improve compute API

README.md

@@ -20,6 +20,13 @@ credential anywhere in the path**.
 This feeder **adds** a Usenet metadata source alongside `meta-feeder-indexer`.
 It replaces nothing; a gateway query fans out to both.
 
+It also **redeems external releases.** The torznab feeder mints `nzb-release`
+(`0x1005`) locators from Prowlarr/Newznab search hits; when a viewer plays one,
+the gateway asks this feeder (`POST /compute` with the locator cid) to grab its
+`.nzb` with the key configured here for that indexer host. The Newznab keys live
+on this feeder — meta-share keeps only the NNTP provider. See
+[Redeeming nzb-release locators](#redeeming-nzb-release-locators).
+
 Design record:
 `meta-gateway/docs/others/self-hosted-usenet-indexer-study.md`.
 
@@ -61,8 +68,12 @@ and there is no hot reload.
 
 | Field | Env seed | What |
 |---|---|---|
-| `db_url` | `NNTMUX_DB_URL` | MariaDB DSN of nntmux's catalog, e.g. `mysql://nntmux:secret@nntmux-db:3306/nntmux`. Blank → the upstream soft-skips and the plugin reports Degraded. |
+| `db_url` | `NNTMUX_DB_URL` | MariaDB DSN of nntmux's catalog, e.g. `mysql://nntmux:secret@nntmux-db:3306/nntmux`. Blank → self-scan search is off. |
 | `nzb_root` | `NNTMUX_NZB_PATH` | nntmux's NZB directory **as mounted into this container**. Must be the same volume nntmux's `PATH_TO_NZBS` points at, or every release resolves to `NotFound`. |
+| `indexers` | — (config page only) | `[{host, api_key}]` Newznab keys for redeeming `nzb-release` locators. `host` is the bare authority (`api.nzbgeek.info` — no scheme, no `/api`). |
+
+Both halves are optional; with neither configured the plugin reports Degraded.
+A grab-only deployment (keys, no nntmux) is valid.
 
 Infra env: `META_FEEDER_HTTP_LISTEN` (default `0.0.0.0:8080`),
 `META_FEEDER_STATE_DIR` (default `/data/meta-feeder`), `RUST_LOG`.
@@ -73,6 +84,32 @@ Keep the connection budget conservative: the scanner and playback draw on the
 same provider slots, so a greedy value does not merely over-scan, it stalls
 playback mid-stream.
 
+## Redeeming nzb-release locators
+
+`POST /compute {upstream_id: "usenet", record_id: <0x1005 cid>}`:
+
+1. Decode `{api_base, id}` from the cid; find the key for its host. No key →
+   `404` (not ours — the gateway tries another claimer, nothing is spent).
+2. `GET https://{api_base}/api?t=get&id=…&apikey=…` with a named User-Agent
+   (nzbgeek answers `109 Invalid User Agent` without one). **This spends the
+   indexer's daily download quota** — the gateway only calls it on a real play,
+   and never again for a release whose `manifest` it already stored.
+3. Strip the `.nzb` `<head>` except `<meta type="password">` (the file is seeded
+   to the whole mesh; the password is needed to unpack a protected RAR set).
+4. Mint the portable `nzb-posting` (`0x1003`) cid from its Message-IDs.
+5. Answer ONE `sha2_256` outcome: the `.nzb` bytes (`file_extension: nzb`) and a
+   record carrying `cids/<nzb-posting>` + `segmentCount`. The gateway stores the
+   file under `/files/plugin/meta-feeder-usenet/`, writes its cid onto the release
+   record as `manifest`, and merges the posting cid — after which any peer with a
+   plain NNTP provider can play the release.
+
+Errors: an indexer credential/account refusal (`100`–`102`, `910`) or an HTML
+page → `422`; request/download limit (`429`, `500`, `501`, or HTTP 429) → `429`;
+no such item (`300`) → `404`.
+
+`GET /redeems` and `/manifest` advertise `{codec: nzb-release, field: manifest,
+hosts: [...]}` for the hosts that have a key; nothing without keys.
+
 ## Build
 
 ```bash
@@ -83,11 +120,26 @@ cargo clippy --workspace --all-targets -- -D warnings
 docker build -f feeder-plugin/usenet-feeder/Dockerfile -t ghcr.io/worph/meta-feeder-usenet:dev .
 ```
 
-`crates/meta-feeder-sdk/` is a **vendored copy** of the SDK, mirrored from
-`meta-gateway`. Independent submodules cannot share a cargo path-dep, so keep it
-in step when the SDK changes — in particular `hash.rs`'s
-`compute_nzb_posting_cid`, whose normalisation rule is the dedup contract and is
-mirrored again on the meta-share side.
+`meta-feeder-sdk` is a git dependency pinned by tag (`v1.3.0`; this repo used to
+vendor a copy). Until that tag is pushed, cargo cannot resolve it — not even
+under a `[patch]` override. To verify against a local SDK checkout, build a
+scratch copy with the dependency swapped for a path (never commit that form —
+this repo is the Docker build context):
+
+```bash
+SCRATCH=/d/workspace/tmp-claude/usenet-feeder; SDK=/d/workspace/MetaMesh/meta-root-v2/packages/plugins/meta-feeder-sdk
+rm -rf $SCRATCH && mkdir -p $SCRATCH && tar cf - --exclude=./target --exclude=./.git . | (cd $SCRATCH && tar xf -)
+sed -i "s#meta-feeder-sdk = { git = .*#meta-feeder-sdk = { path = \"$SDK\" }#" $SCRATCH/feeder-plugin/*/Cargo.toml
+docker run --rm -e RUSTUP_TOOLCHAIN=1.89.0 -e CARGO_TARGET_DIR=/target -v /d/workspace:/d/workspace \
+  -v feeder-cargo-registry:/usr/local/cargo/registry -v usenet-feeder-target:/target -w $SCRATCH \
+  rust:1.89 sh -c 'apt-get install -y -qq pkg-config libssl-dev >/dev/null 2>&1; cargo test'
+```
+
+After the tag is pushed, run `cargo update -p meta-feeder-sdk` here so
+`Cargo.lock` stops pointing at the removed vendored path.
+
+`compute_nzb_posting_cid`'s normalisation rule is the dedup contract and is
+mirrored on the meta-share side — change them together.
 
 ## Gotchas