const express = require('express');
const bodyParser = require('body-parser');
const multer = require('multer');
const cheerio = require('cheerio');
const { minifyHtml } = require('./minify');
const { removeMedia } = require('./removeMedia');

const app = express();

// Configure size limits
const MAX_SIZE = '50mb';

// Configure multer with size limits
const upload = multer({
  limits: {
    fileSize: 50 * 1024 * 1024, // 50MB limit
    fieldSize: 50 * 1024 * 1024 // 50MB limit for fields
  }
});

// Configure body parsers with consistent limits
app.use(express.static('public'));
app.use(bodyParser.json({limit: MAX_SIZE}));
app.use(bodyParser.urlencoded({
  extended: true,
  limit: MAX_SIZE,
  parameterLimit: 50000
}));
app.use(express.json({limit: MAX_SIZE}));
app.use(express.urlencoded({
  limit: MAX_SIZE,
  extended: true,
  parameterLimit: 50000
}));

function compressHtmlForLlm(html, options = {}) {
  const operationStatus = {
    minification: { success: false, error: null },
    cheerioLoad: { success: false, error: null },
    headCleaning: { success: false, error: null },
    scriptRemoval: { success: false, error: null },
    styleRemoval: { success: false, error: null },
    mediaRemoval: { success: false, error: null }, 
    repeatingElements: { success: false, error: null },
    textTruncation: { success: false, error: null }
  };

  let processed = html;
  let $ = null;

  // Step 1: Minification
  if (options.minifyHtml) {
    const minifyResult = minifyHtml(html, {
      removeScripts: options.removeScripts,
      removeStyles: options.removeStyles
    });
    
    if (minifyResult.success) {
      processed = minifyResult.minifiedHtml;
      operationStatus.minification = { success: true, error: null };
    } else {
      operationStatus.minification = { 
        success: false, 
        error: minifyResult.error?.message || 'Minification failed'
      };
    }
  }

  // Step 2: Load with Cheerio
  try {
    $ = cheerio.load(processed, { 
      decodeEntities: false,
      xmlMode: false,
      lowerCaseTags: true
    });
    operationStatus.cheerioLoad.success = true;
  } catch (err) {
    operationStatus.cheerioLoad.error = err.message.substring(0, 100);
    console.error('Cheerio load failed:', err);
    return { html: processed, status: operationStatus };
  }

  // Step 3: Remove scripts
  if (options.removeScripts) {
    try {
      $('script').remove();
      operationStatus.scriptRemoval.success = true;
    } catch (err) {
      operationStatus.scriptRemoval.error = err.message.substring(0, 100);
      console.warn('Script removal failed:', err);
    }
  }

  // Step 4: Remove styles
  if (options.removeStyles) {
    try {
      $('style').remove();
      $('link[rel="stylesheet"]').remove();
      operationStatus.styleRemoval.success = true;
    } catch (err) {
      operationStatus.styleRemoval.error = err.message.substring(0, 100);
      console.warn('Style removal failed:', err);
    }
  }

  // Step 5: Remove media
  if (options.removeMedia) {
    try {
      const mediaResult = removeMedia($);
      if (mediaResult.success) {
        operationStatus.mediaRemoval.success = true;
      } else {
        operationStatus.mediaRemoval.error = mediaResult.error.substring(0, 100);
        console.warn('Media removal failed:', mediaResult.error);
      }
    } catch (err) {
      operationStatus.mediaRemoval.error = err.message.substring(0, 100);
      console.warn('Media removal failed:', err);
    }
  }

  // Step 6: Clean head
  if (options.cleanHead) {
    try {
      cleanHead($);
      operationStatus.headCleaning.success = true;
    } catch (err) {
      operationStatus.headCleaning.error = err.message.substring(0, 100);
    }
  }

  // Step 7: Handle repeating elements
  if (options.handleRepeatingElements) {
    try {
      handleRepeatingElements($);
      operationStatus.repeatingElements.success = true;
    } catch (err) {
      operationStatus.repeatingElements.error = err.message.substring(0, 100);
    }
  }

