<template>
	<view class="tabs">
		<view class="status_bar" :style="winHeight"></view>
		<scroll-view ref="tabbar1" id="tab-bar" class="tab-bar" :scroll="false" :scroll-x="true"
			:scroll-into-view="scrollInto">
			<view class="tab-bar-list">
				<view class="tab-bar-list-wrapper">
					<view class="uni-tab-item" v-for="(tab,index) in tabList" :key="tab.id"
						:ref="'tabitem'+index">
						<text :id="tab.id" :data-id="index" :data-current="index" class="uni-tab-item-title"
							:class="{'uni-tab-item-title-active':tabIndex==index}" @click="ontabtap">{{tab.name}}</text>
					</view>
				</view>
				<view class="scroll-view-indicator">
					<view ref="underline" class="scroll-view-underline" :class="{'scroll-view-animation':isTap}"
						:style="underlineStyle"></view>
				</view>
			</view>
		</scroll-view>
		<swiper ref="swiper1" class="tab-box" :current="tabIndex" :duration="300" @change="onswiperchange"
			@transition="onswiperscroll" @animationfinish="animationfinish" @onAnimationEnd="animationfinish">
			<swiper-item class="swiper-item" v-for="(page, index) in tabList" :key="index">
				<newsPage :ref="'page' + index" class="page-item" :nid="page.newsid"></newsPage>
			</swiper-item>
		</swiper>
	</view>
</template>

<script>
	import {
		mapState
	} from 'vuex'
	
	// #ifdef APP-PLUS
	const dom = weex.requireModule('dom');
	// #endif

	import newsPage from './news-page.nvue';

	// 缓存每页最多
	const MAX_CACHE_DATA = 100;
	// 缓存页签数量
	const MAX_CACHE_PAGE = 3;
	const TAB_PRELOAD_OFFSET = 1;

	export default {
		components: {
			newsPage
		},
		data() {
			return {
				tabList: [{
					id: "tab01",
					name: '全部',
					newsid: 0
				}, {
					id: "tab02",
					name: '待审批',
					newsid: 23
				}, {
					id: "tab03",
					name: '已审批',
					newsid: 223
				}],
				tabIndex: 0,
				cacheTab: [],
				scrollInto: "",
				navigateFlag: false,
				indicatorLineLeft: 0,
				indicatorLineWidth: 0,
				isTap: false,
				// 测试使用观察变化
				_lastTabIndex: 0,
				swiperWidth: 0,
				tabbarWidth: 0,
				tabListSize: {},
				_touchTabIndex: 0,
			}
		},
		computed: {
			underlineStyle() {
				return {
					left: this.indicatorLineLeft + 'px',
					width: this.indicatorLineWidth + 'px'
				}
			},
			...mapState(['sysinfo'])
		},
		onLoad() {
			this.winHeight = `height:${this.sysinfo.safeArea.top}px`
		},
		onReady() {
			this._lastTabIndex = 0;
			this.swiperWidth = 0;
			this.tabbarWidth = 0;
			this.tabListSize = {};
			this._touchTabIndex = 0;

			this.pageList = [];
			for (let i = 0; i < this.tabList.length; i++) {
				let item = this.$refs['page' + i]
				if (Array.isArray(item)) {
					this.pageList.push(item[0])
				} else {
					this.pageList.push(item)
				}
			}
			this.switchTab(this.tabIndex);

			this.selectorQuery();
		},
		methods: {
			ontabtap(e) {
				let index = e.target.dataset.current || e.currentTarget.dataset.current;
				//let offsetIndex = this._touchTabIndex = Math.abs(index - this._lastTabIndex) > 1;

				// #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ
				this.isTap = true;
				var currentSize = this.tabListSize[index];
				this.updateIndicator(currentSize.left, currentSize.width);
				this._touchTabIndex = index;
				// #endif

				this.switchTab(index);
			},
			onswiperchange(e) {
				// 注意：百度小程序会触发2次

				// #ifndef APP-PLUS || H5 || MP-WEIXIN || MP-QQ
				let index = e.target.current || e.detail.current;
				this.switchTab(index);
				// #endif
			},
			onswiperscroll(e) {
				if (this.isTap) {
					return;
				}

				var offsetX = e.detail.dx;
				var preloadIndex = this._lastTabIndex;
				if (offsetX > TAB_PRELOAD_OFFSET) {
					preloadIndex++;
				} else if (offsetX < -TAB_PRELOAD_OFFSET) {
					preloadIndex--;
				}
				if (preloadIndex === this._lastTabIndex || preloadIndex < 0 || preloadIndex > this.pageList.length - 1) {
					return;
				}
				if (this.pageList[preloadIndex].dataList.length === 0) {
					this.loadTabData(preloadIndex);
				}

				// #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ
				var percentage = Math.abs(this.swiperWidth / offsetX);
				var currentSize = this.tabListSize[this._lastTabIndex];
				var preloadSize = this.tabListSize[preloadIndex];
				var lineL = currentSize.left + (preloadSize.left - currentSize.left) / percentage;
				var lineW = currentSize.width + (preloadSize.width - currentSize.width) / percentage;
				this.updateIndicator(lineL, lineW);
				// #endif
			},
			animationfinish(e) {
				// #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ
				let index = e.detail.current;
				if (this._touchTabIndex === index) {
					this.isTap = false;
				}
				this._lastTabIndex = index;
				this.switchTab(index);
				this.updateIndicator(this.tabListSize[index].left, this.tabListSize[index].width);
				// #endif
			},
			selectorQuery() {
				// #ifdef APP-NVUE
				dom.getComponentRect(this.$refs.tabbar1, res => {
					this.tabbarWidth = res.size.width;
				});
				dom.getComponentRect(this.$refs['swiper1'], res => {
					this.swiperWidth = res.size.width;
				});
			
