import { Signal, delay, must, must_err } from "@sammo/util";
import Denque from "denque";
import { ResourceController } from "./ResourceController.js";
import { entriesWithType } from "@sammo/util/converter";
import db from "./connectDB.js";
import type { Mongoose } from "mongoose";
import type { GameEngineMsg } from "./GameEngineDefs.js";
export interface ActionRequest {

}

export interface ActionRequestContainer {
    waiterSeq: number;
    action: ActionRequest;
}

export type ActionSuccess = {
    success: true;
    message?: string;
}

export type ActionFailure = {
    success: false;
    reason: string;
}
export type ActionResult = ActionSuccess | ActionFailure;

type QueueType = 'server' | 'api';
//type QueueType = 'server' | 'npc' | 'api';

export class GameEngine {

    private static instance: GameEngine | null = null;

    private actionSeq = 0;

    private queueWaiters = new Map<number, [resolve: (result: ActionSuccess) => void, reject: (reason: ActionFailure) => void]>();

    private signal = new Signal(30000);

    private actionQueue = {
        server: new Denque<ActionRequestContainer>(),
        //npc: new Denque<ActionRequestContainer>(),
        api: new Denque<ActionRequestContainer>(),
    } as const satisfies Record<QueueType, Denque<ActionRequestContainer>>;

    private rsc: ResourceController

    private constructor(
        db: Mongoose,
        private postStatus: (msg: GameEngineMsg) => void,
    ) {
        this.rsc = new ResourceController(db);
    }

    private continueRun = true;

    private async gameLoop(): Promise<void> {
        let generalWaitTimer: ReturnType<typeof setTimeout> | null = null;
        let prevSaveWaiter: Promise<void> | null = null;

        while (this.continueRun) {
            //가장 빠른 장수
            do {
                const now = new Date();
                const upcomingGeneral = this.rsc.peekGeneralTurntimeQueue();
                if (!upcomingGeneral) {
                    break;
                }
                const upcomingTurn = upcomingGeneral.raw.turntime;

                const waitGeneralTurnMs = upcomingTurn.getTime() - now.getTime();
                if (waitGeneralTurnMs > 0) {
                    generalWaitTimer = setTimeout(() => {
                        this.signal.notify();
                        generalWaitTimer = null;
                    }, waitGeneralTurnMs);
                }
                else {
                    this.signal.notify();
                }
            } while (0);

            for(const queue of Object.values(this.actionQueue)){
                if(!queue.isEmpty()){
                    this.signal.notify();
                    break;
                }
            }

            //이벤트 대기
            await this.signal.wait();

            if (generalWaitTimer) {
                clearTimeout(generalWaitTimer);
            }
            if (!this.continueRun) {
                break;
            }

            const now = new Date();

            let processedGeneralCount = 0;

            while (true) {
                //장수턴 부터 처리
                const upcomingGeneral = this.rsc.popGeneralTurntimeQueue();
                if (!upcomingGeneral) {
                    break;
                }

                const generalTurntime = upcomingGeneral.raw.turntime;
                if (generalTurntime > now) {
                    break;
                }

                //TODO: 턴 수행해야지!

                upcomingGeneral.updateTurntime();
                this.rsc.insertGeneralTurntimeQueue(upcomingGeneral, true);
                this.rsc.gameEnv().update((env)=>{
                    env.lastExecuted = generalTurntime;
                })
                processedGeneralCount++;
            }

            if (processedGeneralCount > 0) {
                await prevSaveWaiter;
                const lastExecuted = this.rsc.gameEnv().raw.lastExecuted;
                prevSaveWaiter = this.rsc.saveAll().then(()=>{
                    this.postStatus({
                        type: 'update',
                        lastExecuted: lastExecuted.toISOString()
                    });
                });
            }

            //서버 이벤트 처리
            for (const [invoker, queue] of entriesWithType(this.actionQueue)) {
                let processEventCount = 0;

                let responseQueue: (() => void)[] = [];

                while (!queue.isEmpty()) {
                    const action = must(queue.shift());

                    //TODO: action 처리
                    const errorReason: string | undefined = undefined;

                    const [ticketResolve, ticketRejected] = must_err(
                        this.queueWaiters.get(action.waiterSeq),
                        Error, `GameEngine: waiterSeq(${action.waiterSeq}) not found`
                    );

                    this.queueWaiters.delete(action.waiterSeq);
                    if (errorReason) {
                        responseQueue.push(() => {
                            ticketRejected(errorReason);
                        });
                    }
                    else {
                        responseQueue.push(() => {
                            ticketResolve({ success: true });
                        });
                    }

                    processEventCount++;
                }

                if (processEventCount > 0) {
                    await prevSaveWaiter;
                    prevSaveWaiter = null;
                    await this.rsc.saveAll();
                    for (const response of responseQueue) {
                        response();
                    }
                }
            }
        }
    }


    private gameLoopPromise: Promise<void> | null = null;

    public static async initInstance(updateHandler: (msg: GameEngineMsg)=>void): Promise<GameEngine> {
        if (GameEngine.instance) {
            throw new Error('GameEngine is already initialized');
        }

        GameEngine.instance = new GameEngine(await db, updateHandler);
        return GameEngine.instance;
    }

    public static getInstance() {
        if (!GameEngine.instance) {
            throw new Error('GameEngine is not initialized');
        }
        return GameEngine.instance;
    }

    public start(): boolean {
        if (this.gameLoopPromise) {
            return false;
        }

        for (const queue of Object.values(this.actionQueue)) {
            queue.clear();
        }

        this.continueRun = true;
        this.gameLoopPromise = this.gameLoop();

        console.info('GameEngine started');
        return true;
    }

    public async stop() {
        this.continueRun = false;
        if (this.gameLoopPromise) {
            await this.signal.abort();
            await this.gameLoopPromise;
            this.gameLoopPromise = null;
        }

        console.log('GameEngine stopped');
    }


    private async pushAction(queueName: QueueType, action: ActionRequest): Promise<ActionResult> {
        const queue = this.actionQueue[queueName];
        if (this.actionSeq >= Number.MAX_SAFE_INTEGER) {
            this.actionSeq = 0;
        }
        const seq = this.actionSeq++;

        if (this.queueWaiters.has(seq)) {
            throw new Error(`GameEngine: seq(${seq}) is already used`);
        }

        let done = false;

        const waiter = new Promise((resolve, reject) => {
            this.queueWaiters.set(seq, [resolve, reject]);
            done = true;
            queue.push({
                waiterSeq: seq,
                action
            });
        });

        await delay(0);
        this.signal.notify();

        if (!done) {
            throw new Error(`GameEngine: pushAction(${queueName}) failed`);
        }

        return waiter as Promise<ActionResult>;
    }

    public async pushServerAction(action: ActionRequest): Promise<ActionResult> {
        return this.pushAction('server', action);
    }

    /*
    public async pushNPCAction(action: ActionRequest): Promise<ActionResult> {
        return this.pushAction('npc', action);
    }
    */

    public async pushAPIAction(action: ActionRequest): Promise<ActionResult> {
        return this.pushAction('api', action);
    }

}