theseus/bundled-addons/pdf-editor/index.js

// PDF Editor — the Node half. Small on purpose: everything interesting
// happens in editor.html, which is a full Theseus tab (the "open-tab"
// capability) rendering with pdf.js and writing with pdf-lib.
//
// This file exists for the three things a file:// page cannot do itself:
//
//   1. Launch. The dock's "Open a PDF…" item opens the editor tab. Nothing
//      is handed over; the editor shows its own drop zone.
//   2. Fetch a PDF the user right-clicked. A file:// page has an opaque
//      origin, so its cross-origin fetch of https://host/doc.pdf is refused
//      by CORS on essentially every real server. electron's `net.fetch`
//      runs on the app session instead, so it follows whatever proxy the
//      user configured, and the bytes land in a scratch file.
//   3. Serve those bytes back. The editor pulls them with
//      invoke("getBytes", {id}).
//
// Handoff is a scratch FILE plus an id in the query string, not a
// storage.__pending entry. The screenshot add-on shipped __pending first
// and had to abandon it: the receiving page drains the entry on first
// paint, so a reload — or Theseus restoring the tab on next launch — finds
// an empty slot and an editor with no document. An id in the URL survives
// both, because the bytes are still on disk. It also keeps a 20 MB PDF out
// of a kv store whose every write rewrites the whole JSON file.

const fs = require("node:fs");
const path = require("node:path");

const SCRATCH_DIR = "pdf-editor-scratch";
const MAX_RECENT = 8;                  // scratch files kept before the oldest is reaped
const MAX_BYTES = 200 * 1024 * 1024;   // refuse anything absurd before we buffer it

module.exports = {
  activate(api) {
    // Per-add-on scratch dir under <userData>/extensions-data/, a sibling of the
    // kv JSON. We never write inside the add-on folder — a user reading the
    // shipped source should see only what shipped.
    const dataParent = path.dirname(path.join(api.folder, ".."));
    // api.dataDir is the host-provided per-extension data folder (<userData>/extensions-data);
    // the fallback rebuilds it for hosts that predate that field.
    const scratchDir = path.join(api.dataDir || path.join(dataParent, "extensions-data"), SCRATCH_DIR);
    try { fs.mkdirSync(scratchDir, { recursive: true }); }
    catch (e) { api.log("scratch mkdir failed:", e?.message); }

    // ---- scratch bookkeeping ------------------------------------------
    // The ring lives in api.storage so it survives restarts, and every read
    // prunes entries whose file has gone missing.
    function readRing() {
      const r = api.storage.get("recent", []);
      return Array.isArray(r) ? r : [];
    }
    function pruneRing(ring) {
      const alive = ring.filter((r) => { try { fs.accessSync(r.path); return true; } catch { return false; } });
      const keep = alive.slice(0, MAX_RECENT);
      for (const r of alive.slice(MAX_RECENT)) { try { fs.unlinkSync(r.path); } catch {} }
      return keep;
    }
    function remember(entry) {
      let ring = readRing();
      ring.unshift(entry);
      ring = pruneRing(ring);
      api.storage.set("recent", ring);
    }
    function findEntry(id) {
      return pruneRing(readRing()).find((r) => r.id === id) || null;
    }
    function newId() {
      return "doc-" + Date.now().toString(36) + "-" + Math.random().toString(36).slice(2, 8);
    }

    // A filename we are willing to put on disk and later show as the
    // document's name. Anything path-ish or non-printable is discarded, not
    // escaped — the fallback name is always acceptable.
    function safeName(raw) {
      const base = String(raw || "").split(/[\\/]/).pop().trim();
      const clean = base.replace(/[\x00-\x1f<>:"|?*]/g, "").slice(0, 120);
      if (!clean || clean === "." || clean === "..") return "document.pdf";
      return /\.pdf$/i.test(clean) ? clean : clean + ".pdf";
    }
    // The last path segment of a URL is the best filename guess we have.
    function nameFromUrl(url) {
      try {
        const u = new URL(url);
        const seg = decodeURIComponent(u.pathname.split("/").filter(Boolean).pop() || "");
        return safeName(seg || u.hostname + ".pdf");
      } catch { return "document.pdf"; }
    }

    function writeScratch(buf, name) {
      const id = newId();
      const file = path.join(scratchDir, id + ".pdf");
      fs.writeFileSync(file, buf);
      const entry = { id, name, path: file, size: buf.length, at: Date.now() };
      remember(entry);
      return entry;
    }

