import { useCallback, useEffect, useRef, useState } from 'react'
import { datasetId, sameId } from '../../pages/task/ids.js'

// 看板卡片列拖动 (重点设计 §7.1)
// 方案要点:
//   1. Pointer Events + setPointerCapture —— 触摸/鼠标统一, 捕获后不丢事件
//   2. 长按 400ms 激活 (激活前移动 >10px 视为滚动, 取消本次拖动)
//   3. 激活后卡片原位抬起 (不跟随手指, 无浮层/无任务名)
//   4. 拖动中持续 elementFromPoint 命中 [data-column-id] 高亮目标列;
//      指针靠近容器左右边缘时 rAF 自动横滚, 可拖到屏幕外的列
//   5. 松手落到目标列 (≠原列) 才提交; pointercancel (浏览器接管手势,
//      如触发纵向滚动) 只放弃不提交
//   6. 防误触: 卡片禁长按系统菜单(contextmenu); 拖动结束后 350ms 内的
//      click 视为拖动余波, 不打开详情 (justEnded)
export default function useColumnDrag({ onDrop, scrollSelector = '.board-wrap' } = {}) {
  const [dragTask, setDragTask] = useState(null)   // 拖动中的任务 (视觉态)
  const [overCol, setOverCol] = useState(null)     // 高亮的目标列 id
  const st = useRef({ timer: null, active: false, startX: 0, startY: 0, task: null, autoScroll: 0, raf: 0, srcEl: null, ghost: null })
  const lastEnd = useRef(0)                        // 拖动结束时刻

  // onDrop 经 ref 桥接实时闭包 (bind 空依赖 useCallback, 防陈旧)
  const onDropRef = useRef(onDrop)
  onDropRef.current = onDrop

  // 跟手浮层: 激活时克隆原卡片挂到 body, 移动时直接改 transform
  const moveGhost = (x, y) => {
    const g = st.current.ghost
    if (g) g.style.transform = `translate(${x}px, ${y}px) translate(-50%, -60%)`
  }
  const mountGhost = (x, y) => {
    const src = st.current.srcEl
    if (!src) return
    const clone = src.cloneNode(true)
    clone.classList.remove('dragging', 'hl')
    clone.style.width = `${src.offsetWidth}px`
    const g = document.createElement('div')
    g.className = 'drag-ghost'
    g.appendChild(clone)
    document.body.appendChild(g)
    st.current.ghost = g
    moveGhost(x, y)
  }

  const stopAutoScroll = () => {
    st.current.autoScroll = 0
    if (st.current.raf) { cancelAnimationFrame(st.current.raf); st.current.raf = 0 }
  }

  const cleanup = useCallback(() => {
    if (st.current.timer) { clearTimeout(st.current.timer); st.current.timer = null }
    st.current.active = false
    st.current.srcEl = null
    if (st.current.ghost) { st.current.ghost.remove(); st.current.ghost = null }
    stopAutoScroll()
    setDragTask(null)
    setOverCol(null)
  }, [])

  useEffect(() => () => cleanup(), [cleanup])

  /** 拖动刚结束 (350ms 内): 抑制松手合成的 click 误开详情页 */
  const justEnded = useCallback(() => Date.now() - lastEnd.current < 350, [])

  // 命中列 id: 本地库列 id 是 uuid 字符串, 不能 Number() (会变 NaN -> 落不下去)
  const hitColumn = (x, y) => {
    const el = document.elementFromPoint(x, y)
    const colEl = el?.closest?.('[data-column-id]')
    return colEl ? datasetId(colEl.dataset.columnId) : null
  }

