// calendar.js — Infinite scrolling week-by-week with overlay event rendering
import {
  monthAbbr,
  DAY_MS,
  WEEK_MS,
  isoWeekInfo,
  toLocalString,
  fromLocalString,
  mondayIndex,
  pad,
  daysInclusive,
  addDaysStr,
  getLocalizedWeekdayNames,
  getLocalizedMonthName,
  formatDateRange,
  lunarPhaseSymbol
} from './date-utils.js'
import { EventManager } from './event-manager.js'

class InfiniteCalendar {
  constructor(config = {}) {
    this.config = {
      select_days: 0,
      min_year: 1900,
      max_year: 2100,
      ...config
    }

    this.weekend = [true, false, false, false, false, false, true]

    // Initialize event manager
    this.eventManager = new EventManager(this)

    this.viewport = document.getElementById('calendar-viewport')
    this.content = document.getElementById('calendar-content')
    this.header = document.getElementById('calendar-header')
    this.jogwheelViewport = document.getElementById('jogwheel-viewport')
    this.jogwheelContent = document.getElementById('jogwheel-content')
    this.selectedDateInput = document.getElementById('selected-date')

    this.rowHeight = this.computeRowHeight()
    this.visibleWeeks = new Map()
    this.baseDate = new Date(2024, 0, 1)  // 2024 begins with Monday

    this.init()
  }  init() {
    this.createHeader()
    this.setupScrollListener()
    this.setupJogwheel()
    this.setupYearScroll()
    this.setupSelectionInput()
    this.setupCurrentDate()
    this.setupInitialView()
  }

  setupInitialView() {
    const minYearDate = new Date(this.config.min_year, 0, 1)
    const maxYearLastDay = new Date(this.config.max_year, 11, 31)
    const lastWeekMonday = new Date(maxYearLastDay)
    lastWeekMonday.setDate(maxYearLastDay.getDate() - mondayIndex(maxYearLastDay))

    this.minVirtualWeek = this.getWeekIndex(minYearDate)
    this.maxVirtualWeek = this.getWeekIndex(lastWeekMonday)
    this.totalVirtualWeeks = this.maxVirtualWeek - this.minVirtualWeek + 1

    this.content.style.height = `${this.totalVirtualWeeks * this.rowHeight}px`
    this.jogwheelContent.style.height = `${(this.totalVirtualWeeks * this.rowHeight) / 10}px`
    const initial = this.config.initial || this.today
    this.navigateTo(fromLocalString(initial))
  }

  setupCurrentDate() {
    const updateDate = () => {
      this.now = new Date()
      const today = toLocalString(this.now)
      if (this.today === today) return
      this.today = today
      for (const cell of this.content.querySelectorAll('.cell.today')) cell.classList.remove('today')
      const cell = this.content.querySelector(`.cell[data-date="${this.today}"]`)
      if (cell) cell.classList.add('today')
      const todayDateElement = document.getElementById('today-date')
      const t = this.now.toLocaleDateString(undefined, { weekday: 'long', month: 'long', day: 'numeric'}).replace(/,? /, "\n")
      todayDateElement.textContent = t.charAt(0).toUpperCase() + t.slice(1)
    }

    const todayDateElement = document.getElementById('today-date')
    todayDateElement.addEventListener('click', () => this.goToToday())
    // Day selection drag functionality is handled through cell event handlers in EventManager
    updateDate()
    setInterval(updateDate, 1000)
  }

  setupYearScroll() {
    let throttled = false
    const handleWheel = e => {
      e.preventDefault()
      e.stopPropagation()
      const currentYear = parseInt(this.yearLabel.textContent)
      const topDisplayIndex = Math.floor(this.viewport.scrollTop / this.rowHeight)
      const currentWeekIndex = topDisplayIndex + this.minVirtualWeek
      const sensitivity = 1/3
      const delta = Math.round(e.deltaY * sensitivity)
      if (!delta) return
      const newYear = Math.max(this.config.min_year, Math.min(this.config.max_year, currentYear + delta))
      if (newYear === currentYear || throttled) return
      throttled = true
      this.navigateToYear(newYear, currentWeekIndex)
      setTimeout(() => throttled = false, 100)
    }
    this.yearLabel.addEventListener('wheel', handleWheel, { passive: false })
  }

