import { throttle } from 'lodash'
import { mapState } from 'vuex'
import menuMixin from '../mixin/menu'
import { createMenu } from '../libs/util.menu'

export default {
    name: 'ibps-layout-header-aside-menu-header',
    mixins: [
        menuMixin
    ],

    data () {
        return {
            active: this.activeHeader,
            isScroll: false,
            scrollWidth: 0,
            contentWidth: 0,
            currentTranslateX: 0,
            throttledCheckScroll: null
        }
    },
    computed: {
        ...mapState('ibps/menu', [
            'activeHeader',
            'header'
        ])
    },
    watch: {
        // $route (to, from) {
        //     if (to.name === 'dashboard') {
        //         this.active = ''
        //     } else {
        //         this.active = this.activeHeader
        //     }
        // }
        'activeHeader': {
            handler (val) {
                if (this.$route.name !== 'dashboard') {
                    this.active = this.activeHeader
                }
            },
            immediate: true
        }
        // '$route.matched': {
        //   handler(val) {
        //     this.active = val[val.length - 1].path
        //   },
        //   immediate: true
        // }
    },
    mounted () {
        // 初始化判断
        // 默认判断父元素和子元素的大小，以确定初始情况是否显示滚动
        window.addEventListener('load', this.checkScroll)
        // 全局窗口变化监听，判断父元素和子元素的大小，从而控制isScroll的开关
        this.throttledCheckScroll = throttle(this.checkScroll, 300)
        window.addEventListener('resize', this.throttledCheckScroll)
        // zxh 初始化延迟以确定初始情况是否显示滚动
        setTimeout(() => {
            this.checkScroll()
        }, 500)
    },
    beforeDestroy () {
        // 取消监听
        window.removeEventListener('resize', this.throttledCheckScroll)
        window.removeEventListener('load', this.checkScroll)
    },
    methods: {
        scroll (direction) {
            if (direction === 'left') {
                // 向右滚动
                this.currentTranslateX = 0
            } else {
                // 向左滚动
                if (this.contentWidth * 2 - this.currentTranslateX <= this.scrollWidth) {
                    this.currentTranslateX -= this.contentWidth
                } else {
                    this.currentTranslateX = this.contentWidth - this.scrollWidth
                }
            }
        },
        checkScroll () {
            let contentWidth = this.$refs.content.clientWidth
            let scrollWidth = this.$refs.scroll.clientWidth
            if (this.isScroll) {
                // 页面依旧允许滚动的情况，需要更新width
                if (this.contentWidth - this.scrollWidth === this.currentTranslateX) {
                    // currentTranslateX 也需要相应变化【在右端到头的情况时】
                    this.currentTranslateX = contentWidth - scrollWidth
                    // 快速的滑动依旧存在判断和计算时对应的contentWidth变成正数，所以需要限制一下
                    if (this.currentTranslateX > 0) {
                        this.currentTranslateX = 0
                    }
                }
                // 更新元素数据
                this.contentWidth = contentWidth
                this.scrollWidth = scrollWidth
                // 判断何时滚动消失: 当scroll > content
                if (contentWidth > scrollWidth) {
                    this.isScroll = false
                }
            }
            // 判断何时滚动出现: 当scroll < content
            if (!this.isScroll && contentWidth < scrollWidth) {
                this.isScroll = true
                // 注意，当isScroll变为true，对应的元素盒子大小会发生变化
                this.$nextTick(() => {
                    contentWidth = this.$refs.content.clientWidth
                    scrollWidth = this.$refs.scroll.clientWidth
                    this.contentWidth = contentWidth
                    this.scrollWidth = scrollWidth
                    this.currentTranslateX = 0
                })
            }
        }
    },
    render (h) {
        return <div
            flex='cross:center'
            class={{ 'ibps-theme-header-menu': true, 'is-scrollable': this.isScroll }}
            ref='page'>
            <div
                ref='content'
                class='ibps-theme-header-menu__content'
                flex-box='1'
                flex>
                <div
                    class='ibps-theme-header-menu__scroll'
                    flex-box='0'
                    style={{ transform: `translateX(${this.currentTranslateX}px)` }}
                    ref='scroll'>
                    <el-menu
                        mode='horizontal'
                        defaultActive={this.active}
                        onSelect={this.handleHeaderMenuSelect}>
                        {this.header.map(menu => createMenu.call(this, h, menu, 'id'))}
                    </el-menu>
                </div>
            </div>
            {
                this.isScroll
                    ? [
                        <div
                            class='ibps-theme-header-menu__prev'
                            flex='main:center cross:center'
                            flex-box='0'
                            onClick={() => this.scroll('left')}>
                            <i class='el-icon-arrow-left'></i>
                        </div>,
                        <div
                            class='ibps-theme-header-menu__next'
                            flex='main:center cross:center'
                            flex-box='0'
                            onClick={() => this.scroll('right')}>
                            <i class='el-icon-arrow-right'></i>
                        </div>
                    ]
                    : []
            }
        </div>
    }
}