import { useState, useRef, useEffect, useMemo } from 'react';
import { useTranslation } from 'react-i18next';
import { ScanLine, Calendar, ArrowRight } from 'lucide-react';
import { format } from 'date-fns';
import { fr } from 'date-fns/locale/fr';
import { enUS } from 'date-fns/locale/en-US';
import { Button } from '@/components/ui/button';

type Period = 'today' | '7days' | 'custom';

interface HeaderProps {
  title: string;
  onScanClick?: () => void;
  activePeriod?: Period;
  onPeriodChange?: (period: Period) => void;
  customStartDate?: string;
  customEndDate?: string;
  onCustomDateChange?: (startDate: string, endDate: string) => void;
}

function computeDateRange(period: Period, customStart?: string, customEnd?: string): { start: Date; end: Date } {
  const now = new Date();
  switch (period) {
    case 'today': {
      const midnight = new Date(now);
      midnight.setHours(0, 0, 0, 0);
      return { start: midnight, end: now };
    }
    case '7days': {
      const sevenDaysAgo = new Date(now);
      sevenDaysAgo.setDate(sevenDaysAgo.getDate() - 7);
      sevenDaysAgo.setHours(0, 0, 0, 0);
      return { start: sevenDaysAgo, end: now };
    }
    case 'custom': {
      if (customStart && customEnd) {
        // Parse as local date (YYYY-MM-DD) to avoid UTC timezone shift
        const [sy, sm, sd] = customStart.split('-').map(Number);
        const [ey, em, ed] = customEnd.split('-').map(Number);
        return { start: new Date(sy, sm - 1, sd), end: new Date(ey, em - 1, ed) };
      }
      return { start: now, end: now };
    }
  }
}

function formatDateLabel(date: Date, locale: string): string {
  const loc = locale === 'fr' ? fr : enUS;
  return format(date, 'd MMM', { locale: loc });
}

export default function Header({
  title,
  onScanClick,
  activePeriod: controlledPeriod,
  onPeriodChange,
  customStartDate,
  customEndDate,
  onCustomDateChange,
}: HeaderProps) {
  const { t, i18n } = useTranslation();
  const [showDatePicker, setShowDatePicker] = useState(false);
  const [internalPeriod, setInternalPeriod] = useState<Period>('today');
  const [internalStart, setInternalStart] = useState('');
  const [internalEnd, setInternalEnd] = useState('');
  const activePeriod = controlledPeriod ?? internalPeriod;
  const startDate = customStartDate ?? internalStart;
  const endDate = customEndDate ?? internalEnd;

  const handlePeriodChange = (p: Period) => {
    setInternalPeriod(p);
    onPeriodChange?.(p);
    if (p === 'custom') {
      setShowDatePicker(true);
    } else {
      setShowDatePicker(false);
    }
  };

  const handleCustomDateChange = (start: string, end: string) => {
    setInternalStart(start);
    setInternalEnd(end);
    onCustomDateChange?.(start, end);
  };

  const datePickerRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    if (!showDatePicker) return;
    function handleClick(e: MouseEvent) {
      if (datePickerRef.current && !datePickerRef.current.contains(e.target as Node)) {
        setShowDatePicker(false);
      }
    }
    document.addEventListener('mousedown', handleClick);
    return () => document.removeEventListener('mousedown', handleClick);
  }, [showDatePicker]);

  const dateRange = useMemo(
    () => computeDateRange(activePeriod, startDate, endDate),
    [activePeriod, startDate, endDate]
  );

  const today = format(new Date(), 'yyyy-MM-dd');

