import { PROTOCOL_VERSION, type ClientMessage, type DeltaMsg, type ServerMessage, type SnapshotMsg, type WelcomeMsg } from '@idle/shared';

export type NetStatus = 'connecting' | 'online' | 'reconnecting';

export function wsUrl(): string {
  const fromEnv = import.meta.env.VITE_WS_URL;
  if (typeof fromEnv === 'string' && fromEnv.length > 0) return fromEnv;
  // сборка раздаётся самим сервером — тот же origin
  const scheme = location.protocol === 'https:' ? 'wss' : 'ws';
  return `${scheme}://${location.host}/ws`;
}

export interface ConnectHandlers {
  onStatus: (status: NetStatus) => void;
  onWelcome: (msg: WelcomeMsg) => void;
  onSnapshot: (msg: SnapshotMsg) => void;
  onDelta: (msg: DeltaMsg) => void;
}

/** Подключение к миру с автопереподключением; возвращает функцию закрытия. */
export function connectWorld(handlers: ConnectHandlers): () => void {
  let ws: WebSocket | null = null;
  let disposed = false;
  let attempt = 0;

  const open = (): void => {
    if (disposed) return;
    handlers.onStatus(attempt === 0 ? 'connecting' : 'reconnecting');
    ws = new WebSocket(wsUrl());

    ws.onopen = () => {
      attempt = 0;
      const hello: ClientMessage = { t: 'hello', v: PROTOCOL_VERSION };
      ws?.send(JSON.stringify(hello));
    };
    ws.onmessage = (ev) => {
      let msg: ServerMessage;
      try {
        msg = JSON.parse(String(ev.data)) as ServerMessage;
      } catch {
        return;
      }
      if (msg.t === 'welcome') {
        handlers.onStatus('online');
        handlers.onWelcome(msg);
      } else if (msg.t === 'snapshot') {
        handlers.onSnapshot(msg);
      } else if (msg.t === 'delta') {
        handlers.onDelta(msg);
      }
    };
    ws.onclose = () => {
      if (disposed) return;
      attempt += 1;
      setTimeout(open, Math.min(500 * 2 ** Math.min(attempt, 4), 8000));
    };
    ws.onerror = () => ws?.close();
  };

  open();
  return () => {
    disposed = true;
    ws?.close();
  };
}