path: root/extension/background.js

// This file is the heart of TabFS. Each route (synthetic file) is
// defined by an entry in the Routes object.

const unix = {
  EPERM: 1,
  ENOENT: 2,
  ESRCH: 3,
  EINTR: 4,
  EIO: 5,
  ENXIO: 6,
  ENOTSUP: 45,
  ETIMEDOUT: 110, // FIXME: not on macOS (?)

  // Unix file types
  S_IFMT: 0170000, // type of file mask
  S_IFIFO: 010000, // named pipe (fifo)
  S_IFCHR: 020000, // character special
  S_IFDIR: 040000, // directory
  S_IFBLK: 060000, // block special
  S_IFREG: 0100000, // regular
  S_IFLNK: 0120000, // symbolic link
  S_IFSOCK: 0140000, // socket
}
class UnixError extends Error {
  constructor(error) { super(); this.name = "UnixError"; this.error = error; }
}

const sanitize = (function() {
  // from https://github.com/parshap/node-sanitize-filename/blob/209c39b914c8eb48ee27bcbde64b2c7822fdf3de/index.js

  // I've added ' ' to the list of illegal characters. it's a
  // decision whether we want to allow spaces in filenames... I think
  // they're annoying, so I'm sanitizing them out for now.
  var illegalRe = /[\/\?<>\\:\*\|" ]/g;
  var controlRe = /[\x00-\x1f\x80-\x9f]/g;
  var reservedRe = /^\.+$/;
  var windowsReservedRe = /^(con|prn|aux|nul|com[0-9]|lpt[0-9])(\..*)?$/i;
  var windowsTrailingRe = /[\. ]+$/;

  function sanitize(input, replacement) {
    if (typeof input !== 'string') {
      throw new Error('Input must be string');
    }
    var sanitized = input
      .replace(illegalRe, replacement)
      .replace(controlRe, replacement)
      .replace(reservedRe, replacement)
      .replace(windowsReservedRe, replacement)
      .replace(windowsTrailingRe, replacement);
    return sanitized.slice(0, 200);
  }
  return input => sanitize(input, '_');
})();

const stringToUtf8Array = (function() {
  const encoder = new TextEncoder("utf-8");
  return str => encoder.encode(str);
})();
const utf8ArrayToString = (function() {
  const decoder = new TextDecoder("utf-8");
  return utf8 => decoder.decode(utf8);
})();

// global so it can be hot-reloaded
window.Routes = {};

// Helper function: you provide getData and setData functions that define
// the contents of an entire file => it returns a proper route handler
// object with a full set of file operations that you can put in
// `Routes` (so clients can read and write sections of the file, stat
// it to get its size and see it show up in ls, etc),
const makeRouteWithContents = (function() {
  const Cache = {
    // used when you open a file to cache the content we got from the
    // browser until you close that file. (so we can respond to
    // individual chunk read() and write() requests without doing a
    // whole new conversation with the browser and regenerating the
    // content -- important for taking a screenshot, for instance)
    store: {}, nextHandle: 0,
    storeObject(path, object) {
      const handle = ++this.nextHandle;
      this.store[handle] = {path, object};
      return handle;
    },
    getObjectForHandle(handle) { return this.store[handle].object; },
    setObjectForHandle(handle, object) { this.store[handle].object = object; },
    removeObjectForHandle(handle) { delete this.store[handle]; },
    setObjectForPath(path, object) {
      for (let storedObject of Object.values(this.store)) {
        if (storedObject.path === path) {
          storedObject.object = object;
        }
      }
    }
  };

  function toUtf8Array(stringOrArray) {
    if (typeof stringOrArray == 'string') { return stringToUtf8Array(stringOrArray); }
    else { return stringOrArray; }
  }

  const makeRouteWithContents = (getData, setData) => ({
    // getData: (req: Request U Vars) -> Promise<contentsOfFile: String|Uint8Array>
    // setData [optional]: (req: Request U Vars, newContentsOfFile: String) -> Promise<>

    // You can override file operations (like `truncate` or `getattr`)
    // in the returned set if you want different behavior from what's
    // defined here.

    async getattr(req) {
      const data = await getData(req);
      if (typeof data === 'undefined') { throw new UnixError(unix.ENOENT); }
      return {
        st_mode: unix.S_IFREG | 0444 | (setData ? 0222 : 0),
        st_nlink: 1,
        // you'll want to override this if getData() is slow, because
        // getattr() gets called a lot more cavalierly than open().
        st_size: toUtf8Array(data).length
      };
    },

