ipx/docs/directory.md

# The directory

`ipx-directory` is a catalogue of public podcasts and blogs that ipx servers share (#204). An ipx
server sends it the public feeds its people subscribe to, and how many of them do. The directory
fetches each feed's title, artwork, category, description and latest twenty items every six hours,
and any server holding a token can browse it. It never downloads a file, and it never stores
one's address: every ipx server still fetches its own feeds.

This server's is at `https://directory.ipxreader.app` (moved from `ipx-dir.sdf1.net`, which answers as well until every server using it has moved, #214), the `ipx-directory` service of the Arcane project
`ipx`, with its database `ipx_directory` on the `databases` project's Postgres.

## In ipx

An admin sets it up in **Admin, Directory**: the directory's address, the token its operator gave
this server, and whether to share. ipx asks the directory on its people's behalf, so the page never
talks to it and never sees the token or a feed's address. With no directory set up, the Directory
says so and feeds are added by their address.

ipx keeps the address and token with its other server settings, in its database (`settings`,
`directory_url` and `directory_token`), not in config.toml. The token is written, never shown
again: the tab says it is set and offers to clear it. To replace one, make a new token on the
directory, paste it over the old, then delete the old token's entry from the directory's config.

With sharing on, ipx sends its snapshot when what it would send has changed (checked after every
scan, and whenever the catalogue or these settings change), and every half hour regardless (#211): each feed checked at least once, with how many people here subscribe,
and the category an admin gave a feed that names none. It never sends an OPML or a Patreon creator
itself (their feeds go instead), or a private feed. A feed's settings have a **Private** switch for
a paid feed iPX does not recognise by its address; anyone subscribed may turn it on, and only an
admin off.

When this server's token is `rwa`, its admins administer the directory from iPX (#206). A feed's
page in the Directory has **Check now** and **Remove from the directory**, which blocks it so no
server's snapshot brings it back. Admin, Directory lists the **Servers** sharing, by token name,
with how many feeds and subscribers each gave, and **Blocked**, by title, with Unblock. Dropping a
server's snapshot takes its feeds and counts out until it next shares; to keep a server out,
revoke its token. An admin's own subscriptions open as their feeds, not as Directory pages, so
removing one of those is done by marking it private, or from another admin's account.

## Tokens

Everything but `/healthz` needs a token, sent as `Authorization: Bearer <token>`. Each one has a
name and one of three levels of access:

| | browse | send snapshots | remove, block, refresh feeds; drop a server's snapshot |
|---|---|---|---|
| `ro` | yes | | |
| `rw` | yes | yes | |
| `rwa` | yes | yes | yes |

Tokens are in the config file and nowhere else, and no level of access can make or revoke one
over the API. To make one:

```sh
docker exec ipx-directory ipx-directory token new <name> --access ro|rw|rwa
```

It prints the token, to give to whoever it is for, and the lines to add to the config file. The file
holds the token's SHA-256, never the token. The directory reads the file again within a minute of
a change, so adding a token and revoking one (deleting its entry) need no restart. A revoked token
also takes the counts its server sent. A file that does not load (a misspelled `access`, two tokens
with one name) leaves the tokens as they were, and the log says why.

## The config file

`/config/directory.toml` in the container (`DIRECTORY_CONFIG`, or `--config`), on Tower
`/mnt/fast/appdata/ipx-directory/directory.toml`:

```toml
bind = "0.0.0.0:8100"
# The environment variable holding the database URL: postgres://... or sqlite://...
database_url_env = "DIRECTORY_DATABASE_URL"

[[tokens]]
name = "tower"
access = "rwa"
token_sha256 = "…"
```

`DIRECTORY_LOG_FORMAT=json` logs one JSON object a line, for Loki, as ipx's `IPX_LOG_FORMAT` does.
Each request is a line with its `method`, `path`, `status`, `duration_ms` and the `token`'s name.

With `OTEL_EXPORTER_OTLP_ENDPOINT` set (`http://host:4318`, OTLP over HTTP), it sends traces: a
span a request, a child of the caller's when the request carries a `traceparent`, as ipx's do, and
a trace a refresher round with a span a feed (#213). `OTEL_RESOURCE_ATTRIBUTES` tags them, as
production does with `deployment.environment.name=production`. Its version is in
`crates/directory/Cargo.toml`, logged at start and answered by `ipx-directory --version`; its
changelog is `crates/directory/CHANGELOG.md`.

## Running one

```yaml
services:
  ipx-directory:
    image: ipx-directory          # docker build -f Dockerfile.directory -t ipx-directory .
    restart: unless-stopped
    environment:
      DIRECTORY_DATABASE_URL: "postgres://ipx_directory:password@db-host:5432/ipx_directory"
    ports:
      - "8100:8100"
    volumes:
      - ./directory:/config:ro    # directory.toml
    healthcheck:
      test: ["CMD", "ipx-directory", "health"]
```

## What it will not hold

A private feed is never meant to reach it. ipx leaves out a feed marked private, one with a
username or password, and one whose address `ipx_feed::url_looks_private` catches: a paid-feed
host, or a key in the query. The directory checks every address it is sent with the same function
and refuses what it catches, so one server's miss does not publish someone's paid feed to every
other. What both miss, an `rwa` token can remove: `DELETE /v1/feeds/{id}` removes the feed and
blocks it, so no snapshot brings it back.

## API

| Route | Access | |
|---|---|---|
| `GET /healthz` | none | `ok` when it can read its database |
| `GET /v1/me` | ro | the token's `name` and `access` |
| `GET /v1/feeds` | ro | every feed A to Z: `id`, `url`, `title`, `image`, `category`, `subcategory`, `podcast`, `subscribers` |
| `GET /v1/popular?limit=10` | ro | the most subscribed, at most 100 |
| `GET /v1/feeds/{id}` | ro | one feed, with `description`, `failing` (why its last check failed, in words) and its latest twenty `items` (`guid`, `title`, `link`, `published`, `duration`, `description`), never their files |
| `POST /v1/snapshot` | rw | `[{"url", "subscribers"}]`, at most 20,000: replaces everything this token sent before; answers what it `accepted` and how many it refused as private, blocked or invalid |
| `DELETE /v1/feeds/{id}` | rwa | remove and block |
| `GET /v1/blocked`, `DELETE /v1/blocked/{id}` | rwa | what is blocked; unblock |
| `GET /v1/instances` | rwa | each token holding a snapshot: its `name`, `feeds` and `subscribers` |
| `DELETE /v1/instances/{name}` | rwa | drop one token's snapshot, its counts with it |
| `POST /v1/feeds/{id}/refresh` | rwa | fetch the feed now, answering with its page |

A feed's `id` is the first 64 bits of the SHA-256 of its address, normalised (scheme and host in
lower case, no default port or fragment), so every server arrives at the same id. `subscribers`
is the sum over every token's latest snapshot. A feed is listed once the directory has read it as
a feed, so an OPML or an address that never worked is not, and goes when no snapshot has it any more. Descriptions
are the feed's own HTML, unsanitized: whoever shows them sanitizes them, as ipx does.