# goose

[![Package Version](https://img.shields.io/hexpm/v/goose)](https://hex.pm/packages/goose)
[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/goose/)

A Gleam WebSocket consumer for AT Protocol Jetstream events.

```sh
gleam add goose@1
```

## Example

```gleam
import goose
import gleam/io
import gleam/option

pub fn main() {
  // Create a default configuration
  let config = goose.default_config()

  // Or configure with custom options
  let config = goose.JetstreamConfig(
    endpoint: "wss://jetstream2.us-east.bsky.network/subscribe",
    wanted_collections: ["app.bsky.feed.post", "app.bsky.feed.like"],
    wanted_dids: [],
    cursor: option.None,
    max_message_size_bytes: option.None,
    compress: False,
    require_hello: False,
  )

  // Start consuming events
  goose.start_consumer(config, fn(json_event) {
    let event = goose.parse_event(json_event)

    case event {
      goose.CommitEvent(did, time_us, commit) -> {
        io.println("Commit: " <> commit.operation <> " in " <> commit.collection)
      }
      goose.IdentityEvent(did, time_us, identity) -> {
        io.println("Identity: " <> identity.handle)
      }
      goose.AccountEvent(did, time_us, account) -> {
        io.println("Account updated: " <> did)
      }
      goose.UnknownEvent(_) -> {
        io.println("Unknown event type")
      }
    }
  })
}
```

## Configuration Options

### `wanted_collections`
An array of Collection NSIDs to filter which records you receive (default: empty = all collections)

- Supports NSID path prefixes like `app.bsky.graph.*` or `app.bsky.*`
- The prefix before `.*` must pass NSID validation
- Incomplete prefixes like `app.bsky.graph.fo*` are not supported
- Account and Identity events are always received regardless of this filter
- Maximum 100 collections/prefixes

**Example:**
```gleam
wanted_collections: ["app.bsky.feed.post", "app.bsky.graph.*"]
```

### `wanted_dids`
An array of Repo DIDs to filter which records you receive (default: empty = all repos)

- Maximum 10,000 DIDs

**Example:**
```gleam
wanted_dids: ["did:plc:example123", "did:plc:example456"]
```

### `cursor`
A unix microseconds timestamp to begin playback from

- Absent cursor or future timestamp results in live-tail operation
- When reconnecting, use `time_us` from your most recently processed event
- Consider subtracting a few seconds as a buffer to ensure gapless playback

**Example:**
```gleam
cursor: option.Some(1234567890123456)
```

### `max_message_size_bytes`
The maximum size of a payload that this client would like to receive

- Zero means no limit
- Negative values are treated as zero
- Default: 0 (no maximum size)

**Example:**
```gleam
max_message_size_bytes: option.Some(1048576)  // 1MB limit
```

### `compress`
Enable zstd compression for WebSocket frames

- Set to `True` to enable compression
- Default: `False`
- Uses zstandard compression with Jetstream's custom dictionary
- Reduces bandwidth by approximately 50%
- Messages are automatically decompressed before reaching your callback
- Requires the `ezstd` library (automatically handled as a dependency)

**Example:**
```gleam
compress: True
```

**Note:** Compression is transparent to your application - compressed messages are automatically decompressed before being passed to your event handler. The bandwidth savings occur on the wire between the server and your client.

### `require_hello`
Pause replay/live-tail until server receives a `SubscriberOptionsUpdatePayload`

- Set to `True` to require initial handshake
- Default: `False`

**Example:**
```gleam
require_hello: True
```

## Full Configuration Example

```gleam
import goose
import gleam/option

let config = goose.JetstreamConfig(
  endpoint: "wss://jetstream2.us-east.bsky.network/subscribe",
  wanted_collections: ["app.bsky.feed.post", "app.bsky.graph.*"],
  wanted_dids: ["did:plc:example123"],
  cursor: option.Some(1234567890123456),
  max_message_size_bytes: option.Some(2097152),  // 2MB
  compress: True,
  require_hello: False,
)

goose.start_consumer(config, handle_event)
```

Further documentation can be found at <https://hexdocs.pm/goose>.

## Development

```sh
gleam build # Build the project
gleam test  # Run the tests
```