feat(electron): main process, vault, search index, links, import, capture

Vault on plain .md files with FTS5 index, link rewriting, canvas files,
history/trash/backup, link previews, image fetch, tasks and unlinked
mentions, Notion/Obsidian importer, quick-capture window and shortcut.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

electron/imagefetch.cjs

@@ -0,0 +1,79 @@
+'use strict';
+// Download a picture from a web address (for a page's cover). Runs in the main process, and has the same rule as
+// link previews: only public http(s) addresses, every redirect checked again (see linkpreview.cjs).
+const path = require('node:path');
+const { allowed, hooks } = require('./linkpreview.cjs');
+
+const MAX_BYTES = 50 * 1024 * 1024;
+const TIMEOUT = 25000;
+const MAX_REDIRECTS = 5;
+const EXT = { 'image/png': 'png', 'image/jpeg': 'jpg', 'image/jpg': 'jpg', 'image/gif': 'gif', 'image/webp': 'webp', 'image/avif': 'avif', 'image/svg+xml': 'svg', 'image/bmp': 'bmp' };
+const KNOWN = /\.(png|jpe?g|gif|webp|avif|svg|bmp)$/i;
+
+// A file name for it: the address's own (when it looks like one), else "cover" with the right extension.
+function nameFor(u, type) {
+  let base = '';
+  try { base = decodeURIComponent(path.posix.basename(u.pathname)); } catch { base = path.posix.basename(u.pathname); }
+  base = base.replace(/[\\/:*?"<>|\u0000-\u001f]/g, '-').trim().slice(0, 80);
+  if (KNOWN.test(base)) return base;
+  const ext = EXT[type] || 'jpg';
+  return `${base && !base.startsWith('.') ? base.replace(/\.[a-z0-9]{1,5}$/i, '') : 'cover'}.${ext}`;
+}
+
+async function readLimited(res, max) {
+  const chunks = [];
+  let size = 0;
+  const reader = res.body.getReader();
+  try {
+    for (;;) {
+      const { done, value } = await reader.read();
+      if (done) break;
+      size += value.length;
+      if (size > max) throw new Error('That image is too big (50 MB at most).');
+      chunks.push(Buffer.from(value));
+    }
+  } finally {
+    reader.cancel().catch(() => {});
+  }
+  return Buffer.concat(chunks);
+}
+
+// -> { bytes: Buffer, name, type }. Throws an Error whose message is meant for the person.
+async function fetchImage(url, { fetch: doFetch, lookup } = {}) {
+  const get = doFetch || hooks.fetch || globalThis.fetch;
+  const look = lookup || hooks.lookup;
+  const signal = AbortSignal.timeout(TIMEOUT);
+  let u = await allowed(String(url || '').trim(), look);
+  if (!u) throw new Error('That is not a public web address (http or https).');
+  for (let hop = 0; hop <= MAX_REDIRECTS; hop++) {
+    let res;
+    try {
+      res = await get(u.href, {
+        redirect: 'manual',
+        signal,
+        headers: { 'user-agent': 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0 Safari/537.36', accept: 'image/*,*/*;q=0.1' }
+      });
+    } catch {
+      throw new Error('Could not reach that address.');
+    }
+    if (res.status >= 300 && res.status < 400) {
+      const loc = res.headers.get('location');
+      const next = loc ? await allowed(new URL(loc, u).href, look) : null;
+      if (!next) throw new Error('That address redirects somewhere that is not allowed.');
+      u = next;
+      continue;
+    }
+    if (!res.ok) throw new Error(`The server answered ${res.status}.`);
+    const type = String(res.headers.get('content-type') || '').split(';')[0].trim().toLowerCase();
+    if (!type.startsWith('image/')) throw new Error('That address is not a picture.');
+    const len = Number(res.headers.get('content-length'));
+    if (len > MAX_BYTES) throw new Error('That image is too big (50 MB at most).');
+    if (!res.body) throw new Error('That address sent nothing.');
+    const bytes = await readLimited(res, MAX_BYTES);
+    if (!bytes.length) throw new Error('That address sent nothing.');
+    return { bytes, name: nameFor(u, type), type };
+  }
+  throw new Error('Too many redirects.');
+}
+
+module.exports = { fetchImage, nameFor };