'use client';

import { useEffect, useState } from 'react';

interface MonthRow {
  monat: number;
  tageFuehrungen: number;
  tageBeob: number;
  tageTD: number;
  tageSonst: number;
  tageBEOS: number;
  tagesToT: number;
  tageGesamt: number;
  besucherRF: number;
  besucherSF: number;
  besucherSonF: number;
  besucherPrF: number;
  besucherToT: number;
  besucherGesamt: number;
}

interface StatsData {
  monthly: MonthRow[];
  cumulative: number;
  tage: number;
  year: number;
}

const MONATE = [
  'Januar','Februar','März','April','Mai','Juni',
  'Juli','August','September','Oktober','November','Dezember',
];

function n(v: number) {
  return v > 0 ? v.toLocaleString('de-DE') : '';
}

export default function Statistik() {
  const [year, setYear] = useState(new Date().getFullYear());
  const [data, setData] = useState<StatsData | null>(null);
  const [fetchError, setFetchError] = useState<number | null>(null);

  const error = fetchError === year ? 'Fehler beim Laden der Statistik.' : '';
  const loading = !error && (!data || data.year !== year);

  useEffect(() => {
    let cancelled = false;
    fetch(`/api/statistik?year=${year}`)
      .then((r) => { if (!r.ok) throw new Error(); return r.json(); })
      .then((d: StatsData) => { if (!cancelled) { setData(d); setFetchError(null); } })
      .catch(() => { if (!cancelled) setFetchError(year); });
    return () => { cancelled = true; };
  }, [year]);

  if (loading) return <div className="text-gray-500 text-sm py-4">Lade Statistik...</div>;
  if (error)   return <div className="text-red-600 text-sm py-4">{error}</div>;

  const rows = data!.monthly;

  function col(key: keyof MonthRow): number {
    return rows.reduce((s, r) => s + (r[key] as number), 0);
  }

  const thTop  = 'px-3 py-2 border border-gray-300 text-xs font-semibold bg-gray-100 text-center text-gray-900';
  const thSub  = 'px-3 py-2 border border-gray-300 text-xs font-semibold bg-gray-50 whitespace-nowrap text-gray-900';
  const thDiv  = 'px-3 py-2 border border-gray-300 border-l-4 border-l-gray-400 text-xs font-semibold bg-gray-50 whitespace-nowrap text-gray-900';
  const td     = 'px-3 py-2 border border-gray-200 text-sm text-right tabular-nums text-gray-900';
  const tdDiv  = 'px-3 py-2 border border-gray-200 border-l-4 border-l-gray-400 text-sm text-right tabular-nums text-gray-900';
  const tdL    = 'px-3 py-2 border border-gray-200 text-sm text-left whitespace-nowrap text-gray-900';
  const tdSum  = 'px-3 py-2 border border-gray-200 text-sm text-right tabular-nums font-semibold bg-gray-50 text-gray-900';
  const tdSumDiv = 'px-3 py-2 border border-gray-200 border-l-4 border-l-gray-400 text-sm text-right tabular-nums font-semibold bg-gray-50 text-gray-900';

  return (
    <div className="space-y-4">
      <div className="flex items-center gap-3 print:hidden">
        <label className="text-sm font-medium text-gray-700">Jahr</label>
        <input
          type="number"
          value={year}
          onChange={(e) => setYear(parseInt(e.target.value, 10) || new Date().getFullYear())}
          min={2000}
          max={2100}
          className="w-24 px-2 py-1 border-2 border-gray-400 rounded-lg bg-white text-gray-900 text-sm focus:border-blue-500 focus:outline-none"
        />
      </div>

