/**
 * 自定义动画指令
 * v-custom-animation.scroll.once.parent="{GetRoot, activeClass}"
 *  修饰符
 *   scroll: 是否监听滚动事件
 *   once: 是否只执行一次
 *   parent: 是否监听父元素滚动事件-优先级（GetRoot > parent > document）
 *	参数
 *   GetRoot: 获取根元素函数-优先级（GetRoot > parent > document）
 *   activeClass: 激活类名-默认值（active）
 * 
 * 子元素动画
 * <div translate-x-s="-100" translate-x="100"></div>
 *  添加动画属性
 *   translate-x-s: 水平方向移动开始位置
 *   translate-x: 水平方向移动结束位置
 * 	 ......(属性支持查看 T 对象)
 * 
*/
const roots = new Map()
const els = new Map()
const T = {
	translateX_s: 'translate-x-s',
	translateX: 'translate-x',
	translateY_s: 'translate-y-s',
	translateY: 'translate-y',
	scale_s: 'scale-s',
	scale: 'scale',
	scaleX_s: 'scale-x-s',
	scaleX: 'scale-x',
	scaleY_s: 'scale-y-s',
	scaleY: 'scale-y',
	rotate_s: 'rotate-s',
	rotate: 'rotate',
	rotateX_s: 'rotate-x-s',
	rotateX: 'rotate-x',
	rotateY_s: 'rotate-y-s',
	rotateY: 'rotate-y',
	rotateZ_s: 'rotate-z-s',
	rotateZ: 'rotate-z',
	opacity_s: 'opacity-s',
	opacity: 'opacity',
}
const types = Object.values(T)
const typesStr = types.map(v => `[${v}]`).join(',')
const resize = new ResizeObserver((e) => {
	e.forEach(({ target }) => {
		requestAnimationFrame(() => handleScroll({ target }))
	})
})

export default {
	name: 'custom-animation',
	mounted(el, binding) {
		const { value, modifiers } = binding
		const {
			GetRoot,// 获取根元素函数
			activeClass = 'active'// 激活类名
		} = value || {}
		const {
			scroll = false,// 是否监听滚动事件
			once = false,// 是否只执行一次
			parent = false,// 是否监听父元素滚动事件
		} = modifiers
		const root = GetRoot ? GetRoot() : parent ? el.parentElement : document;
		if (el === root) return;
		add(el, root)
		els.set(el, {
			root,// 根元素
			scroll,
			once,
			activeClass,
			isActive: false,
		})
	},
	beforeUnmount(el, binding) {
		remove(el)
		els.delete(el)
	}
};
function add(el, root = document) {
	requestAnimationFrame(() => handleScroll({ target: root }))
	resize.observe(el)
	if (roots.has(root)) {
		let obj = roots.get(root)
		obj.els.push(el)
		obj.observer.observe(el)
		return
	}
	resize.observe(isDocumentRoot(root))
	root.addEventListener('scroll', handleScroll)
	const observer = new IntersectionObserver((entries) => {
		entries.forEach((entry) => {
			const { target } = entry
			const obj = els.get(target)
			if (!obj) return
			if (obj.once && obj.isActive) return;// 只执行一次，且已可见，不执行
			obj.isActive = entry.isIntersecting;
			target.classList.toggle(obj.activeClass, obj.isActive)
		})
	}, { root })
	observer.observe(el)
	roots.set(root, { els: [el], observer, resize })
}
function remove(el, root = document) {
	if (!roots.has(root)) return
	const obj = roots.get(root)
	if (obj.els.includes(el)) {
		obj.observer.unobserve(el)
		obj.resize.unobserve(el)
		obj.els.splice(obj.els.indexOf(el), 1)
	}
	if (obj.els.length === 0) {
		obj.observer.disconnect()
		resize.unobserve(isDocumentRoot(root))
		root.removeEventListener('scroll', handleScroll)
		roots.delete(root)
	}
}

var timer = null
async function handleScroll({ target: root }) {
	clearTimeout(timer)
	timer = await new Promise(resolve => setTimeout(resolve, 10))
	const obj = roots.get(root)
	if (!obj) return
	obj.els.forEach((el) => {
		const item = els.get(el)
		if (!item) return
		if (!item.scroll) return
		const children = Array.from(el.querySelectorAll(typesStr))
		if (Object.values(T).some(v => hasAttr(el, v))) children.push(el)
		if (children.length === 0) return
		const rootEl = isDocumentRoot(root)
		const offsetHeight = root === document ? window.innerHeight : rootEl.offsetHeight
		const offsetTop = rootEl.offsetTop
		const scrollTop = rootEl.scrollTop
		const elTop_bottom = offsetHeight - (el.offsetTop - offsetTop - rootEl.scrollTop)
		const maxHeight = offsetHeight + el.offsetHeight
		const p = Math.min(1, Math.max(0, elTop_bottom / maxHeight))
		children.forEach((item) => {
			item.style.transition = 'transform 0.5s ease-out'

			const tX = getCurrentValue(item, T.translateX_s, T.translateX, p)
			const tY = getCurrentValue(item, T.translateY_s, T.translateY, p)
			const sx = getCurrentValue(item, T.scaleX_s, T.scaleX, p, T.scale_s, T.scale, 1)
			const sy = getCurrentValue(item, T.scaleY_s, T.scaleY, p, T.scale_s, T.scale, 1)
			const r = getCurrentValue(item, T.rotate_s, T.rotate, p)
			const rx = getCurrentValue(item, T.rotateX_s, T.rotateX, p)
			const ry = getCurrentValue(item, T.rotateY_s, T.rotateY, p)
			const rz = getCurrentValue(item, T.rotateZ_s, T.rotateZ, p)
			const transform = `translate(${tX}px, ${tY}px) scale(${sx}, ${sy}) rotate(${r}deg) rotateX(${rx}deg) rotateY(${ry}deg) rotateZ(${rz}deg)`
			item.style.transform = transform
			if (hasAttr(item, [T.opacity_s, T.opacity])) {
				item.style.opacity = getCurrentValue(item, T.opacity_s, T.opacity, p, T.opacity_s, T.opacity, 1)
			}
		})
	})
}
function getCurrentValue(el, start, end, progress, bStart, bEnd, defaultValue = 0) {
	// const startNum = Number(el.getAttribute(start) || el.getAttribute(bStart)) || defaultValue
	// const endNum = Number(el.getAttribute(end) || el.getAttribute(bEnd)) || defaultValue
	const startNum = hasAttr(el, start) ? Number(el.getAttribute(start)) : hasAttr(el, bStart) ? Number(el.getAttribute(bStart)) : defaultValue
	const endNum = hasAttr(el, end) ? Number(el.getAttribute(end)) : hasAttr(el, bEnd) ? Number(el.getAttribute(bEnd)) : defaultValue
	return startNum + (endNum - startNum) * progress
}
function hasAttr(el, attr) {
	if (Array.isArray(attr)) {
		return attr.some(v => el.hasAttribute(v))
	} else {
		return el.hasAttribute(attr)
	}
}
// 检查document是否为根元素
function isDocumentRoot(root) {
	return root === document ? document.documentElement : root
}