  navigateTo(date) {
    const targetWeekIndex = this.getWeekIndex(date) - 3
    return this.scrollToTarget(targetWeekIndex)
  }

  navigateToYear(targetYear, weekIndex) {
    const monday = this.getMondayForVirtualWeek(weekIndex)
    const { week } = isoWeekInfo(monday)
    const jan4 = new Date(targetYear, 0, 4)
    const jan4Monday = new Date(jan4)
    jan4Monday.setDate(jan4.getDate() - mondayIndex(jan4))
    const targetMonday = new Date(jan4Monday)
    targetMonday.setDate(jan4Monday.getDate() + (week - 1) * 7)
    this.scrollToTarget(targetMonday)
  }

  scrollToTarget(target, options = {}) {
    const { smooth = false, forceUpdate = true, allowFloating = false } = options
    let targetWeekIndex
    if (target instanceof Date) {
      if (!this.isDateInAllowedRange(target)) return false
      targetWeekIndex = this.getWeekIndex(target)
    } else if (typeof target === 'number') {
      targetWeekIndex = target
    } else {
      return false
    }

    if (allowFloating) {
      if (targetWeekIndex < this.minVirtualWeek - 0.5 || targetWeekIndex > this.maxVirtualWeek + 0.5) return false
    } else {
      if (targetWeekIndex < this.minVirtualWeek || targetWeekIndex > this.maxVirtualWeek) return false
    }

    const targetScrollTop = (targetWeekIndex - this.minVirtualWeek) * this.rowHeight

    if (smooth) this.viewport.scrollTo({ top: targetScrollTop, behavior: 'smooth' })
    else this.viewport.scrollTop = targetScrollTop

    const mainScrollable = Math.max(0, this.content.scrollHeight - this.viewport.clientHeight)
    const jogScrollable = Math.max(0, this.jogwheelContent.scrollHeight - this.jogwheelViewport.clientHeight)
    const jogwheelTarget = mainScrollable > 0 ? (targetScrollTop / mainScrollable) * jogScrollable : 0

    if (smooth) this.jogwheelViewport.scrollTo({ top: jogwheelTarget, behavior: 'smooth' })
    else this.jogwheelViewport.scrollTop = jogwheelTarget

    if (forceUpdate) this.updateVisibleWeeks()
    return true
  }

  computeRowHeight() {
    const el = document.createElement('div')
    el.style.position = 'absolute'
    el.style.visibility = 'hidden'
    el.style.height = 'var(--cell-h)'
    document.body.appendChild(el)
    const h = el.getBoundingClientRect().height || 64
    el.remove()
    return Math.round(h)
  }

  createHeader() {
    this.yearLabel = document.createElement('div')
    this.yearLabel.className = 'year-label'
    this.yearLabel.textContent = isoWeekInfo(new Date()).year
    this.header.appendChild(this.yearLabel)

    const names = getLocalizedWeekdayNames()
    names.forEach((name, i) => {
      const c = document.createElement('div')
      c.classList.add('dow')
      const dayIdx = (i + 1) % 7
      if (this.weekend[dayIdx]) c.classList.add('weekend')
      c.textContent = name
      this.header.appendChild(c)
    })

    const spacer = document.createElement('div')
    spacer.className = 'overlay-header-spacer'
    this.header.appendChild(spacer)
  }

  getWeekIndex(date) {
    const monday = new Date(date)
    monday.setDate(date.getDate() - mondayIndex(date))
    return Math.floor((monday - this.baseDate) / WEEK_MS)
  }

  getMondayForVirtualWeek(virtualWeek) {
    const monday = new Date(this.baseDate)
    monday.setDate(monday.getDate() + virtualWeek * 7)
    return monday
  }

  isDateInAllowedRange(date) {
    const y = date.getFullYear()
    return y >= this.config.min_year && y <= this.config.max_year
  }

