theseus/extensions/docx-editor/index.js

// Word editor — the add-on half. All the document work happens in the
// editor tab; this side owns the sidebar panel, the scratch folder and the
// ring of recently-opened documents.
//
// Flow:
//   panel picks a file (<input type=file>, or a drop) → invokes "stash" with
//   the bytes → we write them to the scratch dir and push them onto the
//   recent ring → panel invokes "openEditor" → we park a pointer under
//   storage.__pending and openTab("editor.html") → the editor drains
//   __pending on its first paint and pulls the bytes with "getBytes".
//
// Only a pointer goes through storage, never the document: add-on storage is
// a single JSON file rewritten in full on every set, and a few megabytes of
// base64 in there would make every unrelated write expensive.

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

const MAX_RECENT  = 8;                     // documents kept in the ring
const SCRATCH_DIR = "docx-scratch";
const MAX_BYTES   = 64 * 1024 * 1024;      // refuse absurd inputs early

module.exports = {
  activate(api) {
    api.registerSidebarPanel({
      id: "main",
      title: "Word editor",
      page: "panel.html",
    });

    // Per-add-on scratch dir under <userData>/addons-data/, same arrangement
    // as the screenshot add-on: never write inside the add-on folder itself,
    // where it would confuse anyone reading the shipped source.
    const dataParent = path.dirname(path.join(api.folder, ".."));
    const scratchDir = path.join(dataParent, "addons-data", SCRATCH_DIR);
    try { fs.mkdirSync(scratchDir, { recursive: true }); }
    catch (e) { api.log("scratch mkdir failed:", e?.message); }

    function stamp() {
      const d = new Date();
      const p = (n) => String(n).padStart(2, "0");
      return `${d.getFullYear()}${p(d.getMonth() + 1)}${p(d.getDate())}-${p(d.getHours())}${p(d.getMinutes())}${p(d.getSeconds())}`;
    }

    // A scratch filename that can't escape the folder however the original
    // was named. The display name is kept separately in the ring.
    function scratchName(displayName) {
      const base = String(displayName || "document")
        .replace(/\.docx$/i, "")
        .replace(/[^\w.\- ]+/g, "_")
        .replace(/\s+/g, " ")
        .trim()
        .slice(0, 60) || "document";
      return `${stamp()}-${base}.docx`;
    }

    function pruneRecent(recent) {
      const alive = recent.filter((r) => { try { fs.accessSync(r.path); return true; } catch { return false; } });
      const keep = alive.slice(0, MAX_RECENT);
      for (const gone of alive.slice(MAX_RECENT)) { try { fs.unlinkSync(gone.path); } catch {} }
      return keep;
    }

    function readRecent() {
      let recent = api.storage.get("recent", []);
      return Array.isArray(recent) ? recent : [];
    }

    function findRecent(id) {
      return readRecent().find((r) => r.id === id) || null;
    }

    function pathOf(id) {
      // Belt and braces: the id came from a renderer, so re-derive the path
      // from the ring rather than joining whatever string arrived.
      const hit = findRecent(id);
      if (!hit) throw new Error(`no document "${id}" in the recent list`);
      const abs = path.resolve(hit.path);
      if (path.dirname(abs) !== path.resolve(scratchDir)) {
        throw new Error("document path escapes the scratch folder");
      }
      return abs;
    }

    // Write bytes to the scratch folder and put them at the head of the ring.
    // `kind` distinguishes what the user opened from what the editor saved
    // back, so the panel can say which is which.
    function stash({ name, base64, kind, replaces }) {
      const buf = Buffer.from(String(base64 || ""), "base64");
      if (!buf.length) throw new Error("no document bytes");
      if (buf.length > MAX_BYTES) throw new Error(`document is too large (${(buf.length / 1048576).toFixed(0)} MB)`);
      // Every .docx is a zip; catching this here beats a confusing parse
      // error three layers deeper in the editor.
      if (!(buf[0] === 0x50 && buf[1] === 0x4b)) {
        throw new Error("that doesn't look like a .docx file");
      }
      const id = scratchName(name);
      const file = path.join(scratchDir, id);
      fs.writeFileSync(file, buf);

      let recent = readRecent();
      if (replaces) recent = recent.filter((r) => r.id !== replaces);
      recent.unshift({
        id,
        name: String(name || "document.docx"),
        path: file,
        bytes: buf.length,
        at: Date.now(),
        kind: kind === "saved" ? "saved" : "opened",
      });
      recent = pruneRecent(recent);
      api.storage.set("recent", recent);
      api.log(`stashed ${id} (${buf.length} bytes, ${kind || "opened"})`);
      return { id, name: String(name || "document.docx"), bytes: buf.length };
    }

    api.onMessage("stash", (payload) => stash(payload || {}));

    // Hand a document to the editor tab. The pointer under __pending is what
    // the editor drains on its first paint; the query string carries the same
    // id so a reload of the tab still finds its document.
    api.onMessage("openEditor", (payload) => {
      const id = payload && payload.id ? String(payload.id) : "";
      if (id) {
        const hit = findRecent(id);
        if (!hit) throw new Error(`no document "${id}" in the recent list`);
        api.storage.set("__pending", { id, name: hit.name, at: Date.now() });
      } else {
        api.storage.set("__pending", null);
      }
      api.openTab("editor.html", id ? { query: { doc: id } } : undefined);
      api.log(id ? `opening editor for ${id}` : "opening editor with a blank document");
      return { ok: true, id };
    });

    api.onMessage("listRecent", () => {
      const recent = pruneRecent(readRecent());
      api.storage.set("recent", recent);
      return recent.map((r) => ({ id: r.id, name: r.name, bytes: r.bytes, at: r.at, kind: r.kind }));
    });

    api.onMessage("getBytes", (payload) => {
      const id = String(payload && payload.id || "");
      const hit = findRecent(id);
      if (!hit) throw new Error(`no document "${id}" in the recent list`);
      const buf = fs.readFileSync(pathOf(id));
      return { id, name: hit.name, base64: buf.toString("base64"), bytes: buf.length, at: hit.at, kind: hit.kind };
    });

    // Autosave. The editor calls this as the user works; each document keeps
    // one autosave entry rather than filling the ring with its own history.
    api.onMessage("autosave", (payload) => {
      const p = payload || {};
      const res = stash({
        name: String(p.name || "document.docx"),
        base64: p.base64,
        kind: "saved",
        replaces: p.replaces ? String(p.replaces) : "",
      });
      return res;
    });

    api.onMessage("clearRecent", (payload) => {
      const id = payload && payload.id ? String(payload.id) : "";
      let recent = readRecent();
      if (id) {
        const hit = recent.find((r) => r.id === id);
        if (hit) { try { fs.unlinkSync(hit.path); } catch {} }
        recent = recent.filter((r) => r.id !== id);
      } else {
        for (const r of recent) { try { fs.unlinkSync(r.path); } catch {} }
        recent = [];
      }
      api.storage.set("recent", recent);
      return { ok: true };
    });

    api.onMessage("openFolder", (payload) => {
      const { shell } = api.require("electron");
      const id = payload && payload.id ? String(payload.id) : "";
      if (id) {
        const hit = findRecent(id);
        if (hit) { shell.showItemInFolder(hit.path); return { ok: true, path: hit.path }; }
      }
      shell.openPath(scratchDir);
      return { ok: true, path: scratchDir };
    });

    api.log("registered docx-editor sidebar panel");
  },
};