base2020/src/Net/LoopbackServer.ts

import { Callbag } from "callbag";
import pipe from "callbag-pipe";
import share from "callbag-share";

import { INPUT_FREQUENCY } from "../Ecs/Lockstep";
import { catchTalkback, defer, interval, makeSubject, map, merge } from "../Utilities/Callbag";
import { ClientMessage, MessageTypes, Server, ServerMessage } from "./LockstepClient";

type Client<LocalInput, State> = Callbag<ServerMessage<LocalInput[], State>, ClientMessage<LocalInput, State>>;

/** Stub loopback server that handles multiple clients, for schemes where GlobalInput = LocalInput[] */
export class LoopbackServer<LocalInput, State> {

    private nextClientId = 0;
    private inputBuffer: LocalInput[] = [];

    private heartbeat = pipe(
        interval(INPUT_FREQUENCY),
        map(() => ({
            t: MessageTypes.INPUT,
            i: this.inputBuffer.slice()
        } as ServerMessage<LocalInput[], State>)),
    );
    private broadcast = makeSubject<ServerMessage<LocalInput[], State>>();

    private serverFeed = share(merge(this.heartbeat, this.broadcast));

    public readonly socket = defer(() => {
        const playerNumber = this.nextClientId++;
        return pipe(
            this.serverFeed,
            catchTalkback<ServerMessage<LocalInput[], State>, ClientMessage<LocalInput, State>>(message => {
                switch (message.t) {
                    case MessageTypes.INPUT:
                        if (playerNumber >= 0) {
                            this.inputBuffer[playerNumber] = message.i;
                        }
                        break;
                }
            }),
            map(message => {
                if (message.t === MessageTypes.SET_STATE && playerNumber >= 0) {
                    return {
                        ...message,
                        u: playerNumber,
                    };
                } else {
                    return message;
                }
            })
        );
    });

    public resetState(newState: Partial<State>) {
        this.broadcast(1, { t: MessageTypes.SET_STATE, u: -1, s: newState });
    }
}