				// 因 nvue 暂不支持 class 查询
				let queryTabSize = uni.createSelectorQuery().in(this);
				for (let i = 0; i < this.tabList.length; i++) {
					queryTabSize.select('#' + this.tabList[i].id).boundingClientRect();
				}
				queryTabSize.exec(rects => {
					rects.forEach((rect) => {
						this.tabListSize[rect.dataset.id] = rect;
					})
					this.updateIndicator(this.tabListSize[this.tabIndex].left, this.tabListSize[this.tabIndex]
						.width);
					this.switchTab(this.tabIndex);
				});
				// #endif

				// #ifdef MP-WEIXIN || H5 || MP-QQ
				uni.createSelectorQuery().in(this).select('.tab-box').fields({
					dataset: true,
					size: true,
				}, (res) => {
					this.swiperWidth = res.width;
				}).exec();
				uni.createSelectorQuery().in(this).selectAll('.uni-tab-item-title').boundingClientRect((rects) => {
					rects.forEach((rect) => {
						this.tabListSize[rect.dataset.id] = rect;
					})
					this.updateIndicator(this.tabListSize[this.tabIndex].left, this.tabListSize[this.tabIndex]
						.width);
				}).exec();
				// #endif
			},
			updateIndicator(left, width) {
				this.indicatorLineLeft = left;
				this.indicatorLineWidth = width;
			},
			switchTab(index) {
				if (this.pageList[index].dataList.length === 0) {
					this.loadTabData(index);
				}

				if (this.tabIndex === index) {
					return;
				}

				// 缓存 tabId
				if (this.pageList[this.tabIndex].dataList.length > MAX_CACHE_DATA) {
					let isExist = this.cacheTab.indexOf(this.tabIndex);
					if (isExist < 0) {
						this.cacheTab.push(this.tabIndex);
					}
				}

				this.tabIndex = index;

				// #ifdef APP-NVUE
				// this.scrollTabTo(index);
				// #endif

				// #ifndef APP-NVUE
				this.scrollInto = this.tabList[index].id;
				// #endif

				// 释放 tabId
				if (this.cacheTab.length > MAX_CACHE_PAGE) {
					let cacheIndex = this.cacheTab[0];
					this.clearTabData(cacheIndex);
					this.cacheTab.splice(0, 1);
				}
			},
			scrollTabTo(index) {
				const el = this.$refs['tabitem' + index][0];
				let offset = 0;
				// TODO fix ios offset
				if (index > 0) {
					offset = this.tabbarWidth / 2 - this.tabListSize[index].width / 2;
					if (this.tabListSize[index].right < this.tabbarWidth / 2) {
						offset = this.tabListSize[0].width;
					}
				}
				dom.scrollToElement(el, {
					offset: -offset
				});
			},
			loadTabData(index) {
				this.pageList[index].loadData();
			},
			clearTabData(index) {
				this.pageList[index].clear();
			}
		}
	}
</script>

<style lang="scss">
	/* #ifndef APP-PLUS */
	page {
		width: 100%;
		min-height: 100%;
		display: flex;
		background: $background-color-1;
	}
	
	.status_bar {
		height: var(--status-bar-height);
	}

	/* #endif */

	.tabs {
		flex: 1;
		flex-direction: column;
		overflow: hidden;
		background-color: #ffffff;
	}

	.tab-bar {
		width: 750rpx;
		height: 42px;
		flex-direction: row;
		/* #ifndef APP-PLUS */
		white-space: nowrap;
		/* #endif */
	}

	/* #ifndef APP-NVUE */
	.tab-bar ::-webkit-scrollbar {
		display: none;
		width: 0 !important;
		height: 0 !important;
		-webkit-appearance: none;
		background: transparent;
	}

	/* #endif */

	.tab-bar-list {
		flex-direction: column;
	}

	.tab-bar-list-wrapper {
		width: 750rpx;
		flex-direction: row;
	}

	.scroll-view-indicator {
		position: relative;
		height: 2px;
		border-radius: 1px;
		background-color: transparent;
	}

	.scroll-view-underline {
		position: absolute;
		top: 0;
		bottom: 0;
		width: 0;
		background-color: $tabbar-color;
	}

	.scroll-view-animation {
		transition-duration: 0.2s;
		transition-property: left;
	}

	.tab-box {
		flex: 1;
		background: $background-color-1;
		padding: 0 16rpx;
	}

	.uni-tab-item {
		/* #ifndef APP-PLUS */
		display: inline-block;
		/* #endif */
		flex-wrap: nowrap;
		padding-left: 6px;
		padding-right: 6px;
		flex: 1;
		justify-content: center;
		text-align: center;
	}

	.uni-tab-item-title {
		color: $text-base-color;
		font-size: 28rpx;
		height: 40px;
		line-height: 40px;
		font-weight: 400;
		flex-wrap: nowrap;
		/* #ifndef APP-PLUS */
		white-space: nowrap;
		/* #endif */
	}

	.uni-tab-item-title-active {
		color: $tabbar-color;
		font-weight: 500;
	}

	.swiper-item {
		flex: 1;
		flex-direction: column;
	}

	.page-item {
		flex: 1;
		flex-direction: row;
		position: absolute;
		left: 16rpx;
		top: 0;
		right: 16rpx;
		bottom: 0;
	}
</style>
