Pick any line to see why it is the way it is: the commit, the pull request and issue it came from, and what the agent was thinking.
| Chat and workspace agents: channels, DMs and named agents you talk to | 1 | /** |
| 2 | * One channel's live room, as a Durable Object named by the channel id. | |
| 3 | * | |
| 4 | * Why an object per channel: everyone looking at a channel must see the | |
| 5 | * same messages in the same order the moment they are written, and one | |
| 6 | * object per channel sees every socket open on it. It holds the sockets | |
| 7 | * with the WebSocket Hibernation API, so a quiet channel with people | |
| 8 | * looking at it costs nothing between messages: the object is evicted | |
| 9 | * from memory and the sockets stay open at the edge. Each socket carries | |
| 10 | * who is behind it (`serializeAttachment`), which survives hibernation. | |
| 11 | * | |
| 12 | * The room authorizes nothing. The Worker checks a viewer may read the | |
| 13 | * channel before forwarding their socket here (src/index.ts, `live`), and | |
| 14 | * tells the room to drop someone's sockets when they leave a private one. | |
| 15 | */ | |
| 16 | import { DurableObject } from "cloudflare:workers"; | |
| 17 | ||
| 18 | import { principalKey, type ChatLiveEvent, type MemberProfile } from "@g1t/contracts"; | |
| 19 | ||
| 20 | import { PERSON_TYPING_MS, isTypingFrame } from "./messages.ts"; | |
| 21 | ||
| 22 | /** Header the Worker sets on a socket it forwards: who it is, as JSON (`RoomMember`). */ | |
| 23 | export const ROOM_MEMBER_HEADER = "x-g1t-chat-member"; | |
| 24 | ||
| 25 | export type RoomMember = { channel_id: string; member: MemberProfile }; | |
| 26 | ||
| 27 | /** The shortest time between two "is typing" events from one socket. */ | |
| 28 | const TYPING_EVERY_MS = 2_000; | |
| 29 | ||
| 30 | export class ChannelRoom extends DurableObject<object> { | |
| 31 | /** When each socket last said it was typing; lost on hibernation, which only lets one more through. */ | |
| 32 | private typedAt = new WeakMap<WebSocket, number>(); | |
| 33 | ||
| 34 | constructor(ctx: DurableObjectState, env: object) { | |
| 35 | super(ctx, env); | |
| 36 | // Keepalives are answered without waking the object. | |
| 37 | ctx.setWebSocketAutoResponse(new WebSocketRequestResponsePair("ping", "pong")); | |
| 38 | } | |
| 39 | ||
| 40 | override async fetch(request: Request): Promise<Response> { | |
| 41 | if (request.headers.get("upgrade")?.toLowerCase() !== "websocket") { | |
| 42 | return new Response("Expected a WebSocket upgrade\n", { status: 426 }); | |
| 43 | } | |
| 44 | let who: RoomMember; | |
| 45 | try { | |
| 46 | who = JSON.parse(request.headers.get(ROOM_MEMBER_HEADER) ?? "") as RoomMember; | |
| 47 | } catch { | |
| 48 | return new Response("Missing member\n", { status: 400 }); | |
| 49 | } | |
| 50 | const pair = new WebSocketPair(); | |
| 51 | const [client, server] = Object.values(pair) as [WebSocket, WebSocket]; | |
| 52 | // Tagged with the member's key, so their sockets can be found to drop. | |
| 53 | this.ctx.acceptWebSocket(server, [principalKey(who.member)]); | |
| 54 | server.serializeAttachment(who); | |
| 55 | return new Response(null, { status: 101, webSocket: client }); | |
| 56 | } | |
| 57 | ||
| 58 | /** Sends `event` to every socket in the room, except those of `except` (a principal key). */ | |
| 59 | broadcast(event: ChatLiveEvent, except: string | null = null): void { | |
| 60 | const text = JSON.stringify(event); | |
| 61 | for (const socket of this.ctx.getWebSockets()) { | |
| 62 | if (except && this.ctx.getTags(socket).includes(except)) continue; | |
| 63 | try { | |
| 64 | socket.send(text); | |
| 65 | } catch { | |
| 66 | // Closing already; webSocketClose tidies up. | |
| 67 | } | |
| 68 | } | |
| 69 | } | |
| 70 | ||
| 71 | /** Closes a member's sockets: they left a private channel and may no longer read it. */ | |
| 72 | drop(principal: string): void { | |
| 73 | for (const socket of this.ctx.getWebSockets(principal)) { | |
| 74 | try { | |
| 75 | socket.close(4403, "No longer a member"); | |
| 76 | } catch { | |
| 77 | // Already closed. | |
| 78 | } | |
| 79 | } | |
| 80 | } | |
| 81 | ||
| 82 | override async webSocketMessage(socket: WebSocket, message: string | ArrayBuffer): Promise<void> { | |
| 83 | const who = socket.deserializeAttachment() as RoomMember | null; | |
| 84 | if (!who) return; | |
| 85 | // The only thing a client says over the socket: it is typing | |
| 86 | // (`{"type":"typing","channel_id":"<id>"}`, at most every 3 s). | |
| 87 | // Everything else (posting, reading) goes through the site, which | |
| 88 | // checks it. | |
| 89 | if (!isTypingFrame(message, who.channel_id)) return; | |
| 90 | const now = Date.now(); | |
| 91 | if (now - (this.typedAt.get(socket) ?? 0) < TYPING_EVERY_MS) return; | |
| 92 | this.typedAt.set(socket, now); | |
| 93 | this.broadcast( | |
| 94 | { | |
| 95 | type: "typing", | |
| 96 | channel_id: who.channel_id, | |
| 97 | member: who.member, | |
| 98 | until: new Date(now + PERSON_TYPING_MS).toISOString(), | |
| 99 | }, | |
| 100 | principalKey(who.member), | |
| 101 | ); | |
| 102 | } | |
| 103 | ||
| 104 | override async webSocketClose(socket: WebSocket, code: number, reason: string): Promise<void> { | |
| 105 | try { | |
| 106 | socket.close(code, reason); | |
| 107 | } catch { | |
| 108 | // Already closed. | |
| 109 | } | |
| 110 | } | |
| 111 | ||
| 112 | override async webSocketError(): Promise<void> { | |
| 113 | // Nothing to keep: the socket is gone, and getWebSockets no longer lists it. | |
| 114 | } | |
| 115 | } |
