Architecture: audiobookshelf (`/abs`) provider design
Design doc for a new `absdy` provider mounted at `/abs` that browses, searches, and plays audiobooks from a self-hosted audiobookshelf server. Shaped on the fyyd provider: an `Abs` reqwest seam faked in tests, an in-memory per-library search-term store, and a `library -> book -> tracks` tree with a per-library `search` subtree. Grounded live against the test server: bearer auth for browse, `?token=` query auth plus HTTP range (206) on the file endpoint, so a track's stream URL is fully derivable from its path with no extra call. The embedded token and the api_key are secrets, redacted from logs/Debug (hard rule). Also gitignores the abs-api-key file so the JWT never lands in a commit. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Test User
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.opencode/
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.explained/
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*.kickstart-new
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# mdbook build output
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docs/book/
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# audiobookshelf API key (secret, do not commit)
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abs-api-key
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# audiobookshelf provider (audiobooks)
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## Context and problem statement
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A new library provider mounted at `/abs` that lets a user **browse, search,
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and play** the audiobooks on a self-hosted
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[audiobookshelf](https://www.audiobookshelf.org/) (ABS) server.
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- Unlike fyyd/tidal/youtube, ABS is **the user's own private server**, reached
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over an authenticated HTTP API with an **API key** (a bearer token). So —
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like tidal — the provider needs credentials, and — unlike tidal — a missing
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or incomplete config disables it non-fatally (it is one optional server, not
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the whole app).
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- ABS organizes content as **libraries → items → audio files**. An audiobook
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*item* is usually split into many audio files (e.g. `Neuromancer-01.opus` …
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`-30.opus`); each file is one **track**. So the tree carries the same
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"one extra level" as fyyd — `library → book → tracks` — plus a per-library
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**search** subtree that mirrors tidal/youtube search-term semantics.
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- **Playing** a track means streaming the file's content endpoint. ABS accepts
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the API key as a `?token=` query parameter on that endpoint and honors HTTP
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range requests, so the URL is exactly the shape the audio player already
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handles — **and the whole URL is derivable from the path**, so playback
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needs no extra API call, no sidecar, no byte-proxying (contrast `/youtube`).
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- **Captures** (`W`, download) come for free: any node that serves tracks and
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raises `is_downloadable` gets `w`/`W` with no wire or TUI work.
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## The audiobookshelf API (grounding — live-validated against the test server)
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Base `https://<host>/api/`. Every call carries `Authorization: Bearer <key>`,
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**except** the file endpoint which also accepts `?token=<key>`. The endpoints
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we use (all verified against the provided test server):
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| Purpose | Endpoint |
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| --- | --- |
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| List libraries | `GET /api/libraries` |
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| List a library's items | `GET /api/libraries/<lib>/items?limit=<n>&sort=…` |
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| Search within a library | `GET /api/libraries/<lib>/search?q=<t>&limit=<n>` |
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| Item detail (tracks) | `GET /api/items/<item>?expanded=1` |
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| **Stream a file** | `GET /api/items/<item>/file/<ino>?token=<key>` |
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Objects (fields we read):
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- **library**: `id`, `name`, `mediaType` (we handle `book`).
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- **item summary** (in the items list): `id`, `mediaType`, `media.metadata`
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(`title`, `authorName`), `media.numAudioFiles`, `media.duration`.
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- **item detail**: `media.metadata.{title,authorName}` and `media.tracks[]`,
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each track: `index`, `title` (the filename, e.g. `Neuromancer-01.opus`),
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`duration` (seconds, float), **`ino`** (stable file id, an integer string),
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`contentUrl` (`/api/items/<item>/file/<ino>` — same components as the path).
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- **search** response: `{ "book": [ { "libraryItem": <item> }, … ], … }`.
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Verified facts that shape the design: the file endpoint returns `200` with
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`?token=` and `401` without; a `Range` request returns `206`; ebook-only items
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report `numAudioFiles == 0`.
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## Assumptions (decided here)
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- The captures/creatable/editable/deletable TUI flows are provider-agnostic
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(confirmed by `/youtube` and `/fyyd`): mirroring tidal's search-term
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semantics costs no TUI or wire change. No proto change, no new
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`ProviderCommand`.
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- ABS needs credentials, so — unlike fyyd — a usable `abs.toml` must carry a
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`base_url` and an `api_key`. A missing file, or one lacking either field,
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**disables the provider non-fatally** (like fyyd/youtube on a failed probe):
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it only costs the `/abs` subtree, never startup.
