# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

InstaArchive Viewer is a React 19 + Vite 6 PWA for browsing archived Instagram data (official Instagram exports and Instaloader archives). All archive *parsing* happens client-side in the browser; the Express backend only indexes and serves files from disk, and never parses archive contents.

## Commands

- `npm install` — install dependencies
- `npm run dev` — Vite dev server on port 3000 (proxies `/api` and `/archives` to `http://localhost:3001`)
- `npm run server` — Express backend (`tsx server.ts`) on port 3001, serving `ARCHIVES_DIR` (defaults to `./_sample-archives`)
- `npm run build` — frontend to `dist/`, backend to `dist-server/`
- `npm run lint` — type-check only (`tsc --noEmit`)
- `npm test` / `npm run test:watch` — vitest
- `npx vitest run src/lib/archive-patterns.test.ts` — a single test file
- `npm run jd2 -- --archives <dir> --dry-run` — generate JDownloader `.crawljob`
  files for every profile on disk (see `scripts/jd2-sync.ts` and
  `docs/jdownloader.md`)

Local development usually needs both `npm run dev` and `npm run server`. Local-folder mode works without the backend; server-mode archives do not.

## Architecture

### Two archive sources, one data model

Loading is unified behind the `ArchiveFile` interface (`src/types/index.ts`, implementations in `src/lib/archive-files.ts`):

- **`LocalArchiveFile`** — wraps a browser `File`. `createObjectUrl()` mints a **disk-backed** blob URL directly from the File; never route media through `arrayBuffer()`, which pulls whole files into memory.
- **`RemoteArchiveFile`** — wraps a file served from `/archives/...`, fetched on demand.

`revocable` tells callers whether the returned URL must be revoked. The scanner tracks every minted URL and releases them on archive teardown.

### Sidecar directories

An archive root holds one directory per profile plus *sidecars* that belong to it:

```
0ct0ber19                                 -> posts (base)
0ct0ber19 - reels                         -> reels
story - 0ct0ber19                         -> stories
story highlights - 0ct0ber19 - Heestory   -> highlight "Heestory"
```

`src/lib/archive-grouping.ts` (shared by server and tests) folds these into a single profile with a `sources` list. Sidecars never appear as standalone archives. Each file the server returns carries its `kind`, so the client routes posts / reels / story ring / highlight circles without re-deriving naming rules.

### Server-side archive index (`src/lib/archive-index.ts`)

**Do not reintroduce per-request filesystem walks.** Archives typically live on network storage where per-file `stat` costs ~1.4ms and does not parallelise; a naive walk of a 110k-file root took ~52s per listing. Instead:

- Each source directory is indexed once and cached, keyed by its **directory mtime** (a directory `stat` is effectively free).
- The index is warmed in the background at startup and persisted to `CACHE_DIR` (mount a volume at `/cache`).
- `GET /api/archives` does no file walking at all — it returns directory-mtime `signature`s, which the client uses for cache invalidation instead of a file count.
- Only media files are stat'd (for `size`, which gates thumbnailing) and only highlights need `mtime` (their filenames carry no date).

### Scanning pipeline (`src/hooks/useArchiveScanner.ts`)

`handleFiles` indexes files, detects format, then parses via one of three largely independent paths that all write into a shared `postsMap`:

1. **JSON manifest** (`posts_1.json`, possibly `.json.xz` via `xz-decompress`) — media matched to entries by URI, then ID, then filename heuristic, in that fallback order.
2. **Filename patterns** — see `src/lib/archive-patterns.ts` for the export / Instaloader / highlight regexes, extracted as pure functions and covered by tests. Prefer changing them there.
3. **Generic grouping fallback** — when nothing else matched, files sharing a basename become one carousel.

Results are cached to IndexedDB. Media records store a stable `path`; **`url` is not persistable** for local archives because blob URLs die with the document.

Three different JSON shapes turn up as `.json`, so they are told apart structurally, not by filename (`src/lib/gallery-dl-sidecar.ts`):

| shape | marker |
|---|---|
| Instagram export manifest | top-level `media` array |
| Instaloader `.json.xz` | GraphQL node under `node` / `__typename` |
| gallery-dl sidecar | flat, `post_shortcode` + `type`, none of the above |

The gallery-dl sidecar is the only source that states what a post *is*: its `type` (`post` / `reel` / `story` / `highlight`) is Instagram's own classification, so `post.isReel` set from it beats every fallback in `post-tabs.ts`. This matters — of the 781 items in `official_artms - reels`, the sidecars say only **360 are reels**; the other 421 are ordinary feed videos the clips endpoint returns via `include_feed_video`. Directory-based classification counted all 781.