    // We call getData() once when the file is opened, then cache that
    // data for all subsequent reads from that application.
    async open(req) {
      const data = await getData(req);
      if (typeof data === 'undefined') { throw new UnixError(unix.ENOENT); }
      return { fh: Cache.storeObject(req.path, toUtf8Array(data)) };
    },
    async read({fh, size, offset}) {
      return { buf: String.fromCharCode(...Cache.getObjectForHandle(fh).slice(offset, offset + size)) };
    },
    async write(req) {
      const {fh, offset, buf} = req;
      let arr = Cache.getObjectForHandle(fh);
      const bufarr = stringToUtf8Array(buf);
      if (offset + bufarr.length > arr.length) {
        const newArr = new Uint8Array(offset + bufarr.length);
        newArr.set(arr.slice(0, Math.min(offset, arr.length)));
        arr = newArr;
        Cache.setObjectForHandle(fh, arr);
      }
      arr.set(bufarr, offset);
      // I guess caller should override write() if they want to actually
      // patch and not just re-set the whole string (for example,
      // if they want to hot-reload just one function the user modified)
      await setData(req, utf8ArrayToString(arr)); return { size: bufarr.length };
    },
    async release({fh}) { Cache.removeObjectForHandle(fh); return {}; },

    async truncate(req) {
      let arr = toUtf8Array(await getData(req));
      if (req.size !== arr.length) {
        const newArr = new Uint8Array(req.size);
        newArr.set(arr.slice(0, Math.min(req.size, arr.length)));
        arr = newArr;
      }
      Cache.setObjectForPath(req.path, arr);
      await setData(req, utf8ArrayToString(arr)); return {};
    }
  });
  makeRouteWithContents.Cache = Cache;
  return makeRouteWithContents;
})();

// Helper function: returns a route handler for `path` based on all
// the children of `path` that already exist in Routes.
// 
// e.g., if `Routes['/tabs/create']` and `Routes['/tabs/by-id']` and
// `Routes['/tabs/last-focused']` are all already defined, then
// `makeDefaultRouteForDirectory('/tabs')` will return a route that
// defines a directory with entries 'create', 'by-id', and
// 'last-focused'.
function makeDefaultRouteForDirectory(path) {
  function depth(p) { return p === '/' ? 0 : (p.match(/\//g) || []).length; }

  // find all direct children
  let entries = Object.keys(Routes)
      .filter(k => k.startsWith(path) && depth(k) === depth(path) + 1)
      .map(k => k.substr((path === '/' ? 0 : path.length) + 1).split('/')[0])
      // exclude entries with variables like :FILENAME in them
      .filter(k => !k.includes("#") && !k.includes(":"));

  entries = [".", "..", ...new Set(entries)];
  return { readdir() { return { entries }; }, __isInfill: true };
}

Routes["/tabs/create"] = {
  description: 'Create a new tab.',
  usage: 'echo "https://www.google.com" > $0',
  async write({buf}) {
    const url = buf.trim();
    await browser.tabs.create({url});
    return {size: stringToUtf8Array(buf).length};
  },
  async truncate() { return {}; }
};

Routes["/tabs/by-title"] = {
  description: 'Open tabs, organized by title; each subfolder represents an open tab.',
  usage: 'ls $0',
  getattr() {
    return {
      st_mode: unix.S_IFDIR | 0777, // writable so you can delete tabs
      st_nlink: 3,
      st_size: 0,
    };
  },
  async readdir() {
    const tabs = await browser.tabs.query({});
    return { entries: [".", "..", ...tabs.map(tab => sanitize(String(tab.title)) + "." + String(tab.id))] };
  }
};
Routes["/tabs/by-title/:TAB_TITLE.#TAB_ID"] = {
  description: `Represents one open tab.
It's a symbolic link to /tabs/by-id/#TAB_ID.`,
  // TODO: date
  usage: ['rm $0'],
  async readlink({tabId}) {
    return { buf: "../by-id/" + tabId };
  },
  async unlink({tabId}) {
    await browser.tabs.remove(tabId);
    return {};
  }
};
Routes["/tabs/last-focused"] = {
  description: `Represents the most recently focused tab.
It's a symbolic link to /tabs/by-id/[ID of most recently focused tab].`,
  async readlink() {
    const id = (await browser.tabs.query({ active: true, lastFocusedWindow: true }))[0].id;
    return { buf: "by-id/" + id };
  }
};