  setupScrollListener() {
    let t
    this.viewport.addEventListener('scroll', () => {
      this.updateVisibleWeeks()
      clearTimeout(t)
      t = setTimeout(() => this.updateVisibleWeeks(), 8)
    })
  }

  updateVisibleWeeks() {
    const scrollTop = this.viewport.scrollTop
    const viewportH = this.viewport.clientHeight

    this.updateYearLabel(scrollTop)

    const buffer = 10
    const startIdx = Math.floor((scrollTop - buffer * this.rowHeight) / this.rowHeight)
    const endIdx = Math.ceil((scrollTop + viewportH + buffer * this.rowHeight) / this.rowHeight)

    const startVW = Math.max(this.minVirtualWeek, startIdx + this.minVirtualWeek)
    const endVW = Math.min(this.maxVirtualWeek, endIdx + this.minVirtualWeek)

    for (const [vw, el] of this.visibleWeeks) {
      if (vw < startVW || vw > endVW) {
        el.remove()
        this.visibleWeeks.delete(vw)
      }
    }

    for (let vw = startVW; vw <= endVW; vw++) {
      if (this.visibleWeeks.has(vw)) continue
      const weekEl = this.createWeekElement(vw)
      weekEl.style.position = 'absolute'
      weekEl.style.left = '0'
      const displayIndex = vw - this.minVirtualWeek
      weekEl.style.top = `${displayIndex * this.rowHeight}px`
      weekEl.style.width = '100%'
      weekEl.style.height = `${this.rowHeight}px`
      this.content.appendChild(weekEl)
      this.visibleWeeks.set(vw, weekEl)
      this.addEventsToWeek(weekEl, vw)
    }

    this.applySelectionToVisible()
  }

  updateYearLabel(scrollTop) {
    const topDisplayIndex = Math.floor(scrollTop / this.rowHeight)
    const topVW = topDisplayIndex + this.minVirtualWeek
    const monday = this.getMondayForVirtualWeek(topVW)
    const { year } = isoWeekInfo(monday)
    if (this.yearLabel.textContent !== String(year)) this.yearLabel.textContent = year
  }

  createWeekElement(virtualWeek) {
    const weekDiv = document.createElement('div')
    weekDiv.className = 'week-row'
    const monday = this.getMondayForVirtualWeek(virtualWeek)

    const wkLabel = document.createElement('div')
    wkLabel.className = 'week-label'
    wkLabel.textContent = `W${pad(isoWeekInfo(monday).week)}`
    weekDiv.appendChild(wkLabel)

    // days grid container to host cells and overlay
    const daysGrid = document.createElement('div')
    daysGrid.className = 'days-grid'
    daysGrid.style.position = 'relative'
    daysGrid.style.display = 'grid'
    daysGrid.style.gridTemplateColumns = 'repeat(7, 1fr)'
    daysGrid.style.gridAutoRows = '1fr'
    daysGrid.style.height = '100%'
    daysGrid.style.width = '100%'
    weekDiv.appendChild(daysGrid)

    // overlay positioned above cells, same 7-col grid
    const overlay = document.createElement('div')
    overlay.className = 'week-overlay'
    overlay.style.position = 'absolute'
    overlay.style.inset = '0'
    overlay.style.pointerEvents = 'none'
    overlay.style.display = 'grid'
    overlay.style.gridTemplateColumns = 'repeat(7, 1fr)'
    overlay.style.gridAutoRows = '1fr'
    overlay.style.zIndex = '15'
    daysGrid.appendChild(overlay)
    weekDiv._overlay = overlay
    weekDiv._daysGrid = daysGrid

    const cur = new Date(monday)
    let hasFirst = false
    let monthToLabel = null
    let labelYear = null

    for (let i = 0; i < 7; i++) {
      const cell = document.createElement('div')
      cell.className = 'cell'
      const dateStr = toLocalString(cur)
      cell.setAttribute('data-date', dateStr)

      const dow = cur.getDay()
      if (this.weekend[dow]) cell.classList.add('weekend')

      const m = cur.getMonth()
      cell.classList.add(monthAbbr[m])

      const isFirst = cur.getDate() === 1
      if (isFirst) {
        hasFirst = true
        monthToLabel = m
        labelYear = cur.getFullYear()
      }

