/**
 * Universal File Server
 * Ensures all attachments and avatars are always visible regardless of ROOT_URL and PORT settings
 * Handles both new Meteor-Files and legacy CollectionFS file serving
 */

import { Meteor } from 'meteor/meteor';
import { WebApp } from 'meteor/webapp';
import { ReactiveCache } from '/imports/reactiveCache';
import Attachments, { fileStoreStrategyFactory as attachmentStoreFactory } from '/models/attachments';
import Avatars, { fileStoreStrategyFactory as avatarStoreFactory } from '/models/avatars';
import { getAttachmentWithBackwardCompatibility, getOldAttachmentStream } from '/models/lib/attachmentBackwardCompatibility';
import fs from 'fs';
import path from 'path';

if (Meteor.isServer) {
  console.log('Universal file server initializing...');

  /**
   * Helper function to set appropriate headers for file serving
   */
  function setFileHeaders(res, fileObj, isAttachment = false) {
    // Decide safe serving strategy
    const nameLower = (fileObj.name || '').toLowerCase();
    const typeLower = (fileObj.type || '').toLowerCase();
    const isPdfByExt = nameLower.endsWith('.pdf');
    
    // Define dangerous types that must never be served inline
    const dangerousTypes = new Set([
      'text/html',
      'application/xhtml+xml',
      'image/svg+xml',
      'text/xml',
      'application/xml',
      'application/javascript',
      'text/javascript'
    ]);
    
    // Define safe types that can be served inline for viewing
    const safeInlineTypes = new Set([
      'application/pdf',
      'image/jpeg',
      'image/jpg',
      'image/png',
      'image/gif',
      'image/webp',
      'image/avif',
      'image/bmp',
      'video/mp4',
      'video/webm',
      'video/ogg',
      'audio/mpeg',
      'audio/mp3',
      'audio/ogg',
      'audio/wav',
      'audio/webm',
      'text/plain',
      'application/json'
    ]);
    
    const isSvg = nameLower.endsWith('.svg') || typeLower === 'image/svg+xml';
  const isDangerous = dangerousTypes.has(typeLower) || isSvg;
  // Consider PDF safe inline by extension if type is missing/mis-set
  const isSafeInline = safeInlineTypes.has(typeLower) || (isAttachment && isPdfByExt);

    // Always send strong caching and integrity headers
    res.setHeader('Cache-Control', 'public, max-age=31536000'); // Cache for 1 year
    res.setHeader('ETag', `"${fileObj._id}"`);
    res.setHeader('X-Content-Type-Options', 'nosniff');

    // Set content length when available
    if (fileObj.size) {
      res.setHeader('Content-Length', fileObj.size);
    }

    if (isAttachment) {
      // Attachments: dangerous types forced to download, safe types can be inline
      if (isDangerous) {
        // SECURITY: Force download for dangerous types to prevent XSS
        res.setHeader('Content-Type', 'application/octet-stream');
        res.setHeader('Content-Disposition', `attachment; filename="${fileObj.name}"`);
        res.setHeader('Content-Security-Policy', "default-src 'none'; sandbox;");
        res.setHeader('X-Frame-Options', 'DENY');
      } else if (isSafeInline) {
        // Safe types: serve inline with proper type and restrictive CSP
        // If the file is a PDF by extension but type is wrong/missing, correct it
        const finalType = (isPdfByExt && typeLower !== 'application/pdf') ? 'application/pdf' : (typeLower || 'application/octet-stream');
        res.setHeader('Content-Type', finalType);
        res.setHeader('Content-Disposition', `inline; filename="${fileObj.name}"`);
        // Restrictive CSP for safe types - allow media/img/object for viewer embeds, no scripts
        res.setHeader('Content-Security-Policy', "default-src 'none'; object-src 'self'; media-src 'self'; img-src 'self'; style-src 'unsafe-inline';");
      } else {
        // Unknown types: force download as fallback
        res.setHeader('Content-Type', 'application/octet-stream');
        res.setHeader('Content-Disposition', `attachment; filename="${fileObj.name}"`);
        res.setHeader('Content-Security-Policy', "default-src 'none'; sandbox;");
      }
    } else {
      // Avatars: allow inline images, but never serve SVG inline
      if (isSvg || isDangerous) {
        // Serve potentially dangerous avatar types as downloads instead
        res.setHeader('Content-Type', 'application/octet-stream');
        res.setHeader('Content-Disposition', `attachment; filename="${fileObj.name}"`);
        res.setHeader('Content-Security-Policy', "default-src 'none'; sandbox;");
        res.setHeader('X-Frame-Options', 'DENY');
      } else {
        // For typical image avatars, use provided type if present, otherwise fall back to a safe generic image type
        res.setHeader('Content-Type', typeLower || 'image/jpeg');
        res.setHeader('Content-Disposition', `inline; filename="${fileObj.name}"`);
      }
    }
  }