Routes["/tabs/by-id"] = {
  description: `Open tabs, organized by ID; each subfolder represents an open tab.`,
  usage: 'ls $0',
  async readdir() {
    const tabs = await browser.tabs.query({});
    return { entries: [".", "..", ...tabs.map(tab => String(tab.id))] };
  }
};

// TODO: temporarily disabled: make tab directory writable

// const tabIdDirectory = createWritableDirectory();
// Routes["/tabs/by-id/#TAB_ID"] = routeDefer(() => {
//   const childrenRoute = makeDefaultRouteForDirectory("/tabs/by-id/#TAB_ID");
//   return {
//     ...tabIdDirectory.routeForRoot, // so getattr is inherited
//     async readdir(req) {
//       const entries =
//             [...(await tabIdDirectory.routeForRoot.readdir(req)).entries,
//              ...(await childrenRoute.readdir(req)).entries];
//       return {entries: [...new Set(entries)]};
//     }
//   };
// });
// Routes["/tabs/by-id/#TAB_ID/:FILENAME"] = tabIdDirectory.routeForFilename;

// TODO: can I trigger 1. nav to Finder and 2. nav to Terminal from toolbar click?

(function() {
  const routeForTab = (readHandler, writeHandler) => makeRouteWithContents(async ({tabId}) => {
    const tab = await browser.tabs.get(tabId);
    return readHandler(tab);

  }, writeHandler ? async ({tabId}, buf) => {
    await browser.tabs.update(tabId, writeHandler(buf));
  } : undefined);

  const routeFromScript = code => makeRouteWithContents(async ({tabId}) => {
    return (await browser.tabs.executeScript(tabId, {code}))[0];
  });

  Routes["/tabs/by-id/#TAB_ID/url.txt"] = {
    description: `Text file containing the current URL of this tab.`,
    usage: ['cat $0',
            'echo "https://www.google.com" > $0'],
    ...routeForTab(tab => tab.url + "\n",
                   buf => ({ url: buf }))
  };
  Routes["/tabs/by-id/#TAB_ID/title.txt"] = {
    description: `Text file containing the current title of this tab.`,
    usage: 'cat $0',
    ...routeForTab(tab => tab.title + "\n")
  };
  Routes["/tabs/by-id/#TAB_ID/text.txt"] = {
    description: `Text file containing the current body text of this tab.`,
    usage: 'cat $0',
    ...routeFromScript(`document.body.innerText`)
  };
  Routes["/tabs/by-id/#TAB_ID/body.html"] = {
    description: `Text file containing the current body HTML of this tab.`,
    usage: 'cat $0',
    ...routeFromScript(`document.body.innerHTML`)
  };

  Routes["/tabs/by-id/#TAB_ID/active"] = {
    description: 'Text file with `true` or `false` depending on whether this tab is active in its window.',
    usage: ['cat $0',
            'echo true > $0'],
    ...routeForTab(
      tab => JSON.stringify(tab.active) + '\n',
      // WEIRD: we do startsWith because you might end up with buf
      // being "truee" (if it was "false", then someone wrote "true")
      buf => ({ active: buf.startsWith("true") })
    )
  };
})();
function createWritableDirectory() {
  // Returns a 'writable directory' object, which represents a
  // writable directory that users can put arbitrary stuff into. It's
  // not itself a route, but it has .routeForRoot and
  // .routeForFilename properties that are routes.
  
  const dir = {};
  return {
    directory: dir,
    routeForRoot: {
      usage: 'ls $0',
      async readdir({path}) {
        // get just last component of keys (filename)
        return { entries: [".", "..",
                           ...Object.keys(dir).map(
                             key => key.substr(key.lastIndexOf("/") + 1)
                           )] };
      },
      getattr() {
        return {
          st_mode: unix.S_IFDIR | 0777, // writable so you can create/rm evals
          st_nlink: 3,
          st_size: 0,
        };
      },
    },
    routeForFilename: {
      usage: ['echo "2 + 2" > $0',
              'cat $0.result'],

      async mknod({path, mode}) {
        dir[path] = '';
        return {};
      },
      async unlink({path}) {
        delete dir[path];
        return {};
      },