      const day = document.createElement('h1')
      day.textContent = String(cur.getDate())

      const date = toLocalString(cur)
      cell.dataset.date = date
      if (this.today && date === this.today) cell.classList.add('today')

      if (this.config.select_days > 0) {
        cell.addEventListener('mousedown', e => {
          e.preventDefault()
          e.stopPropagation()
          this.eventManager.startDrag(dateStr)
        })
        cell.addEventListener('touchstart', e => {
          e.preventDefault()
          e.stopPropagation()
          this.eventManager.startDrag(dateStr)
        })
        cell.addEventListener('mouseenter', () => {
          if (this.eventManager.isDragging) this.eventManager.updateDrag(dateStr)
        })
        cell.addEventListener('mouseup', e => {
          e.stopPropagation()
          if (this.eventManager.isDragging) this.eventManager.endDrag(dateStr)
        })
        cell.addEventListener('touchmove', e => {
          if (this.eventManager.isDragging) {
            e.preventDefault()
            const touch = e.touches[0]
            const elementBelow = document.elementFromPoint(touch.clientX, touch.clientY)
            if (elementBelow && elementBelow.closest('.cell[data-date]')) {
              const cellBelow = elementBelow.closest('.cell[data-date]')
              const touchDateStr = cellBelow.dataset.date
              if (touchDateStr) this.eventManager.updateDrag(touchDateStr)
            }
          }
        })
        cell.addEventListener('touchend', e => {
          e.stopPropagation()
          if (this.eventManager.isDragging) this.eventManager.endDrag(dateStr)
        })
      }

      if (isFirst) {
        cell.classList.add('firstday')
        day.textContent = cur.getMonth() ? monthAbbr[m].slice(0,3).toUpperCase() : cur.getFullYear()
      }

      cell.appendChild(day)
      const luna = lunarPhaseSymbol(cur)
      if (luna) {
        const moon = document.createElement('span')
        moon.className = 'lunar-phase'
        moon.textContent = luna
        cell.appendChild(moon)
      }
      daysGrid.appendChild(cell)
      cur.setDate(cur.getDate() + 1)
    }

    if (hasFirst && monthToLabel !== null) {
      if (labelYear && labelYear > this.config.max_year) return weekDiv
      const overlayCell = document.createElement('div')
      overlayCell.className = 'month-name-label'

      let weeksSpan = 0
      const d = new Date(cur)
      d.setDate(cur.getDate() - 1)
      for (let i = 0; i < 6; i++) {
        d.setDate(cur.getDate() - 1 + i * 7)
        if (d.getMonth() === monthToLabel) weeksSpan++
      }

      const remainingWeeks = Math.max(1, this.maxVirtualWeek - virtualWeek + 1)
      weeksSpan = Math.max(1, Math.min(weeksSpan, remainingWeeks))

      overlayCell.style.height = `${weeksSpan * this.rowHeight}px`
      overlayCell.style.display = 'flex'
      overlayCell.style.alignItems = 'center'
      overlayCell.style.justifyContent = 'center'
      overlayCell.style.zIndex = '15'
      overlayCell.style.pointerEvents = 'none'

      const label = document.createElement('span')
      const year = String((labelYear ?? monday.getFullYear())).slice(-2)
      label.textContent = `${getLocalizedMonthName(monthToLabel)} '${year}`
      overlayCell.appendChild(label)
      weekDiv.appendChild(overlayCell)
      weekDiv.style.zIndex = '18'
    }

    return weekDiv
  }

  setupJogwheel() {
    let lock = null
    const sync = (fromEl, toEl, fromContent, toContent) => {
      if (lock === toEl) return
      lock = fromEl
      const fromScrollable = Math.max(0, fromContent.scrollHeight - fromEl.clientHeight)
      const toScrollable = Math.max(0, toContent.scrollHeight - toEl.clientHeight)
      const ratio = fromScrollable > 0 ? fromEl.scrollTop / fromScrollable : 0
      toEl.scrollTop = ratio * toScrollable
      setTimeout(() => { if (lock === fromEl) lock = null }, 50)
    }

