# Implementation Notes

This documents contains an overview of the most important implementation details for the `rtcd` service
It's important to note that this service is currently meant to be interfaced only by the [Mattermost Calls plugin](https://github.com/mattermost/mattermost-plugin-calls).

## Components

These are the main components (packages) that form the `rtcd` service:

```mermaid
flowchart TD
service-->api[api\nHTTP API Server]
service-->ws[ws\nWebSocket Server]
service-->rtc[rtc\nWebRTC SFU]
service-->store[store\nK/V Store]
service-->auth[auth\nAuthentication Service]
auth-->store
```

### `service`

This is the main entry point to a singleton service that handles everything needed to setup and run a fully functional service.
It's the higher abstraction layer available (excluding the CLI command).

### `api`

The `api` package implements a basic HTTP(s) server. This is decoupled from the actual business logic which is injected through the use of handlers by the higher level (`service`).

### `ws`

The `ws` package provides implementations for both WebSocket client and server. Only the server is used by the `service`. The client is provided to be imported externally (e.g. by Calls plugin) and for testing.

### `rtc`

The `rtc` packages provides implementation for a WebRTC [SFU](https://webrtcglossary.com/sfu/).

### `auth`

The `auth` packages implements a simple authentication service to register, unregister and authenticate clients.

### `store`

Store provides a basic interface to key-value store. Its main implementation is currently based on [bitcask](https://git.mills.io/prologic/bitcask), a persistent embedded key-value store.

## Sample deployment

```mermaid
flowchart TB
    userA((User A))-.->|WebRTCl|rtc
    userB((User B))-.->|WebRTC|rtc
    userC((User C))-.->|WebRTC|rtc

    userA-->|WebSocket|pluginA
    userB-->|WebSocket|pluginA
    userC-->|WebSocket|pluginB

    userD((User D))-.->|WebRTCl|rtc
    userE((User E))-.->|WebRTC|rtc

    userD-->|WebSocket|plugin2
    userE-->|WebSocket|plugin2

    pluginA-->|WebSocket|ws
    pluginB-->|WebSocket|ws
    plugin2-->|WebSocket|ws

    subgraph service [ ]
        direction TB
        rtcd-->api
        rtcd-->api(HTTP API Server)
        rtcd-->ws(WebSocket API Server/Client)
        rtcd-->rtc(WebRTC SFU)
        rtcd-->auth(Auth Service)
        auth-->store(Store)
        rtcd-->store
        store-->db[(Embedded\n K/V Store)]
    end

    subgraph mm [ Installation A ]
        direction TB
        pluginA[Calls Plugin A]
        pluginB[Calls Plugin B]
    end

    subgraph mm2 [ Installation B ]
        direction TB
        plugin2[Calls Plugin]
    end
```