import jsPDF from 'jspdf'
import html2canvas from 'html2canvas'

/*
 * 使用说明
 * ele:需要导出pdf的容器元素(dom节点 不是id)
 * pdfFileName: 导出文件的名字 通过调用outPutPdfFn方法也可传参数改变
 * splitClassName: 避免分段截断的类名 当pdf有多页时需要传入此参数 , 避免pdf分页时截断元素  如表格<tr class="itemClass"></tr>
 * 调用方式 先 let pdf = new PdfLoader(ele, 'pdf' ,'itemClass');
 * 若想改变pdf名称 pdf.outPutPdfFn(fileName);  outPutPdfFn方法返回一个promise 可以使用then方法处理pdf生成后的逻辑
 * */
class PdfLoader {
  constructor (ele, pdfFileName, splitClassName) {
    this.ele = ele
    this.pdfFileName = pdfFileName
    this.splitClassName = splitClassName || ''
    this.A4_WIDTH = 841.89
    this.A4_HEIGHT = 595.28
  }

  async getPDF (resolve) {
    const ele = this.ele
    const pdfFileName = this.pdfFileName
    const eleW = ele.offsetWidth // 获得该容器的宽
    const eleH = ele.scrollHeight // 获得该容器的高
    const eleOffsetTop = ele.offsetTop // 获得该容器到文档顶部的距离
    const eleOffsetLeft = ele.offsetLeft // 获得该容器到文档最左的距离
    window.pageYoffset = 0
    document.documentElement.scrollTop = 0
    document.body.scrollTop = 0
    const canvas = document.createElement('canvas')
    let abs = 0
    // eslint-disable-next-line camelcase
    const win_in = document.documentElement.clientWidth || document.body.clientWidth // 获得当前可视窗口的宽度（不包含滚动条）
    // eslint-disable-next-line camelcase
    const win_out = window.innerWidth // 获得当前窗口的宽度（包含滚动条）
    // eslint-disable-next-line camelcase
    if (win_out > win_in) {
      // eslint-disable-next-line camelcase
      abs = (win_out - win_in) / 2 // 获得滚动条宽度的一半
    }
    canvas.width = eleW * 2 // 将画布宽&&高放大两倍
    canvas.height = eleH * 2
    const context = canvas.getContext('2d')
    context.scale(2, 2) // 增强图片清晰度
    context.translate(-eleOffsetLeft - abs, -eleOffsetTop)
    ele.style.height = ele.scrollHeight + 'px' // 获取元素的滚动高度，用于截取被滚动条隐藏的部分
    html2canvas(ele, {
      backgroundColor: null,
      allowTaint: false,
      dpi: window.devicePixelRatio * 4,
      width: ele.width,
      height: ele.width,
      windowWidth: ele.scrollWidth,
      scale: 4, // 按比例增加分辨率
      useCORS: true // 允许canvas画布内可以跨域请求外部链接图片, 允许跨域请求。
    }).then(async (canvas) => {
      const contentWidth = canvas.width
      const contentHeight = canvas.height
      ele.style.height = ele.clientHeight + 'px' // 获取元素的实际高度，不包括滚动条隐藏的部分
      // 一页pdf显示html页面生成的canvas高度;
      const pageHeight = (contentWidth / this.A4_WIDTH) * this.A4_HEIGHT // 这样写的目的在于保持宽高比例一致 pageHeight/canvas.width = a4纸高度/a4纸宽度// 宽度和canvas.width保持一致
      // 未生成pdf的html页面高度
      let leftHeight = contentHeight
      // 页面偏移
      let position = 0
      // a4纸的尺寸[595,842],单位像素，html页面生成的canvas在pdf中图片的宽高
      const imgWidth = this.A4_WIDTH - 10 // -10为了页面有右边距
      const imgHeight = (this.A4_WIDTH / contentWidth) * contentHeight
      const pageData = canvas.toDataURL('image/jpeg', 1.0)
      const pdf = jsPDF('l', 'pt', 'a4')
      // 有两个高度需要区分，一个是html页面的实际高度，和生成pdf的页面高度(841.89)
      // 当内容未超过pdf一页显示的范围，无需分页
      if (leftHeight < pageHeight) {
        // 在pdf.addImage(pageData, 'JPEG', 左，上，宽度，高度)设置在pdf中显示；
        pdf.addImage(pageData, 'JPEG', 5, 0, imgWidth, imgHeight)
        // pdf.addImage(pageData, 'JPEG', 20, 40, imgWidth, imgHeight);
      } else {
        // 分页
        while (leftHeight > 0) {
          pdf.addImage(
            pageData,
            'JPEG',
            5,
            position,
            imgWidth,
            imgHeight
          )
          leftHeight -= pageHeight
          position -= this.A4_HEIGHT
          // 避免添加空白页
          if (leftHeight > 0) {
            pdf.addPage()
          }
        }
      }
      // pdf.save(pdfFileName + '.pdf', { returnPromise: true }).then(() => {
      //   // 去除添加的空div 防止页面混乱
      //   const doms = document.querySelectorAll('.emptyDiv')
      //   for (let i = 0; i < doms.length; i++) {
      //     doms[i].remove()
      //   }
      // })
      let pdfData = pdf.output('datauristring')
      this.showPreview(pdfData)