    this.jogwheelViewport.addEventListener('scroll', () =>
      sync(this.jogwheelViewport, this.viewport, this.jogwheelContent, this.content)
    )

    this.viewport.addEventListener('scroll', () =>
      sync(this.viewport, this.jogwheelViewport, this.content, this.jogwheelContent)
    )
  }

  setupSelectionInput() {
    if (this.config.select_days === 0) {
      this.selectedDateInput.style.display = 'none'
    } else {
      this.selectedDateInput.style.display = 'block'
      this.selectedDateInput.classList.add('clean-input')
    }
  }

  goToToday() {
    const top = new Date(this.now)
    top.setDate(top.getDate() - 21)
    this.scrollToTarget(top, { smooth: true })
  }

  // -------- Event Rendering (overlay-based) --------

  refreshEvents() {
    for (const [, weekEl] of this.visibleWeeks) {
      this.addEventsToWeek(weekEl)
    }
  }

  forceUpdateVisibleWeeks() {
    // Force complete re-render of all visible weeks by clearing overlays first
    for (const [, weekEl] of this.visibleWeeks) {
      const overlay = weekEl._overlay || weekEl.querySelector('.week-overlay')
      if (overlay) {
        while (overlay.firstChild) overlay.removeChild(overlay.firstChild)
      }
      this.addEventsToWeek(weekEl)
    }
  }

  addEventsToWeek(weekEl) {
    const daysGrid = weekEl._daysGrid || weekEl.querySelector('.days-grid')
    const overlay = weekEl._overlay || weekEl.querySelector('.week-overlay')
    if (!daysGrid || !overlay) return

    const cells = Array.from(daysGrid.querySelectorAll('.cell[data-date]'))

    while (overlay.firstChild) overlay.removeChild(overlay.firstChild)

    const weekEvents = new Map()
    for (const cell of cells) {
      const dateStr = cell.dataset.date
      const events = this.eventManager.events.get(dateStr) || []
      for (const ev of events) {
        if (!weekEvents.has(ev.id)) {
          weekEvents.set(ev.id, {
            ...ev,
            startDateInWeek: dateStr,
            endDateInWeek: dateStr,
            startIdx: cells.indexOf(cell),
            endIdx: cells.indexOf(cell)
          })
        } else {
          const w = weekEvents.get(ev.id)
          w.endDateInWeek = dateStr
          w.endIdx = cells.indexOf(cell)
        }
      }
    }

    // If dragging, hide the original of the dragged event and inject preview if it intersects this week
    if (this.eventManager.dragPreview && this.eventManager.dragPreview.id != null) {
      const pv = this.eventManager.dragPreview
      // Remove original entries of the dragged event for this week to prevent ghosts
      if (weekEvents.has(pv.id)) weekEvents.delete(pv.id)
      // Determine week range
      const weekStart = cells[0]?.dataset?.date
      const weekEnd = cells[cells.length - 1]?.dataset?.date
      if (weekStart && weekEnd) {
        const s = pv.startDate
        const e = pv.endDate
        // Intersect preview with this week
        const startInWeek = s <= weekEnd && e >= weekStart ? (s < weekStart ? weekStart : s) : null
        const endInWeek = s <= weekEnd && e >= weekStart ? (e > weekEnd ? weekEnd : e) : null
        if (startInWeek && endInWeek) {
          // Compute indices
          let sIdx = cells.findIndex(c => c.dataset.date === startInWeek)
          if (sIdx === -1) sIdx = cells.findIndex(c => c.dataset.date > startInWeek)
          if (sIdx === -1) sIdx = 0
          let eIdx = -1
          for (let i = 0; i < cells.length; i++) {
            if (cells[i].dataset.date <= endInWeek) eIdx = i
          }
          if (eIdx === -1) eIdx = cells.length - 1

