const express = require('express');
const path = require('path');
const fs = require('fs');
const { requireAuth, requireRole } = require('../middleware/auth');
const logAudit = require('../helpers/auditLog');

function createKnowledgeBaseRouter(db, upload) {
  const router = express.Router();

  // Helper to sanitize filename
  function sanitizePathSegment(segment) {
    if (!segment || typeof segment !== 'string') return '';
    return segment
      .replace(/\0/g, '')
      .replace(/\.\./g, '')
      .replace(/[\/\\]/g, '')
      .trim();
  }

  // Helper to generate slug from title
  function generateSlug(title) {
    return title
      .toLowerCase()
      .replace(/[^a-z0-9]+/g, '-')
      .replace(/^-+|-+$/g, '')
      .substring(0, 200);
  }

  // Helper to validate file type
  const ALLOWED_EXTENSIONS = new Set([
    '.pdf', '.md', '.txt', '.doc', '.docx',
    '.xls', '.xlsx', '.ppt', '.pptx',
    '.html', '.htm', '.json', '.yaml', '.yml',
    '.png', '.jpg', '.jpeg', '.gif'
  ]);

  function isValidFileType(filename) {
    const ext = path.extname(filename).toLowerCase();
    return ALLOWED_EXTENSIONS.has(ext);
  }

  // POST /api/knowledge-base/upload - Upload new document
  router.post('/upload', requireAuth(db), requireRole(db, 'editor', 'admin'), (req, res, next) => {
    upload.single('file')(req, res, (err) => {
      if (err) {
        console.error('[KB Upload] Multer error:', err);
        return res.status(400).json({ error: err.message || 'File upload failed' });
      }
      next();
    });
  }, async (req, res) => {
    console.log('[KB Upload] Request received:', {
      hasFile: !!req.file,
      body: req.body,
      contentType: req.headers['content-type']
    });

    const uploadedFile = req.file;
    const { title, description, category } = req.body;

    // Validate required fields
    if (!title || !title.trim()) {
      console.error('[KB Upload] Error: Title is missing');
      if (uploadedFile) fs.unlinkSync(uploadedFile.path);
      return res.status(400).json({ error: 'Title is required' });
    }

    if (!uploadedFile) {
      return res.status(400).json({ error: 'No file uploaded' });
    }

    // Validate file type
    if (!isValidFileType(uploadedFile.originalname)) {
      fs.unlinkSync(uploadedFile.path);
      return res.status(400).json({ error: 'File type not allowed' });
    }

    const timestamp = Date.now();
    const sanitizedName = sanitizePathSegment(uploadedFile.originalname);
    const slug = generateSlug(title);
    const kbDir = path.join(__dirname, '..', 'uploads', 'knowledge_base');

    // Create directory if it doesn't exist
    if (!fs.existsSync(kbDir)) {
      fs.mkdirSync(kbDir, { recursive: true });
    }

    const filename = `${timestamp}_${sanitizedName}`;
    const filePath = path.join(kbDir, filename);

    try {
      // Move uploaded file to permanent location
      fs.renameSync(uploadedFile.path, filePath);

      // Check if slug already exists
      db.get('SELECT id FROM knowledge_base WHERE slug = ?', [slug], (err, row) => {
        if (err) {
          fs.unlinkSync(filePath);
          console.error('Error checking slug:', err);
          return res.status(500).json({ error: 'Database error' });
        }

        // If slug exists, append timestamp to make it unique
        const finalSlug = row ? `${slug}-${timestamp}` : slug;

        // Insert new knowledge base entry
        const insertSql = `
          INSERT INTO knowledge_base (
            title, slug, description, category, file_path, file_name,
            file_type, file_size, created_by
          ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
        `;

        db.run(
          insertSql,
          [
            title.trim(),
            finalSlug,
            description || null,
            category || 'General',
            filePath,
            sanitizedName,
            uploadedFile.mimetype,
            uploadedFile.size,
            req.user.id
          ],
          function (err) {
            if (err) {
              fs.unlinkSync(filePath);
              console.error('Error inserting knowledge base entry:', err);
              return res.status(500).json({ error: 'Failed to save document metadata' });
            }

            // Log audit entry
            logAudit(
              db,
              req.user.id,
              req.user.username,
              'CREATE_KB_ARTICLE',
              'knowledge_base',
              this.lastID,
              JSON.stringify({ title: title.trim(), filename: sanitizedName }),
              req.ip
            );

            res.json({
              success: true,
              id: this.lastID,
              title: title.trim(),
              slug: finalSlug,
              category: category || 'General'
            });
          }
        );
      });
    } catch (error) {
      // Clean up file on error
      if (fs.existsSync(filePath)) fs.unlinkSync(filePath);
      console.error('Error uploading knowledge base document:', error);
      res.status(500).json({ error: error.message || 'Failed to upload document' });
    }
  });

  // GET /api/knowledge-base - List all articles
  router.get('/', requireAuth(db), (req, res) => {
    const sql = `
      SELECT
        kb.id, kb.title, kb.slug, kb.description, kb.category,
        kb.file_name, kb.file_type, kb.file_size, kb.created_at, kb.updated_at,
        u.username as created_by_username
      FROM knowledge_base kb
      LEFT JOIN users u ON kb.created_by = u.id
      ORDER BY kb.created_at DESC
    `;

    db.all(sql, [], (err, rows) => {
      if (err) {
        console.error('Error fetching knowledge base articles:', err);
        return res.status(500).json({ error: 'Failed to fetch articles' });
      }

      res.json(rows);
    });
  });

