Download PDF from read.nlc.cn

nlc-getbook.js

async function downloadBook(aid, bid) {
  const [title, myreader, kime, fime] = await getBookKey(aid, bid)

  const r = await fetch(`http://read.nlc.cn/menhu/OutOpenBook/getReader?aid=${aid}&bid=${bid}&kime=${kime}&fime=${fime}`, { method: "POST", headers: { myreader: myreader }})
  const d = await r.arrayBuffer()
  saveByteArray(title + ".pdf", d)
}

async function getBookKey(aid, bid) {
	const r = await fetch(`http://read.nlc.cn/OutOpenBook/OpenObjectBook?aid=${aid}&bid=${bid}`)
	const d = await r.text()
	const title = /var title = \'(.+?)\'/.exec(d)[1]
	const myreader = /tokenKey=\"(\w+)\"/.exec(d)[1]
	const kime = /timeKey=\"(\w+)\"/.exec(d)[1]
	const fime = /timeFlag=\"(\w+)\"/.exec(d)[1]
	return [title, myreader, kime, fime]
}

// https://stackoverflow.com/a/37340749/5488616
function saveByteArray(reportName, byte) {
    var blob = new Blob([byte], {type: "application/pdf"});
    var link = document.createElement('a');
    link.href = window.URL.createObjectURL(blob);
    var fileName = reportName;
    link.download = fileName;
    link.click();
};


downloadBook("403", "8179.0")

// To be executed at http://read.nlc.cn/ in the browser console

nlc-getbook.worker.js

// Project: throbbing-thunder-e93d

addEventListener("fetch", (event) => {
  event.respondWith(
    handleRequest(event.request).catch(
      (err) => new Response(err.stack, { status: 500 })
    )
  );
});

/**
 * Many more examples available at:
 *   https://developers.cloudflare.com/workers/examples
 * @param {Request} request
 * @returns {Promise<Response>}
 */
async function handleRequest(request) {
  const { pathname, params } = new URL(request.url);
  const [_a, _b, aid, bid] = pathname.split("/")
  if (!aid || !bid) {
    return new Response(`Invalid arguments, aid=${aid}, bid=${bid}`, { status: 403 })
  }
  console.log(aid, bid)
  return fetchBook(aid, bid);
}

async function fetchBook(aid, bid) {
  const [title, pdfname, myreader, kime, fime] = await getBookInfo(aid, bid)
  let resp
  console.log(pdfname)
//   const filename = title + pdfname.slice(pdfname.lastIndexOf("/") + 1)
//   const disposition = `inline; filename="${filename.replace('"', '\\"')}"`
  if (pdfname) {
    resp = await fetch("http://read.nlc.cn/doc2/" + pdfname)
    // resp.headers.set('Content-Disposition', disposition)
    status = resp.status
    ok = resp.ok
    if (resp.ok) {
      return resp
    }
  }
    resp = fetch(`http://read.nlc.cn/menhu/OutOpenBook/getReader?aid=${aid}&bid=${bid}&kime=${kime}&fime=${fime}`, { method: "POST", headers: { myreader: myreader }})
    return resp
    // return new Response(JSON.stringify([title, pdfname, myreader, kime, fime, status, ok]))
}

async function getBookInfo(aid, bid) {
	const r = await fetch(`http://read.nlc.cn/OutOpenBook/OpenObjectBook?aid=${aid}&bid=${bid}.0`)
    const d = await r.text()
    if (d.includes("系统内部错误")) {
        throw Error("Upstream error, check the arguments or just retry")
    }
	const title = /var title = \'(.*?)\'/.exec(d)[1] // allow empty
	const pdfname = /var pdfname\s*=\s*\'([^']+)\';/.exec(d)[1]
	const myreader = /tokenKey=\"(\w+)\"/.exec(d)[1]
	const kime = /timeKey=\"(\w+)\"/.exec(d)[1]
	const fime = /timeFlag=\"(\w+)\"/.exec(d)[1]
	return [title, pdfname, myreader, kime, fime]
}

nlc-getbook2.worker.js

// Project: throbbing-thunder-e93d

const DECHUNK_SIZE = 1024 * 1024 * 1024 // 1 GiB

addEventListener("fetch", (event) => {
  event.respondWith(
    handleRequest(event.request).catch(
      (err) => new Response(err.stack, { status: 500 })
    )
  );
});

