import { Component, NewState, Util, Hash } from '@web/state'

export const VirtualScroll = () => {
	const itemHeights = new Map()
	const groupHeights = new Map()
	let groupItemCount = 1
	const avg = Util.newAvg()

	let padTop = 0
	let rowGap = 0
	let topMargin = 0
	let itemMarginTop = null
	let itemMarginBottom = null
	let listInited = false

	return {
		// 核心1：重置与首屏预渲染
		reset: (list, container) => {
			listInited = false
			itemHeights.clear()
			groupHeights.clear()
			avg.clear()
			topMargin = 0
			itemMarginTop = null
			itemMarginBottom = null

			if (!list?.length) return []

			const size = list.length
			groupItemCount = Math.ceil(Math.sqrt(size)) || 10

			const style = window.getComputedStyle(container)
			padTop = parseFloat(style.paddingTop) || 0
			rowGap = parseFloat(style.rowGap) || 0

			return list.slice(0, Math.min(30, size))
		},

		// 核心2：无痛初始化缓存 (通过 rAF 调用)
		init: (list, refreshCallback) => {
			if (listInited) return
			const size = list.length
			const defaultHeight = avg.get() || 32

			for (let i = 0; i < size; i++) {
				if (!itemHeights.has(i)) itemHeights.set(i, defaultHeight)
			}
			for (let i = 0; i < size; i += groupItemCount) {
				let sum = 0
				for (let j = i; j < Math.min(i + groupItemCount, size); j++) {
					sum += itemHeights.get(j)
				}
				groupHeights.set(i, sum)
			}
			listInited = true
			refreshCallback()
		},

		// 核心3：原汁原味的极速高度更新
		update: (absoluteIndex, node) => {
			if (itemMarginTop === null) {
				const style = window.getComputedStyle(node)
				itemMarginTop = parseFloat(style.marginTop) || 0
				itemMarginBottom = parseFloat(style.marginBottom) || 0
			}
			if (absoluteIndex === 0) topMargin = itemMarginTop

			const newHeight = node.offsetHeight + itemMarginTop + itemMarginBottom + rowGap
			const oldHeight = itemHeights.get(absoluteIndex)

			if (newHeight !== oldHeight) {
				itemHeights.set(absoluteIndex, newHeight)
				avg.add(newHeight)
				const offset = newHeight - (oldHeight || 0)
				const groupIndex = absoluteIndex - (absoluteIndex % groupItemCount)
				if (groupHeights.has(groupIndex)) groupHeights.set(groupIndex, groupHeights.get(groupIndex) + offset)
			}
		},

		// 核心4：原汁原味的状态机滚动计算
		calc: (container, list) => {
			if (!listInited || !list) return null

			const size = list.length
			const visibleCount = Math.ceil((container.clientHeight || 100) / (avg.get() || 32))

			let prev = padTop + topMargin + rowGap
			let post = 0
			let status = 0
			let listStartIndex = 0
			let listEndIndex = 0

			for (let i = 0; i < size; i++) {
				if (status === 0) {
					const gh = groupHeights.get(i)
					if (gh && prev + gh < container.scrollTop) {
						prev += gh
						i += Math.min(groupItemCount, size - i) - 1
					} else {
						const ih = itemHeights.get(i)
						if (prev + ih < container.scrollTop) {
							prev += ih
						} else {
							status = 1
							let visibleStartIndex = Math.max(0, i)
							listStartIndex = Math.max(0, visibleStartIndex - visibleCount)
							listEndIndex = Math.min(listStartIndex + visibleCount * 3, size)
							i = listEndIndex - 1
							for (let j = listStartIndex; j < visibleStartIndex; j++) prev -= itemHeights.get(j)
						}
					}
				} else if (status === 1) {
					const gh = groupHeights.get(i)
					if (gh) {
						post += gh
						i += groupItemCount - 1
					} else {
						post += itemHeights.get(i)
					}
				}
			}

			return {
				prevHeight: prev - padTop - topMargin - rowGap,
				postHeight: post,
				renderedList: list.slice(listStartIndex, listEndIndex),
				listStartIndex
			}
		}
	}
}

export const FastListComponent = Component.register('FastList', container => {
	const vs = VirtualScroll()
	container.state.renderedList = []

	container.onItemUpdate = (index, node) => {
		vs.update(index + (container.state._listStartIndex || 0), node)
	}

	container.refresh = () => {
		const res = vs.calc(container, container.state.list)
		if (res) {
			container.state.prevHeight = res.prevHeight
			container.state.postHeight = res.postHeight
			container.state._listStartIndex = res.listStartIndex
			container.state.renderedList = res.renderedList
		}
	}

	container.state.__watch('list', list => {
		container.state._listStartIndex = 0
		container.state.renderedList = vs.reset(list, container) || []

		requestAnimationFrame(() => {
			if (container.state.list !== list) return
			vs.init(list, container.refresh)
		})
	})

