<!--
SPDX-FileCopyrightText: syuilo and misskey-project
SPDX-License-Identifier: AGPL-3.0-only
-->

<template>
<div ref="rootEl" :class="isPulling ? $style.isPulling : null">
	<div v-if="isPulling" :class="$style.frame" :style="`--frame-min-height: ${pullDistance / (PULL_BRAKE_BASE + (pullDistance / PULL_BRAKE_FACTOR))}px;`">
		<div :class="$style.frameContent">
			<MkLoading v-if="isRefreshing" :class="$style.loader" :em="true"/>
			<i v-else class="ti ti-arrow-bar-to-down" :class="[$style.icon, { [$style.refresh]: isPulledEnough }]"></i>
			<div :class="$style.text">
				<template v-if="isPulledEnough">{{ i18n.ts.releaseToRefresh }}</template>
				<template v-else-if="isRefreshing">{{ i18n.ts.refreshing }}</template>
				<template v-else>{{ i18n.ts.pullDownToRefresh }}</template>
			</div>
		</div>
	</div>

	<slot/>
</div>
</template>

<script lang="ts" setup>
import { onMounted, onUnmounted, ref, useTemplateRef } from 'vue';
import { getScrollContainer } from '@@/js/scroll.js';
import { i18n } from '@/i18n.js';
import { isHorizontalSwipeSwiping } from '@/utility/touch.js';

const SCROLL_STOP = 10;
const MAX_PULL_DISTANCE = Infinity;
const FIRE_THRESHOLD = 200;
const RELEASE_TRANSITION_DURATION = 200;
const PULL_BRAKE_BASE = 1.5;
const PULL_BRAKE_FACTOR = 170;

const isPulling = ref(false);
const isPulledEnough = ref(false);
const isRefreshing = ref(false);
const pullDistance = ref(0);

let startScreenY: number | null = null;

const rootEl = useTemplateRef('rootEl');
let scrollEl: HTMLElement | null = null;

const props = withDefaults(defineProps<{
	refresher: () => Promise<void>;
}>(), {
	refresher: () => Promise.resolve(),
});

const emit = defineEmits<{
	(ev: 'refresh'): void;
}>();

function getScreenY(event: TouchEvent | MouseEvent | PointerEvent): number {
	if (event.touches && event.touches[0] && event.touches[0].screenY != null) {
		return event.touches[0].screenY;
	} else {
		return event.screenY;
	}
}

// When at the top of the page, disable vertical overscroll so passive touch listeners can take over.
function lockDownScroll() {
	scrollEl!.style.touchAction = 'pan-x pan-down pinch-zoom';
	scrollEl!.style.overscrollBehavior = 'none';
}

function unlockDownScroll() {
	scrollEl!.style.touchAction = 'auto';
	scrollEl!.style.overscrollBehavior = 'contain';
}

function moveStart(event: PointerEvent) {
	const scrollPos = scrollEl!.scrollTop;
	if (scrollPos === 0) {
		lockDownScroll();
		if (!isPulling.value && !isRefreshing.value) {
			isPulling.value = true;
			startScreenY = getScreenY(event);
			pullDistance.value = 0;

			// タッチデバイスでPointerEventを使うとなんか挙動がおかしいので、TouchEventとMouseEventを使い分ける
			if (event.pointerType === 'mouse') {
				window.addEventListener('mousemove', moving, { passive: true });
				window.addEventListener('mouseup', () => {
					window.removeEventListener('mousemove', moving);
					onPullRelease();
				}, { passive: true, once: true });
			} else {
				window.addEventListener('touchmove', moving, { passive: true });
				window.addEventListener('touchend', () => {
					window.removeEventListener('touchmove', moving);
					onPullRelease();
				}, { passive: true, once: true });
			}
		}
	} else {
		unlockDownScroll();
	}
}