  // 边缘自动滚动 (±36px 触发, 每帧 10px)
  const autoScroll = (container, clientX) => {
    if (!container) { stopAutoScroll(); return }
    const r = container.getBoundingClientRect()
    const edge = 36
    let dir = 0
    if (clientX < r.left + edge) dir = -1
    else if (clientX > r.right - edge) dir = 1
    st.current.autoScroll = dir
    if (!dir) { stopAutoScroll(); return }
    if (st.current.raf) return
    const step = () => {
      if (!st.current.autoScroll) return
      container.scrollLeft += st.current.autoScroll * 10
      st.current.raf = requestAnimationFrame(step)
    }
    st.current.raf = requestAnimationFrame(step)
  }

  const onPointerMove = (ev) => {
    const s = st.current
    if (!s.active) {
      if (s.timer && (Math.abs(ev.clientX - s.startX) > 10 || Math.abs(ev.clientY - s.startY) > 10)) {
        clearTimeout(s.timer); s.timer = null
      }
      return
    }
    ev.preventDefault()
    moveGhost(ev.clientX, ev.clientY)
    const col = hitColumn(ev.clientX, ev.clientY)
    setOverCol(col)
    autoScroll(document.querySelector(scrollSelector), ev.clientX)
  }

  const onPointerUp = (ev) => {
    const s = st.current
    if (s.active) {
      lastEnd.current = Date.now()
      const col = hitColumn(ev.clientX, ev.clientY)
      if (col && s.task && !sameId(col, s.task.columnId)) onDropRef.current?.(s.task, col)
    }
    cleanup()
  }

  // 指针监听装配 (capture + 非 passive touchmove; instant=true 把手路径
  // 再挂 touchstart preventDefault, 浏览器完全不接管该触摸)
  const armListeners = (ev, instant) => {
    try { ev.currentTarget.setPointerCapture(ev.pointerId) } catch { /* ignore */ }
    const el = ev.currentTarget
    const move = (e2) => onPointerMove(e2)
    const tm = (e2) => { if (st.current.active) e2.preventDefault() }
    const ts = (e2) => e2.preventDefault()
    const up = (e2) => { onPointerUp(e2); detach() }
    const cancel = () => {
      if (st.current.active) lastEnd.current = Date.now()
      cleanup()
      detach()
    }
    const detach = () => {
      el.removeEventListener('pointermove', move)
      el.removeEventListener('pointerup', up)
      el.removeEventListener('pointercancel', cancel)
      el.removeEventListener('touchmove', tm)
      el.removeEventListener('touchstart', ts)
    }
    el.addEventListener('pointermove', move)
    el.addEventListener('pointerup', up)
    el.addEventListener('pointercancel', cancel)
    el.addEventListener('touchmove', tm, { passive: false })
    if (instant) el.addEventListener('touchstart', ts, { passive: false })
  }

  const startDrag = (ev, task, instant) => {
    st.current = {
      ...st.current, startX: ev.clientX, startY: ev.clientY, task, active: false,
      srcEl: ev.currentTarget.closest('.bcard'),
    }
    const activate = () => {
      st.current.active = true
      setDragTask(task)
      if (navigator.vibrate) navigator.vibrate(15)
      mountGhost(st.current.startX, st.current.startY)
    }
    if (instant) activate()
    else st.current.timer = setTimeout(activate, 400)
    armListeners(ev, instant)
  }

  /** 绑定到卡片: 需要卡片元素设置 touch-action: pan-y */
  const bind = useCallback((task) => ({
    onPointerDown: (ev) => {
      if (ev.button !== undefined && ev.button !== 0) return
      startDrag(ev, task, false)
    },
    // 长按不弹系统菜单 (配合 CSS user-select:none, 防长按变文字选择)
    onContextMenu: (ev) => ev.preventDefault(),
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }), [])

  /** 绑定到卡片左侧拖动把手: 把手需 touch-action: none, 按下立即拖动 */
  const bindHandle = useCallback((task) => ({
    onPointerDown: (ev) => {
      if (ev.button !== undefined && ev.button !== 0) return
      ev.stopPropagation() // 不触发卡片自身的长按路径
      startDrag(ev, task, true)
    },
    onContextMenu: (ev) => ev.preventDefault(),
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }), [])

  return { dragTask, overCol, bind, bindHandle, cancel: cleanup, justEnded }
}