# Stream transport adapters — shared types

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## Purpose

The `transport.types.ts` module declares the structural contract that
`StreamSession` (authored in chunk A of the `@suaveplan/react-audio-stream`
split) accepts via constructor injection. By co-locating the contract with
the three concrete adapters (WebRTC, WebSocket, Trystero) in chunk B we
guarantee every adapter conforms to the same surface and the session can
hot-swap them without re-implementation. The shapes mirror the canonical
specification
so chunk-A and chunk-B merges remain structurally compatible.

## Features

- `StreamTransportAdapter` — DI contract for any peer-to-peer audio transport.
- `TransportEvent` — discriminated union covering connect, disconnect,
  inbound track, and RTT-probe ticks.
- `SignallingChannel` / `SignallingMessage` — transport-neutral signalling
  envelope used by the WebRTC adapter (callers MUST plug their own channel).
- `IceConfig` — STUN/TURN configuration with no embedded defaults.
- `InterruptionClass` / `InterruptionCause` — disconnect-cause classification
  fed into chunk A's telemetry histogram.
- `ReactAudioStreamErrorLike` — local mirror of chunk A's error shape so
  chunk-B tests can assert on `.code` without a circular merge dependency.

## Usage: Basic

```ts
import type { StreamTransportAdapter } from "@suaveplan/react-audio-stream/transports";

function logId(adapter: StreamTransportAdapter): void {
    console.log(adapter.id);
}
```

## Usage: Advanced

```ts
import type {
    StreamTransportAdapter,
    TransportEvent,
} from "@suaveplan/react-audio-stream/transports";

function watch(adapter: StreamTransportAdapter): () => void {
    return adapter.subscribe((event: TransportEvent) => {
        switch (event.type) {
            case "connected":
                console.log("peer joined", event.peerId);
                break;
            case "disconnected":
                console.warn("peer dropped", event.class, event.cause);
                break;
            case "rtt":
                console.debug("rtt", event.peerId, event.ms, "ms");
                break;
        }
    });
}
```

## API Reference

- `StreamTransportAdapter.connect(roomId)` — join a named room.
- `StreamTransportAdapter.disconnect()` — leave + tear down peer state.
- `StreamTransportAdapter.send(peerId, payload)` — unicast bytes.
- `StreamTransportAdapter.broadcast(payload)` — fan-out bytes.
- `StreamTransportAdapter.getRtt(peerId?)` — sample round-trip in ms.
- `StreamTransportAdapter.subscribe(handler)` — wire `TransportEvent` flow.

## Implementation Notes

The contract is intentionally minimal: it omits opinionated state-machine
hooks because `StreamSession` owns its own FSM (chunk A). Adapters MUST
report disconnects with a fully populated `InterruptionCause` so chunk A's
`InterruptionClassifier` can map ICE state, close code, or media-permission
error names without probabilistic heuristics.