<template>
	<view>
		<view
			id="_drag_button"
			class="cart-icon"
			:style="'left: ' + left + 'px; top:' + top + 'px;'"
			@touchstart="touchstart"
			@touchmove.stop.prevent="touchmove"
			@touchend="touchend"
			@click.stop.prevent="click"
			:class="{transition: isDock && !isMove }"
		>
			<text v-if="cartNum > 0" class="uni-badge uni-badge-error uni-small uni-badge--small icon-num">
				{{cartNum >= 100 ? '99+' : cartNum}}
			</text>
			<image src='https://static.caimei365.com/app/img/icon/icon-cart-active@3x.png' mode="widthFix"></image>
		</view>
	</view>
</template>

<script>
	export default {
		name: 'drag-button',
		props: {
			cartNum:{
				type: Number,
				default: 0
			},
			isDock:{
				type: Boolean,
				default: false
			},
			existTabBar:{
				type: Boolean,
				default: false
			}
		},
		data() {
			return {
				top:518,
				left:314,
				width: 0,
				height: 0,
				offsetWidth: 0,
				offsetHeight: 0,
				windowWidth: 0,
				windowHeight: 0,
				isMove: true,
				edge: 10,
			}
		},
		mounted() {
			const sys = uni.getSystemInfoSync();
			this.windowWidth = sys.windowWidth;
			this.windowHeight = sys.windowHeight;
			// #ifdef APP-PLUS
				this.existTabBar && (this.windowHeight -= 50);
			// #endif
			if (sys.windowTop) {
				this.windowHeight += sys.windowTop;
			}
			// console.log(sys)
			const query = uni.createSelectorQuery().in(this);
			query.select('#_drag_button').boundingClientRect(data => {
				this.width = data.width;
				this.height = data.height;
				this.offsetWidth = data.width / 2;
				this.offsetHeight = data.height / 2;
				this.left = this.windowWidth - this.width - this.edge-5;
				this.top = this.windowHeight - this.height - this.edge-150;
			}).exec();
		},
		methods: {
			click() {
				this.$emit('btnClick');
			},
			touchstart(e) {
				this.$emit('btnTouchstart');
			},
			touchmove(e) {
				// 单指触摸
				if (e.touches.length !== 1) {
					return false;
				}
				this.isMove = true;
				this.left = e.touches[0].clientX - this.offsetWidth;
				let clientY = e.touches[0].clientY - this.offsetHeight;
				// #ifdef H5
					clientY += this.height;
				// #endif
				let edgeBottom = this.windowHeight - this.height - this.edge;
				// 上下触及边界
				if (clientY < this.edge) {
					this.top = this.edge;
				} else if (clientY > edgeBottom) {
					this.top = edgeBottom;
				} else {
					this.top = clientY
				}
			},
			touchend(e) {
				if (this.isDock) {
					let edgeRigth = this.windowWidth - this.width - this.edge;
					
					if (this.left < this.windowWidth / 2 - this.offsetWidth) {
						this.left = this.edge;
					} else {
						this.left = edgeRigth;
					}
					
				}
				
				this.isMove = false;
				this.$emit('btnTouchend');
			},
		}}
</script>

<style lang="scss">
	.cart-icon {
		width: 92rpx;
		height: 92rpx;
		border-radius: 50%;
		background: rgba(0,0,0,0.3);
		position: fixed;
		right: 24rpx;
		bottom: 28%;
		display: flex;
		align-items: center;
		justify-content: center;
		cursor: pointer;
		z-index: 20;
		image {
			width: 58rpx;
			height: 58rpx;
		}
		text {
			font-size: 28rpx;
			position: absolute;
			top: -10rpx;
			right: 0;
		}
		&.transition {
			transition: left .3s ease,top .3s ease;
		}
	}
	
</style>
