import { useMemo } from 'react';
import { Bell } from 'lucide-react';
import { parseISO, isPast, isToday, compareAsc } from 'date-fns';
import type { Reminder } from '@/types';
import { EmptyState } from '@/components/ui/empty-state';
import ReminderItem from './ReminderItem';

interface ReminderListProps {
  reminders: Reminder[];
  onEdit: (reminder: Reminder) => void;
  onAdd: () => void;
}

interface ReminderGroup {
  key: string;
  label: string;
  reminders: Reminder[];
}

function sortByRemindAt(a: Reminder, b: Reminder): number {
  if (!a.remind_at && !b.remind_at) return 0;
  if (!a.remind_at) return 1;
  if (!b.remind_at) return -1;
  return compareAsc(parseISO(a.remind_at), parseISO(b.remind_at));
}

export default function ReminderList({ reminders, onEdit, onAdd }: ReminderListProps) {
  const groups = useMemo(() => {
    const overdue: Reminder[] = [];
    const today: Reminder[] = [];
    const upcoming: Reminder[] = [];
    const noDate: Reminder[] = [];
    const dismissed: Reminder[] = [];

    for (const reminder of reminders) {
      if (reminder.is_dismissed) {
        dismissed.push(reminder);
        continue;
      }

      if (!reminder.remind_at) {
        noDate.push(reminder);
        continue;
      }

      const date = parseISO(reminder.remind_at);
      if (isToday(date)) {
        today.push(reminder);
      } else if (isPast(date)) {
        overdue.push(reminder);
      } else {
        upcoming.push(reminder);
      }
    }

    overdue.sort(sortByRemindAt);
    today.sort(sortByRemindAt);
    upcoming.sort(sortByRemindAt);

    const result: ReminderGroup[] = [];
    if (overdue.length > 0) result.push({ key: 'overdue', label: 'Overdue', reminders: overdue });
    if (today.length > 0) result.push({ key: 'today', label: 'Today', reminders: today });
    if (upcoming.length > 0) result.push({ key: 'upcoming', label: 'Upcoming', reminders: upcoming });
    if (noDate.length > 0) result.push({ key: 'no-date', label: 'No Date', reminders: noDate });
    if (dismissed.length > 0) result.push({ key: 'dismissed', label: 'Dismissed', reminders: dismissed });

    return result;
  }, [reminders]);

  if (reminders.length === 0) {
    return (
      <EmptyState
        icon={Bell}
        title="No reminders"
        description="Create a reminder so you never miss an important date or event."
        actionLabel="Add Reminder"
        onAction={onAdd}
      />
    );
  }

  if (groups.length === 1) {
    return (
      <div className="space-y-0.5">
        {groups[0].reminders.map((reminder) => (
          <ReminderItem key={reminder.id} reminder={reminder} onEdit={onEdit} />
        ))}
      </div>
    );
  }

  return (
    <div className="space-y-5">
      {groups.map((group) => (
        <div key={group.key}>
          <h3 className="text-xs uppercase tracking-wider text-muted-foreground mb-2 px-1">
            {group.label}
            <span className="ml-1.5 tabular-nums">({group.reminders.length})</span>
          </h3>
          <div className="space-y-0.5">
            {group.reminders.map((reminder) => (
              <ReminderItem key={reminder.id} reminder={reminder} onEdit={onEdit} />
            ))}
          </div>
        </div>
      ))}
    </div>
  );
}