  // GET /api/knowledge-base/:id - Get single article details
  router.get('/:id', requireAuth(db), (req, res) => {
    const { id } = req.params;

    const sql = `
      SELECT
        kb.id, kb.title, kb.slug, kb.description, kb.category,
        kb.file_name, kb.file_type, kb.file_size, kb.created_at, kb.updated_at,
        u.username as created_by_username
      FROM knowledge_base kb
      LEFT JOIN users u ON kb.created_by = u.id
      WHERE kb.id = ?
    `;

    db.get(sql, [id], (err, row) => {
      if (err) {
        console.error('Error fetching article:', err);
        return res.status(500).json({ error: 'Failed to fetch article' });
      }

      if (!row) {
        return res.status(404).json({ error: 'Article not found' });
      }

      res.json(row);
    });
  });

  // GET /api/knowledge-base/:id/content - Get document content for display
  router.get('/:id/content', requireAuth(db), (req, res) => {
    const { id } = req.params;

    const sql = 'SELECT file_path, file_name, file_type FROM knowledge_base WHERE id = ?';

    db.get(sql, [id], (err, row) => {
      if (err) {
        console.error('Error fetching document:', err);
        return res.status(500).json({ error: 'Failed to fetch document' });
      }

      if (!row) {
        return res.status(404).json({ error: 'Document not found' });
      }

      if (!fs.existsSync(row.file_path)) {
        return res.status(404).json({ error: 'File not found on disk' });
      }

      // Log audit entry
      logAudit(
        db,
        req.user.id,
        req.user.username,
        'VIEW_KB_ARTICLE',
        'knowledge_base',
        id,
        JSON.stringify({ filename: row.file_name }),
        req.ip
      );

      // Determine content type for inline display
      let contentType = row.file_type || 'application/octet-stream';

      // For markdown files, send as plain text so frontend can parse it
      if (row.file_name.endsWith('.md')) {
        contentType = 'text/plain; charset=utf-8';
      } else if (row.file_name.endsWith('.txt')) {
        contentType = 'text/plain; charset=utf-8';
      }

      res.setHeader('Content-Type', contentType);
      // Use inline instead of attachment to allow browser to display
      res.setHeader('Content-Disposition', `inline; filename="${row.file_name}"`);
      // Allow iframe embedding from frontend origin
      res.removeHeader('X-Frame-Options');
      res.setHeader('Content-Security-Policy', "frame-ancestors 'self' http://71.85.90.9:3000 http://localhost:3000");
      res.sendFile(row.file_path);
    });
  });

  // GET /api/knowledge-base/:id/download - Download document
  router.get('/:id/download', requireAuth(db), (req, res) => {
    const { id } = req.params;

    const sql = 'SELECT file_path, file_name, file_type FROM knowledge_base WHERE id = ?';

    db.get(sql, [id], (err, row) => {
      if (err) {
        console.error('Error fetching document:', err);
        return res.status(500).json({ error: 'Failed to fetch document' });
      }

      if (!row) {
        return res.status(404).json({ error: 'Document not found' });
      }

      if (!fs.existsSync(row.file_path)) {
        return res.status(404).json({ error: 'File not found on disk' });
      }

      // Log audit entry
      logAudit(
        db,
        req.user.id,
        req.user.username,
        'DOWNLOAD_KB_ARTICLE',
        'knowledge_base',
        id,
        JSON.stringify({ filename: row.file_name }),
        req.ip
      );

      res.setHeader('Content-Type', row.file_type || 'application/octet-stream');
      res.setHeader('Content-Disposition', `attachment; filename="${row.file_name}"`);
      res.sendFile(row.file_path);
    });
  });

  // DELETE /api/knowledge-base/:id - Delete article
  router.delete('/:id', requireAuth(db), requireRole(db, 'editor', 'admin'), (req, res) => {
    const { id } = req.params;

    const sql = 'SELECT file_path, title FROM knowledge_base WHERE id = ?';

    db.get(sql, [id], (err, row) => {
      if (err) {
        console.error('Error fetching article for deletion:', err);
        return res.status(500).json({ error: 'Failed to fetch article' });
      }

      if (!row) {
        return res.status(404).json({ error: 'Article not found' });
      }

      // Delete database record
      db.run('DELETE FROM knowledge_base WHERE id = ?', [id], (err) => {
        if (err) {
          console.error('Error deleting article:', err);
          return res.status(500).json({ error: 'Failed to delete article' });
        }

        // Delete file
        if (fs.existsSync(row.file_path)) {
          fs.unlinkSync(row.file_path);
        }

        // Log audit entry
        logAudit(
          db,
          req.user.id,
          req.user.username,
          'DELETE_KB_ARTICLE',
          'knowledge_base',
          id,
          JSON.stringify({ title: row.title }),
          req.ip
        );

        res.json({ success: true });
      });
    });
  });

  return router;
}

module.exports = createKnowledgeBaseRouter;