      ...makeRouteWithContents(
        async ({path}) => dir[path],
        async ({path}, buf) => { dir[path] = buf; }
      )
    }
  };
}


(function() {
  const evals = createWritableDirectory();
  Routes["/tabs/by-id/#TAB_ID/evals"] = evals.routeForRoot;
  Routes["/tabs/by-id/#TAB_ID/evals/:FILENAME"] = {
    ...evals.routeForFilename,
    async write(req) {
      const ret = await evals.routeForFilename.write(req);
      const code = evals.directory[req.path];
      evals.directory[req.path + '.result'] = JSON.stringify((await browser.tabs.executeScript(req.tabId, {code}))[0]) + '\n';
      return ret;
    }
  };
})();
(function() {
  const watches = {};
  Routes["/tabs/by-id/#TAB_ID/watches"] = {
    async readdir({tabId}) {
      return { entries: [".", "..", ...Object.keys(watches[tabId] || [])] };
    },
    getattr() {
      return {
        st_mode: unix.S_IFDIR | 0777, // writable so you can create/rm watches
        st_nlink: 3,
        st_size: 0,
      };
    },
  };
  Routes["/tabs/by-id/#TAB_ID/watches/:EXPR"] = {
    // NOTE: eval runs in extension's content script, not in original page JS context
    async mknod({tabId, expr, mode}) {
      watches[tabId] = watches[tabId] || {};
      watches[tabId][expr] = async function() {
        return (await browser.tabs.executeScript(tabId, {code: expr}))[0];
      };
      return {};
    },
    async unlink({tabId, expr}) {
      delete watches[tabId][expr]; // TODO: also delete watches[tabId] if empty
      return {};
    },

    ...makeRouteWithContents(async ({tabId, expr}) => {
      if (!watches[tabId] || !(expr in watches[tabId])) { throw new UnixError(unix.ENOENT); }
      return JSON.stringify(await watches[tabId][expr]()) + '\n';

    }, () => {
      // setData handler -- only providing this so that getattr reports
      // that the file is writable, so it can be deleted without annoying prompt.
      throw new UnixError(unix.EPERM);
    })
  };
})();

Routes["/tabs/by-id/#TAB_ID/window"] = {
  // a symbolic link to /windows/[id for this window]
  async readlink({tabId}) {
    const tab = await browser.tabs.get(tabId);
    return { buf: "../../../windows/" + tab.windowId };
  }
};
Routes["/tabs/by-id/#TAB_ID/control"] = {
  // see https://developer.chrome.com/extensions/tabs
  usage: ['echo remove > $0',
          'echo reload > $0',
          'echo goForward > $0',
          'echo goBack > $0',
          'echo discard > $0'],
  async write({tabId, buf}) {
    const command = buf.trim();
    await browser.tabs[command](tabId);
    return {size: stringToUtf8Array(buf).length};
  },
  async truncate({size}) { return {}; }
};
// debugger/ : debugger-API-dependent (Chrome-only)
(function() {
  if (!chrome.debugger) return;

  async function attachDebugger(tabId) {
    return new Promise((resolve, reject) => chrome.debugger.attach({tabId}, "1.3", () => {
      if (chrome.runtime.lastError) { reject(chrome.runtime.lastError); }
      else { resolve(); }
    }));
  }
  async function detachDebugger(tabId) {
    return new Promise((resolve, reject) => chrome.debugger.detach({tabId}, () => {
      if (chrome.runtime.lastError) { reject(chrome.runtime.lastError); }
      else { resolve(); }
    }));
  }
  const TabManager = (function() {
    if (chrome.debugger) chrome.debugger.onEvent.addListener((source, method, params) => {
      console.log(source, method, params);
      if (method === "Page.frameStartedLoading") {
        // we're gonna assume we're always plugged into both Page and Debugger.
        TabManager.scriptsForTab[source.tabId] = {};