/**
 * Many more examples available at:
 *   https://developers.cloudflare.com/workers/examples
 * @param {Request} request
 * @returns {Promise<Response>}
 */
async function handleRequest(request) {
  const ranging = !!request.headers.get("range")
  const { pathname, searchParams: params } = new URL(request.url)
  const pdfname = params.get("file_path")
  if (pdfname) {
    return await fetchPath(pdfname, ranging)
  }
  const [_a, _b, aid, bid] = pathname.split("/")
  if (!aid || !bid) {
    return new Response(`Invalid arguments, aid=${aid}, bid=${bid}`, { status: 403 })
  }
  console.log(aid, bid, ranging)
  return fetchBook(aid, bid, ranging);
}

async function fetchPath(file_path, ranging) {
  const resps = await Promise.all([1,2,3].map((i) => fetch(`http://read.nlc.cn/doc${i}/${file_path}`, {'method': 'HEAD'})))
  const effres = resps.find((resp) => resp.ok)
  if (!effres) {
    return
  }
  const cl = parseInt(effres.headers.get('content-length'))
  console.log("size:", cl)
  console.log(Object.fromEntries(effres.headers.entries()))
  // workers does not support Range?
  if (ranging || cl <= DECHUNK_SIZE /*|| effres.headers.get('accept-ranges') != 'bytes'*/) {
    console.log("direct streaming")
    let resp = await fetch(effres.url)
    resp = new Response(resp.body, resp)
    // resp.headers.set('x-client-ranging', new String(ranging))
    // resp.headers.set('x-server-headers', JSON.stringify(Object.fromEntries(resp.headers.entries())))
    resp.headers.set('x-stream-type', 'direct')
    resp.headers.set('x-orig-url', effres.url)
    // resp.headers.set('content-disposition', )
    return resp
  } else {
    console.log("dechunk streaming")
    // https://community.cloudflare.com/t/workers-pipe-a-sequential-series-of-streams-to-response-without-blocking/311695/7
    const { readable, writable } = new  FixedLengthStream(cl)
    const chunk = Math.ceil(cl / DECHUNK_SIZE)
    const stream = async () => {
      for (const i of Array.from(Array(chunk).keys())) {
        const s = i * DECHUNK_SIZE
        const e = Math.min((i + 1) * DECHUNK_SIZE, cl)
        const resp = await fetch(effres.url, {'headers': {'Range': `bytes=${s}-${e - 1}`}})
        console.log(`piping bytes=${s}..${e} (=${resp.headers.get('content-length')}), preventing close: ${e < cl}`)
        // await resp.body.pipeTo(writable, {preventClose: e < cl})
        await resp.body.pipeTo(writable, {preventClose: true})
      }
      console.log("closing")
      const r = await writable.getWriter().close()
      console.log("closed")
      return r
    }
    stream()
    const resp = new Response(readable, effres)
    resp.headers.set('x-stream-type', 'dechunk')
    resp.headers.set('x-orig-url', effres.url)
    resp.headers.set('x-chunk-number', chunk)
    return resp
  }
}

async function fetchBook(aid, bid, ranging) {
  const [title, pdfname, myreader, kime, fime] = await getBookInfo(aid, bid)
  let resp
  console.log(pdfname)
  //   const filename = title + pdfname.slice(pdfname.lastIndexOf("/") + 1)
  //   const disposition = `inline; filename="${filename.replace('"', '\\"')}"`
  if (pdfname) {
    const resp = await fetchPath(pdfname, ranging)
    if (resp) {
      return resp
    }
  }
  resp = fetch(`http://read.nlc.cn/menhu/OutOpenBook/getReader?aid=${aid}&bid=${bid}&kime=${kime}&fime=${fime}`, { method: "POST", headers: { myreader: myreader } })
  return resp
  // return new Response(JSON.stringify([title, pdfname, myreader, kime, fime, status, ok]))
}

async function getBookInfo(aid, bid) {
  const r = await fetch(`http://read.nlc.cn/OutOpenBook/OpenObjectBook?aid=${aid}&bid=${bid}.0`)
  const d = await r.text()
  if (d.includes("系统内部错误")) {
    throw Error("Upstream error, check the arguments or just retry")
  }
  const title = /var title = \'(.*?)\'/.exec(d)[1] // allow empty
  const pdfname = /var pdfname\s*=\s*\'([^']+)\';/.exec(d)[1]
  const myreader = /tokenKey=\"(\w+)\"/.exec(d)[1]
  const kime = /timeKey=\"(\w+)\"/.exec(d)[1]
  const fime = /timeFlag=\"(\w+)\"/.exec(d)[1]
  return [title, pdfname, myreader, kime, fime]
}