/**
 * Config Schema Validation for DashCaddy
 * Validates config.json structure to catch typos and invalid values early.
 */

const VALID_TIMEZONES_SAMPLE = [
  'UTC', 'America/New_York', 'America/Chicago', 'America/Denver', 'America/Los_Angeles',
  'Europe/London', 'Europe/Paris', 'Europe/Berlin', 'Asia/Tokyo', 'Asia/Shanghai',
  'Asia/Singapore', 'Australia/Sydney', 'Pacific/Auckland'
];

/**
 * Validate a config object and return errors/warnings.
 * @param {object} config - The config object to validate
 * @returns {{ valid: boolean, errors: string[], warnings: string[] }}
 */
function validateConfig(config) {
  const errors = [];
  const warnings = [];

  if (!config || typeof config !== 'object') {
    return { valid: false, errors: ['Config must be a non-null object'], warnings };
  }

  // TLD validation
  if (config.tld !== undefined) {
    if (typeof config.tld !== 'string') {
      errors.push('tld must be a string');
    } else {
      const tld = config.tld.startsWith('.') ? config.tld : '.' + config.tld;
      if (!/^\.[a-z0-9][a-z0-9-]*$/.test(tld)) {
        errors.push(`tld "${config.tld}" contains invalid characters (use lowercase alphanumeric)`);
      }
      if (tld.length > 20) {
        warnings.push(`tld "${config.tld}" is unusually long`);
      }
    }
  }

  // DNS config validation
  if (config.dns !== undefined) {
    if (typeof config.dns !== 'object' || config.dns === null) {
      errors.push('dns must be an object');
    } else {
      if (config.dns.ip !== undefined && typeof config.dns.ip !== 'string') {
        errors.push('dns.ip must be a string');
      }
      if (config.dns.ip && !/^[\d.]+$/.test(config.dns.ip) && !/^[a-zA-Z0-9.-]+$/.test(config.dns.ip)) {
        errors.push(`dns.ip "${config.dns.ip}" is not a valid IP address or hostname`);
      }
      if (config.dns.port !== undefined) {
        const port = parseInt(config.dns.port, 10);
        if (isNaN(port) || port < 1 || port > 65535) {
          errors.push(`dns.port "${config.dns.port}" is not a valid port number (1-65535)`);
        }
      }
      if (config.dns.servers !== undefined) {
        if (typeof config.dns.servers !== 'object' || config.dns.servers === null) {
          errors.push('dns.servers must be an object');
        }
      }
      // DNS provider validation
      if (config.dns.provider !== undefined) {
        const validProviders = ['technitium', 'cloudflare', 'rfc2136', 'manual'];
        if (typeof config.dns.provider !== 'string') {
          errors.push('dns.provider must be a string');
        } else if (!validProviders.includes(config.dns.provider)) {
          warnings.push(`dns.provider "${config.dns.provider}" is not one of: ${validProviders.join(', ')}. It may still work if a custom adapter is installed.`);
        }
      }
    }
  }

  // Dashboard host validation
  if (config.dashboardHost !== undefined) {
    if (typeof config.dashboardHost !== 'string') {
      errors.push('dashboardHost must be a string');
    } else if (config.dashboardHost && !/^[a-zA-Z0-9][a-zA-Z0-9.-]*$/.test(config.dashboardHost)) {
      errors.push(`dashboardHost "${config.dashboardHost}" contains invalid characters`);
    }
  }

  // Timezone validation
  if (config.timezone !== undefined) {
    if (typeof config.timezone !== 'string') {
      errors.push('timezone must be a string');
    } else if (config.timezone) {
      // Basic format check — full validation would require Intl API
      try {
        Intl.DateTimeFormat(undefined, { timeZone: config.timezone });
      } catch {
        errors.push(`timezone "${config.timezone}" is not a recognized IANA timezone`);
      }
    }
  }

  // Theme validation
  if (config.theme !== undefined) {
    const validThemes = ['dark', 'light', 'blue'];
    if (!validThemes.includes(config.theme)) {
      warnings.push(`theme "${config.theme}" is not one of: ${validThemes.join(', ')}`);
    }
  }

  // Routing mode validation
  if (config.routingMode !== undefined) {
    const validModes = ['subdomain', 'subdirectory'];
    if (!validModes.includes(config.routingMode)) {
      errors.push(`routingMode "${config.routingMode}" is not one of: ${validModes.join(', ')}`);
    }
  }

  // Domain validation
  if (config.domain !== undefined) {
    if (typeof config.domain !== 'string') {
      errors.push('domain must be a string');
    } else if (config.domain && !/^[a-z0-9][a-z0-9.-]*\.[a-z]{2,}$/i.test(config.domain)) {
      warnings.push(`domain "${config.domain}" may not be a valid domain name`);
    }
  }

  // Warn on unknown top-level keys
  const knownKeys = [
    'tld', 'caName', 'dns', 'dnsServers', 'dashboardHost', 'timezone', 'theme',
    'updatedAt', 'timestamp', 'logo', 'logoPosition', 'favicon', 'weather',
    'setupComplete', 'setupCompleted', 'setupMode', 'onboardingCompleted',
    'configurationType', 'defaults', 'customLogo', 'customFavicon',
    'dashboardTitle', 'tailscale', 'license', 'skipped',
    'routingMode', 'domain', 'email', 'defaultIP', 'pylon',
    'customLogoDark', 'customLogoLight'
  ];
  for (const key of Object.keys(config)) {
    if (!knownKeys.includes(key)) {
      warnings.push(`Unknown config key "${key}" — possible typo?`);
    }
  }

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

module.exports = { validateConfig };
