import React, { useState, useRef, useEffect } from 'react'
import ReactDOM from 'react-dom'
import { Calendar, Clock, ChevronLeft, ChevronRight, ChevronUp, ChevronDown } from 'lucide-react'
import { useTranslation } from '../../i18n'

function daysInMonth(year, month) { return new Date(year, month + 1, 0).getDate() }
function getWeekday(year, month, day) { return new Date(year, month, day).getDay() }

// ── Datum-Only Picker ────────────────────────────────────────────────────────
export function CustomDatePicker({ value, onChange, placeholder, style = {} }) {
  const { locale, t } = useTranslation()
  const [open, setOpen] = useState(false)
  const ref = useRef(null)
  const dropRef = useRef(null)

  const parsed = value ? new Date(value + 'T00:00:00') : null
  const [viewYear, setViewYear] = useState(parsed?.getFullYear() || new Date().getFullYear())
  const [viewMonth, setViewMonth] = useState(parsed?.getMonth() ?? new Date().getMonth())

  useEffect(() => {
    const handler = (e) => {
      if (ref.current?.contains(e.target)) return
      if (dropRef.current?.contains(e.target)) return
      setOpen(false)
    }
    if (open) document.addEventListener('mousedown', handler)
    return () => document.removeEventListener('mousedown', handler)
  }, [open])

  useEffect(() => {
    if (open && parsed) { setViewYear(parsed.getFullYear()); setViewMonth(parsed.getMonth()) }
  }, [open])

  const prevMonth = () => { if (viewMonth === 0) { setViewMonth(11); setViewYear(y => y - 1) } else setViewMonth(m => m - 1) }
  const nextMonth = () => { if (viewMonth === 11) { setViewMonth(0); setViewYear(y => y + 1) } else setViewMonth(m => m + 1) }

  const monthLabel = new Date(viewYear, viewMonth).toLocaleDateString(locale, { month: 'long', year: 'numeric' })
  const days = daysInMonth(viewYear, viewMonth)
  const startDay = (getWeekday(viewYear, viewMonth, 1) + 6) % 7 // Mo=0
  const weekdays = Array.from({ length: 7 }, (_, i) => new Date(2024, 0, i + 1).toLocaleDateString(locale, { weekday: 'narrow' }))

  const displayValue = parsed ? parsed.toLocaleDateString(locale, { day: 'numeric', month: 'short', year: 'numeric' }) : null

  const selectDay = (day) => {
    const y = String(viewYear)
    const m = String(viewMonth + 1).padStart(2, '0')
    const d = String(day).padStart(2, '0')
    onChange(`${y}-${m}-${d}`)
    setOpen(false)
  }

  const selectedDay = parsed && parsed.getFullYear() === viewYear && parsed.getMonth() === viewMonth ? parsed.getDate() : null
  const today = new Date()
  const isToday = (d) => today.getFullYear() === viewYear && today.getMonth() === viewMonth && today.getDate() === d

  return (
    <div ref={ref} style={{ position: 'relative', ...style }}>
      <button type="button" onClick={() => setOpen(o => !o)}
        style={{
          width: '100%', display: 'flex', alignItems: 'center', gap: 8,
          padding: '8px 14px', borderRadius: 10,
          border: '1px solid var(--border-primary)',
          background: 'var(--bg-input)', color: displayValue ? 'var(--text-primary)' : 'var(--text-faint)',
          fontSize: 13, fontFamily: 'inherit', cursor: 'pointer', outline: 'none',
          transition: 'border-color 0.15s',
        }}
        onMouseEnter={e => e.currentTarget.style.borderColor = 'var(--text-faint)'}
        onMouseLeave={e => { if (!open) e.currentTarget.style.borderColor = 'var(--border-primary)' }}>
        <Calendar size={14} style={{ color: 'var(--text-faint)', flexShrink: 0 }} />
        <span>{displayValue || placeholder || t('common.date')}</span>
      </button>