      } else if (method === "Debugger.scriptParsed") {
        TabManager.scriptsForTab[source.tabId] = TabManager.scriptsForTab[source.tabId] || {};
        TabManager.scriptsForTab[source.tabId][params.scriptId] = params;
      }
    });

    return {
      scriptsForTab: {},
      debugTab: async function(tabId) {
        // meant to be higher-level wrapper for raw attach/detach
        // TODO: could we remember if we're already attached? idk if it's worth it
        try { await attachDebugger(tabId); }
        catch (e) {
          if (e.message.indexOf('Another debugger is already attached') !== -1) {
            await detachDebugger(tabId);
            await attachDebugger(tabId);
          }
        }
        // TODO: detach automatically? some kind of reference counting thing?
      },
      enableDomainForTab: async function(tabId, domain) {
        // TODO: could we remember if we're already enabled? idk if it's worth it
        if (domain === 'Debugger') { TabManager.scriptsForTab[tabId] = {}; }
        await sendDebuggerCommand(tabId, `${domain}.enable`, {});
      }
    };
  })();
  function sendDebuggerCommand(tabId, method, commandParams) {
    return new Promise((resolve, reject) =>
      chrome.debugger.sendCommand({tabId}, method, commandParams, result => {
        if (result) { resolve(result); } else { reject(chrome.runtime.lastError); }
      })
    );
  }

  // possible idea: console (using Log API instead of monkey-patching)
  // resources/
  // TODO: scripts/ TODO: allow creation, eval immediately

  Routes["/tabs/by-id/#TAB_ID/debugger/resources"] = {
    async readdir({tabId}) {
      await TabManager.debugTab(tabId); await TabManager.enableDomainForTab(tabId, "Page");
      const {frameTree} = await sendDebuggerCommand(tabId, "Page.getResourceTree", {});
      return { entries: [".", "..", ...frameTree.resources.map(r => sanitize(String(r.url)))] };
    }
  };
  Routes["/tabs/by-id/#TAB_ID/debugger/resources/:SUFFIX"] = makeRouteWithContents(async ({path, tabId, suffix}) => {
    await TabManager.debugTab(tabId); await TabManager.enableDomainForTab(tabId, "Page");

    const {frameTree} = await sendDebuggerCommand(tabId, "Page.getResourceTree", {});
    for (let resource of frameTree.resources) {
      const resourceSuffix = sanitize(String(resource.url));
      if (resourceSuffix === suffix) {
        let {base64Encoded, content} = await sendDebuggerCommand(tabId, "Page.getResourceContent", {
          frameId: frameTree.frame.id,
          url: resource.url
        });
        if (base64Encoded) { return Uint8Array.from(atob(content), c => c.charCodeAt(0)); }
        return content;
      }
    }
    throw new UnixError(unix.ENOENT);
  });
  Routes["/tabs/by-id/#TAB_ID/debugger/scripts"] = {
    async opendir({tabId}) {
      await TabManager.debugTab(tabId); await TabManager.enableDomainForTab(tabId, "Debugger");
      return { fh: 0 };
    },
    async readdir({tabId}) {
      // it's useful to put the ID first in the script filenames, so
      // the .js extension stays on the end
      const scriptFileNames = Object.values(TabManager.scriptsForTab[tabId])
            .map(params => params.scriptId + "_" + sanitize(params.url));
      return { entries: [".", "..", ...scriptFileNames] };
    }
  };
  function pathScriptInfo(tabId, filename) {
    const [scriptId, ...rest] = filename.split("_");
    const scriptInfo = TabManager.scriptsForTab[tabId][scriptId];
    if (!scriptInfo || sanitize(scriptInfo.url) !== rest.join("_")) {
      throw new UnixError(unix.ENOENT);
    }
    return scriptInfo;
  }
  Routes["/tabs/by-id/#TAB_ID/debugger/scripts/:FILENAME"] = makeRouteWithContents(async ({tabId, filename}) => {
    await TabManager.debugTab(tabId);
    await TabManager.enableDomainForTab(tabId, "Page");
    await TabManager.enableDomainForTab(tabId, "Debugger");

    const {scriptId} = pathScriptInfo(tabId, filename);
    const {scriptSource} = await sendDebuggerCommand(tabId, "Debugger.getScriptSource", {scriptId});
    return scriptSource;

  }, async ({tabId, filename}, buf) => {
    await TabManager.debugTab(tabId); await TabManager.enableDomainForTab(tabId, "Debugger");

    const {scriptId} = pathScriptInfo(tabId, filename);
    await sendDebuggerCommand(tabId, "Debugger.setScriptSource", {scriptId, scriptSource: buf});
  });
})();

