background.js

const NEED_UI_DOWNLOAD = "NEED_UI_DOWNLOAD";
const DOWNLOADED = "DOWNLOADED";
const LINK_NOT_FOUND = "LINK_NOT_FOUND";
const DOWNLOAD_FAILED = "DOWNLOAD_FAILED";

const linkList = [];

async function canFetchVideo(url) {
  const response = await fetch(url, {
    method: "GET"
  });
  return !!response.ok;
}

async function downloadFile(url, filename) {
  console.log("downloadFile", url, filename);
  const ableToDownload = await canFetchVideo(url);
  if (!ableToDownload) {
    return Promise.resolve({ status: NEED_UI_DOWNLOAD, url, filename });
  }
  return new Promise((resolve, reject) => {
    chrome.downloads.download({ url, filename }, () => {
      if (chrome.runtime.lastError) {
        reject(chrome.runtime.lastError.message);
      } else {
        resolve({ status: DOWNLOADED });
      }
    });
  });
}

// 操作系统对文件名有长度限制
function sanitizeFilename(filename) {
  // Characters disallowed in Windows and Unix/Linux
  const invalidChars = /[<>:"/\\|?*\x00-\x1F]/g;

  // Replace invalid characters with an empty space
  let sanitized = filename.replace(invalidChars, "");

  // Further handling for Windows filenames
  // Trim spaces and periods at the end of the filename
  sanitized = sanitized.replace(/[\s.]+$/, "");
  return sanitized;
}

chrome.webRequest.onBeforeRequest.addListener(
  (details) => {
    const link = details.url;
    if (
      (link.includes("douyinvod") || link.includes("zjcdn")) &&
      linkList.at(-1) !== link
    ) {
      if (linkList.length > 100) {
        linkList.shift();
      }
      linkList.push(link);
    }
  },
  { urls: ["https://*.douyinvod.com/*", "https://*.zjcdn.com/*"] }
);

chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
  console.log("in background", request);
  const videoLink =
    request.videoLink ??
    linkList.find((link) => link.includes(request.videoId));

  if (!videoLink) {
    sendResponse({ status: LINK_NOT_FOUND });
    return true;
  }

  const fileName = sanitizeFilename(request.fileName);

  downloadFile(videoLink, fileName)
    .then((response) => {
      sendResponse(response);
    })
    .catch((error) => {
      console.log("download error", error);
      sendResponse({ status: DOWNLOAD_FAILED });
    });

  // Return true to keep the message channel open
  return true;
});