// #167: with line wrapping on, a logical line can occupy several visual
// lines; the gutter must show one number per VISUAL line, and each number
// must sit on the visual row where its logical line STARTS. Per-line spans
// give each logical line its own box so offsetTop order stays correct even
// when highlighting spans cross no line boundaries.
(function () {
  var body = document.getElementById('codebody');
  var gutter = document.getElementById('gutter');
  var code = document.getElementById('code');
  if (!body || !gutter || !code) return;

  var wrapOn = function () {
    return document.documentElement.hasAttribute('data-wrap');
  };

  // Wrap each logical line (split on newline; spans never contain newlines
  // because HighlightCode highlights per line) in a .codeline block. The
  // spans are display:block, so they are joined with '' — a '\n' join leaves
  // newline text nodes between blocks that pre-wrap renders as an extra line
  // box per line, which would shift every following number down one row (#167).
  function splitLines() {
    var html = body.innerHTML;
    var parts = html.split('\n');
    var out = [];
    for (var i = 0; i < parts.length; i++) {
      out.push('<span class="codeline">' + parts[i] + '</span>');
    }
    body.innerHTML = out.join('');
  }

  // One .gutline block per visual row. Numbers are placed at the gutter row
  // whose top matches their .codeline's top; filler rows pad the gaps so
  // alignment is driven by measured geometry, not by uniform row counts.
  function renumber() {
    var lines = body.querySelectorAll('.codeline');
    if (!wrapOn() || !lines.length) {
      // wrap OFF: one number per logical line (pre-existing behavior,
      // including the gutter scrolling with horizontal scroll).
      var s = '';
      for (var k = 1; k <= lines.length; k++) s += k + '\n';
      gutter.textContent = lines.length ? s.slice(0, -1) : '1';
      return;
    }

    // Measure each logical line's offsetTop (viewport-relative for
    // comparison with gutter rows rendered in the same scroll flow).
    // Reading all rects first avoids interleaved layout reads/writes.
    var tops = [];
    for (var i = 0; i < lines.length; i++) {
      tops.push(lines[i].getBoundingClientRect().top);
    }
    // Build one gutline per visual row of the tallest column (the code
    // body itself); each number is assigned to the visual row whose top
    // is closest to its line's top.
    var bodyTop = body.getBoundingClientRect().top;
    var lh = parseFloat(getComputedStyle(body).lineHeight) || 1;
    var totalRows = Math.max(lines.length, Math.ceil(body.getBoundingClientRect().height / lh));
    gutter.textContent = '';
    var frag = document.createDocumentFragment();
    var spans = [];
    for (var r = 0; r < totalRows; r++) {
      var cell = document.createElement('span');
      cell.className = 'gutline';
      cell.textContent = '\u00a0';
      spans.push(cell);
      frag.appendChild(cell);
    }
    gutter.appendChild(frag);
    for (var j = 0; j < tops.length; j++) {
      var row = Math.round((tops[j] - bodyTop) / lh);
      if (row < 0) row = 0;
      if (row > totalRows - 1) row = totalRows - 1;
      spans[row].textContent = String(j + 1);
    }
    // A wrapped line whose last visual row is only partially filled can
    // settle a hair under N * line-height after the gutter is rebuilt; a
    // gutter pass that changes the code column width reflows it. Verify the
    // placement one frame later and re-run if any line's row moved (#167).
    var placed = {};
    for (var q = 0; q < tops.length; q++) placed[q] = Math.round((tops[q] - bodyTop) / lh);
    requestAnimationFrame(function () {
      var moved = false;
      var tops2 = [];
      for (var q2 = 0; q2 < lines.length; q2++) tops2.push(lines[q2].getBoundingClientRect().top);
      var bodyTop2 = body.getBoundingClientRect().top;
      for (var q3 = 0; q3 < tops2.length; q3++) {
        if (Math.round((tops2[q3] - bodyTop2) / lh) !== placed[q3]) { moved = true; break; }
      }
      if (moved) renumber();
    });
  }

  splitLines();
  renumber();

  // Re-renumber on toggle (theme.js toggles data-wrap on <html>) and on any
  // size change (paste of lots of text, window resize, zoom). Only width
  // changes of the code column affect wrapping, so observe width only —
  // height changes caused by our own renumbering must not re-trigger.
  var mo = new MutationObserver(renumber);
  mo.observe(document.documentElement, { attributes: true, attributeFilter: ['data-wrap'] });
  var lastW = body.getBoundingClientRect().width;
  if (window.ResizeObserver) {
    var ro = new ResizeObserver(function () {
      var w = body.getBoundingClientRect().width;
      if (Math.abs(w - lastW) < 0.5) return;
      lastW = w;
      renumber();
    });
    ro.observe(body);
  } else {
    window.addEventListener('resize', renumber);
  }
})();