      {open && ReactDOM.createPortal(
        <div ref={dropRef} style={{
          position: 'fixed',
          ...(() => {
            const r = ref.current?.getBoundingClientRect()
            if (!r) return { top: 0, left: 0 }
            const w = 268, pad = 8
            const vw = window.innerWidth
            const vh = window.innerHeight
            let left = r.left
            let top = r.bottom + 4
            // Keep within viewport horizontally
            if (left + w > vw - pad) left = Math.max(pad, vw - w - pad)
            // If not enough space below, open above
            if (top + 320 > vh) top = Math.max(pad, r.top - 320)
            // On very small screens, center horizontally
            if (vw < 360) left = Math.max(pad, (vw - w) / 2)
            return { top, left }
          })(),
          zIndex: 99999,
          background: 'var(--bg-card)', border: '1px solid var(--border-primary)',
          borderRadius: 14, boxShadow: '0 8px 32px rgba(0,0,0,0.12)', padding: 12, width: 268,
          maxWidth: 'calc(100vw - 16px)',
          animation: 'selectIn 0.15s ease-out',
          backdropFilter: 'blur(24px)', WebkitBackdropFilter: 'blur(24px)',
        }}>
          {/* Month nav */}
          <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', marginBottom: 10 }}>
            <button type="button" onClick={prevMonth} style={{ background: 'none', border: 'none', cursor: 'pointer', padding: 4, borderRadius: 6, display: 'flex', color: 'var(--text-faint)' }}
              onMouseEnter={e => e.currentTarget.style.color = 'var(--text-primary)'} onMouseLeave={e => e.currentTarget.style.color = 'var(--text-faint)'}>
              <ChevronLeft size={16} />
            </button>
            <span style={{ fontSize: 13, fontWeight: 600, color: 'var(--text-primary)' }}>{monthLabel}</span>
            <button type="button" onClick={nextMonth} style={{ background: 'none', border: 'none', cursor: 'pointer', padding: 4, borderRadius: 6, display: 'flex', color: 'var(--text-faint)' }}
              onMouseEnter={e => e.currentTarget.style.color = 'var(--text-primary)'} onMouseLeave={e => e.currentTarget.style.color = 'var(--text-faint)'}>
              <ChevronRight size={16} />
            </button>
          </div>

          {/* Weekday headers */}
          <div style={{ display: 'grid', gridTemplateColumns: 'repeat(7, 1fr)', gap: 2, marginBottom: 4 }}>
            {weekdays.map((d, i) => (
              <div key={i} style={{ textAlign: 'center', fontSize: 10, fontWeight: 600, color: 'var(--text-faint)', padding: '2px 0' }}>{d}</div>
            ))}
          </div>

          {/* Days grid */}
          <div style={{ display: 'grid', gridTemplateColumns: 'repeat(7, 1fr)', gap: 2 }}>
            {Array.from({ length: startDay }, (_, i) => <div key={`e-${i}`} />)}
            {Array.from({ length: days }, (_, i) => {
              const d = i + 1
              const sel = d === selectedDay
              const td = isToday(d)
              return (
                <button key={d} type="button" onClick={() => selectDay(d)}
                  style={{
                    width: 32, height: 32, borderRadius: 8, border: 'none',
                    background: sel ? 'var(--accent)' : 'transparent',
                    color: sel ? 'var(--accent-text)' : 'var(--text-primary)',
                    fontSize: 12, fontWeight: sel ? 700 : td ? 600 : 400,
                    cursor: 'pointer', display: 'flex', alignItems: 'center', justifyContent: 'center',
                    outline: td && !sel ? '2px solid var(--border-primary)' : 'none', outlineOffset: -2,
                    transition: 'background 0.1s',
                  }}
                  onMouseEnter={e => { if (!sel) e.currentTarget.style.background = 'var(--bg-hover)' }}
                  onMouseLeave={e => { if (!sel) e.currentTarget.style.background = 'transparent' }}>
                  {d}
                </button>
              )
            })}
          </div>

          {/* Clear */}
          {value && (
            <div style={{ marginTop: 8, display: 'flex', justifyContent: 'center' }}>
              <button type="button" onClick={() => { onChange(''); setOpen(false) }}
                style={{ background: 'none', border: 'none', cursor: 'pointer', fontSize: 11, color: 'var(--text-faint)', padding: '3px 8px', borderRadius: 6 }}
                onMouseEnter={e => e.currentTarget.style.color = '#ef4444'} onMouseLeave={e => e.currentTarget.style.color = 'var(--text-faint)'}>
                ✕
              </button>
            </div>
          )}
        </div>,
        document.body
      )}

      <style>{`@keyframes selectIn { from { opacity: 0; transform: translateY(-4px); } to { opacity: 1; transform: translateY(0); } }`}</style>
    </div>
  )
}

// ── DateTime Picker (Datum + Uhrzeit kombiniert) ─────────────────────────────
export function CustomDateTimePicker({ value, onChange, placeholder, style = {} }) {
  const { locale } = useTranslation()
  // value = "2024-03-15T14:30" oder ""
  const [datePart, timePart] = (value || '').split('T')

  const handleDateChange = (d) => {
    onChange(d ? `${d}T${timePart || '12:00'}` : '')
  }
  const handleTimeChange = (t) => {
    const d = datePart || new Date().toISOString().split('T')[0]
    onChange(t ? `${d}T${t}` : `${d}T00:00`)
  }

  return (
    <div style={{ display: 'flex', gap: 8, ...style }}>
      <CustomDatePicker value={datePart || ''} onChange={handleDateChange} style={{ flex: 1, minWidth: 0 }} />
      <div style={{ width: 110, flexShrink: 0 }}>
        <CustomTimePicker value={timePart || ''} onChange={handleTimeChange} />
      </div>
    </div>
  )
}

// Inline re-export for convenience
import CustomTimePicker from './CustomTimePicker'