# TODO

Known issues and deferred work. Agent-facing notes belong in the `AGENTS.md` files;
this is for things that are broken or missing and not yet scheduled.

## Backend

### Identifier extraction drops most ISBNs

`backend/src/chitai/services/metadata_extractor.py` — `EpubExtractor._extract_identifiers`

The EPUB path validates `DC:identifier` values verbatim:

```python
for id in epub.get_metadata("DC", "identifier"):
    if is_valid_isbn(id[0]):
        ...
```

`is_valid_isbn` branches on `len(isbn)` being exactly 10 or 13, so anything carrying
formatting fails. Two consequences:

- **Hyphenated ISBNs are silently dropped.** `978-0-486-28211-4` is 17 characters, so it
  never reaches the checksum. Most EPUBs write ISBNs hyphenated, so the majority are lost.
  The PDF path already does this correctly — `_extract_isbns` calls
  `match.replace("-", "")` before validating.
- **`urn:isbn:` prefixes are dropped** for the same reason. This is a common EPUB form.

Fix: normalise before validating — strip a leading `urn:isbn:`, then remove everything
that isn't `0-9` or `X`. Reuse the PDF path's approach rather than duplicating it.

Note this only runs at upload, so fixing it changes nothing for books already imported.
A backfill would need to re-read the files on disk.

### Non-ISBN identifiers are discarded

Same function. Anything that isn't a valid ISBN is thrown away, including values EPUBs
routinely carry: `urn:uuid:…`, `calibre:…`, Google Books volume IDs and ASINs.

The `Identifier` model is already generic (`name` + `value`, unique per book), so storing
them needs no schema change — only the extractor decides what survives. The frontend
already renders ISBN, ASIN and DOI as links and shows unknown types as plain values, so
anything stored will display sensibly.

Worth adding at the same time:

- A DOI regex (`10.\d{4,9}/\S+`) alongside the ISBN scan in `PdfExtractor._extract_isbns`
  — academic PDFs carry one and it is the most useful identifier they have.
- Deriving ISBN-10 from ISBN-13 when only the latter is present. It is a pure checksum
  conversion and doubles the chance of an external lookup matching.

### Any authenticated user can delete any library or book

`backend/src/chitai/database/models/library.py`, `backend/src/chitai/database/models/user.py`

There is no authorization tier. `Library` has no owner column, and `User` carries only
`email` and `password` — no role, no `is_active`. So every authenticated account can create
and delete libraries, and delete books along with their files on disk. Per-user scoping
exists only for reading progress and bookshelves, which `provide_book_service` restricts
correctly.

For a single-household deployment that may well be acceptable. The point is that it is
emergent rather than chosen. The cheapest meaningful step is an `is_admin` flag gating
library deletion and `delete_books` — a model change plus a migration.

### Basic auth answers a malformed header with a 500

`backend/src/chitai/middleware/basic_auth.py` — line 22

```python
username, password = b64decode(auth_header.split("Basic ")[1]).decode().split(":")
```

Nothing guards the parse. A `Bearer` token raises `IndexError`, non-base64 raises
`binascii.Error`, and a credential with no colon raises `ValueError` — as does a password
that *contains* one, since there is no `maxsplit=1`. Every case surfaces as a 500 on an
unauthenticated endpoint. All of them should be 401.

### An unknown KOSync API key returns 404

`backend/src/chitai/middleware/kosync_auth.py` — line 32

`KosyncDeviceService.get_by_api_key` uses `get_one`, which raises `NotFoundError`, but the
middleware catches only `PermissionDeniedException`. The global handler in
`exceptions/handlers.py` then renders it as a 404, so a device presenting a bad key is told
the route does not exist rather than that it is unauthorized. The same file still carries a
leftover `print(exc)`.

Worth doing at the same time: `KosyncDeviceService._generate_api_key` uses
`secrets.token_hex(8)`. 64 bits is thin for a long-lived bearer credential where 32 bytes
is the convention.