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- The audio player streams the `?token=` file URL directly (its windowed-HTTP
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path): ABS serves the raw file with range support, so there is no
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`/youtube`-style URL-lifetime or ~1 MiB-cap problem. Audiobook files are
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ordinary media (opus/mp3/m4a/flac) the existing decoder already handles.
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- Items and files are addressed by their **ABS ids**: the library id and item
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id are UUIDs, and the file `ino` is an integer string — all already
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URL-safe. Only user-typed **search terms** are percent-encoded.
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- The stream URL embeds a secret (`?token=`), so it must **never** be logged;
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and `api_key` must be redacted from `Debug`/config dumps (hard rule:
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redact secrets from logs and error reports).
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## Decisions
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### D1 — Crate `absdy`, mounted at `/abs`, non-fatal init
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New workspace crate `absdy` implementing `ProviderClient`, shaped on `fyyd`
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(the closest analog: remote, search-driven, one extra container level, plain
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streamable URLs). Wired into `ProviderOrchestrator` with an
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`abs_client: Option<Arc<absdy::Client>>` field, `abs_owns()`/`abs_provider()`
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helpers, a `build()` block that reads `abs.toml` (non-fatal), a `get_lib_root`
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child gated on `self.abs_client.is_some()`, and one routing arm in each
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dispatch method. `crabidy-server`'s settings gain `abs` in `ALL_PROVIDERS` (now
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7), in `ProviderToggles`, in `all()`, and in `provider_toggles()`.
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### D2 — HTTP behind a trait, faked in tests
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All network access goes through one seam — an `Abs` trait
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(`libraries`, `library_items`, `search_items`, `item_detail`) behind
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`Box<dyn Abs>` — with a `reqwest`-based `AbsApi` (bearer auth) for production
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and a `FakeApi` in tests, exactly as `fyyd` hides `reqwest` behind `Fyyd`.
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Provider logic (tree shaping, path parsing, term store, stream-URL building) is
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then unit-tested with zero network. The trait's error type maps to
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`ProviderError::FetchError` at the boundary; malformed paths are
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`MalformedPath`; empty create/rename input is `InvalidInput`; missing
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credentials at init are `Config`.
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### D3 — Tree shape (libraries, books, tracks, per-library search)
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Item ids are UUIDs and file inos are integers, so neither can equal the
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reserved segment `search`; the parser uses that to split the two branches.
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- `/abs` — children: one node per library from `/api/libraries` (a fixed
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browse; the provider is useful with zero typing). Not itself queueable.
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- `/abs/<lib>` — children: a reserved `search` child (`is_creatable`) **plus**
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the library's items (bounded, see D5) as book children. A book child's
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`is_queable` is set from `numAudioFiles > 0`, so ebook-only items show but
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are not queueable/capturable.
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- `/abs/<lib>/<item>` — lists that book's audio files as **tracks**;
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queueable and downloadable (homogeneous tracks).
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- `/abs/<lib>/<item>/<ino>` — the track leaf.
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- `/abs/<lib>/search` — `is_creatable`; children are the in-memory search
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terms (`RwLock<Vec<String>>`, dedup, recreated implicitly on stale paths),
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each `is_editable` + `is_deletable`, like tidal/youtube/fyyd. Search terms
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are stored **per library** (keyed by library id).
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- `/abs/<lib>/search/<term>` — lists matching **books** as children (same book
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shape as a direct library child).
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- `/abs/<lib>/search/<term>/<item>` and `.../<item>/<ino>` — identical book
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node and track leaf as under the direct browse; the two branches share the
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book-node and track-leaf builders.
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Terms are percent-encoded into one segment (`encode_segment`/
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`decode_segment`); library ids, item ids, and inos are already URL-safe.
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### D4 — Streams, metadata, no extra call for playback
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- `get_urls_for_track`: parse `item` + `ino` from the path and build
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`<base>/api/items/<item>/file/<ino>?token=<key>`. **No API call** — the URL
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is fully derivable from the path; the token is appended last and never
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logged. An unparseable path is `MalformedPath`.
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- Track fields (from the item detail's `tracks[]`): `title` = track title (the
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file name), `artist` = the book's `authorName`, `album` = the book title,
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`duration` = track duration (seconds → `Option<u32>`), `provider_item_id` =
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`"<item>:<ino>"` (stable per file, keys the content store for captures).
