const path = require('path');
const fs = require('fs');
const logger = require('./logger');

class ConfigLoader {
  constructor() {
    this.config = {};
    this.env = process.env.NODE_ENV || 'development';
    this.loadConfig();
  }

  loadConfig() {
    try {
      // Load base configuration
      this.loadBaseConfig();
      
      // Load environment-specific configuration
      this.loadEnvConfig();
      
      // Validate configuration
      this.validateConfig();
      
      logger.info(`Configuration loaded for environment: ${this.env}`);
    } catch (error) {
      logger.error('Configuration loading failed:', error);
      throw error;
    }
  }

  loadBaseConfig() {
    // Load from appConfig.js
    const { appConfig } = require('../config/appConfig');
    this.config = { ...appConfig };
  }

  loadEnvConfig() {
    const envFile = path.join(__dirname, '../../', `env.${this.env}`);
    
    if (fs.existsSync(envFile)) {
      logger.info(`Loading environment configuration from: ${envFile}`);
      
      // Parse environment file
      const envContent = fs.readFileSync(envFile, 'utf8');
      const envVars = this.parseEnvFile(envContent);
      
      // Override configuration with environment-specific values
      Object.assign(process.env, envVars);
      
      // Reload configuration with new environment variables
      const { appConfig } = require('../config/appConfig');
      this.config = { ...appConfig };
    } else {
      logger.warn(`Environment configuration file not found: ${envFile}`);
    }
  }

  parseEnvFile(content) {
    const envVars = {};
    const lines = content.split('\n');
    
    for (const line of lines) {
      const trimmedLine = line.trim();
      
      // Skip empty lines and comments
      if (!trimmedLine || trimmedLine.startsWith('#')) {
        continue;
      }
      
      // Parse KEY=VALUE format
      const equalIndex = trimmedLine.indexOf('=');
      if (equalIndex > 0) {
        const key = trimmedLine.substring(0, equalIndex).trim();
        const value = trimmedLine.substring(equalIndex + 1).trim();
        
        // Remove quotes if present
        const cleanValue = value.replace(/^["']|["']$/g, '');
        envVars[key] = cleanValue;
      }
    }
    
    return envVars;
  }

  validateConfig() {
    const errors = [];
    const warnings = [];

    // Required fields validation
    if (!this.config.apis.groq.apiKey) {
      errors.push('GROQ_API_KEY is required');
    }

    if (!this.config.auth.jwtSecret) {
      errors.push('JWT_SECRET is required');
    }

    if (!this.config.database.password) {
      errors.push('DB_PASSWORD is required');
    }

    // Environment-specific validations
    if (this.env === 'production') {
      if (this.config.auth.jwtSecret === 'dev_secret_key_change_in_production') {
        errors.push('JWT_SECRET must be changed for production');
      }

      if (!this.config.database.ssl) {
        warnings.push('Database SSL is recommended for production');
      }
    }

    // Log warnings
    warnings.forEach(warning => {
      logger.warn(`Configuration warning: ${warning}`);
    });

    // Throw errors
    if (errors.length > 0) {
      const errorMessage = `Configuration errors: ${errors.join(', ')}`;
      logger.error(errorMessage);
      throw new Error(errorMessage);
    }
  }

  get(key, defaultValue = null) {
    const keys = key.split('.');
    let value = this.config;
    
    for (const k of keys) {
      if (value && typeof value === 'object' && k in value) {
        value = value[k];
      } else {
        return defaultValue;
      }
    }
    
    return value;
  }

  getAll() {
    return this.config;
  }

  getServerConfig() {
    return this.config.server;
  }

  getDatabaseConfig() {
    return this.config.database;
  }

  getApiConfig() {
    return this.config.apis;
  }

  getAuthConfig() {
    return this.config.auth;
  }

  getUploadConfig() {
    return this.config.upload;
  }

  getRateLimitConfig() {
    return this.config.rateLimit;
  }

  getLoggingConfig() {
    return this.config.logging;
  }

  getModelConfig() {
    return this.config.models;
  }

  getSecurityConfig() {
    return this.config.security;
  }

  getMonitoringConfig() {
    return this.config.monitoring;
  }

  getDevelopmentConfig() {
    return this.config.development;
  }

  isDevelopment() {
    return this.env === 'development';
  }

  isProduction() {
    return this.env === 'production';
  }

  isTest() {
    return this.env === 'test';
  }

  getEnvironment() {
    return this.env;
  }
}

// Create singleton instance
const configLoader = new ConfigLoader();

module.exports = configLoader;