}, Util.makeDom(/*html*/`
<div class="overflow-auto" onscroll="this.refresh()" style="overflow-anchor:none">
    <div $if="this.state.prevHeight>0" $style="height:\${this.state.prevHeight}px;" class="flex-shrink-0"></div>
    <div slot-id="item" class="flex-shrink-0" $each="this.state.renderedList" $onupdate="this.onItemUpdate(index,thisNode)"></div>
    <div $if="this.state.postHeight>0" $style="height:\${this.state.postHeight}px;" class="flex-shrink-0"></div>
</div>
`))

Component.attachSelectFeature = (container, eventName = 'itemclick', selectActionName = 'selectItem', activeActionName = 'itemActiveTag', selectedItemKey = 'selectedItem', idfieldKey = 'idfield', selectableAttr = 'auto-select') => {
	const selectable = selectableAttr && container.hasAttribute(selectableAttr)
	container[selectActionName] = (item, index) => {
		if (selectable) container.state[selectedItemKey] = container.state[selectedItemKey] === item[container[idfieldKey]] ? null : item[container[idfieldKey]]
		container.dispatchEvent(new CustomEvent(eventName, { bubbles: false, detail: !selectable || container.state[selectedItemKey] ? { item, index } : { item: {}, index: null } }))
	}
	container[activeActionName] = (item) => container.state[selectedItemKey] !== null && container.state[selectedItemKey] === item[container[idfieldKey]] ? 'active' : ''
}

Component.register('List', container => {
	Component.attachSelectFeature(container)
	const defaultSets = { idfield: 'id', labelfield: 'label', summaryfield: 'summary' }
	container.state.__watch('list', oldList => {
		Util.updateDefaults(container, defaultSets)
	})
}, Util.makeDom(/*html*/`
<div class="list-group overflow-auto">
  <div slot="item" slot-id="item" $each="this.state.list" $onclick="this.selectItem(item,index)" $class="list-group-item list-group-item-action list-group-item-heading d-inline-flex pe-auto align-items-baseline \${this.itemActiveTag?.(item)}">
    <span $if="this.itemicon" class="bi bi-\${this.itemicon} text-body"></span>
    <div class="flex-shrink-0 px-1" $text>\${item[this.labelfield]}</div>
    <div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
    <div slot-id="item-actions"></div>
  </div>
</div>
`))

Component.register('GroupedList', container => {
	Component.getSetupFunction('List')(container)
	container._selectItem = container.selectItem
	container.selectItem = (item, index) => {
		container.state.selectedGroup = null
		container._selectItem(item, index)
	}
	Component.attachSelectFeature(container, 'groupclick', 'selectGroup', 'groupActiveTag', 'selectedGroup', 'groupidfield', container.hasAttribute('auto-select-group') || container.hasAttribute('auto-select') && 'group-selectable')
	container._selectGroup = container.selectGroup
	container.selectGroup = (item, index) => {
		container.state.selectedItem = null
		container._selectGroup(item, index)
	}

	const defaultSets = { typefield: 'type', groupidfield: 'id', grouplabelfield: 'label', groupsummaryfield: 'summary', groupfield: 'group' }
	container.state.__watch('list', oldList => {
		Util.updateDefaults(container, defaultSets)
		const newList = [];
		(container.state.groups || []).forEach(group => {
			newList.push({ [container.typefield]: 'group', ...group })
			if (oldList) oldList.forEach(item => {
				if (item[container.groupfield] === group[container.groupidfield]) {
					newList.push({ [container.typefield]: 'item', ...item })
				}
			})
		})
		return newList
	})
}, Util.makeDom(/*html*/`
<div class="list-group overflow-auto">
  <template $each="this.state.list">
    <div slot-id="group" $if="item.type === 'group'" $onclick="this.selectGroup(item,index)" style="height: 36px" $class="list-group-item list-group-item-action small d-inline-flex align-items-center ps-2 pe-2 \${this.groupActiveTag(item)}">
      <span $if="this.groupicon" $class="bi bi-\${this.groupicon} text-body"></span>
      <div class="flex-shrink-0 px-1" $text>\${item[this.grouplabelfield]}</div>
      <div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.groupsummaryfield]"></div>
      <div slot-id="group-actions"></div>
    </div>
    <div slot-id="item" $if="item.type === 'item'" $onclick="this.selectItem(item,index)" $class="list-group-item list-group-item-action d-inline-flex align-items-baseline ps-3 pe-2 \${this.itemActiveTag?.(item)}">
      <span $if="this.itemicon" $class="bi bi-\${this.itemicon} text-body"></span>
      <div class="flex-shrink-0 px-1" $text>\${item[this.labelfield]}</div>
      <div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
      <div slot-id="item-actions"></div>
    </div>
  </template>
</div>
`))

