const Busboy = require('busboy');
const JSZip = require('jszip');
const { applyCorsHeaders, handleCorsPreflight } = require('../lib/cors-middleware');

// Helper function to send JSON with proper headers
function sendJson(res, status, data) {
  res.setHeader('Content-Type', 'application/json');
  res.status(status).end(JSON.stringify(data));
}

module.exports = async (req, res) => {
  if (handleCorsPreflight(req, res, { allowedMethods: 'POST, OPTIONS' })) {
    return;
  }
  applyCorsHeaders(req, res, { allowedMethods: 'POST, OPTIONS' });

  if (req.method !== 'POST') {
    sendJson(res, 405, { error: 'Method not allowed' });
    return;
  }

  try {
    const busboy = Busboy({ headers: req.headers });
    let fileData = null;
    let filename = null;

    busboy.on('file', (fieldname, file, info) => {
      filename = info.filename;
      const chunks = [];
      
      file.on('data', (chunk) => {
        chunks.push(chunk);
      });
      
      file.on('end', () => {
        fileData = Buffer.concat(chunks);
      });
    });

    busboy.on('finish', async () => {
      if (!fileData || !filename) {
        res.status(400).json({ error: 'No file uploaded' });
        return;
      }

      if (!filename.toLowerCase().endsWith('.docx')) {
        res.status(400).json({ error: 'Please upload a .docx file' });
        return;
      }

      try {
        const remediatedFile = await remediateDocx(fileData, filename);
        
        // Always fix filename: replace underscores with hyphens and add -remediated suffix
        let suggestedName = filename
          .replace(/_/g, '-')  // Replace all underscores with hyphens
          .replace(/\.docx$/i, '-remediated.docx');  // Add -remediated before extension

        res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document');
        res.setHeader('Content-Disposition', `attachment; filename="${suggestedName}"`);
        res.status(200).send(remediatedFile);
        
      } catch (error) {
        res.status(500).json({ error: error.message });
      }
    });

    req.pipe(busboy);

  } catch (error) {
    res.status(500).json({ error: error.message });
  }
};

async function remediateDocx(fileData, filename) {
  try {
    const zip = await JSZip.loadAsync(fileData);
    
    // Helper function to write only if content changed
    const writeIfChanged = (filename, original, modified) => {
      if (original !== modified && modified !== null) {
        zip.file(filename, modified);
        return true;
      }
      return false;
    };
    
    // Process document.xml
    const docFile = zip.file('word/document.xml');
    if (docFile) {
      const origDocXml = await docFile.async('string');
      const afterShadows = removeShadowsOnly(origDocXml);
      const afterInlineContent = applyInlineContentFixes(afterShadows || origDocXml);
      writeIfChanged('word/document.xml', origDocXml, afterInlineContent);
    }
    
    // Process styles.xml
    const stylesFile = zip.file('word/styles.xml');
    if (stylesFile) {
      const origStylesXml = await stylesFile.async('string');
      const afterStylesShadows = removeShadowsOnly(origStylesXml);
      writeIfChanged('word/styles.xml', origStylesXml, afterStylesShadows);
    }
    
    // Process theme files
    const themeFile = zip.file('word/theme/theme1.xml');
    if (themeFile) {
      const origThemeXml = await themeFile.async('string');
      const afterTheme = removeShadowsOnly(origThemeXml);
      writeIfChanged('word/theme/theme1.xml', origThemeXml, afterTheme);
    }
    
    // Protection removal
    try {
      const settingsFile = zip.file('word/settings.xml');
      if (settingsFile) {
        const origSettings = await settingsFile.async('string');
        const hasAnyProt = /<w:(?:documentProtection|writeProtection|readOnlyRecommended|editRestrictions|formProtection|protection|docProtection|enforcement|locked|trackRevisions|crypt)\b/.test(origSettings);
        if (hasAnyProt) {
          let cleaned = origSettings;
          
          cleaned = cleaned.replace(/<w:(?:documentProtection|writeProtection|readOnlyRecommended|editRestrictions|formProtection|protection|docProtection)[^>]*\/>/g, '');
          cleaned = cleaned.replace(/<w:(?:documentProtection|writeProtection|readOnlyRecommended|editRestrictions|formProtection|protection|docProtection)[^>]*>[\s\S]*?<\/w:(?:documentProtection|writeProtection|readOnlyRecommended|editRestrictions|formProtection|protection|docProtection)>/g, '');
          cleaned = cleaned.replace(/<w:(?:enforcement|locked|trackRevisions)[^>]*\/>/g, '');
          cleaned = cleaned.replace(/<w:(?:enforcement|locked|trackRevisions)[^>]*>[\s\S]*?<\/w:(?:enforcement|locked|trackRevisions)>/g, '');
          cleaned = cleaned.replace(/<w:crypt[^>]*\/>/g, '');
          cleaned = cleaned.replace(/<w:crypt[^>]*>[\s\S]*?<\/w:crypt[^>]*>/g, '');
          cleaned = cleaned.replace(/\s?w:(?:locked|trackRevisions|enforcement)="[^"]*"/g, '');
          
          writeIfChanged('word/settings.xml', origSettings, cleaned);
        }
      }
    } catch (e) {
      console.warn('[remediateDocx] Protection removal failed:', e.message);
    }
    
    // Generate with proper compression
    const remediatedBuffer = await zip.generateAsync({ 
      type: 'nodebuffer',
      compression: 'DEFLATE',
      compressionOptions: { level: 6 }
    });
    
    return remediatedBuffer;
    
  } catch (error) {
    throw new Error(`Failed to remediate document: ${error.message}`);
  }
}



function applyInlineContentFixes(xmlContent) {
  if (!xmlContent) return null;
  
  const original = xmlContent;
  let fixedXml = xmlContent;

