import { DurableObject } from "cloudflare:workers";

const MAX_SOCKETS = 200;

type Presence = { name: string };

/** One instance per project: fans out change notifications and presence to connected board viewers. */
export class ProjectRoom extends DurableObject<Env> {
  async fetch(request: Request): Promise<Response> {
    if (request.headers.get("upgrade") !== "websocket") return new Response("Expected websocket", { status: 426 });
    if (this.ctx.getWebSockets().length >= MAX_SOCKETS) return new Response("Room is full", { status: 503 });
    const name = request.headers.get("x-stig-viewer") ?? "anonymous";
    const pair = new WebSocketPair();
    this.ctx.acceptWebSocket(pair[1]);
    pair[1].serializeAttachment({ name } satisfies Presence);
    this.broadcastPresence();
    return new Response(null, { status: 101, webSocket: pair[0] });
  }

  /** Called by server functions after a project mutation so open boards refresh. */
  async notifyChanged(actor: string): Promise<void> {
    this.send(JSON.stringify({ type: "changed", actor }));
  }

  async webSocketMessage(socket: WebSocket, message: string | ArrayBuffer): Promise<void> {
    if (message === "ping") socket.send("pong");
  }

  async webSocketClose(socket: WebSocket): Promise<void> {
    socket.close();
    this.broadcastPresence();
  }

  private send(payload: string): void {
    for (const socket of this.ctx.getWebSockets()) {
      try {
        socket.send(payload);
      } catch {
        socket.close();
      }
    }
  }

  private broadcastPresence(): void {
    const names = new Set<string>();
    for (const socket of this.ctx.getWebSockets()) {
      if (socket.readyState !== WebSocket.OPEN) continue;
      const presence: Presence | null = socket.deserializeAttachment();
      if (presence) names.add(presence.name);
    }
    this.send(JSON.stringify({ type: "presence", viewers: [...names] }));
  }
}