// Matrix rain background effect — header-scoped build for packages.danix.xyz
// Derived from danix2-hugo-theme/assets/js/matrix-rain.js
(function() {
  if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) return;

  var header = document.querySelector('.site-header');
  if (!header) return;

  // Canvas
  var canvas = document.createElement('canvas');
  canvas.id = 'matrix-rain';
  canvas.style.cssText = 'position:absolute;top:0;right:0;height:100%;pointer-events:none;z-index:0;';
  header.appendChild(canvas);

  // Gradient fade div — covers left portion of canvas area, left→transparent
  var fade = document.createElement('div');
  fade.style.cssText = 'position:absolute;top:0;right:0;bottom:0;width:65%;background:linear-gradient(to right,var(--bg-card) 0%,transparent 60%);pointer-events:none;z-index:1;';
  header.appendChild(fade);

  var ctx = canvas.getContext('2d');

  var columns = [];
  var frameCount = 0;
  var colors = { accent: '#5c9cf5', accent2: '#4ec97b', bg: '#161b25', head: '#ffffff' };

  var ASCII = Array.from({ length: 94 }, function(_, i) { return String.fromCharCode(33 + i); });
  var KATA  = Array.from({ length: 96 }, function(_, i) { return String.fromCodePoint(0x30a0 + i); });
  var CHARS = shuffle([].concat(ASCII, KATA, KATA, KATA));

  function shuffle(arr) {
    for (var i = arr.length - 1; i > 0; i--) {
      var j = Math.floor(Math.random() * (i + 1));
      var tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp;
    }
    return arr;
  }

  function hexToRgba(color, alpha) {
    var rgbMatch = color.match(/rgb\((\d+),\s*(\d+),\s*(\d+)\)/);
    if (rgbMatch) return 'rgba(' + rgbMatch[1] + ',' + rgbMatch[2] + ',' + rgbMatch[3] + ',' + alpha + ')';
    var hex = color.replace('#', '');
    var r = parseInt(hex.substring(0, 2), 16);
    var g = parseInt(hex.substring(2, 4), 16);
    var b = parseInt(hex.substring(4, 6), 16);
    return 'rgba(' + r + ',' + g + ',' + b + ',' + alpha + ')';
  }

  function sampleColors() {
    var style = getComputedStyle(document.documentElement);
    var isDark = !document.documentElement.classList.contains('theme-light');
    colors.accent  = style.getPropertyValue('--accent').trim()  || '#5c9cf5';
    colors.accent2 = style.getPropertyValue('--accent2').trim() || '#4ec97b';
    colors.bg      = style.getPropertyValue('--bg-card').trim() || '#161b25';
    colors.head    = isDark ? '#ffffff' : '#1a0533';
  }

  function resizeCanvas() {
    canvas.width  = Math.floor(header.offsetWidth * 0.65);
    canvas.height = header.offsetHeight;
    ctx.font = '14px "IBM Plex Mono", monospace';
    ctx.textBaseline = 'top';
    initColumns();
  }

  function initColumns() {
    columns = [];
    var columnWidth = 14;
    var columnCount = Math.floor(canvas.width / columnWidth);
    for (var i = 0; i < columnCount; i++) {
      columns.push({
        x:         i * columnWidth,
        y:         -Math.floor(Math.random() * 40),
        speed:     2 + Math.floor(Math.random() * 3),
        color:     Math.random() < 0.6 ? 'accent2' : 'accent',
        charIndex: Math.floor(Math.random() * CHARS.length),
        length:    8 + Math.floor(Math.random() * 13)
      });
    }
  }

  function setupThemeObserver() {
    var observer = new MutationObserver(function(mutations) {
      for (var i = 0; i < mutations.length; i++) {
        if (mutations[i].attributeName === 'class') { sampleColors(); break; }
      }
    });
    observer.observe(document.documentElement, { attributes: true, attributeFilter: ['class'] });
  }

  function drawFrame() {
    frameCount++;
    ctx.fillStyle = hexToRgba(colors.bg, 0.085);
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    for (var ci = 0; ci < columns.length; ci++) {
      var col = columns[ci];
      if (frameCount % col.speed !== 0) continue;

      ctx.fillStyle = colors[col.color];
      for (var i = 1; i <= col.length; i++) {
        var trailY = (col.y - i) * 14;
        if (trailY < 0) continue;
        var trailCharIndex = (col.charIndex - i + CHARS.length) % CHARS.length;
        ctx.fillText(CHARS[trailCharIndex], col.x, trailY);
      }

      ctx.fillStyle = colors.head;
      ctx.fillText(CHARS[col.charIndex % CHARS.length], col.x, col.y * 14);

      col.y++;
      col.charIndex = (col.charIndex + 1) % CHARS.length;

      if (col.y * 14 > canvas.height + col.length * 14) {
        col.y         = -Math.floor(Math.random() * 20);
        col.charIndex = Math.floor(Math.random() * CHARS.length);
        col.color     = Math.random() < 0.6 ? 'accent2' : 'accent';
      }
    }

    requestAnimationFrame(drawFrame);
  }

  sampleColors();
  resizeCanvas();
  setupThemeObserver();

  var resizeTimer;
  window.addEventListener('resize', function() {
    clearTimeout(resizeTimer);
    resizeTimer = setTimeout(resizeCanvas, 150);
  });

  document.fonts.ready.then(function() {
    requestAnimationFrame(drawFrame);
  });
})();