'use client'

import { useState, useEffect, useCallback, useMemo } from 'react'
import { useRouter } from 'next/navigation'
import { elternApi, type ParentMeResponse, type ParentLesson } from '@/lib/eltern/api'
import { translateSubject } from '@/lib/calendar/subject-i18n'

const DAY_LABELS: Record<string, string[]> = {
  de: ['Mo', 'Di', 'Mi', 'Do', 'Fr'],
  en: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri'],
  tr: ['Pzt', 'Sal', 'Çar', 'Per', 'Cum'],
  ar: ['الإثنين', 'الثلاثاء', 'الأربعاء', 'الخميس', 'الجمعة'],
  uk: ['Пн', 'Вт', 'Ср', 'Чт', 'Пт'],
  ru: ['Пн', 'Вт', 'Ср', 'Чт', 'Пт'],
  pl: ['Pon', 'Wt', 'Śr', 'Czw', 'Pt'],
  fr: ['Lun', 'Mar', 'Mer', 'Jeu', 'Ven'],
}

const HEADINGS: Record<string, { greeting: string; selectChild: string; period: string; logout: string; noPlan: string }> = {
  de: { greeting: 'Willkommen', selectChild: 'Kind auswählen', period: 'Stunde', logout: 'Abmelden', noPlan: 'Noch kein Stundenplan veröffentlicht.' },
  en: { greeting: 'Welcome', selectChild: 'Select child', period: 'Period', logout: 'Sign out', noPlan: 'No timetable published yet.' },
  tr: { greeting: 'Hoş geldiniz', selectChild: 'Çocuk seç', period: 'Ders', logout: 'Çıkış', noPlan: 'Henüz ders programı yayımlanmadı.' },
  ar: { greeting: 'مرحبًا', selectChild: 'اختر الطفل', period: 'حصة', logout: 'خروج', noPlan: 'لم يتم نشر جدول حصص بعد.' },
  uk: { greeting: 'Ласкаво просимо', selectChild: 'Виберіть дитину', period: 'Урок', logout: 'Вийти', noPlan: 'Розклад ще не опубліковано.' },
  ru: { greeting: 'Добро пожаловать', selectChild: 'Выберите ребёнка', period: 'Урок', logout: 'Выйти', noPlan: 'Расписание ещё не опубликовано.' },
  pl: { greeting: 'Witamy', selectChild: 'Wybierz dziecko', period: 'Lekcja', logout: 'Wyloguj', noPlan: 'Plan lekcji nie jest jeszcze opublikowany.' },
  fr: { greeting: 'Bienvenue', selectChild: 'Choisir un enfant', period: 'Cours', logout: 'Déconnexion', noPlan: 'Aucun emploi du temps publié.' },
}

function t(lang: string, key: keyof typeof HEADINGS['de']): string {
  const code = (lang || 'de').slice(0, 2)
  return HEADINGS[code]?.[key] ?? HEADINGS.de[key]
}

export default function ElternPage() {
  const router = useRouter()
  const [me, setMe] = useState<ParentMeResponse | null>(null)
  const [selected, setSelected] = useState<string>('')
  const [lessons, setLessons] = useState<ParentLesson[]>([])
  const [error, setError] = useState<string | null>(null)

  const lang = me?.parent.preferred_language || 'de'
  const dayLabels = DAY_LABELS[lang.slice(0, 2)] || DAY_LABELS.de

  const loadMe = useCallback(async () => {
    try {
      const data = await elternApi.me()
      setMe(data)
      if (data.children.length > 0) setSelected(data.children[0].tt_class_id)
    } catch (e) {
      // Not logged in → redirect to login.
      if (e instanceof Error && /session/i.test(e.message)) {
        router.replace('/eltern/login')
        return
      }
      setError(e instanceof Error ? e.message : 'Laden fehlgeschlagen')
    }
  }, [router])

  useEffect(() => { loadMe() }, [loadMe])

  const loadTimetable = useCallback(async () => {
    if (!selected) return
    try {
      const data = await elternApi.timetable(selected)
      setLessons(data || [])
      setError(null)
    } catch (e) {
      setError(e instanceof Error ? e.message : 'Stundenplan laden fehlgeschlagen')
    }
  }, [selected])