  /**
   * Helper function to handle conditional requests
   */
  function handleConditionalRequest(req, res, fileObj) {
    const ifNoneMatch = req.headers['if-none-match'];
    if (ifNoneMatch && ifNoneMatch === `"${fileObj._id}"`) {
      res.writeHead(304);
      res.end();
      return true;
    }
    return false;
  }

  /**
   * Extract first path segment (file id) from request URL.
   * Works whether req.url is the full path or already trimmed by the mount path.
   */
  function extractFirstIdFromUrl(req, mountPrefix) {
    // Strip query string
    let urlPath = (req.url || '').split('?')[0];
    // If url still contains the mount prefix, remove it
    if (mountPrefix && urlPath.startsWith(mountPrefix)) {
      urlPath = urlPath.slice(mountPrefix.length);
    }
    // Ensure leading slash removed for splitting
    if (urlPath.startsWith('/')) {
      urlPath = urlPath.slice(1);
    }
    const parts = urlPath.split('/').filter(Boolean);
    return parts[0] || null;
  }

  /**
   * Check if the request explicitly asks to download the file
   * Recognizes ?download=true or ?download=1 (case-insensitive for key)
   */
  function isDownloadRequested(req) {
    const q = (req.url || '').split('?')[1] || '';
    if (!q) return false;
    const pairs = q.split('&');
    for (const p of pairs) {
      const [rawK, rawV] = p.split('=');
      const k = decodeURIComponent((rawK || '').trim()).toLowerCase();
      const v = decodeURIComponent((rawV || '').trim());
      if (k === 'download' && (v === '' || v === 'true' || v === '1')) {
        return true;
      }
    }
    return false;
  }

  /**
   * Helper function to stream file with error handling
   */
  function streamFile(res, readStream, fileObj) {
    readStream.on('error', (error) => {
      console.error('File stream error:', error);
      if (!res.headersSent) {
        res.writeHead(500);
        res.end('Error reading file');
      }
    });

    readStream.on('end', () => {
      if (!res.headersSent) {
        res.writeHead(200);
      }
    });

    readStream.pipe(res);
  }

  // ============================================================================
  // NEW METEOR-FILES ROUTES (URL-agnostic)
  // ============================================================================

  /**
   * Serve attachments from new Meteor-Files structure
   * Route: /cdn/storage/attachments/{fileId} or /cdn/storage/attachments/{fileId}/original/{filename}
   */
  WebApp.connectHandlers.use('/cdn/storage/attachments', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    try {
      const fileId = extractFirstIdFromUrl(req, '/cdn/storage/attachments');
      
      if (!fileId) {
        res.writeHead(400);
        res.end('Invalid attachment file ID');
        return;
      }

      // Get attachment from database
      const attachment = ReactiveCache.getAttachment(fileId);
      if (!attachment) {
        res.writeHead(404);
        res.end('Attachment not found');
        return;
      }

      // Check permissions
      const board = ReactiveCache.getBoard(attachment.meta.boardId);
      if (!board) {
        res.writeHead(404);
        res.end('Board not found');
        return;
      }

