# atproto_client

> **Alpha, pre-release.** Pre-1.0, evolving alongside
> [at-record](https://tangled.org/@mokkenstorm.dev/at-record); expect breaking
> changes between 0.x releases.

A small, transport-agnostic [atproto](https://atproto.com/) client for Gleam.
No app or lexicon knowledge: XRPC, identity resolution, OAuth discovery,
blobs, and generic repo CRUD. Dual-target (erlang + javascript); browser-only
consumers want the sibling [`atproto_browser`](https://hex.pm/packages/atproto_browser) instead,
which owns the `atproto/browser/*` namespace within the shared `atproto/`
prefix.

## Installation

```sh
gleam add atproto_client
```

## Usage

The client carries a `send` function instead of a hardcoded HTTP backend, so
you choose the transport per target. On Erlang, `gleam_httpc`'s `send_bits`
maps onto the client's `TransportError` channel:

```gleam
import atproto/xrpc
import atproto_core/xrpc as core_xrpc
import gleam/httpc
import gleam/result
import gleam/string

fn client() -> xrpc.Client {
  xrpc.Client(send: fn(req) {
    httpc.send_bits(req)
    |> result.map_error(fn(error) {
      case error {
        httpc.ResponseTimeout -> core_xrpc.Timeout
        httpc.FailedToConnect(_, _) ->
          core_xrpc.ConnectionFailed(string.inspect(error))
        _ -> core_xrpc.Other(string.inspect(error))
      }
    })
  })
}
```

Resolve an identity, then read its records:

```gleam
import atproto/identity
import atproto/repo
import gleam/dynamic/decode

let assert Ok(pds) =
  identity.resolve_pds(client(), identity.default_resolver, "someone.bsky.social")

let assert Ok(rows) =
  repo.list_records(
    client(),
    pds,
    access_token,
    did,
    "app.bsky.feed.post",
    decode.dynamic,
  )
```

For the full walkthrough, including both authentication routes, see the
[getting started guide](https://hexdocs.pm/atproto_client/getting-started.html).

## Architecture

### Core

| Module                  | What it does                                                                           |
| ----------------------- | -------------------------------------------------------------------------------------- |
| `atproto/xrpc`          | `Client`, `TransportError`, `XrpcError`, `get`/`post_json`, `parse`                    |
| `atproto/identity`      | `resolve_pds` (handle/DID -> PDS) via Slingshot `resolveMiniDoc`                       |
| `atproto/auth`          | `create_session`/`refresh_session` (`com.atproto.server.createSession`)                |
| `atproto/repo`          | `list_records`/`create_record`/`get_record`/`put_record`/`delete_record`/`upload_blob` |
| `atproto/blob`          | `Blob` type, its codec, and `public_url` for refs returned by `repo.upload_blob`       |
| `atproto/uri`           | at-uri helpers (`rkey`)                                                                |
| `atproto/constellation` | `get_backlinks` against the microcosm backlink index                                   |

### OAuth

The full atproto OAuth client flow for a confidential client, one module per
step:

| Module                   | What it does                                                                   |
| ------------------------ | ------------------------------------------------------------------------------ |
| `atproto/oauth/metadata` | Discover the authorization server and its endpoints from a PDS                 |
| `atproto/oauth/flow`     | `start`: PAR + PKCE + DPoP, returns the authorization URL and a pending `Flow` |
| `atproto/oauth/tokens`   | `exchange_code`/`refresh`/`revoke` against the token endpoint                  |
| `atproto/oauth/resource` | Wraps a `Client` so every request carries the DPoP-bound access token          |
| `atproto/oauth/runner`   | Interprets the sans-io effect kernel against a synchronous `Client`            |

The modules above are sync wrappers over the sans-io effect kernel in
[`atproto_core`](https://hex.pm/packages/atproto_core). Its
`TransportError`/`XrpcError` types are aliased through `atproto/xrpc`;
constructing the variants needs `atproto_core/xrpc`.

## Development

```sh
gleam test
```