import jwt from 'jsonwebtoken';
import bcrypt from 'bcryptjs';
import User from '../models/User.js';
import dotenv from 'dotenv';

dotenv.config();

const SECRET_KEY = process.env.JWT_SECRET_KEY || 'your-super-secret-key-change-in-production';
const ALGORITHM = 'HS256';
export const ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24; // 24 hours

class AuthService {
  /**
   * Verify a password against its hash
   */
  verifyPassword(plainPassword, hashedPassword) {
    return bcrypt.compareSync(plainPassword, hashedPassword);
  }
  
  /**
   * Hash a password
   */
  getPasswordHash(password) {
    const salt = bcrypt.genSaltSync(10);
    return bcrypt.hashSync(password, salt);
  }
  
  /**
   * Create a JWT access token
   */
  createAccessToken(data, expiresInMinutes = ACCESS_TOKEN_EXPIRE_MINUTES) {
    const payload = {
      ...data,
      exp: Math.floor(Date.now() / 1000) + (expiresInMinutes * 60)
    };
    return jwt.sign(payload, SECRET_KEY, { algorithm: ALGORITHM });
  }
  
  /**
   * Decode and validate a JWT token
   */
  decodeToken(token) {
    try {
      const payload = jwt.verify(token, SECRET_KEY, { algorithms: [ALGORITHM] });
      const userId = payload.sub;
      const email = payload.email;
      const role = payload.role;
      
      if (!userId) {
        return null;
      }
      
      return { userId, email, role };
    } catch (error) {
      return null;
    }
  }
  
  /**
   * Get a user by email
   */
  async getUserByEmail(email) {
    return await User.findByEmail(email);
  }
  
  /**
   * Get a user by ID
   */
  async getUserById(userId) {
    try {
      return await User.findById(userId);
    } catch (error) {
      return null;
    }
  }
  
  /**
   * Create a new user
   */
  async createUser(userData) {
    // Check if user already exists
    const existingUser = await this.getUserByEmail(userData.email);
    if (existingUser) {
      throw new Error('User with this email already exists');
    }
    
    // Create user with Mongoose model
    const user = new User({
      email: userData.email,
      name: userData.name,
      role: userData.role || UserRole.DOCTOR,
      hashed_password: userData.password, // Will be hashed by pre-save hook
      is_active: true
    });
    
    await user.save();
    return user;
  }
  
  /**
   * Authenticate a user by email and password
   */
  async authenticateUser(email, password) {
    const user = await this.getUserByEmail(email);
    if (!user) {
      return null;
    }
    
    const isValid = await user.comparePassword(password);
    if (!isValid) {
      return null;
    }
    
    return user;
  }
  
  /**
   * Convert a user document to a response object
   */
  userToResponse(user) {
    if (user.toResponse) {
      return user.toResponse();
    }
    return {
      id: user._id.toString(),
      email: user.email,
      name: user.name,
      role: user.role,
      created_at: user.created_at,
      is_active: user.is_active !== false
    };
  }
  
  /**
   * Update a user's information
   */
  async updateUser(userId, updateData) {
    try {
      const user = await User.findByIdAndUpdate(
        userId,
        { $set: updateData },
        { new: true, runValidators: true }
      );
      return user;
    } catch (error) {
      return null;
    }
  }

  /**
   * Delete a user by ID
   */
  async deleteUser(userId) {
    try {
      const result = await User.findByIdAndDelete(userId);
      return result !== null;
    } catch (error) {
      return false;
    }
  }

  /**
   * Get all users
   */
  async getAllUsers() {
    return await User.find().sort({ created_at: -1 });
  }

  /**
   * Get all doctors
   */
  async getDoctors() {
    return await User.findActiveDoctors();
  }

  /**
   * Get all admins
   */
  async getAdmins() {
    return await User.findActiveAdmins();
  }
}

// Singleton instance
export const authService = new AuthService();