      this.ele.style.height = ''
      resolve()
    })
  }

  // 此方法是防止（图表之类）内容因为A4纸张问题被截断
  async outPutPdfFn (pdfFileName) {
    return new Promise((resolve, reject) => {
      this.ele.style.height = 'initial'
      // eslint-disable-next-line no-unused-expressions
      pdfFileName ? (this.pdfFileName = pdfFileName) : null
      const target = this.ele
      const pageHeight = (target.scrollWidth / this.A4_WIDTH) * this.A4_HEIGHT
      if (this.splitClassName !== '' || this.splitClassName != null) {
        // 获取分割dom，此处为class类名为item的dom
        const domList = document.getElementsByClassName(this.splitClassName)
        // 进行分割操作，当dom内容已超出a4的高度，则将该dom前插入一个空dom，把他挤下去，分割
        let pageNum = 1 // pdf页数
        const eleBounding = this.ele.getBoundingClientRect()
        for (let i = 0; i < domList.length; i++) {
          const node = domList[i]
          const bound = node.getBoundingClientRect()
          const offset2Ele = bound.top - eleBounding.top
          const currentPage = Math.ceil(
            (bound.bottom - eleBounding.top) / pageHeight
          ) // 当前元素应该在哪一页
          if (pageNum < currentPage) {
            pageNum++
            const divParent = domList[i].parentNode // 获取该div的父节点
            const newNode = document.createElement('div')
            newNode.className = 'emptyDiv'
            newNode.style.background = 'white'
            newNode.style.height =
              pageHeight * (pageNum - 1) - offset2Ele + 30 + 'px' // +30为了在换下一页时有顶部的边距
            newNode.style.width = '100%'
            divParent.insertBefore(newNode, node) // 在每一个节点前面插入一个空的新节点，防止内容被分割截断
          }
        }
      }
      // 异步函数，导出成功后处理交互
      this.getPDF(resolve, reject)
    })
  }

  async showPreview (pdfData) {
    // const pdfPreview = this.$refs.pdfPreview
    const iframe = document.createElement('iframe')
    iframe.src = pdfData
    iframe.style.width = '100%'
    iframe.style.height = '600px'

    this.ele.innerHTML = ''
    this.ele.appendChild(iframe)
    // let loction = window.location.href
    // let url = loction + 'pdf/' + this.pdfFileName + '.pdf'

    // // 这一步是关键，使用window.URL.createObjectURL把blob数据转为本地URL
    // let url = window.URL.createObjectURL(new Blob([pdfData]))
    // let content = `/pdfjs/viewer.html?file=${url}`
    // window.open(content, '_blank')

    // let msg = open('cnrose', 'DisplayWindow', 'toolbar=no,,menubar=no,location=no,scrollbars=no')
    // msg.document.write('<HEAD><TITLE>sunset</TITLE></HEAD>')
    // msg.document.write('<CENTER>http://www.cjpfw.com/</CENTER>')
    // console.log(msg.document.body)
    // let iframe = msg.document.body.createElement('iframe')
    // iframe.src = pdfData
    // iframe.style.width = '100%'
    // iframe.style.height = '600px'
    // msg.document.write(iframe)
  }
}

export default PdfLoader