) {
      throw new UnauthorizedException('Invalid credentials');
    }

    await this.verificationService.verifyLoginOtp(user, code);

    const fresh = (await this.usersService.findById(user.id)) ?? user;
    const tokens = await this.generateTokens(fresh);
    return { user: this.publicUser(fresh), ...tokens };
  }

  async refreshToken(refreshToken: string) {
    try {
      const payload = this.jwtService.verify(refreshToken, {
        secret: this.configService.get('jwt.refreshSecret'),
      });

      const user = await this.usersService.findById(payload.sub);
      if (!user || !user.isActive) {
        throw new UnauthorizedException();
      }

      return this.generateTokens(user);
    } catch {
      throw new UnauthorizedException('Invalid refresh token');
    }
  }

  private publicUser(user: User) {
    return {
      id: user.id,
      phone: user.phone,
      email: user.email,
      phoneVerified: user.phoneVerified,
      firstName: user.firstName,
      lastName: user.lastName,
      role: user.role,
    };
  }

  private async generateTokens(user: User) {
    // `email` may be null; use phone as the human-readable identity claim.
    const payload = {
      sub: user.id,
      email: user.email ?? user.phone,
      role: user.role,
    };

    const [accessToken, refreshToken] = await Promise.all([
      this.jwtService.signAsync(payload),
      this.jwtService.signAsync(payload, {
        secret: this.configService.get('jwt.refreshSecret'),
        expiresIn: this.configService.get('jwt.refreshExpiresIn'),
      }),
    ]);

    return { accessToken, refreshToken };
  }
}