// 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
} from './date-utils.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]

    // Event storage
    this.events = new Map() // Map of date strings to arrays of events
    this.eventIdCounter = 1

    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

    // unified selection state (single or range)
    this.selStart = null
    this.selEnd = null
    this.isDragging = false
    this.dragAnchor = null

    this.init()
  }

  init() {
    this.createHeader()
    this.setupScrollListener()
    this.setupJogwheel()
    this.setupYearScroll()
    this.setupSelectionInput()
    this.setupCurrentDate()
  this.setupEventDialog()
    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())
    if (this.config.select_days > 1) this.setupGlobalDragHandlers()
    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.startDrag(dateStr)
        })
        cell.addEventListener('touchstart', e => {
          e.preventDefault()
          e.stopPropagation()
          this.startDrag(dateStr)
        })
        cell.addEventListener('mouseenter', () => {
          if (this.isDragging) this.updateDrag(dateStr)
        })
        cell.addEventListener('mouseup', e => {
          e.stopPropagation()
          if (this.isDragging) this.endDrag(dateStr)
        })
        cell.addEventListener('touchmove', e => {
          if (this.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.updateDrag(touchDateStr)
            }
          }
        })
        cell.addEventListener('touchend', e => {
          e.stopPropagation()
          if (this.isDragging) this.endDrag(dateStr)
        })
      }

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

      cell.appendChild(day)
      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 })
  }

  // -------- Selection --------

  clampRange(anchorStr, otherStr) {
    if (this.config.select_days <= 1) return [otherStr, otherStr]
    const limit = this.config.select_days
    const forward = fromLocalString(otherStr) >= fromLocalString(anchorStr)
    const span = daysInclusive(anchorStr, otherStr)
    if (span <= limit) {
      const a = [anchorStr, otherStr].sort()
      return [a[0], a[1]]
    }
    if (forward) return [anchorStr, addDaysStr(anchorStr, limit - 1)]
    return [addDaysStr(anchorStr, -(limit - 1)), anchorStr]
  }

  setSelection(aStr, bStr) {
    const [start, end] = this.clampRange(aStr, bStr)
    this.selStart = start
    this.selEnd = end
    this.applySelectionToVisible()
    this.selectedDateInput.value = formatDateRange(fromLocalString(start), fromLocalString(end))
  }

  clearSelection() {
    this.selStart = null
    this.selEnd = null
    for (const [, weekEl] of this.visibleWeeks) {
      weekEl.querySelectorAll('.cell.selected').forEach(c => c.classList.remove('selected'))
    }
    this.selectedDateInput.value = ''
  }

  applySelectionToVisible() {
    for (const [, weekEl] of this.visibleWeeks) {
      const cells = weekEl.querySelectorAll('.cell[data-date]')
      for (const cell of cells) {
        if (!this.selStart || !this.selEnd) {
          cell.classList.remove('selected')
          continue
        }
        const ds = cell.dataset.date
        const inRange = ds >= this.selStart && ds <= this.selEnd
        cell.classList.toggle('selected', inRange)
      }
    }
  }

  setupGlobalDragHandlers() {
    document.addEventListener('mouseup', () => {
      if (!this.isDragging) return
      this.isDragging = false
      document.body.style.cursor = 'default'
    })
    document.addEventListener('touchend', () => {
      if (!this.isDragging) return
      this.isDragging = false
      document.body.style.cursor = 'default'
    })
    document.addEventListener('touchmove', e => {
      if (!this.isDragging) return
      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.updateDrag(touchDateStr)
      }
    }, { passive: false })
    document.addEventListener('selectstart', e => {
      if (this.isDragging) e.preventDefault()
    })
    document.addEventListener('contextmenu', e => {
      if (this.isDragging) e.preventDefault()
    })
  }

  startDrag(dateStr) {
    if (this.config.select_days === 0) return
    this.isDragging = true
    this.dragAnchor = dateStr
    this.setSelection(dateStr, dateStr)
  }

  updateDrag(dateStr) {
    if (!this.isDragging) return
    this.setSelection(this.dragAnchor, dateStr)
    document.body.style.cursor = 'default'
  }

  endDrag(dateStr) {
    if (!this.isDragging) return
    this.isDragging = false
    this.setSelection(this.dragAnchor, dateStr)
    document.body.style.cursor = 'default'
    if (this.selStart && this.selEnd) {
  setTimeout(() => this.showEventDialog('create'), 50)
    }
  }

