import { writePsd } from 'ag-psd';
import { filterSvgByColors } from './svgFilter';

async function renderSvgToCanvas(svgEl, width, height) {
  const serializer = new XMLSerializer();
  const svgString = serializer.serializeToString(svgEl);
  const blob = new Blob([svgString], { type: 'image/svg+xml;charset=utf-8' });
  const url = URL.createObjectURL(blob);

  const img = new Image();
  await new Promise((resolve, reject) => {
    img.onload = resolve;
    img.onerror = reject;
    img.src = url;
  });

  const canvas = document.createElement('canvas');
  canvas.width = width;
  canvas.height = height;
  const ctx = canvas.getContext('2d');
  ctx.clearRect(0, 0, width, height);
  ctx.drawImage(img, 0, 0, width, height);
  URL.revokeObjectURL(url);
  return canvas;
}

export async function exportPSD(svgDoc, groups, uniqueColors, onProgress) {
  const svgEl = svgDoc.querySelector('svg');
  let width, height;
  const vb = svgEl.getAttribute('viewBox');
  if (vb) {
    const parts = vb.split(/[\s,]+/).map(Number);
    width = parts[2]; height = parts[3];
  } else {
    width = parseFloat(svgEl.getAttribute('width')) || 512;
    height = parseFloat(svgEl.getAttribute('height')) || 512;
  }

  const maxDim = 4096;
  if (width > maxDim || height > maxDim) {
    const scale = maxDim / Math.max(width, height);
    width = Math.round(width * scale);
    height = Math.round(height * scale);
  } else {
    width = Math.round(width);
    height = Math.round(height);
  }

  const total = groups.length;
  const children = [];

  for (let gi = 0; gi < total; gi++) {
    onProgress?.('レイヤーをレンダリング中...', `${gi + 1} / ${total}`, Math.round((gi / (total + 1)) * 100));
    await new Promise((r) => setTimeout(r, 0));

    const groupColors = new Set(groups[gi].map((ci) => uniqueColors[ci].hex));
    const filteredSvg = svgEl.cloneNode(true);
    filterSvgByColors(filteredSvg, groupColors);

    const canvas = await renderSvgToCanvas(filteredSvg, width, height);
    children.push({
      name: `Group ${gi + 1} (${groups[gi].map((ci) => uniqueColors[ci].hex).join(', ')})`,
      canvas,
      transparencyProtected: false,
      hidden: false,
      opacity: 255,
      blendMode: 'normal',
    });
  }

  onProgress?.('PSDを生成中...', '', 90);
  await new Promise((r) => setTimeout(r, 0));

  const buffer = writePsd({ width, height, channels: 4, bitsPerChannel: 8, colorMode: 3, children });

  onProgress?.('ダウンロード中...', '', 100);
  await new Promise((r) => setTimeout(r, 0));

  const blob = new Blob([buffer], { type: 'application/octet-stream' });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = 'color_groups.psd';
  a.click();
  URL.revokeObjectURL(url);
}