### The multi-book download cannot be driven from a test

`backend/src/chitai/services/book.py` — `BookService.get_files`

`/books/download` is the only handler returning a Litestar `Stream`, and it cannot be
exercised through `AsyncTestClient`. The request itself succeeds, then fixture teardown
hangs: the test transport never sends the `http.disconnect` that the streaming response
waits on, so the app's lifespan shutdown never completes. Coverage therefore sits at the
service level, on `get_files` directly.

Unresolved whether the endpoint also stalls behind a real ASGI server, where that
disconnect does arrive. Worth one manual check against `litestar run` before relying on it.

### The production image runs the development server

`backend/Dockerfile` — the final `CMD`

```
CMD ["litestar", "--app-dir", "chitai", "run", "--host", "0.0.0.0", "--port", "8000"]
```

`litestar run` is the CLI development runner. Production should invoke uvicorn or granian
directly, with a worker count.

### No type checker on the backend

Formatting, linting and tests now run in CI (`.gitea/workflows/ci.yml`) and block, and the
tree is clean against them. What is still missing is a type checker: nothing runs one despite
`# type: ignore` comments in the tree.

`pyproject.toml` gained a `[tool.ruff.lint.per-file-ignores]` section for `__init__.py`
re-exports, but no rule selection — so only ruff's default `E4/E7/E9/F` rules run. Widening
that set is worthwhile and will surface a fresh batch of findings.

## Frontend

### Scripted EPUBs run against the app origin

**This is a regression from the foliate-js migration, not a pre-existing gap.**

The old epub.js reader never passed `allowScriptedContent`. epub.js defaults it to
`false`, which sets `iframe.sandbox = "allow-same-origin"` — no `allow-scripts` — so
script inside a book never ran. The vendored foliate-js sets, unconditionally:

```js
// paginator.js — and the same in fixed-layout.js
// `allow-scripts` is needed for events because of WebKit bug
this.#iframe.setAttribute("sandbox", "allow-same-origin allow-scripts");
```

`allow-same-origin` together with `allow-scripts` is the combination that makes the
sandbox attribute do nothing. Sections are served as same-origin `blob:` URLs, so script
in a book can reach `/api/*` with the session cookie attached. foliate's README says as
much and tells you to use a CSP instead; we have not added one.

This is not theoretical. Audiobookshelf shipped the same combination and got
**CVE-2024-35236** — scripted EPUB plus an unrestricted upload gave remote code
execution; fixed in 2.10.0 by making scripted content a per-library opt-in, off by
default. Kavita (CVE-2024-39307) and Jellyfin (fixed 10.9.8) are variations on it.
Write-up: <https://gebir.ge/blog/every-trick-in-the-book/>.

**An app-wide CSP is the wrong shape.** `kit.csp` with `script-src: ['self']` also blocks
`mode-watcher`'s inline `setInitialMode`, which sets the dark class before first paint —
SvelteKit only nonces the bootstrap script it injects itself, so every page load would
flash the light theme. Pinning a hash of a third-party inline script breaks silently on
upgrade.

**Grimmory solves it properly**, and it runs foliate-js too. Rather than handing foliate
the whole file, it serves each EPUB entry from its own endpoint and puts the strict
policy on that response:

```java
// EpubReaderController.java
response.setHeader("Content-Security-Policy", "script-src 'none'");
```

The app shell keeps its own, more permissive policy. That works because each section is
then a real same-origin document with its own header, rather than a `blob:` — and a
`blob:` inherits the CSP of the document that created it, which is exactly why a header
on `/api/books/download/…` would achieve nothing today.

Two ways forward:

1. **Cheap.** Patch the vendored `sandbox` attribute to drop `allow-scripts`, restoring
   what epub.js gave us. Cost is the WebKit bug the upstream comment cites: events inside
   the iframe get swallowed, which would likely break touch/swipe paging and possibly the
   in-iframe keyboard handling in `foliate-view.svelte`. Needs testing before trusting.
2. **Right.** Follow grimmory: serve individual EPUB entries from the backend with
   `script-src 'none'` on each response, and drive foliate through its loader hooks
   instead of a whole-file blob. This is **net-new capability on both sides**, not a
   rewiring of something that exists — see below.

