DlheVikendy.tsx

import React, { useEffect, useMemo, useState } from 'react';
import { getLang, persistLang, type Lang } from './tools-i18n';
import { holidaysForYear, restHolidaySet, dkey, type Country } from './holidaysSkCz';

/* Nájde "mosty": okná dní, kde za cenu N dní dovolenky (pracovné dni v okne)
   získaš súvislé voľno dlhé M dní. Okno musí začínať aj končiť voľným dňom
   a obsahovať aspoň jeden sviatok (inak je to obyčajná dovolenka). */

interface Plan {
  start: Date; end: Date;
  cost: number;        // vacation days needed
  total: number;       // total consecutive days off
  days: Array<{ date: Date; kind: 'weekend' | 'holiday' | 'vacation' }>;
  holidays: string[];  // names of holidays inside
}

function findBridges(year: number, country: Country, lang: Lang, maxCost: number): Plan[] {
  const rest = restHolidaySet(year, country);
  const hols = holidaysForYear(year, country).filter((h) => h.rest);
  const holName = new Map(hols.map((h) => [dkey(h.date), lang === 'sk' ? h.sk : h.en]));

  // build day array (with 10-day margins into neighbouring years)
  const start = Date.UTC(year, 0, 1) - 10 * 86400000;
  const nDays = 365 + 20 + 1;
  const prevRest = restHolidaySet(year - 1, country);
  const nextRest = restHolidaySet(year + 1, country);
  const isOff: boolean[] = [];
  const dates: Date[] = [];
  for (let i = 0; i < nDays; i++) {
    const d = new Date(start + i * 86400000);
    dates.push(d);
    const dow = d.getUTCDay();
    const k = dkey(d);
    isOff.push(dow === 0 || dow === 6 || rest.has(k) || prevRest.has(k) || nextRest.has(k));
  }

  const cands: Plan[] = [];
  const MAXLEN = 17;
  for (let i = 0; i < nDays; i++) {
    if (!isOff[i] || (i > 0 && isOff[i - 1])) continue; // window starts at the beginning of an off-run
    for (let j = i; j < Math.min(i + MAXLEN, nDays); j++) {
      if (!isOff[j]) continue;
      if (j + 1 < nDays && isOff[j + 1]) continue;      // extend to the end of its off-run
      let cost = 0;
      let holCount = 0;
      const days: Plan['days'] = [];
      for (let x = i; x <= j; x++) {
        const d = dates[x];
        const k = dkey(d);
        if (!isOff[x]) { cost++; days.push({ date: d, kind: 'vacation' }); }
        else if (holName.has(k) || prevRest.has(k) || nextRest.has(k)) { holCount++; days.push({ date: d, kind: 'holiday' }); }
        else days.push({ date: d, kind: 'weekend' });
      }
      if (cost < 1 || cost > maxCost || holCount === 0) continue;
      const total = j - i + 1;
      if (total < cost + 3) continue; // worth it: e.g. 1 vacation day → 4+ days off
      // the plan must belong to this year (majority of days)
      if (dates[i].getUTCFullYear() !== year && dates[j].getUTCFullYear() !== year) continue;
      const names = [...new Set(days.filter((d) => d.kind === 'holiday').map((d) => holName.get(dkey(d.date)) || '').filter(Boolean))];
      cands.push({ start: dates[i], end: dates[j], cost, total, days, holidays: names });
    }
  }

  // pick best non-overlapping by efficiency, then order by date
  cands.sort((a, b) => (b.total / b.cost) - (a.total / a.cost) || b.total - a.total);
  const picked: Plan[] = [];
  for (const c of cands) {
    if (picked.some((p) => c.start <= p.end && c.end >= p.start)) continue;
    picked.push(c);
  }
  picked.sort((a, b) => a.start.getTime() - b.start.getTime());
  return picked;
}

export default function DlheVikendy() {
  const [lang, setLang] = useState<Lang>(getLang());
  const t = (sk: string, en: string) => (lang === 'sk' ? sk : en);
  useEffect(() => { persistLang(lang); }, [lang]);

  const thisYear = new Date().getUTCFullYear();
  const [country, setCountry] = useState<Country>('sk');
  const [year, setYear] = useState(thisYear);
  const [maxCost, setMaxCost] = useState(4);

  const plans = useMemo(() => findBridges(year, country, lang, maxCost), [year, country, lang, maxCost]);
  const hols = useMemo(() => holidaysForYear(year, country), [year, country]);
  const totalVac = plans.reduce((s, p) => s + p.cost, 0);
  const totalOff = plans.reduce((s, p) => s + p.total, 0);

  const loc = lang === 'sk' ? 'sk-SK' : 'en-GB';
  const fmtD = (d: Date) => d.toLocaleDateString(loc, { day: 'numeric', month: 'numeric', timeZone: 'UTC' });
  const fmtDL = (d: Date) => d.toLocaleDateString(loc, { weekday: 'short', day: 'numeric', month: 'long', timeZone: 'UTC' });
  const now = new Date();
  const isPast = (d: Date) => d.getTime() < Date.UTC(now.getFullYear(), now.getMonth(), now.getDate());

  return (
    <div className="dv-app">
      <header className="dv-top">
        <div className="dv-logo"><span className="sym" aria-hidden="true">☀</span>{t('Dlhé víkendy', 'Long weekends')} <span className="yr">{year}</span></div>
        <span className="dv-spacer" />
        <div className="lang-switch">
          <button className={lang === 'sk' ? 'on' : ''} onClick={() => setLang('sk')}>SK</button>
          <button className={lang === 'en' ? 'on' : ''} onClick={() => setLang('en')}>EN</button>
        </div>
        <a className="dv-back" href="/#tools">← {t('Portfólio', 'Portfolio')}</a>
      </header>