  return (
    <header className="flex h-20 items-center justify-between bg-background px-8 z-10 sticky top-0 border-b border-border/50">
      <h2 className="text-2xl font-bold tracking-tight text-slate-900">{title}</h2>
      <div className="flex items-center gap-4">
        {/* Period filter */}
        <div className="flex items-center gap-2 bg-card p-1 rounded-lg border border-border shadow-sm">
          <button
            onClick={() => handlePeriodChange('today')}
            className={`px-3 py-1.5 text-xs font-medium rounded-md transition-colors ${
              activePeriod === 'today'
                ? 'bg-slate-100 text-slate-900 hover:bg-slate-200'
                : 'text-slate-500 hover:bg-slate-50 hover:text-slate-900'
            }`}
          >
            {t('scan.today')}
          </button>
          <button
            onClick={() => handlePeriodChange('7days')}
            className={`px-3 py-1.5 text-xs font-medium rounded-md transition-colors ${
              activePeriod === '7days'
                ? 'bg-slate-100 text-slate-900 hover:bg-slate-200'
                : 'text-slate-500 hover:bg-slate-50 hover:text-slate-900'
            }`}
          >
            {t('scan.last7days')}
          </button>
          <div className="relative" ref={datePickerRef}>
            <button
              onClick={() => {
                if (activePeriod === 'custom') {
                  setShowDatePicker(!showDatePicker);
                } else {
                  handlePeriodChange('custom');
                }
              }}
              className={`px-3 py-1.5 text-xs font-medium rounded-md flex items-center gap-1.5 transition-colors ${
                activePeriod === 'custom'
                  ? 'bg-primary/10 text-primary border border-primary/20 hover:bg-primary/20'
                  : 'text-slate-500 hover:bg-slate-50 hover:text-slate-900'
              }`}
            >
              <span>{t('scan.custom')}</span>
              <Calendar className="h-3.5 w-3.5" />
            </button>

            {/* Custom date picker dropdown */}
            {showDatePicker && (
              <div className="absolute right-0 top-full mt-2 w-72 rounded-xl bg-white p-4 shadow-lg border border-slate-200 z-50">
                <div className="space-y-3">
                  <div>
                    <label className="block text-xs font-medium text-slate-500 uppercase tracking-wide mb-1.5">
                      {t('scan.startDate')}
                    </label>
                    <input
                      type="date"
                      max={endDate || today}
                      value={startDate}
                      onChange={(e) => handleCustomDateChange(e.target.value, endDate)}
                      className="w-full rounded-lg border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-900 focus:border-primary focus:ring-1 focus:ring-primary/30 outline-none transition-colors"
                    />
                  </div>
                  <div>
                    <label className="block text-xs font-medium text-slate-500 uppercase tracking-wide mb-1.5">
                      {t('scan.endDate')}
                    </label>
                    <input
                      type="date"
                      min={startDate}
                      max={today}
                      value={endDate}
                      onChange={(e) => handleCustomDateChange(startDate, e.target.value)}
                      className="w-full rounded-lg border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-900 focus:border-primary focus:ring-1 focus:ring-primary/30 outline-none transition-colors"
                    />
                  </div>
                  {startDate && endDate && (
                    <button
                      onClick={() => setShowDatePicker(false)}
                      className="w-full rounded-lg bg-primary px-3 py-2 text-sm font-medium text-white hover:bg-primary/90 transition-colors"
                    >
                      {t('common.save')}
                    </button>
                  )}
                </div>
              </div>
            )}
          </div>
        </div>

        {/* Date range display */}
        <div className="hidden sm:flex items-center gap-2 bg-card px-3 py-1.5 rounded-lg border border-border shadow-sm text-sm text-slate-600">
          <span className="font-medium text-slate-900">
            {formatDateLabel(dateRange.start, i18n.language)}
          </span>
          <ArrowRight className="h-3.5 w-3.5 text-slate-400" />
          <span className="font-medium text-slate-900">
            {formatDateLabel(dateRange.end, i18n.language)}
          </span>
        </div>

        <div className="h-8 w-px bg-slate-200 mx-2" />

        {/* Scan Button */}
        <Button
          onClick={onScanClick}
          className="gap-2 shadow-md shadow-blue-500/20 hover:shadow-blue-500/30 active:scale-95 transition-all"
        >
          <ScanLine className="h-[18px] w-[18px]" />
          {t('header.scanNow')}
        </Button>

      </div>
    </header>
  );
}