function moveBySystem(to: number): Promise<void> {
	return new Promise(r => {
		const startHeight = pullDistance.value;
		const overHeight = pullDistance.value - to;
		if (overHeight < 1) {
			r();
			return;
		}
		const startTime = Date.now();
		let intervalId = window.setInterval(() => {
			const time = Date.now() - startTime;
			if (time > RELEASE_TRANSITION_DURATION) {
				pullDistance.value = to;
				window.clearInterval(intervalId);
				r();
				return;
			}
			const nextHeight = startHeight - (overHeight / RELEASE_TRANSITION_DURATION) * time;
			if (pullDistance.value < nextHeight) return;
			pullDistance.value = nextHeight;
		}, 1);
	});
}

async function fixOverContent() {
	if (pullDistance.value > FIRE_THRESHOLD) {
		await moveBySystem(FIRE_THRESHOLD);
	}
}

async function closeContent() {
	if (pullDistance.value > 0) {
		await moveBySystem(0);
	}
}

function onPullRelease() {
	window.document.body.removeAttribute('inert');
	startScreenY = null;
	if (isPulledEnough.value) {
		isPulledEnough.value = false;
		isRefreshing.value = true;
		fixOverContent().then(() => {
			emit('refresh');
			props.refresher().then(() => {
				refreshFinished();
			});
		});
	} else {
		closeContent().then(() => isPulling.value = false);
	}
}

function toggleScrollLockOnTouchEnd() {
	const scrollPos = scrollEl!.scrollTop;
	if (scrollPos === 0) {
		lockDownScroll();
	} else {
		unlockDownScroll();
	}
}

function moving(event: MouseEvent | TouchEvent) {
	if (!isPulling.value || isRefreshing.value) return;

	if ((scrollEl?.scrollTop ?? 0) > SCROLL_STOP + pullDistance.value || isHorizontalSwipeSwiping.value) {
		pullDistance.value = 0;
		isPulledEnough.value = false;
		onPullRelease();
		return;
	}

	if (startScreenY === null) {
		startScreenY = getScreenY(event);
	}
	const moveScreenY = getScreenY(event);

	const moveHeight = moveScreenY - startScreenY!;
	pullDistance.value = Math.min(Math.max(moveHeight, 0), MAX_PULL_DISTANCE);

	// マウスでのpull時、画面上のテキスト選択が発生して画面がスクロールされたりするのを防ぐ
	if (pullDistance.value > 3) { // ある程度遊びを持たせないと通常のクリックでも発火しクリックできなくなる
		window.document.body.setAttribute('inert', 'true');
	}

	isPulledEnough.value = pullDistance.value >= FIRE_THRESHOLD;
}

/**
 * emit(refresh)が完了したことを知らせる関数
 *
 * タイムアウトがないのでこれを最終的に実行しないと出たままになる
 */
function refreshFinished() {
	closeContent().then(() => {
		isPulling.value = false;
		isRefreshing.value = false;
	});
}

onMounted(() => {
	if (rootEl.value == null) return;
	scrollEl = getScrollContainer(rootEl.value);
	lockDownScroll();
	rootEl.value.addEventListener('pointerdown', moveStart, { passive: true });
	rootEl.value.addEventListener('touchend', toggleScrollLockOnTouchEnd, { passive: true });
});

onUnmounted(() => {
	if (rootEl.value) rootEl.value.removeEventListener('pointerdown', moveStart);
	if (rootEl.value) rootEl.value.removeEventListener('touchend', toggleScrollLockOnTouchEnd);
});
</script>

<style lang="scss" module>
.isPulling {
	will-change: contents;
}

.frame {
	position: relative;
	overflow: clip;

	width: 100%;
	min-height: var(--frame-min-height, 0px);

	mask-image: linear-gradient(90deg, #000 0%, #000 80%, transparent);
	-webkit-mask-image: -webkit-linear-gradient(90deg, #000 0%, #000 80%, transparent);

	pointer-events: none;
}

.frameContent {
	position: absolute;
	bottom: 0;
	width: 100%;
	margin: 5px 0;
	display: flex;
	flex-direction: column;
	align-items: center;

	> .icon, > .loader {
		margin: 6px 0;
	}

	> .icon {
		transition: transform .25s;

		&.refresh {
			transform: rotate(180deg);
		}
	}

	> .text {
		margin: 5px 0;
		font-size: 90%;
	}
}
</style>