      <div className="overflow-x-auto">
        <table className="w-full border-collapse text-sm">
          <thead>
            <tr>
              <th className={thTop} rowSpan={2}>Monat</th>
              <th className={thTop} colSpan={6}>Besucher</th>
              <th className={`${thTop} border-l-4 border-l-gray-400`} colSpan={7}>Anzahl</th>
            </tr>
            <tr>
              <th className={thSub}>RF</th>
              <th className={thSub}>SF</th>
              <th className={thSub}>SonF</th>
              <th className={thSub}>PrF</th>
              <th className={thSub}>ToT</th>
              <th className={thSub}>Gesamt</th>
              <th className={thDiv}>Führ.</th>
              <th className={thSub}>Beob.</th>
              <th className={thSub}>TD</th>
              <th className={thSub}>Sonst.</th>
              <th className={thSub}>BEOS</th>
              <th className={thSub}>ToT</th>
              <th className={thSub}>Gesamt</th>
            </tr>
          </thead>
          <tbody>
            {MONATE.map((name, idx) => {
              const m = idx + 1;
              const r = rows.find((row) => row.monat === m);
              const hasData = r && r.tageGesamt > 0;
              const cls = hasData ? '' : 'text-gray-400';
              return (
                <tr key={name} className={cls}>
                  <td className={tdL}>{name}</td>
                  <td className={td}>{r ? n(r.besucherRF) : ''}</td>
                  <td className={td}>{r ? n(r.besucherSF) : ''}</td>
                  <td className={td}>{r ? n(r.besucherSonF) : ''}</td>
                  <td className={td}>{r ? n(r.besucherPrF) : ''}</td>
                  <td className={td}>{r ? n(r.besucherToT) : ''}</td>
                  <td className={`${td} font-semibold`}>{r ? n(r.besucherGesamt) : ''}</td>
                  <td className={`${tdDiv} font-semibold`}>{r ? n(r.tageFuehrungen) : ''}</td>
                  <td className={td}>{r ? n(r.tageBeob) : ''}</td>
                  <td className={td}>{r ? n(r.tageTD) : ''}</td>
                  <td className={td}>{r ? n(r.tageSonst) : ''}</td>
                  <td className={td}>{r ? n(r.tageBEOS) : ''}</td>
                  <td className={td}>{r ? n(r.tagesToT) : ''}</td>
                  <td className={`${td} font-semibold`}>{r ? n(r.tageGesamt) : ''}</td>
                </tr>
              );
            })}
            <tr>
              <td className={tdL + ' font-semibold'}>Summe</td>
              <td className={tdSum}>{n(col('besucherRF'))}</td>
              <td className={tdSum}>{n(col('besucherSF'))}</td>
              <td className={tdSum}>{n(col('besucherSonF'))}</td>
              <td className={tdSum}>{n(col('besucherPrF'))}</td>
              <td className={tdSum}>{n(col('besucherToT'))}</td>
              <td className={tdSum}>{n(col('besucherGesamt'))}</td>
              <td className={tdSumDiv}>{n(col('tageFuehrungen'))}</td>
              <td className={tdSum}>{n(col('tageBeob'))}</td>
              <td className={tdSum}>{n(col('tageTD'))}</td>
              <td className={tdSum}>{n(col('tageSonst'))}</td>
              <td className={tdSum}>{n(col('tageBEOS'))}</td>
              <td className={tdSum}>{n(col('tagesToT'))}</td>
              <td className={tdSum}>{n(col('tageGesamt'))}</td>
            </tr>
          </tbody>
        </table>
      </div>

      <div className="grid grid-cols-2 gap-4 w-full max-w-sm">
        <div className="border-2 border-gray-300 rounded-xl p-4 bg-white">
          <div className="text-xs text-gray-500 mb-1">Besucher {year}</div>
          <div className="text-2xl font-bold text-gray-900">{data?.cumulative.toLocaleString('de-DE') ?? 0}</div>
        </div>
        <div className="border-2 border-gray-300 rounded-xl p-4 bg-white">
          <div className="text-xs text-gray-500 mb-1">Führungen {year}</div>
          <div className="text-2xl font-bold text-gray-900">{data?.tage ?? 0}</div>
        </div>
      </div>
    </div>
  );
}