Option 2 also fixes the memory cost below, which is why it is worth more than it looks.

#### What option 2 actually involves

Today the browser fetches the whole `.epub` from `download/{book_id}/{file_id}`, which
returns a Litestar `File` and knows nothing about the archive's contents. foliate then
opens the zip **in the browser** (`makeZipLoader` in `view.js`) and turns every chapter,
image and stylesheet into a `blob:` URL via `Loader.createURL` in `epub.js`. A `blob:`
carries no headers of its own — it inherits the CSP of the document that created it —
which is why there is nowhere to attach a policy except the app shell.

foliate's parser never touches the zip directly. `EPUB` is constructed with a loader:

```js
// view.js — makeZipLoader is one implementation; makeDirectoryLoader below is another
return { entries, loadText, loadBlob, getSize };
```

`name` is the **zip entry path**, because `makeZipLoader` keys its map on
`entry.filename` — so `OEBPS/Text/chapter01.xhtml`, `OEBPS/Images/cover.jpg`. The parser
resolves hrefs from the OPF manifest into those names and asks the loader for them,
without caring where the bytes come from. A third implementation that fetches over HTTP
is the same shape.

**Backend.** An endpoint taking a path inside the archive, e.g.
`GET books/{book_id}/files/{file_id}/entry/{path:path}`, returning a `Stream` over
`zipfile.ZipFile.open(name)` so an entry never lands in memory whole, with the content
type from the manifest and `Content-Security-Policy: script-src 'none'` on the response.

Two things to get right:

- **`path` is caller-supplied.** Resolve it against the archive's `namelist()` and reject
  anything absent, rather than trusting the string — `../` traversal is the hazard.
- **`getSize` is synchronous** in foliate's loader contract, and it feeds `SectionProgress`,
  which produces the reading percentage. So the endpoint needs a companion that returns
  entry names and sizes up front — one extra call at open — because sizes cannot be
  discovered per request.

Opening the zip per request costs a central-directory read each time. Probably fine for
chapter-sized reads, worth measuring rather than assuming.

Note the backend already reads inside EPUBs — `metadata_extractor.py` uses ebooklib at
ingest for title, authors, identifiers and the cover. What is missing is serving an
arbitrary entry by path, not the ability to open the archive.

**Frontend.** `foliate-view.svelte` stops calling `view.open(file)` and builds an `EPUB`
around a loader backed by that endpoint. The whole-file fetch in `epub-reader.svelte`
goes away with it.

### The proxy buffers whole files and drops range headers

Two separate problems that both live in `frontend/src/routes/api/[...path]/+server.ts`.

**Buffering.** Litestar already streams: `ASGIFileResponse` reads in 1 MB chunks
(`response/file.py`), so the backend never holds a file whole. The proxy then undoes it
with `await response.arrayBuffer()`, which does not resolve until the last byte arrives —
so the whole file sits in the node process, per concurrent reader, and the browser gets
nothing until it completes. Passing `response.body` straight through restores the stream
and is a small change.

This is now **responses only**. The request side was fixed for the Calibre archive upload,
which cannot be held in memory: POST and PATCH pass `request.body` through with
`duplex: 'half'` (`bodyOf` in the same file). The response side is the same shape of fix.

**Range.** The proxy forwards only `Content-Type`, `Content-Disposition` and
`Content-Length`. It never sends the client's `Range` upstream, and would drop
`Accept-Ranges` and `Content-Range` coming back — a 206 without `Content-Range` is
broken. So range support cannot work until the proxy is fixed, whatever the backend does.

**Litestar has no range support of its own.** In 2.21.1 the only mention of 206 in the
whole package is the `HTTP_206_PARTIAL_CONTENT` constant; there is no `Accept-Ranges` or
`Content-Range` handling anywhere. This has to be written.

