/* Shared SVG optimisation used by the generator UI (index.html) and the embed page (404.html). */
(function(global) {
  'use strict';

  function optimizeSVG(svg) {
    // Parse the existing SVG to extract the QR data
    const uses = svg.querySelectorAll('use');
    const qrData = [];
    let maxX = 0, maxY = 0;
    
    // Extract positions from use elements
    uses.forEach(use => {
      const x = parseInt(use.getAttribute('x') || '0');
      const y = parseInt(use.getAttribute('y') || '0');
      if (!qrData[y]) qrData[y] = [];
      qrData[y][x] = true;
      maxX = Math.max(maxX, x);
      maxY = Math.max(maxY, y);
    });
    
    // Get the color from the original template
    const template = svg.querySelector('#template, rect[id]');
    const color = template ? template.getAttribute('fill') || '#000' : '#000';
    
    // Create optimized SVG
    const optimizedSVG = createOptimizedSVG(qrData, maxX + 1, maxY + 1, color);
    
    // Replace the old SVG with the optimized one
    svg.parentNode.replaceChild(optimizedSVG, svg);
    
    return optimizedSVG;
  }

  function createOptimizedSVG(qrData, width, height, color) {
    const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
    svg.setAttribute('xmlns', 'http://www.w3.org/2000/svg');
    svg.setAttribute('viewBox', `0 0 ${width} ${height}`);
    svg.setAttribute('width', width * 10);
    svg.setAttribute('height', height * 10);
    
    // Create defs section with reusable cell (no fill - will inherit)
    const defs = document.createElementNS('http://www.w3.org/2000/svg', 'defs');
    const cellTemplate = document.createElementNS('http://www.w3.org/2000/svg', 'rect');
    cellTemplate.setAttribute('id', 'cell');
    cellTemplate.setAttribute('width', '1');
    cellTemplate.setAttribute('height', '1');
    defs.appendChild(cellTemplate);
    svg.appendChild(defs);
    
    // Create main group with fill color
    const mainGroup = document.createElementNS('http://www.w3.org/2000/svg', 'g');
    mainGroup.setAttribute('fill', color);
    svg.appendChild(mainGroup);
    
    // Create optimized structure
    for (let y = 0; y < height; y++) {
      if (!qrData[y]) continue;
      
      // Find consecutive cells and group them
      let x = 0;
      while (x < width) {
        if (qrData[y][x]) {
          // Count consecutive cells
          let consecutiveCount = 1;
          while (x + consecutiveCount < width && qrData[y][x + consecutiveCount]) {
            consecutiveCount++;
          }
          
          if (consecutiveCount > 1) {
            // Use a single rect for multiple consecutive cells (inherits fill from group)
            const rect = document.createElementNS('http://www.w3.org/2000/svg', 'rect');
            rect.setAttribute('x', x);
            rect.setAttribute('y', y);
            rect.setAttribute('width', consecutiveCount);
            rect.setAttribute('height', '1');
            mainGroup.appendChild(rect);
          } else {
            // Use individual use elements for single cells (inherits fill from group)
            const use = document.createElementNS('http://www.w3.org/2000/svg', 'use');
            use.setAttribute('href', '#cell');
            use.setAttribute('x', x);
            use.setAttribute('y', y);
            mainGroup.appendChild(use);
          }
          
          x += consecutiveCount;
        } else {
          x++;
        }
      }
    }
    
    return svg;
  }

  global.optimizeQRSVG = optimizeSVG;
})(window);