/**
 * Keychain Manager for DashCaddy
 * Provides secure credential storage using OS-native keychains
 * Falls back to encrypted file storage if keychain is unavailable
 */

const { execSync } = require('child_process');
const os = require('os');
const crypto = require('crypto');

const SERVICE_NAME = 'DashCaddy';
const ACCOUNT_PREFIX = 'dashcaddy';

class KeychainManager {
  constructor() {
    this.platform = os.platform();
    this.available = this.checkAvailability();
  }

  /**
   * Check if OS keychain is available
   * @returns {boolean}
   */
  checkAvailability() {
    try {
      if (this.platform === 'win32') {
        // Check if PowerShell is available
        execSync('powershell -Command "Get-Command Get-Credential"', { stdio: 'ignore' });
        return true;
      } else if (this.platform === 'darwin') {
        // Check if security command is available
        execSync('which security', { stdio: 'ignore' });
        return true;
      } else if (this.platform === 'linux') {
        // Check if secret-tool (libsecret) is available
        try {
          execSync('which secret-tool', { stdio: 'ignore' });
          return true;
        } catch {
          // Try gnome-keyring
          execSync('which gnome-keyring-daemon', { stdio: 'ignore' });
          return true;
        }
      }
      return false;
    } catch {
      console.warn('[Keychain] OS keychain not available, will use encrypted file storage');
      return false;
    }
  }

  /**
   * Store a credential in the OS keychain
   * @param {string} key - Credential identifier
   * @param {string} value - Credential value
   * @returns {Promise<boolean>} Success status
   */
  async store(key, value) {
    if (!this.available) {
      return false;
    }

    const account = `${ACCOUNT_PREFIX}.${key}`;

    try {
      if (this.platform === 'win32') {
        return await this.storeWindows(account, value);
      } else if (this.platform === 'darwin') {
        return await this.storeMacOS(account, value);
      } else if (this.platform === 'linux') {
        return await this.storeLinux(account, value);
      }
      return false;
    } catch (error) {
      console.error(`[Keychain] Failed to store ${key}:`, error.message);
      return false;
    }
  }

  /**
   * Retrieve a credential from the OS keychain
   * @param {string} key - Credential identifier
   * @returns {Promise<string|null>} Credential value or null
   */
  async retrieve(key) {
    if (!this.available) {
      return null;
    }

    const account = `${ACCOUNT_PREFIX}.${key}`;

    try {
      if (this.platform === 'win32') {
        return await this.retrieveWindows(account);
      } else if (this.platform === 'darwin') {
        return await this.retrieveMacOS(account);
      } else if (this.platform === 'linux') {
        return await this.retrieveLinux(account);
      }
      return null;
    } catch (error) {
      console.error(`[Keychain] Failed to retrieve ${key}:`, error.message);
      return null;
    }
  }

  /**
   * Delete a credential from the OS keychain
   * @param {string} key - Credential identifier
   * @returns {Promise<boolean>} Success status
   */
  async delete(key) {
    if (!this.available) {
      return false;
    }

    const account = `${ACCOUNT_PREFIX}.${key}`;

    try {
      if (this.platform === 'win32') {
        return await this.deleteWindows(account);
      } else if (this.platform === 'darwin') {
        return await this.deleteMacOS(account);
      } else if (this.platform === 'linux') {
        return await this.deleteLinux(account);
      }
      return false;
    } catch (error) {
      console.error(`[Keychain] Failed to delete ${key}:`, error.message);
      return false;
    }
  }

  // Windows Credential Manager implementation
  async storeWindows(account, value) {
    const escapedValue = value.replace(/"/g, '""');
    const script = `
      $password = ConvertTo-SecureString -String "${escapedValue}" -AsPlainText -Force
      $credential = New-Object System.Management.Automation.PSCredential("${account}", $password)
      cmdkey /generic:"${SERVICE_NAME}:${account}" /user:"${account}" /pass:"${escapedValue}"
    `;
    execSync(`powershell -Command "${script.replace(/\n/g, ' ')}"`, { stdio: 'ignore' });
    return true;
  }

  async retrieveWindows(account) {
    try {
      const script = `
        $cred = cmdkey /list:"${SERVICE_NAME}:${account}"
        if ($cred -match "Password: (.+)") { $matches[1] }
      `;
      const result = execSync(`powershell -Command "${script.replace(/\n/g, ' ')}"`, { encoding: 'utf8' });
      return result.trim() || null;
    } catch {
      return null;
    }
  }

  async deleteWindows(account) {
    execSync(`cmdkey /delete:"${SERVICE_NAME}:${account}"`, { stdio: 'ignore' });
    return true;
  }

  // macOS Keychain implementation
  async storeMacOS(account, value) {
    // Delete existing entry first
    try {
      execSync(`security delete-generic-password -s "${SERVICE_NAME}" -a "${account}"`, { stdio: 'ignore' });
    } catch {
      // Ignore if doesn't exist
    }

    // Add new entry
    execSync(`security add-generic-password -s "${SERVICE_NAME}" -a "${account}" -w "${value}"`, { stdio: 'ignore' });
    return true;
  }

  async retrieveMacOS(account) {
    try {
      const result = execSync(`security find-generic-password -s "${SERVICE_NAME}" -a "${account}" -w`, { encoding: 'utf8' });
      return result.trim() || null;
    } catch {
      return null;
    }
  }

  async deleteMacOS(account) {
    execSync(`security delete-generic-password -s "${SERVICE_NAME}" -a "${account}"`, { stdio: 'ignore' });
    return true;
  }

  // Linux Secret Service implementation
  async storeLinux(account, value) {
    try {
      // Try secret-tool first (libsecret)
      execSync(`secret-tool store --label="${SERVICE_NAME}:${account}" service "${SERVICE_NAME}" account "${account}"`, {
        input: value,
        stdio: ['pipe', 'ignore', 'ignore']
      });
      return true;
    } catch {
      // Fallback to gnome-keyring if available
      try {
        const script = `
          echo "${value}" | gnome-keyring-daemon --unlock
          echo "${value}" | gnome-keyring --set-password "${SERVICE_NAME}:${account}"
        `;
        execSync(script, { stdio: 'ignore' });
        return true;
      } catch {
        return false;
      }
    }
  }

  async retrieveLinux(account) {
    try {
      // Try secret-tool first
      const result = execSync(`secret-tool lookup service "${SERVICE_NAME}" account "${account}"`, { encoding: 'utf8' });
      return result.trim() || null;
    } catch {
      return null;
    }
  }

  async deleteLinux(account) {
    try {
      execSync(`secret-tool clear service "${SERVICE_NAME}" account "${account}"`, { stdio: 'ignore' });
      return true;
    } catch {
      return false;
    }
  }
}

module.exports = new KeychainManager();