  // Step 8: Truncate text
  if (options.truncateText) {
    try {
      truncateText($, options.truncateLength);
      operationStatus.textTruncation.success = true;
    } catch (err) {
      operationStatus.textTruncation.error = err.message.substring(0, 100);
    }
  }

  let finalHtml = '';
  try {
    finalHtml = $.html();
  } catch (err) {
    console.error('Final HTML generation failed:', err);
    finalHtml = processed;
  }

  const structure = generateStructureJson($);

  return {
    html: finalHtml,
    json: JSON.stringify(structure, null, 2),
    status: operationStatus
  };
}

function cleanHead($) {
  $('head').each((_, head) => {
    $(head).find('link').remove();
    $(head).find('script').remove();
    $(head).find('meta').each((_, meta) => {
      const name = $(meta).attr('name')?.toLowerCase();
      const property = $(meta).attr('property')?.toLowerCase();
      if (!['charset', 'viewport', 'description', 'keywords'].includes(name) && 
          !property?.includes('og:')) {
        $(meta).remove();
      }
    });
  });
}

function handleRepeatingElements($) {
  $('*').each((_, elem) => {
    const $elem = $(elem);
    const children = $elem.children();
    if (children.length > 3 && areElementsSimilar(children, $)) {
      children.slice(1, -1).each((i, child) => {
        if (i !== Math.floor(children.length / 2) - 1) {
          $(child).remove();
        }
      });
    }
  });
}

function truncateText($, truncateLength) {
  $('*').each((_, elem) => {
    const $elem = $(elem);
    if ($elem.children().length === 0) {
      let text = $elem.text();
      if (text.length > truncateLength) {
        text = text.substring(0, truncateLength/2) + '...' + 
               text.substring(text.length - truncateLength/2);
        $elem.text(text);
      }
    }
  });
}

function areElementsSimilar(elements, $) {
  if (elements.length < 4) return false;
  
  const firstTag = elements[0].tagName;
  const firstClasses = $(elements[0]).attr('class');
  
  let similarCount = 0;
  elements.each((_, elem) => {
    if (elem.tagName === firstTag && $(elem).attr('class') === firstClasses) {
      similarCount++;
    }
  });

  return similarCount / elements.length > 0.7;
}

function generateStructureJson($) {
  try {
    const structure = [];
    $('*').each((_, el) => {
      const $el = $(el);
      const attributes = {};
      
      Object.entries($el.attr() || {}).forEach(([key, value]) => {
        attributes[key] = value;
      });

      const textContent = $el.clone().children().remove().end().text().trim();
      const truncatedText = textContent.length > 50 
        ? textContent.substring(0, 25) + '...' + textContent.substring(textContent.length - 25)
        : textContent;

      structure.push({
        tag: el.tagName,
        attributes: Object.keys(attributes).length ? attributes : undefined,
        textContent: truncatedText || undefined,
        childrenCount: $el.children().length,
        selector: generateSelector($, el)
      });
    });
    return structure;
  } catch (err) {
    console.error('Structure generation failed:', err);
    return [];
  }
}

function generateSelector($, element) {
  try {
    const $el = $(element);
    let selector = element.tagName;
    
    if ($el.attr('id')) {
      selector += `#${$el.attr('id')}`;
    } else if ($el.attr('class')) {
      selector += `.${$el.attr('class').replace(/\s+/g, '.')}`;
    }
    
    return selector;
  } catch (err) {
    console.warn('Selector generation failed:', err);
    return element.tagName || 'unknown';
  }
}

function computeStats(html, processed) {
  try {
    const $ = cheerio.load(html);
    const $processed = cheerio.load(processed);

    const stats = {
      originalElementCount: $('*').length,
      processedElementCount: $processed('*').length,
      originalTextLength: html.length,
      processedTextLength: processed.length,
    };