          // Build/override entry
          const baseEv = this.eventManager.getEventById(pv.id)
          if (baseEv) {
            const entry = {
              ...baseEv,
              startDateInWeek: startInWeek,
              endDateInWeek: endInWeek,
              startIdx: sIdx,
              endIdx: eIdx
            }
            weekEvents.set(pv.id, entry)
          }
        }
      }
    }

    const timeToMin = t => {
      if (typeof t !== 'string') return 1e9
      const m = t.match(/^(\d{2}):(\d{2})/)
      if (!m) return 1e9
      return Number(m[1]) * 60 + Number(m[2])
    }

    const spans = Array.from(weekEvents.values()).sort((a, b) => {
      if (a.startIdx !== b.startIdx) return a.startIdx - b.startIdx
      // Prefer longer spans to be placed first for packing
      const aLen = a.endIdx - a.startIdx
      const bLen = b.endIdx - b.startIdx
      if (aLen !== bLen) return bLen - aLen
      // Within the same day and same span length, order by start time
      const at = timeToMin(a.startTime)
      const bt = timeToMin(b.startTime)
      if (at !== bt) return at - bt
      // Stable fallback by id
      return (a.id || 0) - (b.id || 0)
    })

    const rowsLastEnd = []
    for (const w of spans) {
      let placedRow = 0
      while (placedRow < rowsLastEnd.length && !(w.startIdx > rowsLastEnd[placedRow])) placedRow++
      if (placedRow === rowsLastEnd.length) rowsLastEnd.push(-1)
      rowsLastEnd[placedRow] = w.endIdx
      w._row = placedRow + 1
    }

    const numRows = Math.max(1, rowsLastEnd.length)

    // Decide between "comfortable" layout (with gaps, not stretched)
    // and "compressed" layout (fractional rows, no gaps) based on fit.
    const cs = getComputedStyle(overlay)
    const overlayHeight = overlay.getBoundingClientRect().height
    const marginTopPx = parseFloat(cs.marginTop) || 0
    const available = Math.max(0, overlayHeight - marginTopPx)
    const baseEm = parseFloat(cs.fontSize) || 16
    const rowPx = 1.2 * baseEm      // preferred row height ~ 1.2em
    const gapPx = 0.2 * baseEm      // preferred gap ~ .2em
    const needed = numRows * rowPx + (numRows - 1) * gapPx

    if (needed <= available) {
      // Comfortable: keep gaps and do not stretch rows to fill
      overlay.style.gridTemplateRows = `repeat(${numRows}, ${rowPx}px)`
      overlay.style.rowGap = `${gapPx}px`
    } else {
      // Compressed: use fractional rows so everything fits; remove gaps
      overlay.style.gridTemplateRows = `repeat(${numRows}, 1fr)`
      overlay.style.rowGap = '0'
    }

    // Create the spans
    for (const w of spans) this.createOverlaySpan(overlay, w, weekEl)
  }

  createOverlaySpan(overlay, w, weekEl) {
    const span = document.createElement('div')
    span.className = `event-span event-color-${w.colorId}`
    span.style.gridColumn = `${w.startIdx + 1} / ${w.endIdx + 2}`
    span.style.gridRow = `${w._row}`
    span.textContent = w.title
    span.title = `${w.title} (${w.startDate === w.endDate ? w.startDate : w.startDate + ' - ' + w.endDate})`
    span.dataset.eventId = String(w.id)
    if (this.eventManager.dragEventState && this.eventManager.dragEventState.id === w.id) span.classList.add('dragging')

    // Click opens edit if not dragging
    span.addEventListener('click', e => {
      e.stopPropagation()
      if (this.eventManager.dragEventState || this.eventManager.justDragged) return
      this.eventManager.showEventDialog('edit', { id: w.id })
    })

    // Add resize handles
    const left = document.createElement('div')
    left.className = 'resize-handle left'
    const right = document.createElement('div')
    right.className = 'resize-handle right'
    span.appendChild(left)
    span.appendChild(right)