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- **Metadata source.** Listing a book fetches the item detail once and builds
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every track from `tracks[]` (title/duration/author all present). A
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*directly* fetched track (`get_metadata_for_track` on a bare track path)
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fetches the same item detail and picks the matching `ino`. A missing field
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degrades to an empty string / `None`, never an error.
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### D5 — Bounds and freshness
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- `items_per_library` (default 200), `search_results` (default 50) cap every
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listing so a huge library cannot stall the tree or queue resolution;
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`call_timeout_secs` (default 30) bounds each HTTP call (hard rule: timeouts
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on external calls).
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- Listings are fetched fresh per call (no cross-call cache), like the other
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remote providers. Only the search *terms* are stored, in memory, per library.
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### D6 — Out of scope (explicitly)
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- **Podcast** libraries (`mediaType: "podcast"`, `media.episodes`): the test
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server has none; the book-node builder reads `media.tracks`. A podcast
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library's items would show no tracks (non-queueable). Adding an episodes
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branch is a later, additive change — noted as the extension point.
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- ABS user accounts beyond the single API key, playback-progress sync back to
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ABS, series/authors/collections/genre browse, and tag filtering.
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- Transcoding / HLS sessions — we stream the raw file with range requests.
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- Cover art, chapters, and ebook reading.
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- Pagination past the configured caps (one page is fetched per listing).
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## Structure
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```d2
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direction: right
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server: crabidy-server {
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orch: ProviderOrchestrator
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}
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absdy: "absdy (crate)" {
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client: "Client\n(ProviderClient)"
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terms: "search terms\n(in-memory, per library)"
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api: "AbsApi\n(reqwest seam: Abs trait,\nbearer auth)"
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client -> terms
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client -> api
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}
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abs: "audiobookshelf\n(/api, bearer auth)" { shape: cloud }
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player: audio-player { shape: hexagon }
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server.orch -> absdy.client: "/abs/..."
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absdy.api -> abs: "libraries / items / search / detail (JSON, timeout)"
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server.orch -> player: "file URL with ?token="
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player -> abs: "windowed HTTP stream (Range → 206)"
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```
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## Key flow: browse a library, play a track
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```d2
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shape: sequence_diagram
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tui: TUI
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orch: Orchestrator
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a: absdy
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api: audiobookshelf
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tui -> orch: "open /abs"
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orch -> a: "get_lib_root / get_lib_node"
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a -> api: "GET /api/libraries"
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api -> a: "libraries (id, name)"
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a -> tui: "libraries as children"
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tui -> orch: "open a library"
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orch -> a: "get_lib_node(/abs/<lib>)"
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a -> api: "GET /api/libraries/<lib>/items"
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api -> a: "items (id, title, numAudioFiles)"
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a -> tui: "[search] + books as children"
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tui -> orch: "open a book"
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orch -> a: "get_lib_node(/abs/<lib>/<item>)"
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a -> api: "GET /api/items/<item>?expanded=1"
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api -> a: "tracks (ino, title, duration)"
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a -> tui: "book node: files as tracks (queueable)"
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tui -> orch: "queue + play a track"
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orch -> a: "get_urls_for_track(.../<ino>)"
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a -> a: "build /api/items/<item>/file/<ino>?token= (no call)"
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orch -> orch: "player streams the file"
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```
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## Risks and open questions
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- **API-key lifetime.** ABS API keys are long-lived tokens, but if the
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configured value is a short-lived session JWT it will eventually expire; a
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`401` then surfaces as a typed `FetchError` (a skipped track / an unreadable
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node), never a crash. Re-issue the key in `abs.toml` to recover.
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- **Token leakage.** The stream URL embeds the key. It must never reach a log,
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trace, or error report — enforced by building the URL only at the boundary,
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a redacting `Debug`, and logging paths/context (never the built URL). This
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is a quality gate.
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- **Summary vs detail drift.** A book child's `is_queable` comes from the
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summary's `numAudioFiles`; the actual track count comes from the detail.
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A mismatch only means an optimistic flag — resolution of an empty book
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yields no tracks (skipped), never an error.
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- **Large libraries.** Capped by `items_per_library`; deep browsing past the
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cap needs pagination (out of scope). The cap is `log`-ged so truncation is
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visible, not silent.
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- **Field / envelope drift across ABS versions.** DTOs decode defensively
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(`#[serde(default)]`, missing fields degrade); a renamed field is a local
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fix in `AbsApi`. **Live validation is a task-plan gate** (already exercised
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during design against the test server).
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