/*
 * -------------------------------------------------------------------------
 * This file is part of the MindStudio project.
 * Copyright (c) 2025 Huawei Technologies Co.,Ltd.
 *
 * MindStudio is licensed under Mulan PSL v2.
 * You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
 *
 *          http://license.coscl.org.cn/MulanPSL2
 *
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PSL v2 for more details.
 * -------------------------------------------------------------------------
 */
import { pull } from 'lodash';
import { useEffect } from 'react';

export type EventHandler<T> = (arg?: T) => void;

class EventBus<T> {
    private readonly _events: Map<string, Array<EventHandler<T>>>;
    private readonly _maxListeners: number = 10; // 设立监听上限

    constructor() {
        this._events = new Map(); // 储存事件/回调键值对
    }

    // 触发事件
    public emit(event: string, args?: T): void {
        const handler = this._getHandlers(event);
        for (let i = 0; i < handler.length; i++) {
            const fn = handler[i];
            fn(args);
        }
    }

    // 监听事件
    public on(event: string, handler: EventHandler<T>): void {
        const handlers = this._getHandlers(event);
        handlers.push(handler);
    }

    // 移除事件
    public off(event: string, handler?: EventHandler<T>): void {
        if (handler) {
            const handlers = this._getHandlers(event);
            pull(handlers, handler);
        } else {
            this._events.delete(event);
        }
    }

    // 一次监听
    public once(event: string, handler: EventHandler<T>): void {
        const cb = (arg?: T): void => {
            this.off(event, cb);
            handler(arg);
        };
        this.on(event, cb);
    }

    private _getHandlers(event: string): Array<EventHandler<T>> {
        let handlers = this._events.get(event);
        if (!handlers) {
            handlers = [];
            this._events.set(event, handlers);
        };
        return handlers;
    }
}

// 事件总线
const eventBus = new EventBus();

export function useEventBus(event: string, handler: EventHandler<unknown>): void {
    useEffect(() => {
        eventBus.on(event, handler);
        return () => {
            eventBus.off(event, handler);
        };
    }, []);
}

export default eventBus;