// Side previews: reduce the previous fill size by 20%, center the photograph,
// then move it down by 5% of its
// scaled height. Bake once; never let the native image crop it again.
var W = 208.7, H = 184.5;
function rectangle(width, height) {
  if (!(typeof width === 'number' && isFinite(width) && width > 0 &&
      typeof height === 'number' && isFinite(height) && height > 0)) return null;
  var scale = Math.max(W / width, H / height) * 1.4 * .8;
  var w = width * scale, h = height * scale;
  return { left: Math.max(W - w, Math.min(0, (W - w) / 2)),
    top: (H - h) / 2 + h * .05,
    width: w, height: h };
}
function bake(platform, options) {
  return new Promise(function (resolve, reject) {
    var rect = rectangle(options.width, options.height), settled = false;
    function fail(error) { if (!settled) { settled = true; reject(error || new Error('图片生成失败')); } }
    function accept(result) {
      if (settled) return;
      var src = typeof result === 'string' ? result : result && (result.dataURL || result.dataUrl);
      if (typeof src !== 'string' || !/^data:image\/(jpeg|png);base64,/.test(src)) { fail(new Error('图片导出失败')); return; }
      settled = true; resolve(src);
    }
    if (!rect || !platform || typeof platform.createCanvasContext !== 'function') { fail(); return; }
    try {
      var ctx = platform.createCanvasContext('report-side-zoom-canvas');
      if (!ctx || typeof ctx.toDataURL !== 'function') { fail(); return; }
      // Fixed, mounted canvas; all photo/layer coordinates share this scale.
      var scale = 4, width = 835, height = 738;
      ctx.clearRect(0, 0, width, height);
      ctx.setFillStyle('#F6F6F6'); ctx.fillRect(0, 0, width, height);
      ctx.drawImage(options.photo, rect.left * scale, rect.top * scale, rect.width * scale, rect.height * scale);
      if (options.dark) {
        ctx.setFillStyle('rgba(0,0,0,' + options.dark + ')'); ctx.fillRect(0, 0, width, height);
      }
      (options.layers || []).forEach(function (layer) {
        ctx.drawImage(layer, rect.left * scale, rect.top * scale, rect.width * scale, rect.height * scale);
      });
      ctx.draw(false, function () {
        if (settled) return;
        try {
          var result = ctx.toDataURL({ x: 0, y: 0, width: width, height: height,
            destWidth: width, destHeight: height, fileType: 'jpg', quality: .95, success: accept, fail: fail });
          if (result && typeof result.then === 'function') Promise.resolve(result).then(accept, fail);
          else if (typeof result === 'string') accept(result);
        } catch (error) { fail(error); }
      });
    } catch (error) { fail(error); }
  });
}
module.exports = { rectangle: rectangle, bake: bake };