/*
 * @version: v 1.0.0
 * @Github: https://github.com/GitHubGanKai
 * @Author: GitHubGanKai
 * @Date: 2020-04-03 16:45:31
 * @LastEditors: gankai
 * @LastEditTime: 2020-04-03 18:43:34
 * @FilePath: /utils/VueEventEmitter.js
 */

class EventBus {
    constructor (vue) {
        // Maintain event subscription behavior
        this.events = {}
        if (!this.events) {
            Reflect.defineProperty(this, 'events', {
                value: {},
                enumerable: false
            })
        }
        this.Vue = vue
        this.eventMapUid = {}
    }

    /**
     * Map all subscribed event types in uid to the same array
     * @param {String} uid
     * @param {String} type
     */
    setEventMapUid (uid, type) {
        if (!this.eventMapUid[uid]) {
            this.eventMapUid[uid] = []
        }
        this.eventMapUid[uid].push(type)
    }

    /**
     * Register for event subscription
     * @param {String} type
     * @param {Function} func
     * @param {Object} vm
     */
    subscribe (type, func, vm) {
        if (!this.events[type]) {
            this.events[type] = []
        }
        this.events[type].push(func)
        if (vm instanceof this.Vue) {
            this.setEventMapUid(vm._uid, type)
        }
    }

    /**
     * Post event
     * @param {String} type 
     * @param  {...any} args 
    */
    publish (type, ...args) {
        if (this.events[type]) {
            this.events[type].forEach(func => func(...args))
        }
    }

    /**
     * Remove subscription behavior under an event type
     * @param {String} type 
     * @param {Function} func 
    */
    unsubscribe (type, func) {
        // If func is passed, then find the function in the event type and delete it from the event type
        if (func && this.events[type]) {
            const index = this.events[type].findIndex(fn => fn === func)
            if (~index) {
                this.events[type].splice(index, 1)
            }
            return
        }
        // If func is not passed, all subscription behaviors under the entire event type are deleted by default!
        delete this.events[type]
    }

    /**
     * Remove all subscription behaviors under the uid component
     * @param {String} uid 
    */
    unsubscribeAll (uid) {
        const currentAllEvents = this.eventMapUid[uid] || []
        currentAllEvents.forEach(currentEvent => {
            this.unsubscribe(currentEvent)
        })
    }
}

export default {
    install (Vue, option = {}) {
        Reflect.defineProperty(Vue.prototype, '$eventBus', {
            value: new EventBus(Vue)
        })
        Vue.mixin({
            beforeDestroy () {
            // Intercept the beforeDestroy hook to automatically destroy all its subscribed events
                this.$eventBus.unsubscribeAll(this._uid)
            }
        })
    }
}