**Dates are ranked, not last-write-wins** (`src/lib/post-dates.ts`): sidecar (what Instagram reported) beats filename (what the fetcher wrote) beats mtime (when the file hit disk, and unrelated to when it was posted). Ties keep the incumbent. Several files describe one post and they are scanned in directory order, not in order of trustworthiness, so without the ranking the date was decided by whichever file came first. Only JDownloader highlights fall to mtime at all — `parseArchiveFilename` flags those via `dateFromMtime`.

### Cache and local-archive persistence (`src/lib/archive-cache.ts`)

IndexedDB keys are namespaced (`archive:`, `thumb:`, `handle:`) so listing archives does not deserialize every cached thumbnail blob, and thumbnails are scoped per archive to avoid cross-archive collisions.

Restoring an archive **rehydrates URLs from `path`**: server archives rebuild HTTP URLs; local archives re-open a persisted `FileSystemDirectoryHandle` and mint fresh blob URLs. If the folder is unreachable (permission lapsed, or the browser lacks `showDirectoryPicker` — Firefox/Safari), the app re-prompts rather than rendering broken images.

### Thumbnails (`src/hooks/useThumbnailQueue.ts` + `src/lib/thumbnail-worker.ts`)

Images over 1MiB are downscaled in a Web Worker via `OffscreenCanvas`. The queue is **serial on purpose** — decoding several 50MP+ images at once OOMs the tab. `requestThumbnail` must keep a stable identity (it reads cache state through a ref), or every completed thumbnail re-runs the effect in all mounted thumbnails.

### Profile tabs (`src/lib/post-tabs.ts`)

The grid holds **everything**, reels included, and the Reels tab is a *filtered view* of that same set. Only the Reels tab filters. The tabs were mutually exclusive until v1.7.0, which hid a lot: 1100 of `loonatheworld`'s 3813 posts and 533 of `for.heejin`'s 1225 never appeared in the grid at all.

This *approximates* Instagram rather than matching it. Instagram's grid includes a reel only if the creator shared it to feed — a per-post choice, measured live on 2026-08-16: `official_artms` had 21 reels in its first 34 grid tiles, `0ct0ber19` just 1 in 214. That flag appears nowhere in an archive (JD2 stores no metadata, and Instaloader's `product_type` says what a post *is*, not whether it was shared to feed), so showing everything is the closest reachable behaviour. Instagram's "N posts" counter equals its grid, which is why the header counts `postsForTab(allPosts, 'posts')` and not `allPosts` — the raw list still holds both copies of a double-fetched post.

When checking the live site, note that grid reels link to `/reel/<code>/` while ordinary posts link to `/<user>/p/<code>/`. Matching only `/p/` silently drops every reel, which once produced a confident and completely wrong conclusion that Instagram never shows reels in the grid.

Deciding *what is a reel* has no good answer for most archives. Instagram's own marker is `product_type` on the post's GraphQL node (`clips` = reel, `feed` = ordinary feed video, `igtv`, `story`) — `__typename` is `GraphVideo` for all three, and aspect ratio does not separate them either. But:

- Only Instaloader archives carry that metadata, and only newer captures. A survey of `gibiofficial` found `product_type` on 1101 of 5919 sidecars, and just **2** posts marked `clips`.
- JDownloader archives carry none at all — media plus a `.txt` holding the bare caption.

So the viewer believes a `- reels` sidecar directory when one exists, and otherwise falls back to treating a lone video as a reel. **The fallback is a guess**: it cannot tell a reel from a feed video or an old IGTV upload, and it misses videos inside carousels.

`dedupePostCopies` exists because the JDownloader flow crawls the profile URL and the `/reels/` URL separately (the profile page misses some reels), so the two overlap and a reel can land on disk twice. Those become two posts with distinct directory-scoped ids, which the grid would otherwise render side by side. It dedupes by shortcode, preferring the reels-source copy. It is only safe over `allPosts` — stories and highlights are excluded there, and a shortcode may legitimately appear in both a profile and a highlight.