  useEffect(() => { loadTimetable() }, [loadTimetable])

  const periodIndices = useMemo(() => {
    const set = new Set<number>()
    for (const l of lessons) set.add(l.PeriodIndex)
    return Array.from(set).sort((a, b) => a - b)
  }, [lessons])

  const cell = (day: number, idx: number) =>
    lessons.find(l => l.DayOfWeek === day && l.PeriodIndex === idx)

  const handleLogout = async () => {
    try { await elternApi.logout() } catch { /* ignore */ }
    router.replace('/eltern/login')
  }

  if (!me) {
    return (
      <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-indigo-900 via-purple-900 to-pink-800 text-white">
        {error ? <span className="text-red-200">{error}</span> : <span className="opacity-70">Laedt …</span>}
      </div>
    )
  }

  const activeChild = me.children.find(c => c.tt_class_id === selected)

  return (
    <div className="min-h-screen bg-gradient-to-br from-indigo-900 via-purple-900 to-pink-800 text-white p-6" data-testid="eltern-page">
      <div className="max-w-5xl mx-auto">
        <header className="flex items-center justify-between mb-6">
          <div>
            <h1 className="text-3xl font-bold">{t(lang, 'greeting')}, {me.parent.email}</h1>
            <p className="text-sm text-white/60 mt-1">
              {activeChild ? `${activeChild.first_name} ${activeChild.last_name} · ${activeChild.class_name}` : ''}
            </p>
          </div>
          <button onClick={handleLogout} data-testid="eltern-logout" className="px-3 py-1.5 rounded-lg bg-white/10 hover:bg-white/20 text-sm">
            {t(lang, 'logout')}
          </button>
        </header>

        {me.children.length > 1 && (
          <div className="mb-4">
            <label className="block text-sm mb-1 opacity-70">{t(lang, 'selectChild')}</label>
            <select
              value={selected}
              onChange={e => setSelected(e.target.value)}
              data-testid="child-selector"
              className="px-3 py-2 rounded-lg border bg-white/10 border-white/20 text-white"
            >
              {me.children.map(c => (
                <option key={c.id} value={c.tt_class_id} className="text-slate-900">
                  {c.first_name} {c.last_name} ({c.class_name})
                </option>
              ))}
            </select>
          </div>
        )}

        {error && <div className="mb-3 p-3 rounded-lg bg-red-500/20 border border-red-500/40 text-red-200">{error}</div>}

        {periodIndices.length === 0 ? (
          <div className="rounded-2xl bg-white/10 border border-white/20 p-8 text-center opacity-70">
            {t(lang, 'noPlan')}
          </div>
        ) : (
          <div className="rounded-2xl bg-white/10 border border-white/20 overflow-hidden">
            <table className="w-full">
              <thead className="bg-white/5">
                <tr>
                  <th className="text-left px-3 py-3 text-sm font-medium opacity-70 w-16">{t(lang, 'period')}</th>
                  {dayLabels.map(d => <th key={d} className="text-left px-3 py-3 text-sm font-medium opacity-70">{d}</th>)}
                </tr>
              </thead>
              <tbody>
                {periodIndices.map(idx => (
                  <tr key={idx} className="border-t border-white/10">
                    <td className="px-3 py-2 font-medium text-sm">{idx}.</td>
                    {[1, 2, 3, 4, 5].map(d => {
                      const l = cell(d, idx)
                      if (!l) return <td key={d} className="px-3 py-2 opacity-20 text-xs">—</td>
                      return (
                        <td key={d} className="px-2 py-1" data-testid={`eltern-cell-${d}-${idx}`}>
                          <div className="rounded-md p-2 text-xs space-y-0.5 bg-indigo-500/30 border-l-2 border-indigo-300">
                            <div className="font-semibold">{translateSubject(l.SubjectName, lang)}</div>
                            <div className="opacity-80">{l.TeacherName.split(',')[0]}</div>
                            {l.RoomName && <div className="opacity-60">{l.RoomName}</div>}
                          </div>
                        </td>
                      )
                    })}
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
        )}
      </div>
    </div>
  )
}