import { Namespace } from "../../utils/namespace"
import { DOMExtension } from "../../utils/extensions/dom";
import { throttle } from "../../utils/throttle";

const namespace = Namespace.Create('list')

import Loading from '../loading/loading.jsx'
export default {
    name: namespace.name,
    components:{
        Loading,
    },
    data() {
        return {
            scrollParent: null,
            check: null,
            distanceY: -1,
        }
    },
    props: {
        loadingText: {
            type: String,
        },
        loading: {
            type: Boolean,
            default: false
        },
        finished: {
            type: Boolean,
            default: false
        },
        finishedText: {
            type: String,
            default: '没有更多了'
        },
        error: {
            type: Boolean,
            default: false
        },
        errorText: {
            type: String,
            default: '加载失败，点击重试'
        },
        offset:{
            type: Number,
            default: 50
        },
        loadingType:{
            type: String,
            default: 'spinner'
        },
        immediateCheck: {
            type: Boolean,
            default: true
        },
        direction: {
            type: String,
            default: 'up'
        },
        laodingType: {
            type: String,
            default: 'spinner'
        }
    },
    computed: {
        cls () {
            return namespace.derive();
        },
        tipCls() {
            return namespace.derive(['tip'])
        },
    },
    methods:{
        getElementTop(element) {
            return DOMExtension.GetBoundingClientRect(element).top + DOMExtension.GetScrollTop(window)
        },
        checkScroll() {
            const el = this.$el;
            // 当前元素的上拥有滚动条元素的高度
            const scrollerEleHeight = DOMExtension.GetBoundingClientRect(this.scrollParent).height;
            // 当前元素的高度
            const docHeight = DOMExtension.GetBoundingClientRect(el).height;
            // 当前元素拥有滚动条上元素的滚动高度
            const scrollTop = DOMExtension.GetScrollTop(this.scrollParent);
            const totalHeight = scrollTop + scrollerEleHeight;
            let isScrollFlag = false;
            if (el === this.scrollParent) {
                isScrollFlag = this.scrollParent.scrollHeight - totalHeight <= this.offset && scrollTop > this.distanceY;
            } else {
                isScrollFlag = docHeight - totalHeight <= this.offset && scrollTop > this.distanceY;
            }
            this.distanceY = scrollTop; 
            if (isScrollFlag) {
                this.$emit('input',true)
                this.$emit('load')
            }
        }
    },
    mounted() {
        this.scrollParent = DOMExtension.GetScrollParent(this.$el);
        this.check = throttle(this.checkScroll, 500, 2)
        DOMExtension.AddEventListener(this.scrollParent,'scroll', this.check);
        if(this.immediateCheck) {
            this.checkScroll();
        }
    },
    destroyed() {
        DOMExtension.RemoveEventListener(this.scrollParent, 'scroll', this.check)
    },
    render() {
        const onClick = () => {
            this.$emit('input',false);
            this.$emit('load');
            this.checkScroll();
        }
        const renderLoadingText = () => {
            if (this.loading && !this.finished) {
                return (
                    <div>
                        {
                            this.$slots.loading ? this.$slots.loading :
                            <p class={this.tipCls}> 
                                <mx-loading type={this.laodingType}>{this.loadingText}</mx-loading>
                            </p>
                        }
                    </div>
                )
            }
        }
        const renderFinishedText = () =>{
            if(this.finished) {
                return (
                    <div>
                        {
                            this.$slots.finished ? this.$slots.finished :
                            <p class={this.tipCls}>{this.finishedText}</p>
                        }
                    </div> 
                )
            }
        }
        const renderDefaultText = () =>{
            if (!this.loading && !this.finished && !this.error) {
                return (
                    <div>
                        <p class={this.tipCls}>上拉加载更多</p>
                    </div>
                )
            }
        }
        const renderErrorText = () => {
            if (this.error) {
                return (
                    <div>
                        {
                            this.$slots.error ? this.$slots.error :
                            <p class={this.tipCls} vOn:click={onClick}>{ this.errorText}</p>
                        }
                    </div>
                    
                )
            }
        }
        return (
            <div class={this.cls}>
                {this.$slots.default}
                {renderDefaultText()}
                {renderLoadingText()}
                {renderFinishedText()}
                {renderErrorText()}
            </div>
        )
    }

}