Battle-for-Tismo/client/js/net.js

// Browser network role: talks to the authoritative Node server over a WebSocket
// and exposes high-level events so the screens do not care about the transport.

export const DEFAULT_PORT = 27015;
export const DEFAULT_PATH = "/ws";

export class Network {
  constructor() {
    this.socket = null;
    this.isAdmin = false;
    this.localPlayerId = 0;
    this.players = {};
    this._handlers = {};
    // The last full game state, with deltas merged into it. GameScreen always
    // sees a complete snapshot even though the wire only carries what changed.
    this._gameState = null;
    this._loginFailure = "";
    this._connectResolve = null;
    this._connectReject = null;
  }

  on(event, handler) {
    if (!this._handlers[event]) this._handlers[event] = [];
    this._handlers[event].push(handler);
  }

  _emit(event, ...args) {
    for (const handler of this._handlers[event] || []) handler(...args);
  }

  isClientConnected() {
    return this.localPlayerId !== 0;
  }

  defaultServerUrl() {
    const location = window.location;
    if (location.protocol === "http:" || location.protocol === "https:") {
      const scheme = location.protocol === "https:" ? "wss" : "ws";
      return `${scheme}://${location.host}${DEFAULT_PATH}`;
    }
    return `ws://127.0.0.1:${DEFAULT_PORT}${DEFAULT_PATH}`;
  }

  // Accepts a bare hostname or a full ws(s):// or http(s):// URL.
  normalizeUrl(host, port = DEFAULT_PORT) {
    let url = String(host || "").trim().replace(/\/+$/, "");
    if (url.startsWith("https://")) url = "wss://" + url.slice("https://".length);
    else if (url.startsWith("http://")) url = "ws://" + url.slice("http://".length);
    else if (!url.startsWith("ws://") && !url.startsWith("wss://")) {
      url = `ws://${url}:${port}`;
    }
    const afterScheme = url.slice(url.indexOf("://") + 3);
    if (!afterScheme.includes("/")) url += DEFAULT_PATH;
    return url;
  }

  connect(url) {
    this.close();
    this._loginFailure = "";
    this.localPlayerId = 0;
    this.isAdmin = false;
    this._gameState = null;
    return new Promise((resolve, reject) => {
      let socket;
      try {
        socket = new WebSocket(url);
      } catch (error) {
        reject(error);
        return;
      }
      this.socket = socket;
      this._connectResolve = resolve;
      this._connectReject = reject;
      socket.onopen = () => {
        if (this._connectResolve) {
          this._connectResolve();
          this._connectResolve = null;
          this._connectReject = null;
        }
      };
      socket.onerror = () => {
        if (this._connectReject) {
          this._connectReject(new Error("connection failed"));
          this._connectResolve = null;
          this._connectReject = null;
        }
      };
      socket.onclose = () => {
        const failure = this._loginFailure;
        this._loginFailure = "";
        this.localPlayerId = 0;
        this.isAdmin = false;
        if (this._connectReject) {
          this._connectReject(new Error("connection closed"));
          this._connectResolve = null;
          this._connectReject = null;
          return;
        }
        if (failure) this._emit("session_failed", failure);
        else this._emit("server_disconnected");
      };
      socket.onmessage = (event) => {
        let message;
        try {
          message = JSON.parse(event.data);
        } catch {
          return;
        }
        this._handleMessage(message);
      };
    });
  }

  requestGameList(url) {
    return this.connect(url).then(() => {
      this._send({ t: "request_games" });
    });
  }

  joinGame(url, name, password) {
    return this.connect(url).then(() => {
      this._send({ t: "login", name, password });
    });
  }

  claimCiv(index) {
    this._send({ t: "claim_civ", civ: index });
  }

  sendOrder(order) {
    this._send({ t: "order", order });
  }

  close() {
    if (!this.socket) return;
    const socket = this.socket;
    this.socket = null;
    socket.onopen = null;
    socket.onerror = null;
    socket.onclose = null;
    socket.onmessage = null;
    try {
      socket.close();
    } catch {
      // ignore
    }
  }

  _send(message) {
    if (this.socket && this.socket.readyState === WebSocket.OPEN) {
      this.socket.send(JSON.stringify(message));
    }
  }

  // Folds a delta into the last full state. A message without `delta` replaces
  // it. `exploredAdded` carries only the tiles discovered since the last one, so
  // the explored list (which only grows) is never re-sent in full.
  _mergeGameState(state) {
    if (!state || !state.delta || !this._gameState) {
      this._gameState = state;
      return;
    }
    const merged = { ...this._gameState, ...state };
    if (state.exploredAdded) {
      merged.explored = (this._gameState.explored || []).concat(state.exploredAdded);
      delete merged.exploredAdded;
    }
    this._gameState = merged;
  }

  _handleMessage(message) {
    switch (message.t) {
      case "assigned":
        this.localPlayerId = message.playerId;
        this.isAdmin = !!message.admin;
        this._emit("session_started", message);
        break;
      case "players":
        this.players = message.players || {};
        this._emit("players_updated", this.players);
        break;
      case "game_list":
        this._emit("game_list_received", message.games || []);
        break;
      case "login_rejected":
        this._loginFailure = message.reason || "Login failed.";
        this._emit("session_failed", this._loginFailure);
        this.close();
        break;
      case "choose_civ":
        this._emit("choose_civ_received", message.civs || []);
        break;
      case "civ_assigned":
        this._emit("civ_assigned", message.civ);
        break;
      case "game_state":
        this._mergeGameState(message.state);
        this._emit("game_state_received", this._gameState);
        break;
      default:
        break;
    }
  }
}