import { nextTick, computed } from 'vue';
import { useMainStore } from '@/store';
import { ElLoading } from 'element-plus';
import html2canvas from 'html2canvas';
import jsPDF from 'jspdf';
import { showMessage } from './common';

const mainStore = useMainStore();
const expanded = computed(() => mainStore.getExpanded);
const isLoadOver = computed(() => mainStore.getIsLoadOver);

export const downloadPDF = async (pdfContent?: HTMLElement) => {
  if (!isLoadOver.value) {
    showMessage({ type: 'warning', message: '数据加载中，请稍后再试' });
    return;
  }

  const loading = ElLoading.service({
    lock: true,
    text: '生成中...',
    background: 'rgba(0,0,0,0.7)',
  });

  try {
    if (!pdfContent) pdfContent = document.querySelector('.record') as HTMLElement;

    if (!expanded.value) {
      mainStore.setExpanded(true);
      await nextTick();
    }
    await nextTick();

    // 高分辨率 canvas
    const canvas = await html2canvas(pdfContent, { scale: 2, useCORS: true, backgroundColor: '#fff' });
    const canvasWidth = canvas.width;
    const canvasHeight = canvas.height;

    const pdf = new jsPDF('p', 'mm', 'a4');
    const pageWidth = pdf.internal.pageSize.getWidth();
    const pageHeight = pdf.internal.pageSize.getHeight();
    const ratio = pageWidth / canvasWidth; // 宽度缩放比例
    const pagePixelHeight = pageHeight / ratio; // PDF 一页对应 canvas 的高度

    let positionY = 0;

    while (positionY < canvasHeight) {
      const h = Math.min(pagePixelHeight, canvasHeight - positionY);

      // 创建临时 canvas 截取当前页
      const pageCanvas = document.createElement('canvas');
      pageCanvas.width = canvasWidth;
      pageCanvas.height = h;
      const ctx = pageCanvas.getContext('2d');
      ctx?.drawImage(canvas, 0, positionY, canvasWidth, h, 0, 0, canvasWidth, h);

      const imgData = pageCanvas.toDataURL('image/jpeg', 0.95);
      pdf.addImage(imgData, 'JPEG', 0, 0, pageWidth, h * ratio);

      positionY += h;
      if (positionY < canvasHeight) pdf.addPage();
    }

    pdf.save('analysis.pdf');
  } catch (error) {
    console.error(error);
    showMessage({ type: 'error', message: '生成失败，请稍后再试' });
  } finally {
    mainStore.setExpanded(false);
    setTimeout(() => loading.close(), 500);
  }
};