/*! Admin heatmap overlay renderer (Hotjar-like radial blobs over page preview). */
(function () {
  function colorFor(t) {
    // green -> yellow -> red
    if (t < 0.33) {
      var k = t / 0.33;
      return [67 + (255 - 67) * k, 160 + (235 - 160) * k, 71 * (1 - k)];
    }
    if (t < 0.66) {
      var k2 = (t - 0.33) / 0.33;
      return [255, 235 - (235 - 152) * k2, 0];
    }
    var k3 = (t - 0.66) / 0.34;
    return [255, 152 * (1 - k3), 0];
  }

  function paint() {
    var canvas = document.getElementById("admin-heatmap");
    var stage = document.getElementById("admin-heatmap-stage");
    if (!canvas || !stage) return;

    var grid = parseInt(canvas.getAttribute("data-grid"), 10) || 40;
    var max = parseInt(canvas.getAttribute("data-max"), 10) || 1;
    var cells = [];
    try {
      cells = JSON.parse(canvas.getAttribute("data-cells") || "[]");
    } catch (e) {
      cells = [];
    }

    var width = Math.max(stage.clientWidth, 320);
    var height = Math.max(stage.clientHeight, 480);
    canvas.width = width;
    canvas.height = height;
    canvas.style.width = width + "px";
    canvas.style.height = height + "px";

    var ctx = canvas.getContext("2d");
    ctx.clearRect(0, 0, width, height);

    var cellW = width / grid;
    var cellH = height / grid;
    var radius = Math.max(cellW, cellH) * 1.8;

    cells.forEach(function (cell) {
      var intensity = Math.min(1, cell.c / max);
      if (intensity <= 0) return;
      var cx = (cell.x + 0.5) * cellW;
      var cy = (cell.y + 0.5) * cellH;
      var rgb = colorFor(intensity);
      var grd = ctx.createRadialGradient(cx, cy, 0, cx, cy, radius);
      grd.addColorStop(0, "rgba(" + rgb[0] + "," + rgb[1] + "," + rgb[2] + "," + (0.2 + intensity * 0.55) + ")");
      grd.addColorStop(1, "rgba(" + rgb[0] + "," + rgb[1] + "," + rgb[2] + ",0)");
      ctx.fillStyle = grd;
      ctx.beginPath();
      ctx.arc(cx, cy, radius, 0, Math.PI * 2);
      ctx.fill();
    });
  }

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", paint);
  } else {
    paint();
  }
  window.addEventListener("resize", paint);
})();