      <div className="dv-controls">
        <div className="dv-seg" role="tablist" aria-label={t('Krajina', 'Country')}>
          <button role="tab" aria-selected={country === 'sk'} className={country === 'sk' ? 'on' : ''} onClick={() => setCountry('sk')}>🇸🇰 Slovensko</button>
          <button role="tab" aria-selected={country === 'cz'} className={country === 'cz' ? 'on' : ''} onClick={() => setCountry('cz')}>🇨🇿 Česko</button>
        </div>
        <div className="dv-years">
          {[thisYear, thisYear + 1, thisYear + 2].map((y) => (
            <button key={y} className={y === year ? 'on' : ''} onClick={() => setYear(y)}>{y}</button>
          ))}
        </div>
        <div className="dv-maxc">
          <span>{t('Max. dní dovolenky na jeden most:', 'Max vacation days per bridge:')}</span>
          {[1, 2, 3, 4, 5].map((n) => (
            <button key={n} className={n === maxCost ? 'on' : ''} onClick={() => setMaxCost(n)}>{n}</button>
          ))}
        </div>
      </div>

      <div className="dv-summary">
        {t(
          `Za ${totalVac} dní dovolenky získaš spolu ${totalOff} dní voľna v ${plans.length} blokoch.`,
          `${totalVac} vacation days buy you ${totalOff} days off in ${plans.length} blocks.`
        )}
      </div>

      <div className="dv-plans">
        {plans.map((p, i) => (
          <article key={i} className={`dv-plan ${year === thisYear && isPast(p.end) ? 'past' : ''}`}>
            <div className="dv-plan-head">
              <div className="range">
                <strong>{fmtDL(p.start)} – {fmtDL(p.end)}</strong>
                <span className="hols">{p.holidays.join(' · ')}</span>
              </div>
              <div className="score">
                <span className="deal">{p.cost} {t(p.cost === 1 ? 'deň dovolenky' : p.cost < 5 ? 'dni dovolenky' : 'dní dovolenky', p.cost === 1 ? 'vacation day' : 'vacation days')}</span>
                <span className="arrow" aria-hidden="true">→</span>
                <span className="gain">{p.total} {t('dní voľna', 'days off')}</span>
                <span className="mult">{(p.total / p.cost).toFixed(1)}×</span>
              </div>
            </div>
            <div className="dv-strip" role="img" aria-label={t('Vizualizácia dní', 'Day visualization')}>
              {p.days.map((d, x) => (
                <span key={x} className={`cell ${d.kind}`} title={`${fmtD(d.date)} — ${d.kind === 'vacation' ? t('dovolenka', 'vacation') : d.kind === 'holiday' ? t('sviatok', 'holiday') : t('víkend', 'weekend')}`}>
                  <em>{d.date.getUTCDate()}</em>
                  {d.kind === 'vacation' ? 'D' : ''}
                </span>
              ))}
            </div>
          </article>
        ))}
        {plans.length === 0 && <p className="dv-empty">{t('Pre zvolený filter sa nenašli žiadne mosty.', 'No bridges found for the chosen filter.')}</p>}
      </div>

      <div className="dv-legend">
        <span><i className="sw weekend" /> {t('víkend', 'weekend')}</span>
        <span><i className="sw holiday" /> {t('sviatok', 'holiday')}</span>
        <span><i className="sw vacation" /> {t('dovolenka (D)', 'vacation (D)')}</span>
      </div>

      <section className="dv-hols">
        <h2>{t(`Sviatky ${country === 'sk' ? 'na Slovensku' : 'v Česku'} v roku ${year}`, `Public holidays in ${country === 'sk' ? 'Slovakia' : 'Czechia'} ${year}`)}</h2>
        <div className="list">
          {hols.map((h) => (
            <div key={h.sk + h.date.getTime()} className={`row ${h.rest ? '' : 'work'}`}>
              <span className="d">{h.date.getUTCDate()}. {h.date.toLocaleDateString(loc, { month: 'short', timeZone: 'UTC' })}</span>
              <span className="dow">{h.date.toLocaleDateString(loc, { weekday: 'long', timeZone: 'UTC' })}</span>
              <span className="nm">{lang === 'sk' ? h.sk : h.en}</span>
              {!h.rest && <span className="tag">{t('pracovný deň', 'working day')}</span>}
            </div>
          ))}
        </div>
        {country === 'sk' && year === 2026 && (
          <p className="dv-note">{t('8. máj a 15. september sú v roku 2026 sviatkami, ale pracovnými dňami (zák. 261/2025) — v mostoch preto nefigurujú.', 'In 2026, 8 May and 15 September are holidays but working days (Act 261/2025), so they are not part of any bridge.')}</p>
        )}
      </section>
    </div>
  );
}