    // Pointer down handlers
    const onPointerDown = (mode, ev) => {
      ev.preventDefault()
      ev.stopPropagation()
      const point = ev.touches ? ev.touches[0] : ev
      const hitAtStart = this.getDateUnderPointer(point.clientX, point.clientY)
      this.eventManager.dragEventState = {
        mode,
        id: w.id,
        originWeek: weekEl,
        originStartIdx: w.startIdx,
        originEndIdx: w.endIdx,
        pointerStartX: point.clientX,
        pointerStartY: point.clientY,
        startDate: w.startDate,
        endDate: w.endDate,
        usingPointer: ev.type && ev.type.startsWith('pointer')
      }
      // compute anchor offset within the event based on where the pointer is
      const spanDays = daysInclusive(w.startDate, w.endDate)
      let anchorOffset = 0
      if (hitAtStart && hitAtStart.date) {
        const anchorDate = hitAtStart.date
        // clamp anchorDate to within event span
        if (anchorDate < w.startDate) anchorOffset = 0
        else if (anchorDate > w.endDate) anchorOffset = spanDays - 1
        else anchorOffset = daysInclusive(w.startDate, anchorDate) - 1
      }
      this.eventManager.dragEventState.anchorOffset = anchorOffset
      this.eventManager.dragEventState.originSpanDays = spanDays
      this.eventManager.dragEventState.originalStartDate = w.startDate
      this.eventManager.dragEventState.originalEndDate = w.endDate
      // capture pointer to ensure we receive the up even if cursor leaves element
      if (this.eventManager.dragEventState.usingPointer && span.setPointerCapture && ev.pointerId != null) {
        try { span.setPointerCapture(ev.pointerId) } catch {}
      }
      this.eventManager.dragEventState.element = span
      this.eventManager.dragEventState.currentOverlay = overlay
      this.eventManager._eventDragMoved = false
      span.classList.add('dragging')
      this.eventManager.installGlobalEventDragHandlers()
    }
    // Mouse
    left.addEventListener('mousedown', e => onPointerDown('resize-left', e))
    right.addEventListener('mousedown', e => onPointerDown('resize-right', e))
    span.addEventListener('mousedown', e => {
      if ((e.target).classList && (e.target).classList.contains('resize-handle')) return
      onPointerDown('move', e)
    })
    // Pointer (preferred)
    left.addEventListener('pointerdown', e => onPointerDown('resize-left', e))
    right.addEventListener('pointerdown', e => onPointerDown('resize-right', e))
    span.addEventListener('pointerdown', e => {
      if ((e.target).classList && (e.target).classList.contains('resize-handle')) return
      onPointerDown('move', e)
    })
    // Touch support
    left.addEventListener('touchstart', e => onPointerDown('resize-left', e), { passive: false })
    right.addEventListener('touchstart', e => onPointerDown('resize-right', e), { passive: false })
    span.addEventListener('touchstart', e => {
      if ((e.target).classList && (e.target).classList.contains('resize-handle')) return
      onPointerDown('move', e)
    }, { passive: false })
    overlay.appendChild(span)
  }

  getDateUnderPointer(clientX, clientY) {
    const el = document.elementFromPoint(clientX, clientY)
    if (!el) return null
    // Fast path: directly find the cell under the pointer
    const directCell = el.closest && el.closest('.cell[data-date]')
    if (directCell) {
      const weekEl = directCell.closest('.week-row')
      return weekEl ? { weekEl, overlay: (weekEl._overlay || weekEl.querySelector('.week-overlay')), col: -1, date: directCell.dataset.date } : null
    }
    const weekEl = el.closest && el.closest('.week-row')
    if (!weekEl) return null
    const overlay = weekEl._overlay || weekEl.querySelector('.week-overlay')
    const daysGrid = weekEl._daysGrid || weekEl.querySelector('.days-grid')
    if (!overlay || !daysGrid) return null
    const rect = overlay.getBoundingClientRect()
    if (rect.width <= 0) return null
    const colWidth = rect.width / 7
    let col = Math.floor((clientX - rect.left) / colWidth)
    if (clientX < rect.left) col = 0
    if (clientX > rect.right) col = 6
    col = Math.max(0, Math.min(6, col))
    const cells = Array.from(daysGrid.querySelectorAll('.cell[data-date]'))
    const cell = cells[col]
    return cell ? { weekEl, overlay, col, date: cell.dataset.date } : null
  }
}

document.addEventListener('DOMContentLoaded', () => {
  new InfiniteCalendar({
    select_days: 1000
  })
})