      // TODO: Implement proper authentication via cookies/headers
      // Meteor.userId() returns undefined in WebApp.connectHandlers middleware
      // For now, allow access - ostrio:files protected() method provides fallback auth
      // const userId = null; // Need to extract from req.headers.cookie
      // if (!board.isPublic() && (!userId || !board.hasMember(userId))) {
      //   res.writeHead(403);
      //   res.end('Access denied');
      //   return;
      // }

      // Handle conditional requests
      if (handleConditionalRequest(req, res, attachment)) {
        return;
      }

      // Get file strategy and stream
  const strategy = attachmentStoreFactory.getFileStrategy(attachment, 'original');
      const readStream = strategy.getReadStream();

      if (!readStream) {
        res.writeHead(404);
        res.end('Attachment file not found in storage');
        return;
      }

      // Set headers and stream file
      if (isDownloadRequested(req)) {
        // Force download if requested via query param
        res.setHeader('Cache-Control', 'public, max-age=31536000');
        res.setHeader('ETag', `"${attachment._id}"`);
        if (attachment.size) res.setHeader('Content-Length', attachment.size);
        res.setHeader('X-Content-Type-Options', 'nosniff');
        res.setHeader('Content-Type', 'application/octet-stream');
        res.setHeader('Content-Disposition', `attachment; filename="${attachment.name}"`);
        res.setHeader('Content-Security-Policy', "default-src 'none'; sandbox;");
      } else {
        setFileHeaders(res, attachment, true);
      }
      streamFile(res, readStream, attachment);

    } catch (error) {
      console.error('Attachment server error:', error);
      if (!res.headersSent) {
        res.writeHead(500);
        res.end('Internal server error');
      }
    }
  });

  /**
   * Serve avatars from new Meteor-Files structure
   * Route: /cdn/storage/avatars/{fileId} or /cdn/storage/avatars/{fileId}/original/{filename}
   */
  WebApp.connectHandlers.use('/cdn/storage/avatars', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    try {
      const fileId = extractFirstIdFromUrl(req, '/cdn/storage/avatars');
      
      if (!fileId) {
        res.writeHead(400);
        res.end('Invalid avatar file ID');
        return;
      }

      // Get avatar from database
      const avatar = ReactiveCache.getAvatar(fileId);
      if (!avatar) {
        res.writeHead(404);
        res.end('Avatar not found');
        return;
      }

      // TODO: Implement proper authentication for avatars
      // Meteor.userId() returns undefined in WebApp.connectHandlers middleware
      // For now, allow avatar viewing - they're typically public anyway

      // Handle conditional requests
      if (handleConditionalRequest(req, res, avatar)) {
        return;
      }

      // Get file strategy and stream
  const strategy = avatarStoreFactory.getFileStrategy(avatar, 'original');
      const readStream = strategy.getReadStream();

      if (!readStream) {
        res.writeHead(404);
        res.end('Avatar file not found in storage');
        return;
      }

      // Set headers and stream file
      setFileHeaders(res, avatar, false);
      streamFile(res, readStream, avatar);

    } catch (error) {
      console.error('Avatar server error:', error);
      if (!res.headersSent) {
        res.writeHead(500);
        res.end('Internal server error');
      }
    }
  });

  // ============================================================================
  // LEGACY COLLECTIONFS ROUTES (Backward compatibility)
  // ============================================================================

  /**
   * Serve legacy attachments from CollectionFS structure
   * Route: /cfs/files/attachments/{attachmentId}
   */
  WebApp.connectHandlers.use('/cfs/files/attachments', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    try {
      const attachmentId = extractFirstIdFromUrl(req, '/cfs/files/attachments');
      
      if (!attachmentId) {
        res.writeHead(400);
        res.end('Invalid attachment ID');
        return;
      }

      // Try to get attachment with backward compatibility
      const attachment = getAttachmentWithBackwardCompatibility(attachmentId);
      if (!attachment) {
        res.writeHead(404);
        res.end('Attachment not found');
        return;
      }

      // Check permissions
      const board = ReactiveCache.getBoard(attachment.meta.boardId);
      if (!board) {
        res.writeHead(404);
        res.end('Board not found');
        return;
      }

