/**
 * 画个标 · 海报导出：SVG / PNG（按画布规格导出）
 */
const HGB_PosterExporter = (function () {
  'use strict';

  function buildSvg(spec, elements) {
    return HGB_PosterRenderer.render(spec, elements);
  }

  function download(name, blob) {
    const a = document.createElement('a');
    a.href = URL.createObjectURL(blob);
    a.download = name;
    document.body.appendChild(a);
    a.click();
    setTimeout(() => { URL.revokeObjectURL(a.href); a.remove(); }, 0);
  }

  function exportSvg(spec, elements, base) {
    const svg = buildSvg(spec, elements);
    download((base || '海报') + '.svg', new Blob([svg], { type: 'image/svg+xml' }));
  }

  /** 渲染 SVG 到位图并下载（scale 控制放大倍数，默认 1） */
  function svgToCanvas(spec, elements, scale) {
    return new Promise((resolve, reject) => {
      const svg = buildSvg(spec, elements);
      const img = new Image();
      img.onload = () => {
        const w = Math.round(spec.w * scale), h = Math.round(spec.h * scale);
        const c = document.createElement('canvas');
        c.width = w; c.height = h;
        const ctx = c.getContext('2d');
        ctx.drawImage(img, 0, 0, w, h);
        resolve(c);
      };
      img.onerror = () => reject(new Error('SVG 渲染失败'));
      img.src = 'data:image/svg+xml;charset=utf-8,' + encodeURIComponent(svg);
    });
  }

  async function exportPng(spec, elements, base, scale) {
    const c = await svgToCanvas(spec, elements, scale || 1);
    const blob = await new Promise(res => c.toBlob(res, 'image/png'));
    download((base || '海报') + '.png', blob);
  }

  return { buildSvg, exportSvg, exportPng, svgToCanvas };
})();