cdnUploader.js

const fs = require('fs').promises;
const path = require('path');

/**
 * CDN Uploader Service
 * Supports multiple CDN providers: Cloudflare, AWS S3, Azure Blob Storage
 * Uses mock implementation for demonstration, easily swappable with real CDN clients
 */
class CDNUploader {
  constructor(config = {}) {
    this.config = {
      provider: config.provider || 'mock', // 'mock', 'cloudflare', 's3', 'azure'
      apiKey: config.apiKey,
      apiToken: config.apiToken,
      accountId: config.accountId,
      bucket: config.bucket,
      zone: config.zone,
      region: config.region || 'us-east-1',
      cdnUrl: config.cdnUrl || 'https://cdn.example.com',
      cacheTTL: config.cacheTTL || 31536000, // 1 year
      ...config
    };

    this.uploadMetrics = {
      totalUploads: 0,
      successfulUploads: 0,
      failedUploads: 0,
      totalBytesUploaded: 0
    };

    this._initializeProvider();
  }

  /**
   * Initialize CDN provider client
   * @private
   */
  _initializeProvider() {
    switch (this.config.provider.toLowerCase()) {
      case 'cloudflare':
        this._initCloudflareClient();
        break;
      case 's3':
        this._initS3Client();
        break;
      case 'azure':
        this._initAzureClient();
        break;
      case 'mock':
      default:
        console.log('🟡 Using mock CDN provider for development');
        break;
    }
  }

  /**
   * Initialize Cloudflare client (placeholder for real implementation)
   * @private
   */
  _initCloudflareClient() {
    console.log('Initializing Cloudflare CDN provider...');
    // In production: const CloudflareClient = require('@cloudflare/javascript_sdk');
    // this.client = new CloudflareClient({ token: this.config.apiToken });
  }

  /**
   * Initialize AWS S3 client (placeholder for real implementation)
   * @private
   */
  _initS3Client() {
    console.log('Initializing AWS S3 CDN provider...');
    // In production: const AWS = require('aws-sdk');
    // this.client = new AWS.S3({ region: this.config.region });
  }

  /**
   * Initialize Azure Blob Storage client (placeholder for real implementation)
   * @private
   */
  _initAzureClient() {
    console.log('Initializing Azure Blob Storage provider...');
    // In production: const { BlobServiceClient } = require('@azure/storage-blob');
    // this.client = BlobServiceClient.fromConnectionString(connectionString);
  }

  /**
   * Upload file to CDN
   * @param {string} filePath - Local file path
   * @param {Object} metadata - File metadata
   * @returns {Promise<string>} CDN URL
   */
  async uploadFile(filePath, metadata = {}) {
    this.uploadMetrics.totalUploads++;

    try {
      const fileBuffer = await fs.readFile(filePath);
      const fileName = path.basename(filePath);
      
      let cdnUrl;

      switch (this.config.provider.toLowerCase()) {
        case 'cloudflare':
          cdnUrl = await this._uploadToCloudflare(fileBuffer, fileName, metadata);
          break;
        case 's3':
          cdnUrl = await this._uploadToS3(fileBuffer, fileName, metadata);
          break;
        case 'azure':
          cdnUrl = await this._uploadToAzure(fileBuffer, fileName, metadata);
          break;
        case 'mock':
        default:
          cdnUrl = await this._uploadMock(fileBuffer, fileName, metadata);
          break;
      }

      this.uploadMetrics.successfulUploads++;
      this.uploadMetrics.totalBytesUploaded += fileBuffer.length;

      console.log(`✅ CDN Upload: ${fileName} → ${cdnUrl}`);
      return cdnUrl;
    } catch (error) {
      this.uploadMetrics.failedUploads++;
      console.error(`❌ CDN upload failed for ${metadata.imageId}:`, error.message);
      throw new Error(`CDN upload failed: ${error.message}`);
    }
  }

  /**
   * Upload to Cloudflare Images/Workers KV (placeholder)
   * @private
   */
  async _uploadToCloudflare(fileBuffer, fileName, metadata) {
    // Real implementation would use Cloudflare API
    // Example:
    // const formData = new FormData();
    // formData.append('file', new Blob([fileBuffer], { type: metadata.mimeType }), fileName);
    // const response = await fetch(`https://api.cloudflare.com/client/v4/accounts/${this.config.accountId}/images/v1`, {
    //   method: 'POST',
    //   headers: { Authorization: `Bearer ${this.config.apiToken}` },
    //   body: formData
    // });

    console.warn('⚠️  Cloudflare upload not implemented. Using mock URL.');
    return this._generateMockCDNUrl(fileName, metadata);
  }

