/**
 * Environment Variable Validation
 *
 * Validates required environment variables at startup and provides
 * helpful error messages for production deployments.
 */

/**
 * Required environment variables for production
 */
const REQUIRED_ENV_VARS = {
  // Deployment Configuration
  DEPLOYMENT_TARGET: {
    required: true,
    description: 'Deployment environment (dev, docker-local, production)',
    validate: val => ['dev', 'docker-local', 'production'].includes(val)
  },

  // Server Configuration
  NODE_ENV: {
    required: true,
    description: 'Environment mode (development, production)',
    validate: val => ['development', 'production', 'test'].includes(val)
  },
  PORT: {
    required: true,
    description: 'Server port number',
    validate: val =>
      !isNaN(parseInt(val)) && parseInt(val) > 0 && parseInt(val) < 65536
  },

  // Frontend URL for CORS
  FRONTEND_URL: {
    required: true,
    description: 'Frontend URL for CORS',
    validate: (val, env) => {
      if (!val) return false;
      
      // Validate that FRONTEND_URL matches DEPLOYMENT_TARGET (if set)
      const target = env?.DEPLOYMENT_TARGET;
      if (!target) return true; // Skip validation if target not set yet
      
      if (target === 'dev' && !val.includes('localhost:5173')) {
        console.error('⚠️  FRONTEND_URL should be http://localhost:5173 for dev target');
        return false;
      }
      if (target === 'docker-local' && !val.includes('localhost:8099')) {
        console.error('⚠️  FRONTEND_URL should be http://localhost:8099 for docker-local target');
        return false;
      }
      if (target === 'production' && !val.includes('app.pokedex.online')) {
        console.error('⚠️  FRONTEND_URL should be https://app.pokedex.online for production target');
        return false;
      }
      
      return true;
    }
  },

  // Optional but recommended for production
  SESSION_SECRET: {
    required: false,
    description: 'Secret key for session encryption',
    warn: val =>
      !val || val.length < 32
        ? 'SESSION_SECRET should be at least 32 characters for security'
        : null
  },

  // Challonge OAuth (optional)
  CHALLONGE_CLIENT_ID: {
    required: false,
    description: 'Challonge OAuth client ID'
  },
  CHALLONGE_CLIENT_SECRET: {
    required: false,
    description: 'Challonge OAuth client secret'
  },
  CHALLONGE_REDIRECT_URI: {
    required: false,
    description: 'OAuth redirect URI'
  }
};

/**
 * Validate environment variables
 * @returns {Object} Validation result with errors and warnings
 */
export function validateEnvironment() {
  const errors = [];
  const warnings = [];
  const missing = [];

  // Check required variables
  for (const [key, config] of Object.entries(REQUIRED_ENV_VARS)) {
    const value = process.env[key];

    // Check if required variable is missing
    if (config.required && !value) {
      errors.push(
        `Missing required environment variable: ${key} - ${config.description}`
      );
      missing.push(key);
      continue;
    }

    // Validate value if present
    if (value && config.validate && !config.validate(value)) {
      errors.push(
        `Invalid value for ${key}: "${value}" - ${config.description}`
      );
    }

    // Check for warnings
    if (config.warn) {
      const warning = config.warn(value, process.env);
      if (warning) {
        warnings.push(`${key}: ${warning}`);
      }
    }
  }

  return {
    valid: errors.length === 0,
    errors,
    warnings,
    missing
  };
}

/**
 * Validate environment and exit if critical errors found
 * @param {boolean} exitOnError - Whether to exit process on validation errors (default: true)
 */
export function validateOrExit(exitOnError = true) {
  const result = validateEnvironment();

  // Print validation results
  console.log('\n🔍 Environment Validation:');
  console.log(`   DEPLOYMENT_TARGET: ${process.env.DEPLOYMENT_TARGET || 'not set'}`);
  console.log(`   NODE_ENV: ${process.env.NODE_ENV || 'not set'}`);
  console.log(`   PORT: ${process.env.PORT || 'not set'}`);
  console.log(`   FRONTEND_URL: ${process.env.FRONTEND_URL || 'not set'}`);

  // Show errors
  if (result.errors.length > 0) {
    console.error('\n❌ Environment Validation Errors:');
    result.errors.forEach(error => console.error(`   - ${error}`));

    if (result.missing.length > 0) {
      console.error('\n💡 Tip: Create a .env file with these variables:');
      result.missing.forEach(key => {
        console.error(`   ${key}=your_value_here`);
      });
      console.error('\n   See .env.example for reference');
    }

    if (exitOnError) {
      console.error('\n❌ Server cannot start due to environment errors\n');
      process.exit(1);
    }
  } else {
    console.log('   ✅ All required variables present');
  }

  // Show warnings
  if (result.warnings.length > 0) {
    console.warn('\n⚠️  Environment Warnings:');
    result.warnings.forEach(warning => console.warn(`   - ${warning}`));
  }

  console.log('');
  return result;
}

/**
 * Get configuration object with validated environment variables
 * @returns {Object} Configuration object
 */
export function getConfig() {
  const deploymentTarget = process.env.DEPLOYMENT_TARGET || 'dev';
  const frontendUrl = process.env.FRONTEND_URL;
  
  return {
    deploymentTarget,
    nodeEnv: process.env.NODE_ENV || 'development',
    port: parseInt(process.env.PORT || '3001'),
    isProduction: process.env.NODE_ENV === 'production',
    isDevelopment: process.env.NODE_ENV === 'development',

    // Challonge OAuth
    challonge: {
      clientId: process.env.CHALLONGE_CLIENT_ID,
      clientSecret: process.env.CHALLONGE_CLIENT_SECRET,
      redirectUri: process.env.CHALLONGE_REDIRECT_URI,
      configured: !!(
        process.env.CHALLONGE_CLIENT_ID && process.env.CHALLONGE_CLIENT_SECRET
      )
    },

    // CORS - Single origin based on deployment target
    cors: {
      origin: frontendUrl,
      credentials: true
    },

    // Security
    session: {
      secret: process.env.SESSION_SECRET || 'dev-secret-change-in-production'
    },

    // Discord User Permissions
    discord: {
      adminUsers: process.env.DISCORD_ADMIN_USERS
        ? process.env.DISCORD_ADMIN_USERS.split(',').map(u =>
            u.trim().toLowerCase()
          )
        : []
    }
  };
}

// Run validation when executed directly
if (import.meta.url === `file://${process.argv[1]}`) {
  validateOrExit();
}