<template>
<transition-group
	name="staggered-fade"
	tag="div"
	:css="false"
	@before-enter="beforeEnter"
	@enter="enter"
	@leave="leave"
	mode="out-in"
	appear
>
	<slot></slot>
</transition-group>
</template>

<script lang="ts">
import Vue from 'vue';

export default Vue.extend({
	props: {
		delay: {
			type: Number,
			required: false,
			default: 40
		},
		direction: {
			type: String,
			required: false,
			default: 'down'
		},
		reversed: {
			type: Boolean,
			required: false,
			default: false
		}
	},
	data() {
		return {
			currentChildren: [] as Node[],
			index: 0
		};
	},
	methods: {
		updateChildren() {
			this.currentChildren = this.$slots.default!.filter(n => n.elm != null).map(n => n.elm!);
		},
		beforeEnter(el) {
			el.style.opacity = 0;
			el.style.transform = this.direction === 'down' ? 'translateY(-64px)' : 'translateY(64px)';
		},
		enter(el, done) {
			let index = this.index;
			// TODO
			//if (this.reversed) index = ...;
			//console.log(index);
			el.style.transition = [getComputedStyle(el).transition, 'transform 0.7s cubic-bezier(0.23, 1, 0.32, 1)', 'opacity 0.7s cubic-bezier(0.23, 1, 0.32, 1)'].filter(x => x != '').join(',');
			setTimeout(() => {
				el.style.opacity = 1;
				el.style.transform = 'translateY(0px)';
				setTimeout(() => {
					done();
					this.index--;
				}, 700);
			}, this.delay * index)
			this.index++;
		},
		leave(el, done) {
			el.style.opacity = 0;
			el.style.transform = this.direction === 'down' ? 'translateY(64px)' : 'translateY(-64px)';
			setTimeout(done, 700);
		},
		focus() {
			this.$slots.default[0].elm.focus();
		}
	}
});
</script>

<style lang="scss">
.staggered-fade-move {
	transition: transform 0.7s !important;
}
</style>