  /**
   * Upload to AWS S3 (placeholder)
   * @private
   */
  async _uploadToS3(fileBuffer, fileName, metadata) {
    // Real implementation would use AWS SDK
    // Example:
    // const params = {
    //   Bucket: this.config.bucket,
    //   Key: `images/${fileName}`,
    //   Body: fileBuffer,
    //   ContentType: metadata.mimeType,
    //   CacheControl: `max-age=${this.config.cacheTTL}`,
    //   Metadata: metadata
    // };
    // const result = await this.client.upload(params).promise();
    // return result.Location;

    console.warn('⚠️  S3 upload not implemented. Using mock URL.');
    return this._generateMockCDNUrl(fileName, metadata);
  }

  /**
   * Upload to Azure Blob Storage (placeholder)
   * @private
   */
  async _uploadToAzure(fileBuffer, fileName, metadata) {
    // Real implementation would use Azure SDK
    // Example:
    // const containerClient = this.client.getContainerClient('images');
    // const blockBlobClient = containerClient.getBlockBlobClient(fileName);
    // await blockBlobClient.upload(fileBuffer, fileBuffer.length);
    // return blockBlobClient.url;

    console.warn('⚠️  Azure upload not implemented. Using mock URL.');
    return this._generateMockCDNUrl(fileName, metadata);
  }

  /**
   * Mock CDN upload (for development/testing)
   * @private
   */
  async _uploadMock(fileBuffer, fileName, metadata) {
    // Simulate network delay
    await new Promise(resolve => setTimeout(resolve, Math.random() * 200));
    return this._generateMockCDNUrl(fileName, metadata);
  }

  /**
   * Generate mock CDN URL for testing
   * @private
   */
  _generateMockCDNUrl(fileName, metadata) {
    const cdnPath = `images/${metadata.imageId}/${fileName}`;
    return `${this.config.cdnUrl}/${cdnPath}?v=${Date.now()}`;
  }

  /**
   * Batch upload multiple files
   * @param {Array<string>} filePaths - Array of local file paths
   * @param {Object} metadata - Common metadata
   * @returns {Promise<Array<string>>} Array of CDN URLs
   */
  async uploadBatch(filePaths, metadata = {}) {
    const uploadTasks = filePaths.map(filePath =>
      this.uploadFile(filePath, { ...metadata, fileName: path.basename(filePath) })
    );

    return Promise.all(uploadTasks);
  }

  /**
   * Delete file from CDN
   * @param {string} fileName - File name or path on CDN
   * @returns {Promise<boolean>}
   */
  async deleteFile(fileName) {
    try {
      switch (this.config.provider.toLowerCase()) {
        case 'cloudflare':
          // Cloudflare implementation
          break;
        case 's3':
          // S3 delete implementation
          break;
        case 'azure':
          // Azure delete implementation
          break;
        case 'mock':
        default:
          await new Promise(resolve => setTimeout(resolve, 100));
          console.log(`🗑️  Mock delete: ${fileName}`);
          break;
      }
      return true;
    } catch (error) {
      console.error(`Failed to delete ${fileName}:`, error.message);
      return false;
    }
  }

  /**
   * Invalidate cache for specific files
   * @param {Array<string>} filePaths - Files to purge from cache
   * @returns {Promise<boolean>}
   */
  async purgeCache(filePaths) {
    try {
      switch (this.config.provider.toLowerCase()) {
        case 'cloudflare':
          // Example: await this._purgeCloudflareCache(filePaths);
          console.log('🔄 Purging Cloudflare cache...');
          break;
        case 's3':
          // CloudFront invalidation
          console.log('🔄 Creating CloudFront invalidation...');
          break;
        default:
          console.log('🔄 Cache purge initiated for mock CDN');
          break;
      }
      return true;
    } catch (error) {
      console.error('Cache purge failed:', error.message);
      return false;
    }
  }

  /**
   * Get CDN upload metrics
   * @returns {Object} Upload statistics
   */
  getMetrics() {
    return {
      ...this.uploadMetrics,
      averageFileSizeKB: (this.uploadMetrics.totalBytesUploaded / this.uploadMetrics.successfulUploads / 1024).toFixed(2),
      successRate: ((this.uploadMetrics.successfulUploads / this.uploadMetrics.totalUploads) * 100).toFixed(2)
    };
  }

  /**
   * Generate signed URL for temporary access (if needed)
   * @param {string} fileName - File name
   * @param {number} expirationSeconds - URL expiration time
   * @returns {Promise<string>} Signed URL
   */
  async generateSignedUrl(fileName, expirationSeconds = 3600) {
    try {
      switch (this.config.provider.toLowerCase()) {
        case 'cloudflare':
          // Cloudflare signed URL generation
          break;
        case 's3':
          // S3 signed URL generation
          break;
        case 'azure':
          // Azure SAS URL generation
          break;
        case 'mock':
        default:
          return `${this.config.cdnUrl}/images/${fileName}?expires=${Date.now() + expirationSeconds * 1000}`;
      }
    } catch (error) {
      console.error('Signed URL generation failed:', error.message);
      throw error;
    }
  }
}

module.exports = CDNUploader;