  // Apply the same patterns as in the analysis function
  const floatingPatterns = [
    // DrawingML anchor patterns (modern Word drawings)
    {
      pattern: /<wp:anchor[^>]*>([\s\S]*?)<\/wp:anchor>/g,
      replacement: function(match, content) {
        // Convert anchor (floating) to inline
        return `<wp:inline>${content}</wp:inline>`;
      }
    },
    // Text wrapping patterns
    {
      pattern: /<wp:wrapSquare[^>]*\/>/g,
      replacement: ''
    },
    {
      pattern: /<wp:wrapTight[^>]*>[\s\S]*?<\/wp:wrapTight>/g,
      replacement: ''
    },
    {
      pattern: /<wp:wrapThrough[^>]*>[\s\S]*?<\/wp:wrapThrough>/g,
      replacement: ''
    },
    {
      pattern: /<wp:wrapTopAndBottom[^>]*\/>/g,
      replacement: ''
    },
    {
      pattern: /<wp:wrapNone[^>]*\/>/g,
      replacement: ''
    },
    // Position and alignment patterns
    {
      pattern: /<wp:positionH[^>]*>[\s\S]*?<\/wp:positionH>/g,
      replacement: ''
    },
    {
      pattern: /<wp:positionV[^>]*>[\s\S]*?<\/wp:positionV>/g,
      replacement: ''
    },
    // VML patterns for legacy compatibility
    {
      pattern: /mso-position-horizontal:[^;]*;?/g,
      replacement: ''
    },
    {
      pattern: /mso-position-vertical:[^;]*;?/g,
      replacement: ''
    },
    {
      pattern: /mso-wrap-style:[^;]*;?/g,
      replacement: ''
    },
    {
      pattern: /left:\s*[^;]*;?/g,
      replacement: ''
    },
    {
      pattern: /top:\s*[^;]*;?/g,
      replacement: ''
    }
  ];

  // Apply fixes for floating elements
  floatingPatterns.forEach(patternObj => {
    const { pattern, replacement } = patternObj;
    
    if (typeof replacement === 'function') {
      fixedXml = fixedXml.replace(pattern, replacement);
    } else {
      fixedXml = fixedXml.replace(pattern, replacement);
    }
  });

  // Special handling for drawing elements - ensure they are inline
  const drawingPattern = /<w:drawing[^>]*>[\s\S]*?<\/w:drawing>/g;
  const drawingMatches = fixedXml.match(drawingPattern);
  
  if (drawingMatches) {
    drawingMatches.forEach(drawing => {
      // Check if this drawing contains floating elements
      if (drawing.includes('wp:anchor') && !drawing.includes('wp:inline')) {
        // Convert anchor to inline within the drawing
        let fixedDrawing = drawing.replace(/<wp:anchor[^>]*>/g, '<wp:inline>');
        fixedDrawing = fixedDrawing.replace(/<\/wp:anchor>/g, '</wp:inline>');
        
        if (fixedDrawing !== drawing) {
          fixedXml = fixedXml.replace(drawing, fixedDrawing);
        }
      }
    });
  }

  // If nothing changed, return null
  if (fixedXml === original) return null;
  return fixedXml;
}

function removeShadowsOnly(xmlContent) {
  const original = xmlContent;
  let fixedXml = xmlContent;
  
  // 1. Remove basic Word text shadows
  fixedXml = fixedXml.replace(/<w:shadow\s*\/>/g, '');
  fixedXml = fixedXml.replace(/<w:shadow[^>]*>.*?<\/w:shadow>/g, '');
  fixedXml = fixedXml.replace(/\s+\w*shadow\w*\s*=\s*"[^"]*"/g, '');
  
  // 2. Remove advanced DrawingML shadow effects
  fixedXml = fixedXml.replace(/<a:outerShdw[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<a:outerShdw[^>]*>.*?<\/a:outerShdw>/g, '');
  fixedXml = fixedXml.replace(/<a:innerShdw[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<a:innerShdw[^>]*>.*?<\/a:innerShdw>/g, '');
  fixedXml = fixedXml.replace(/<a:prstShdw[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<a:prstShdw[^>]*>.*?<\/a:prstShdw>/g, '');
  
  // 3. Remove Office 2010+ shadow effects
  fixedXml = fixedXml.replace(/<w14:shadow[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<w14:shadow[^>]*>.*?<\/w14:shadow>/g, '');
  fixedXml = fixedXml.replace(/<w15:shadow[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<w15:shadow[^>]*>.*?<\/w15:shadow>/g, '');
  
  // 4. Remove shadow-related text effects and 3D properties
  fixedXml = fixedXml.replace(/<w14:glow[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<w14:glow[^>]*>.*?<\/w14:glow>/g, '');
  fixedXml = fixedXml.replace(/<w14:reflection[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<w14:reflection[^>]*>.*?<\/w14:reflection>/g, '');
  fixedXml = fixedXml.replace(/<w14:props3d[^>]*\/>/g, '');
  fixedXml = fixedXml.replace(/<w14:props3d[^>]*>.*?<\/w14:props3d>/g, '');
  
  // 5. Remove shadow properties and attributes (safely)
  // Remove only within attribute values, not entire element names
  fixedXml = fixedXml.replace(/\s+\w*shdw\w*\s*=\s*"[^"]*"/g, '');
  
  // NOTE: Font normalization, font size fixes, and line spacing fixes have been 
  // removed - these are now flagged for user attention instead of auto-fixed
  
  // If nothing changed, return null so callers can avoid rewriting the part
  if (fixedXml === original) return null;
  return fixedXml;
}