Routes["/tabs/by-id/#TAB_ID/inputs"] = {
  async readdir({tabId}) {
    // TODO: assign new IDs to inputs without them?
    const code = `Array.from(document.querySelectorAll('textarea, input[type=text]'))
                    .map(e => e.id).filter(id => id)`;
    const ids = (await browser.tabs.executeScript(tabId, {code}))[0];
    return { entries: [".", "..", ...ids.map(id => `${id}.txt`)] };
  }
};
Routes["/tabs/by-id/#TAB_ID/inputs/:INPUT_ID.txt"] = makeRouteWithContents(async ({tabId, inputId}) => {
  const code = `document.getElementById('${inputId}').value`;
  const inputValue = (await browser.tabs.executeScript(tabId, {code}))[0];
  if (inputValue === null) { throw new UnixError(unix.ENOENT); } /* FIXME: hack to deal with if inputId isn't valid */
  return inputValue;

}, async ({tabId, inputId}, buf) => {
  const code = `document.getElementById('${inputId}').value = unescape('${escape(buf)}')`;
  await browser.tabs.executeScript(tabId, {code});
});

Routes["/windows"] = {
  async readdir() {
    const windows = await browser.windows.getAll();
    return { entries: [".", "..", ...windows.map(window => String(window.id))] };
  }
};
Routes["/windows/last-focused"] = {
  // a symbolic link to /windows/[id for this window]
  async readlink() {
    const windowId = (await browser.windows.getLastFocused()).id;
    return { buf: windowId };
  }
};
(function() {
  const withWindow = (readHandler, writeHandler) => makeRouteWithContents(async ({windowId}) => {
    const window = await browser.windows.get(windowId);
    return readHandler(window);

  }, writeHandler ? async ({windowId}, buf) => {
    await browser.windows.update(windowId, writeHandler(buf));
  } : undefined);

  Routes["/windows/#WINDOW_ID/focused"] =
    withWindow(window => JSON.stringify(window.focused) + '\n',
               buf => ({ focused: buf.startsWith('true') }));
})();
Routes["/windows/#WINDOW_ID/visible-tab.png"] = { ...makeRouteWithContents(async ({windowId}) => {
  // screen capture is a window thing and not a tab thing because you
  // can only capture the visible tab for each window anyway; you
  // can't take a screenshot of just any arbitrary tab
  const dataUrl = await browser.tabs.captureVisibleTab(windowId, {format: 'png'});
  return Uint8Array.from(atob(dataUrl.substr(("data:image/png;base64,").length)),
                         c => c.charCodeAt(0));

}), async getattr() {
  return {
    st_mode: unix.S_IFREG | 0444,
    st_nlink: 1,
    st_size: 10000000 // hard-code to 10MB for now
  };
} };


Routes["/extensions"] = {  
  async readdir() {
    const infos = await browser.management.getAll();
    return { entries: [".", "..", ...infos.map(info => `${sanitize(info.name)}.${info.id}`)] };
  }
};
Routes["/extensions/:EXTENSION_TITLE.:EXTENSION_ID/enabled"] = { ...makeRouteWithContents(async ({extensionId}) => {
  const info = await browser.management.get(extensionId);
  return String(info.enabled) + '\n';

}, async ({extensionId}, buf) => {
  await browser.management.setEnabled(extensionId, buf.trim() === "true");

  // suppress truncate so it doesn't accidentally flip the state when you do, e.g., `echo true >`
}), truncate() { return {}; } };

Routes["/runtime/reload"] = {
  async write({buf}) {
    await browser.runtime.reload();
    return {size: stringToUtf8Array(buf).length};
  },
  truncate() { return {}; }
};

window.fetch(chrome.runtime.getURL('background.js'))
  .then(async r => { window.__backgroundJS = await r.text(); });

Routes["/runtime/routes.html"] = makeRouteWithContents(async () => {
  if (!window.__backgroundJS) throw new UnixError(unix.EIO);