      // TODO: Implement proper authentication via cookies/headers
      // Meteor.userId() returns undefined in WebApp.connectHandlers middleware
      // For now, allow access for compatibility

      // Handle conditional requests
      if (handleConditionalRequest(req, res, attachment)) {
        return;
      }

      // For legacy attachments, try to get GridFS stream
  const fileStream = getOldAttachmentStream(attachmentId);
      if (fileStream) {
        if (isDownloadRequested(req)) {
          // Force download if requested
          res.setHeader('Cache-Control', 'public, max-age=31536000');
          res.setHeader('ETag', `"${attachment._id}"`);
          if (attachment.size) res.setHeader('Content-Length', attachment.size);
          res.setHeader('X-Content-Type-Options', 'nosniff');
          res.setHeader('Content-Type', 'application/octet-stream');
          res.setHeader('Content-Disposition', `attachment; filename="${attachment.name}"`);
          res.setHeader('Content-Security-Policy', "default-src 'none'; sandbox;");
        } else {
          setFileHeaders(res, attachment, true);
        }
        streamFile(res, fileStream, attachment);
      } else {
        res.writeHead(404);
        res.end('Legacy attachment file not found in GridFS');
      }

    } catch (error) {
      console.error('Legacy attachment server error:', error);
      if (!res.headersSent) {
        res.writeHead(500);
        res.end('Internal server error');
      }
    }
  });

  /**
   * Serve legacy avatars from CollectionFS structure
   * Route: /cfs/files/avatars/{avatarId}
   */
  WebApp.connectHandlers.use('/cfs/files/avatars', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    try {
      const avatarId = extractFirstIdFromUrl(req, '/cfs/files/avatars');
      
      if (!avatarId) {
        res.writeHead(400);
        res.end('Invalid avatar ID');
        return;
      }

      // Try to get avatar from database (new structure first)
      let avatar = ReactiveCache.getAvatar(avatarId);
      
      // If not found in new structure, try to handle legacy format
      if (!avatar) {
        // For legacy avatars, we might need to handle different ID formats
        // This is a fallback for old CollectionFS avatars
        res.writeHead(404);
        res.end('Avatar not found');
        return;
      }

      // TODO: Implement proper authentication for legacy avatars
      // Meteor.userId() returns undefined in WebApp.connectHandlers middleware
      // For now, allow avatar viewing for compatibility

      // Handle conditional requests
      if (handleConditionalRequest(req, res, avatar)) {
        return;
      }

      // Get file strategy and stream
  const strategy = avatarStoreFactory.getFileStrategy(avatar, 'original');
      const readStream = strategy.getReadStream();

      if (!readStream) {
        res.writeHead(404);
        res.end('Avatar file not found in storage');
        return;
      }

      // Set headers and stream file
      setFileHeaders(res, avatar, false);
      streamFile(res, readStream, avatar);

    } catch (error) {
      console.error('Legacy avatar server error:', error);
      if (!res.headersSent) {
        res.writeHead(500);
        res.end('Internal server error');
      }
    }
  });

  // ============================================================================
  // ALTERNATIVE ROUTES (For different URL patterns)
  // ============================================================================

  /**
   * Alternative attachment route for different URL patterns
   * Route: /attachments/{fileId}
   */
  WebApp.connectHandlers.use('/attachments', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    // Redirect to standard route
    const fileId = extractFirstIdFromUrl(req, '/attachments');
    const newUrl = `/cdn/storage/attachments/${fileId}`;
    res.writeHead(301, { 'Location': newUrl });
    res.end();
  });

  /**
   * Alternative avatar route for different URL patterns
   * Route: /avatars/{fileId}
   */
  WebApp.connectHandlers.use('/avatars', (req, res, next) => {
    if (req.method !== 'GET') {
      return next();
    }

    // Redirect to standard route
    const fileId = extractFirstIdFromUrl(req, '/avatars');
    const newUrl = `/cdn/storage/avatars/${fileId}`;
    res.writeHead(301, { 'Location': newUrl });
    res.end();
  });

  console.log('Universal file server initialized successfully');
}