#### What pdf.js actually needs

It decides from the **initial 200 response**, not from anything on a 206.
`validateRangeRequestCapabilities` in `frontend/static/pdfjs/build/pdf.mjs`:

```js
if (responseHeaders.get("Accept-Ranges") !== "bytes") {
  return returnValues; // allowRangeRequests stays false
}
```

It also needs a parseable `Content-Length`, `Content-Encoding: identity`, and a length
greater than twice `rangeChunkSize`. Miss any of those and it downloads the whole file
however good the range support is.

So the single highest-value header is **`Accept-Ranges: bytes` on the ordinary 200** —
that is what makes pdf.js switch to fetching progressively at all.

#### Approach

Put it on the existing `get_file` handler in `controllers/book.py`, which already resolves
`book_id`/`file_id` through the service with library scoping and auth:

- No `Range` → `Stream` the file with `Accept-Ranges: bytes` and `Content-Length`.
- `Range` present → parse, seek, `Stream` with 206 and `Content-Range`.
- Proxy: forward `Range` up; pass `response.body` through; forward `Accept-Ranges`,
  `Content-Range` and the status back.

There are `RangeRequestMiddleware` snippets circulating for Litestar that wrap
`create_static_files_router`. They are the wrong shape here — book files are served by an
authenticated handler resolving database ids, not by a directory mapping, and using one
would mean exposing disk paths as URLs and re-solving ownership checks that already
exist. The common version also only sets `Accept-Ranges` on the 206, so it would not
switch pdf.js over, and it derives its path with `str.lstrip(prefix)`, which strips a
character set rather than a prefix — `/static/castle.pdf` becomes `le.pdf`. Worth reading
its `parse_range_header` for the parsing rules and writing the rest fresh.

### Remove the epub.js locations-cache purge

`frontend/src/lib/reader/legacy-cache.ts` — `purgeLegacyLocationCache`

The epub.js reader cached generated locations in `localStorage` under
`${bookId}-locations`, a few hundred KB of JSON per long book. foliate computes
progress from section byte sizes at open time, so nothing writes those keys any
more, but existing browsers still hold them — and a reader near the 5–10 MB
origin quota would make the new reader-settings write throw `QuotaExceededError`.

The reader clears them once per browser, behind a `chitai:locations-purged` flag.
Delete the module, its call in `epub-reader.svelte` and the flag once deployments
have had a release or two to run it — after roughly 2026-12.

### Cover dimensions are unknown until load

`book-cover.svelte` renders covers at a fixed height with natural width so nothing is
cropped or distorted. Because the intrinsic size is not known ahead of time, the text
beside the cover settles once when the image loads. `min-width` bounds the movement but
does not remove it.

Removing it properly means storing cover dimensions at ingest and emitting them as
`width`/`height` attributes so the browser reserves exact space. That is a model change
plus a migration.

### No series navigation

`Book` has `series` and `series_position`, and the detail page shows both, but there is no
way to reach the other volumes. The books list endpoint filters by author, publisher, tag,
shelf and progress — a `series` filter would need adding in
`backend/src/chitai/services/filters/book.py` and wiring through
`services/dependencies.py`, following the existing `AuthorFilter` pattern.

### Book pages are sparse for most books

EPUB metadata is thin: most imports arrive with a title, an author and nothing else. Two
independent directions, neither started:

- **Use what exists.** "More by this author" (the list endpoint already accepts
  `authors=`), and exposing `Book.created_at` and `BookProgress.updated_at` — both are in
  the database, neither is on `BookRead` / `BookProgressRead`.
- **Fetch from outside.** Open Library or Google Books lookup by ISBN for descriptions and
  covers. This is what actually fixes the sparseness, but it needs outbound requests, rate
  limiting, a manual-vs-automatic decision, and a rule for not clobbering hand-edited
  metadata.