    return {
      elementReduction: `${(1 - stats.processedElementCount / stats.originalElementCount) * 100}%`,
      sizeReduction: `${(1 - stats.processedTextLength / stats.originalTextLength) * 100}%`,
      originalElements: stats.originalElementCount,
      remainingElements: stats.processedElementCount,
      originalSize: stats.originalTextLength,
      processedSize: stats.processedTextLength
    };
  } catch (err) {
    console.error('Stats computation failed:', err);
    return {
      elementReduction: 'N/A',
      sizeReduction: 'N/A',
      originalElements: 'N/A',
      remainingElements: 'N/A',
      originalSize: html.length,
      processedSize: processed.length
    };
  }
}

function validateScript(scriptContent) {
  if (!scriptContent.includes('function extract(')) {
    throw new Error('Script must contain a function named "extract"');
  }
}

function executeCheerioScript(html, scriptContent) {
  try {
    validateScript(scriptContent);
    
    const context = {
      cheerio,
      input: html
    };

    const extractorFunction = new Function('input', 'cheerio', `
      ${scriptContent}
      return extract(input, cheerio);
    `);

    const result = extractorFunction(html, cheerio);

    if (!result || typeof result !== 'object') {
      throw new Error('Extract function must return an object');
    }

    if (!('success' in result && 'data' in result && 'error' in result)) {
      throw new Error('Return object must contain success, data, and error fields');
    }

    return result;

  } catch (err) {
    return {
      success: false,
      data: null,
      error: err.message
    };
  }
}

app.post('/process', upload.single('htmlFile'), (req, res) => {
  try {
    const startTime = Date.now();
    let htmlContent = req.file 
      ? req.file.buffer.toString('utf8')
      : req.body.html || '';

    if (!htmlContent.trim()) {
      return res.status(400).json({ error: 'No HTML content provided.' });
    }

    const options = {
      cleanHead: req.body.cleanHead === 'true',
      removeScripts: req.body.removeScripts === 'true',
      removeStyles: req.body.removeStyles === 'true',
      handleRepeatingElements: req.body.handleRepeatingElements === 'true',
      truncateText: req.body.truncateText === 'true',
      truncateLength: parseInt(req.body.truncateLength) || 100,
      minifyHtml: req.body.minifyHtml === 'true',
      removeMedia: req.body.removeMedia === 'true'
    };

    const processed = compressHtmlForLlm(htmlContent, options);
    const stats = computeStats(htmlContent, processed.html);

    return res.json({
      success: true,
      result: processed,
      stats: {
        processingTime: `${Date.now() - startTime}ms`,
        elementReduction: stats.elementReduction,
        sizeReduction: stats.sizeReduction,
        originalElements: stats.originalElements,
        remainingElements: stats.remainingElements,
        originalSize: `${stats.originalSize} chars`,
        processedSize: `${stats.processedSize} chars`
      },
      options,
      operationStatus: processed.status
    });

  } catch (err) {
    console.error('Processing failed:', err);
    return res.status(500).json({ 
      error: 'Internal server error.',
      details: err.message.substring(0, 100)
    });
  }
});

app.post('/extract', upload.single('htmlFile'), (req, res) => {
  try {
    const startTime = Date.now();
    let htmlContent = req.file 
      ? req.file.buffer.toString('utf8')
      : req.body.html || '';

    const extractorScript = req.body.script;

    if (!htmlContent.trim()) {
      return res.status(400).json({ error: 'No HTML content provided.' });
    }

    if (!extractorScript) {
      return res.status(400).json({ error: 'No extractor script provided.' });
    }

    const result = executeCheerioScript(htmlContent, extractorScript);

    return res.json({
      success: result.success,
      data: result.data,
      error: result.error,
      processingTime: `${Date.now() - startTime}ms`
    });

  } catch (err) {
    console.error('Extraction failed:', err);
    return res.status(500).json({ 
      success: false,
      error: 'Internal server error.',
      details: err.message.substring(0, 100)
    });
  }
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`);
});