### URL state (`src/App.tsx`, `src/lib/routing.ts`)

Paths mirror Instagram: `/<archive>/`, `/<archive>/reels/`, `/<archive>/p/<shortcode>/`. The old `?a=&t=&p=` form is still parsed for existing links but never written. Reserved prefixes (`api`, `archives`, `assets`…) can't be mistaken for a profile name.

A post URL carries no tab, as on Instagram — the tab is re-derived from the post's `source`, so a reel link lands on the Reels tab and pages through reels. Sidecar posts keep directory-scoped ids internally but expose only the shortcode.

Three rules, all learned from real bugs:

- The initial route is captured into a ref on first render; the URL is rewritten from state as soon as anything loads, so reading `window.location` later sees the rewrite, not the user's link.
- URL writing is gated on `hasInitialLoaded`, otherwise it erases the deep link before the loader consumes it.
- Deep-link resolution waits on the archive fetch having *settled* (`archivesFetched`), not on `isServerMode`, which is still false while the request is in flight.

### Mobile feed (`src/components/PostFeed.tsx`)

Below `md`, opening a post renders a scrolling feed page rather than the modal (`useIsMobile` decides). Only a window of posts is mounted; it grows both ways, and prepending corrects `scrollTop` in a `useLayoutEffect` so content doesn't jump. Only the post crossing the viewport centre plays its video and drives the URL. Desktop keeps `PostModal`; both share `MediaCarousel`.

### Backend (`server.ts`)

Serves `/api/archives`, `/api/archives/:name/files`, static `/archives`, and the built SPA. Notes:

- Express decodes route params **after** segment matching, so `..%2f` reaches the handler as `../`. All user-supplied archive names go through `resolveArchivePath`.
- `os.userInfo()` throws for a UID with no `/etc/passwd` entry, which is what `--user 1234:1234` produces — use `describeUser()`.

### CSP: do not tighten `script-src` or `connect-src` without testing xz

The xz decompressor for Instaloader `.json.xz` sidecars is **WebAssembly**, embedded as a `data:` URL the library fetches at startup. The policy must keep:

```
script-src  'self' 'wasm-unsafe-eval'     // compile wasm, without allowing eval() of JS
connect-src 'self' data:                  // fetch the embedded module
```

Removing either breaks decoding with a bare `TypeError: Failed to fetch` **and no stack** — it surfaces through `new Response(stream).json()`, so it reads like a network fault rather than a policy block. The visible symptom is not an error page: archives silently lose captions, story flags and all profile metadata (follower counts, bio, name). This shipped broken for several releases.

To check quickly, run in the page console:

```js
await fetch('data:application/wasm;base64,AGFzbQEAAAA=')            // connect-src
await WebAssembly.instantiate(Uint8Array.of(0,97,115,109,1,0,0,0))  // script-src
```

**The Vite dev server does not send these headers**, so anything CSP-related is invisible in `npm run dev`. Verify security-header and PWA behaviour by building and serving `dist/` through `server.js`, not against the dev server.

### PWA: server-only changes do not reach installed clients

The service worker precaches `index.html` **together with its response headers**. A change that touches only the server (a CSP fix, a new header) leaves the client build byte-identical, so the precache manifest and `sw.js` are unchanged, the worker never updates, and installed clients keep replaying the old shell with the old headers — indefinitely.

`vite.config.ts` therefore compiles the package version into the client via `define: { __APP_VERSION__ }`, and `App.tsx` renders it in the footer. That is **load-bearing**: it makes every release change the bundle hash → `index.html` → its precache revision → `sw.js`, which is what browsers byte-compare to decide whether to update. Don't remove it as dead weight.

To recover a client stuck on an old shell: unregister the service worker, delete its caches, reload.

### Deployment

Live archives live in `<share>/Instagram-archive/archives/` — one directory per profile plus sidecars. Directories that are not Instagram profiles (tool output, exports from other services) sit *outside* that folder so they never reach the viewer.

Container runs as non-root. The image defaults to `node`, but the archive share must be *listable* by that UID — a mode-711 share owned by another account needs `user: "<uid>:<gid>"` in compose. Mount a volume at `/cache` so the index survives restarts.

### PWA / build quirks

- `vite.config.ts` sets `hmr: process.env.DISABLE_HMR !== 'true'` — intentional, leave it.
- `workbox.navigateFallbackDenylist` excludes `/api` and `/archives` so those hit the real server.
- Fonts and icons are vendored in `public/` — do not reintroduce CDN references; the app advertises offline support and local-only processing.