    // ---- launch paths -------------------------------------------------
    // Dock → "Open a PDF…": a bare editor tab. The editor's own drop zone
    // and File → Open take it from there, so no bytes cross IPC at all.
    api.onMessage("menu-select", (payload) => {
      const item = String(payload && payload.id || "");
      if (item !== "open") throw new Error(`unknown menu item: ${item}`);
      api.openTab("editor.html");
      api.log("opened an empty editor tab");
      return { ok: true };
    });

    // Right-click a link → fetch it here, hand the editor an id.
    api.onMessage("context-menu", async (payload) => {
      if (String(payload && payload.itemId || "") !== "open-link") return;
      const url = String(payload && payload.linkURL || "").trim();
      if (!url) { api.log("context-menu fired with no link"); return { ok: false }; }
      let parsed;
      try { parsed = new URL(url); } catch { throw new Error(`not a URL: ${url.slice(0, 80)}`); }
      if (!/^https?:$/.test(parsed.protocol)) {
        throw new Error(`refusing to fetch a ${parsed.protocol} link`);
      }
      const { net } = api.require("electron");
      api.log(`fetching ${parsed.origin}${parsed.pathname.slice(0, 60)} …`);
      const res = await net.fetch(url);
      if (!res.ok) throw new Error(`${res.status} ${res.statusText || "fetch failed"}`);
      const len = Number(res.headers.get("content-length") || 0);
      if (len > MAX_BYTES) throw new Error(`refusing ${(len / 1048576).toFixed(0)} MB — over the ${MAX_BYTES / 1048576} MB cap`);
      const buf = Buffer.from(await res.arrayBuffer());
      if (buf.length > MAX_BYTES) throw new Error(`refusing ${(buf.length / 1048576).toFixed(0)} MB — over the cap`);
      // %PDF is the only header a PDF can start with. A server that answered
      // an HTML error page with 200 would otherwise reach the editor and
      // fail there with a much less useful message.
      if (buf.subarray(0, 5).toString("latin1") !== "%PDF-") {
        throw new Error("that link did not answer with a PDF");
      }
      const entry = writeScratch(buf, nameFromUrl(url));
      api.openTab("editor.html", { query: { doc: entry.id } });
      api.log(`fetched ${entry.name} (${entry.size} bytes) → ${entry.id}`);
      return { ok: true, id: entry.id };
    });

    // ---- editor-facing handlers ---------------------------------------
    // Bytes go across as a Buffer, which structured-clones into a
    // Uint8Array on the page side. Base64 would inflate a 20 MB file to 27
    // MB of string for no benefit.
    api.onMessage("getBytes", (payload) => {
      const id = String(payload && payload.id || "");
      const hit = findEntry(id);
      if (!hit) throw new Error(`no scratch document "${id}"`);
      return { id: hit.id, name: hit.name, size: hit.size, at: hit.at, data: fs.readFileSync(hit.path) };
    });

    // The editor calls this when the user closes a document it had been
    // handed, so a fetched PDF does not sit in scratch forever. Missing ids
    // are fine — the ring may already have reaped it.
    api.onMessage("release", (payload) => {
      const id = String(payload && payload.id || "");
      const hit = findEntry(id);
      if (hit) { try { fs.unlinkSync(hit.path); } catch {} }
      api.storage.set("recent", readRing().filter((r) => r.id !== id));
      return { ok: true };
    });

    // A link inside a PDF, clicked. It must NOT navigate the editor's own tab —
    // that would throw away an unsaved editing session — so the editor hands
    // the URL here and we open it as a new tab instead.
    api.onMessage("openExternal", (payload) => {
      const url = String(payload && payload.url || "").trim();
      let parsed;
      try { parsed = new URL(url); } catch { throw new Error("not a URL"); }
      if (!/^https?:$/.test(parsed.protocol)) throw new Error(`refusing to open a ${parsed.protocol} link`);
      api.openTab(parsed.href);
      return { ok: true };
    });

    // Reveal the scratch dir. Useful when a save went somewhere the user
    // cannot find, and for support questions about what is cached.
    api.onMessage("openScratch", () => {
      const { shell } = api.require("electron");
      shell.openPath(scratchDir);
      return { ok: true, path: scratchDir };
    });

    // Reap on activation: scratch is a cache, and a crash mid-session can
    // leave files with no ring entry pointing at them.
    try {
      const known = new Set(readRing().map((r) => path.basename(r.path)));
      for (const f of fs.readdirSync(scratchDir)) {
        if (!known.has(f)) fs.unlinkSync(path.join(scratchDir, f));
      }
    } catch (e) { api.log("scratch reap skipped:", e?.message); }

    api.log("registered pdf-editor toolbar menu + link context-menu item");
  },
};