  // WIP
  const jsLines = (window.__backgroundJS).split('\n');
  function findRouteLineRange(path) {
    for (let i = 0; i < jsLines.length; i++) {
      if (jsLines[i].includes(`Routes["${path}"] = `)) {
        if (jsLines[i].match(/;/)) { return [i, i]; } // hacky: if it's a one-liner
        const result = jsLines[i].match(/Routes\[[^\]]*\] = [^\(\{]*([\(\{])/);
        const startBracket = result[1];
        const startBracketIndex = result.index + result[0].length;

        const endBracket = ({'(': ')', '{': '}'})[startBracket];
        let counter = 1;
        for (let j = i; j < jsLines.length; j++) {
          for (let k = (j === i) ? startBracketIndex + 1 : 0;
               k < jsLines[j].length;
               k++) {
            if (jsLines[j][k] === startBracket) { counter++; }
            else if (jsLines[j][k] === endBracket) { counter--; }

            if (counter === 0) { return [i, j]; }
          }
        }
        return null; // did not find
      }
    }
    return null; // did not find
  }
  return `
<html>
  <head>
    <style>
      dt:not(:first-of-type) { margin-top: 1em; }
    </style>
  </head>
  <body>
    <p>(work in progress)</p>
    <dl>
      ` + Object.entries(Routes).map(([path, {usage, description, __isInfill}]) => {
        if (__isInfill) { return ''; }
        let usages = usage ? (Array.isArray(usage) ? usage : [usage]) : [];
        usages = usages.map(u => u.replace('\$0', path.substring(1) /* drop leading / */));
        const lineRange = findRouteLineRange(path);
        return `
          <dt>${path.substring(1)}</dt>
          ${description ? `<dd>Description: ${description}</dd>` :
                          '<dd style="background-color: #f99">No description found!</dd>'}
          ${usages.length > 0 ? `<dd>Usage:
            <ul>
              ${usages.map(u => `<li>${u}</li>`).join('\n')}
            </ul>
          </dd>` : '<dd style="background-color: #f99">No usage found!</dd>'}
          ${lineRange ?
            `<dd><details>
              <summary>Source code (<a href="https://github.com/osnr/TabFS/blob/master/extension/background.js#L${lineRange[0]+1}-L${lineRange[1]+1}">on GitHub</a>)</summary>
              <pre><code>${
                jsLines.slice(lineRange[0], lineRange[1] + 1).join('\n')
                // FIXME: escape for HTML
              }</code></pre>
            </details></dd>` : '<dd style="background-color: #f99">No source code found!</dd>'}
        `;
      }).join('\n') + `
    </dl>
  </body>
</html>
`;
});

// Ensure that there are routes for all ancestors. This algorithm is
// probably not correct, but whatever. Basically, you need to start at
// the deepest level, fill in all the parents 1 level up that don't
// exist yet, then walk up one level at a time. It's important to go
// one level at a time so you know (for each parent) what all the
// children will be.
for (let i = 10; i >= 0; i--) {
  for (let path of Object.keys(Routes).filter(key => key.split("/").length === i)) {
    path = path.substr(0, path.lastIndexOf("/"));
    if (path == '') path = '/';

    if (!Routes[path]) { Routes[path] = makeDefaultRouteForDirectory(path); }
  }
  // I also think it would be better to compute this stuff on the fly,
  // so you could patch more routes in at runtime, but I need to think
  // a bit about how to make that work with wildcards.
}


for (let key in Routes) {
  // /tabs/by-id/#TAB_ID/url.txt -> RegExp \/tabs\/by-id\/(?<int$TAB_ID>[0-9]+)\/url.txt
  Routes[key].__matchVarCount = 0;
  Routes[key].__regex = new RegExp(
    '^' + key
      .split('/')
      .map(keySegment => keySegment
           .replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
           .replace(/([#:])([A-Z_]+)/g, (_, sigil, varName) => {
             Routes[key].__matchVarCount++;
             return `(?<${sigil === '#' ? 'int$' : 'string$'}${varName}>` +
                         (sigil === '#' ? '[0-9]+' : '[^/]+') + `)`;
           }))
      .join('/') + '$');

  Routes[key].__match = function(path) {
    const result = Routes[key].__regex.exec(path);
    if (!result) { return; }

    const vars = {};
    for (let [typeAndVarName, value] of Object.entries(result.groups || {})) {
      let [type_, varName] = typeAndVarName.split('$');
      // TAB_ID -> tabId
      varName = varName.toLowerCase();
      varName = varName.replace(/_([a-z])/g, c => c[1].toUpperCase());
      vars[varName] = type_ === 'int' ? parseInt(value) : value;
    }
    return vars;
  };

  // Fill in default implementations of fs ops:

  // if readdir -> directory -> add getattr, opendir, releasedir
  if (Routes[key].readdir) {
    Routes[key] = {
      getattr() { 
        return {
          st_mode: unix.S_IFDIR | 0755,
          st_nlink: 3,
          st_size: 0,
        };
      },
      opendir({path}) { return { fh: 0 }; },
      releasedir({path}) { return {}; },
      ...Routes[key]
    };

  } else if (Routes[key].readlink) {
    Routes[key] = {
      async getattr(req) {
        const st_size = (await this.readlink(req)).buf.length + 1;
        return {
          st_mode: unix.S_IFLNK | 0444,
          st_nlink: 1,
          // You _must_ return correct linkee path length from getattr!
          st_size
        };
      },
      ...Routes[key]
    };
    
  } else if (Routes[key].read || Routes[key].write) {
    Routes[key] = {
      async getattr() {
        return {
          st_mode: unix.S_IFREG | ((Routes[key].read && 0444) | (Routes[key].write && 0222)),
          st_nlink: 1,
          st_size: 100 // FIXME
        };
      },
      open() { return { fh: 0 }; },
      release() { return {}; },
      ...Routes[key]
    };
  }
}

// most specific (lowest matchVarCount) routes should match first
const sortedRoutes = Object.values(Routes).sort((a, b) =>
  a.__matchVarCount - b.__matchVarCount
);
function tryMatchRoute(path) {
  if (path.match(/\/\._[^\/]+$/)) {
    // Apple Double ._whatever file for xattrs
    throw new UnixError(unix.ENOTSUP); 
  }

  for (let route of sortedRoutes) {
    const vars = route.__match(path);
    if (vars) { return [route, vars]; }
  }
  throw new UnixError(unix.ENOENT);
}

let port;
async function onMessage(req) {
  if (req.buf) req.buf = atob(req.buf);
  console.log('req', req);

  let response = { op: req.op, error: unix.EIO };
  let didTimeout = false, timeout = setTimeout(() => {
    // timeout is very useful because some operations just hang
    // (like trying to take a screenshot, until the tab is focused)
    didTimeout = true; console.error('timeout');
    port.postMessage({ id: req.id, op: req.op, error: unix.ETIMEDOUT });
  }, 1000);

  /* console.time(req.op + ':' + req.path);*/
  try {
    const [route, vars] = tryMatchRoute(req.path);
    response = await route[req.op]({...req, ...vars});
    response.op = req.op;
    if (response.buf) { response.buf = btoa(response.buf); }

  } catch (e) {
    console.error(e);
    response = {
      op: req.op,
      error: e instanceof UnixError ? e.error : unix.EIO
    };
  }
  /* console.timeEnd(req.op + ':' + req.path);*/

  if (!didTimeout) {
    clearTimeout(timeout);

    console.log('resp', response);
    response.id = req.id;
    port.postMessage(response);
  }
};

function tryConnect() {
  // Safari is very weird -- it has this native app that we have to talk to,
  // so we poke that app to wake it up, get it to start the TabFS process
  // and boot a WebSocket, then connect to it.
  // Is there a better way to do this?
  if (chrome.runtime.getURL('/').startsWith('safari-web-extension://')) { // Safari-only
    chrome.runtime.sendNativeMessage('com.rsnous.tabfs', {op: 'safari_did_connect'}, resp => {
      console.log(resp);

      let socket;
      function connectSocket(checkAfterTime) {
        socket = new WebSocket('ws://localhost:9991');
        socket.addEventListener('message', event => {
          onMessage(JSON.parse(event.data));
        });

        port = { postMessage(message) {
          socket.send(JSON.stringify(message));
        } };

        setTimeout(() => {
          if (socket.readyState === 1) {
          } else {
            console.log('ws connection failed, retrying in', checkAfterTime);
            connectSocket(checkAfterTime * 2);
          }
        }, checkAfterTime);
      }
      connectSocket(200);
    });
    return;
  }
  
  port = chrome.runtime.connectNative('com.rsnous.tabfs');
  port.onMessage.addListener(onMessage);
  port.onDisconnect.addListener(p => {
    console.log('disconnect', p);
  });
}


if (typeof process === 'object') {
  // we're running in node (as part of a test)
  // return everything they might want to test
  module.exports = {Routes, tryMatchRoute}; 

} else {
  tryConnect();
}