Component.register('FastGroupedList', container => {
	Component.getSetupFunction('List')(container)
	Component.getSetupFunction('GroupedList')(container)
}, Util.makeDom(/*html*/`
<FastList class="list-group">
  <div slot="item">
    <div slot-id="group" $if="item.type === 'group'" $onclick="this.selectGroup(item,index)" style="height: 36px" $class="list-group-item list-group-item-action small d-inline-flex align-items-center ps-2 pe-2 \${this.groupActiveTag(item)}">
      <span $if="this.groupicon" $class="bi bi-\${this.groupicon} text-body"></span>
      <div class="flex-shrink-0 px-1" $text>\${item[this.grouplabelfield]}</div>
      <div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.groupsummaryfield]"></div>
      <div slot-id="group-actions"></div>
    </div>
    <div slot-id="item" $if="item.type === 'item'" $onclick="this.selectItem(item,index)" $class="list-group-item list-group-item-action d-inline-flex align-items-baseline ps-3 pe-2 \${this.itemActiveTag?.(item)}">
      <span $if="this.itemicon" $class="bi bi-\${this.itemicon} text-body"></span>
      <div class="flex-shrink-0 px-1" $text>\${item[this.labelfield]}</div>
      <div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
      <div slot-id="item-actions"></div>
    </div>
  </div>
</FastList>
`))

Component.register('Tree', container => {
	const defaultSets = { parentfield: 'parent', groupicon: 'folder', itemicon: 'file' }
	container.state.__watch('list', () => {
		Util.updateDefaults(container, defaultSets)
		const childrenMap = {};
		(container.state.list || []).forEach(item => (childrenMap[item[container.parentfield] || ''] ??= []).push(item))
		const newList = []
		const traverse = (list, level) => list.forEach(item => {
			const id = item[container.idfield]
			const hasChildren = !!childrenMap[id]?.length
			newList.push({ ...item, _level: level, _hasChildren: hasChildren })
			if (hasChildren) traverse(childrenMap[id], level + 1)
		})
		traverse(childrenMap[''] || [], 0)
		return newList
	})
}, Util.makeDom(/*html*/`
<List>
	<div slot="item" $class="list-group-item list-group-item-action d-flex ps-2 align-items-center \${this.itemActiveTag?.(item)}" $onclick="this.selectItem(item,index)">
		<div $style="width:\${item._level * 16}px" class="flex-shrink-0"></div>
		<div $class="text-muted bi bi-\${item._hasChildren?this.groupicon:this.itemicon}"></div>
		<div class="flex-grow-1 text-truncate px-2" $text="item[this.labelfield]"></div>
		<div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
		<div slot-id="item-actions"></div>
	</div>
</List>
`))

export const FastTreeComponent = Component.register('FastTree', container => {
	Component.getSetupFunction('List')(container)
	Component.getSetupFunction('Tree')(container)
}, Util.makeDom(/*html*/`
<FastList class="list-group list-group-action">
	<div slot="item" $class="list-group-item list-group-item-action d-flex ps-2 align-items-center \${this.itemActiveTag?.(item)}" $onclick="this.selectItem(item,index)">
		<div $style="width:\${item._level * 16}px" class="flex-shrink-0"></div>
		<div $class="text-muted bi bi-\${item._hasChildren?this.groupicon:this.itemicon}"></div>
		<div class="flex-grow-1 text-truncate px-2" $text="item[this.labelfield]"></div>
		<div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
		<div slot-id="item-actions"></div>
	</div>
</FastList>
`))

Component.register('CollapseTree', container => {
	Component.attachSelectFeature(container)
	const defaultSets = { idfield: 'id', parentfield: 'parent', labelfield: 'label', summaryfield: 'summary' }
	container.collapsed = NewState({})
	container.state.__watch('list', () => {
		Util.updateDefaults(container, defaultSets)
		const childrenMap = {};
		(container.state.list || []).forEach(item => (childrenMap[item[container.parentfield] || ''] ??= []).push(item))
		const newList = []
		const traverse = (list, level, parents) => list.forEach(item => {
			const id = item[container.idfield]
			const hasChildren = !!childrenMap[id]?.length
			newList.push({ ...item, _level: level, _hasChildren: hasChildren, _parents: parents })
			if (hasChildren) traverse(childrenMap[id], level + 1, [...parents, id])
		})
		traverse(childrenMap[''] || [], 0, [])
		return newList
	})
}, Util.makeDom(/*html*/`
<List>
	<div slot="item" slot-id="item" $if="!item._parents.some(cur=>this.collapsed[cur])" $class="list-group-item list-group-item-action d-flex ps-2 align-items-center \${this.itemActiveTag?.(item)}"  $onclick="this.selectItem(item,index)">
		<div $style="width:\${item._level * 16 + 16}px; cursor: pointer;" class="text-end text-muted flex-shrink-0" $onclick="event.stopPropagation();this.collapsed[item[this.idfield]] = !this.collapsed[item[this.idfield]]">
			<i $if="item._hasChildren" $class="bi \${this.collapsed[item[this.idfield]] ? 'bi-caret-right-fill' : 'bi-caret-down-fill'}"></i>
		</div>
		<div class="flex-grow-1 text-truncate px-1" $text="item[this.labelfield]"></div>
		<div class="text-muted small flex-fill text-end text-truncate" style="width: 0" $text="item[this.summaryfield]"></div>
		<div slot-id="item-actions"></div>
	</div>
</List>
`))