  // -------- Event Management (overlay-based) --------

  // Build dialog DOM once
  setupEventDialog() {
    const tpl = document.createElement('template')
    tpl.innerHTML = `
      <div class="ec-modal-backdrop" part="backdrop" hidden>
        <div class="ec-modal" role="dialog" aria-modal="true" aria-labelledby="ec-modal-title">
          <form class="ec-form" novalidate>
            <header class="ec-header">
              <h2 id="ec-modal-title">Event</h2>
            </header>
            <div class="ec-body">
              <label class="ec-field">
                <span>Title</span>
                <input type="text" name="title" autocomplete="off" required />
              </label>
              <div class="ec-row">
                <label class="ec-field">
                  <span>Start day</span>
                  <input type="date" name="startDate" />
                </label>
                <label class="ec-field">
                  <span>Duration</span>
                  <select name="duration">
                    <option value="15">15 minutes</option>
                    <option value="30">30 minutes</option>
                    <option value="45">45 minutes</option>
                    <option value="60" selected>1 hour</option>
                    <option value="90">1.5 hours</option>
                    <option value="120">2 hours</option>
                    <option value="180">3 hours</option>
                    <option value="240">4 hours</option>
                    <option value="480">8 hours</option>
                    <option value="720">12 hours</option>
                    <option value="1440">Full day</option>
                    <option value="2880">2 days</option>
                    <option value="4320">3 days</option>
                    <option value="10080">7 days</option>
                  </select>
                </label>
              </div>
              <div class="ec-row ec-time-row">
                <label class="ec-field">
                  <span>Start time</span>
                  <input type="time" name="startTime" step="300" />
                </label>
                <div></div>
              </div>
              <div class="ec-color-swatches">
                ${Array.from({ length: 8 }, (_, i) => `
                    <input class="swatch event-color-${i}" type="radio" name="colorId" value="${i}">
                `).join('')}
              </div>
            </div>
            <footer class="ec-footer">
              <button type="button" class="ec-btn" data-action="cancel">Cancel</button>
              <button type="submit" class="ec-btn primary">Save</button>
            </footer>
          </form>
        </div>
      </div>`

    document.body.appendChild(tpl.content)
    this.eventModal = document.querySelector('.ec-modal-backdrop')
    this.eventForm = this.eventModal.querySelector('form.ec-form')
    this.eventTitleInput = this.eventForm.elements['title']
  this.eventStartDateInput = this.eventForm.elements['startDate']
  this.eventStartTimeInput = this.eventForm.elements['startTime']
  this.eventDurationInput = this.eventForm.elements['duration']
  this.eventTimeRow = this.eventForm.querySelector('.ec-time-row')
  this.eventColorInputs = Array.from(this.eventForm.querySelectorAll('input[name="colorId"]'))
  // duration change toggles time visibility
  this.eventDurationInput.addEventListener('change', () => this.updateTimeVisibilityByDuration())
    // color selection visual state
    this.eventColorInputs.forEach(radio => {
      radio.addEventListener('change', () => {
        const swatches = this.eventForm.querySelectorAll('.ec-color-swatches .swatch')
        swatches.forEach(s => s.classList.toggle('selected', s.checked))
      })
    })

    this.eventForm.addEventListener('submit', e => {
      e.preventDefault()
      const data = this.readEventForm()
      if (!data.title.trim()) return
      if (this._dialogMode === 'create') {
        const computed = this.computeDatesFromForm(data)
        this.createEvent({
          title: data.title.trim(),
          startDate: computed.startDate,
          endDate: computed.endDate,
          colorId: data.colorId,
          startTime: data.startTime,
          durationMinutes: data.duration
        })
        this.clearSelection()
      } else if (this._dialogMode === 'edit' && this._editingEventId != null) {
        const computed = this.computeDatesFromForm(data)
        this.applyEventEdit(this._editingEventId, { ...data, ...computed })
      }
      this.hideEventDialog()
    })

    this.eventForm.querySelector('[data-action="cancel"]').addEventListener('click', () => {
      this.hideEventDialog()
      if (this._dialogMode === 'create') this.clearSelection()
    })

    this.eventModal.addEventListener('click', e => {
      if (e.target === this.eventModal) this.hideEventDialog()
    })
    document.addEventListener('keydown', e => {
      if (this.eventModal.hidden) return
      if (e.key === 'Escape') {
        this.hideEventDialog()
        if (this._dialogMode === 'create') this.clearSelection()
      }
    })
  }

  showEventDialog(mode, opts = {}) {
    this._dialogMode = mode
    this._editingEventId = null

    if (mode === 'create') {
      // Defaults for new event
      this.eventTitleInput.value = ''
      this.eventStartTimeInput.value = '09:00'
      // start date defaults
      this.eventStartDateInput.value = this.selStart || toLocalString(new Date())
      // duration defaults from selection (full days) or 60 min
      if (this.selStart && this.selEnd) {
        const days = daysInclusive(this.selStart, this.selEnd)
        this.setDurationValue(days * 1440)
      } else {
        this.setDurationValue(60)
      }
      // suggest least-used color across range
      const suggested = this.selectEventColorId(this.selStart, this.selEnd)
      this.eventColorInputs.forEach(r => r.checked = Number(r.value) === suggested)
      this.updateTimeVisibilityByDuration()
    } else if (mode === 'edit') {
      const ev = this.getEventById(opts.id)
      if (!ev) return
      this._editingEventId = ev.id
      this.eventTitleInput.value = ev.title || ''
      this.eventStartDateInput.value = ev.startDate
      if (ev.startDate !== ev.endDate) {
        const days = daysInclusive(ev.startDate, ev.endDate)
        this.setDurationValue(days * 1440)
      } else {
        this.setDurationValue(ev.durationMinutes || 60)
      }
      this.eventStartTimeInput.value = ev.startTime || '09:00'
      this.eventColorInputs.forEach(r => r.checked = Number(r.value) === (ev.colorId ?? 0))
      this.updateTimeVisibilityByDuration()
    }
    this.eventModal.hidden = false
    // simple focus
    setTimeout(() => this.eventTitleInput.focus(), 0)
  }

  toggleTimeRow(show) {
    if (!this.eventTimeRow) return
    this.eventTimeRow.style.display = show ? '' : 'none'
  }

  updateTimeVisibilityByDuration() {
    const minutes = Number(this.eventDurationInput.value || 0)
    const isFullDayOrMore = minutes >= 1440
    this.toggleTimeRow(!isFullDayOrMore)
  }

  hideEventDialog() {
    this.eventModal.hidden = true
  }

  readEventForm() {
    const colorId = Number(this.eventForm.querySelector('input[name="colorId"]:checked')?.value ?? 0)
    const timeRowVisible = this.eventTimeRow && this.eventTimeRow.style.display !== 'none'
    return {
      title: this.eventTitleInput.value,
      startDate: this.eventStartDateInput.value,
      startTime: timeRowVisible ? (this.eventStartTimeInput.value || '09:00') : null,
      duration: timeRowVisible ? Math.max(15, Number(this.eventDurationInput.value) || 60) : null,
      colorId
    }
  }

  setDurationValue(minutes) {
    const v = String(minutes)
    const exists = Array.from(this.eventDurationInput.options).some(o => o.value === v)
    if (!exists) {
      const opt = document.createElement('option')
      opt.value = v
      const days = Math.floor(minutes / 1440)
      opt.textContent = days >= 1 ? `${days} day${days > 1 ? 's' : ''}` : `${minutes} minutes`
      this.eventDurationInput.appendChild(opt)
    }
    this.eventDurationInput.value = v
  }

  computeDatesFromForm(data) {
    const minutes = Number(this.eventDurationInput.value || 0)
    if (minutes >= 1440) {
      const days = Math.max(1, Math.floor(minutes / 1440))
      return { startDate: data.startDate, endDate: addDaysStr(data.startDate, days - 1) }
    }
    return { startDate: data.startDate, endDate: data.startDate }
  }

  createEvent(eventData) {
    const singleDay = eventData.startDate === eventData.endDate
    const event = {
      id: this.eventIdCounter++,
      title: eventData.title,
      startDate: eventData.startDate,
      endDate: eventData.endDate,
      colorId: eventData.colorId ?? this.selectEventColorId(eventData.startDate, eventData.endDate),
      startTime: singleDay ? (eventData.startTime || '09:00') : null,
      durationMinutes: singleDay ? (eventData.durationMinutes || 60) : null
    }

    const startDate = new Date(fromLocalString(event.startDate))
    const endDate = new Date(fromLocalString(event.endDate))

    for (let d = new Date(startDate); d <= endDate; d.setDate(d.getDate() + 1)) {
      const dateStr = toLocalString(d)
      if (!this.events.has(dateStr)) this.events.set(dateStr, [])
      this.events.get(dateStr).push({ ...event, isSpanning: startDate < endDate })
    }

    this.refreshEvents()
  }

  applyEventEdit(eventId, data) {
    // Update all instances of this event across dates
    for (const [, list] of this.events) {
      for (let i = 0; i < list.length; i++) {
        if (list[i].id === eventId) {
          const isMulti = list[i].startDate !== list[i].endDate
          list[i] = {
            ...list[i],
            title: data.title.trim(),
            colorId: data.colorId,
            startTime: isMulti ? null : data.startTime,
            durationMinutes: isMulti ? null : data.duration
          }
        }
      }
    }
    this.refreshEvents()
  }

  getEventById(id) {
    for (const [, list] of this.events) {
      const found = list.find(e => e.id === id)
      if (found) return found
    }
    return null
  }

  selectEventColorId(startDateStr, endDateStr) {
    // Count frequency of each color used on the date range
    const colorCounts = [0, 0, 0, 0, 0, 0, 0, 0]
    const startDate = new Date(fromLocalString(startDateStr))
    const endDate = new Date(fromLocalString(endDateStr))

    for (let d = new Date(startDate); d <= endDate; d.setDate(d.getDate() + 1)) {
      const dateStr = toLocalString(d)
      const dayEvents = this.events.get(dateStr) || []
      for (const event of dayEvents) {
        if (event.colorId >= 0 && event.colorId < 8) {
          colorCounts[event.colorId]++
        }
      }
    }

    // Find the color with the lowest count
    // For equal counts, prefer the lowest color number
    let minCount = colorCounts[0]
    let selectedColor = 0

    for (let colorId = 1; colorId < 8; colorId++) {
      if (colorCounts[colorId] < minCount) {
        minCount = colorCounts[colorId]
        selectedColor = colorId
      }
    }

    return selectedColor
  }

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

    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)
  }

  createOverlaySpan(overlay, w) {
    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.addEventListener('click', e => {
      e.stopPropagation()
      this.showEventDialog('edit', { id: w.id })
    })
    overlay.appendChild(span)
  }
}

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