"use client";

import { useMemo, useState } from "react";

export type CalendarMarker = {
  date: Date;
  status: "pending" | "confirmed" | "rejected" | "cancelled" | "past" | "public" | "private";
};

const WEEKDAY_LABELS = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"];

const markerColor: Record<CalendarMarker["status"], string> = {
  pending: "bg-anouma-sand",
  confirmed: "bg-anouma-sage",
  rejected: "bg-red-400",
  cancelled: "bg-anouma-taupe",
  past: "bg-anouma-taupe/50",
  public: "bg-anouma-rose",
  private: "bg-anouma-mauve-dark",
};

function startOfMonth(d: Date) {
  return new Date(d.getFullYear(), d.getMonth(), 1);
}
function dateKey(d: Date) {
  return d.toISOString().slice(0, 10);
}

export function MonthCalendar({
  markers,
  onSelectDay,
  selectedDay,
}: {
  markers: CalendarMarker[];
  onSelectDay?: (day: Date) => void;
  selectedDay?: Date | null;
}) {
  const [month, setMonth] = useState(() => startOfMonth(new Date()));

  const markersByDay = useMemo(() => {
    const map = new Map<string, CalendarMarker[]>();
    for (const marker of markers) {
      const key = dateKey(marker.date);
      map.set(key, [...(map.get(key) ?? []), marker]);
    }
    return map;
  }, [markers]);

  const weeks = useMemo(() => {
    const first = startOfMonth(month);
    const firstWeekday = (first.getDay() + 6) % 7; // Monday = 0
    const daysInMonth = new Date(month.getFullYear(), month.getMonth() + 1, 0).getDate();

    const cells: (Date | null)[] = Array(firstWeekday).fill(null);
    for (let d = 1; d <= daysInMonth; d++) {
      cells.push(new Date(month.getFullYear(), month.getMonth(), d));
    }
    while (cells.length % 7 !== 0) cells.push(null);

    const result: (Date | null)[][] = [];
    for (let i = 0; i < cells.length; i += 7) result.push(cells.slice(i, i + 7));
    return result;
  }, [month]);

  const monthLabel = month.toLocaleDateString("de-DE", { month: "long", year: "numeric" });
  const today = dateKey(new Date());

  return (
    <div className="rounded-3xl bg-white p-6">
      <div className="flex items-center justify-between">
        <button
          type="button"
          onClick={() => setMonth(new Date(month.getFullYear(), month.getMonth() - 1, 1))}
          aria-label="Vorheriger Monat"
          className="flex h-9 w-9 items-center justify-center rounded-full text-anouma-plum hover:bg-anouma-cream-light"
        >
          ‹
        </button>
        <p className="font-serif text-lg font-medium capitalize text-anouma-plum">{monthLabel}</p>
        <button
          type="button"
          onClick={() => setMonth(new Date(month.getFullYear(), month.getMonth() + 1, 1))}
          aria-label="Nächster Monat"
          className="flex h-9 w-9 items-center justify-center rounded-full text-anouma-plum hover:bg-anouma-cream-light"
        >
          ›
        </button>
      </div>

      <div className="mt-4 grid grid-cols-7 gap-1 text-center text-xs font-medium uppercase tracking-wide text-anouma-plum/50">
        {WEEKDAY_LABELS.map((d) => (
          <div key={d}>{d}</div>
        ))}
      </div>

      <div className="mt-1 space-y-1">
        {weeks.map((week, i) => (
          <div key={i} className="grid grid-cols-7 gap-1">
            {week.map((day, j) => {
              if (!day) return <div key={j} />;
              const key = dateKey(day);
              const dayMarkers = markersByDay.get(key) ?? [];
              const isSelected = selectedDay && dateKey(selectedDay) === key;
              return (
                <button
                  key={j}
                  type="button"
                  onClick={() => onSelectDay?.(day)}
                  className={`flex aspect-square flex-col items-center justify-center rounded-xl text-sm transition-colors ${
                    isSelected ? "bg-anouma-mauve-dark text-white" : "text-anouma-plum hover:bg-anouma-cream-light"
                  } ${key === today && !isSelected ? "font-semibold" : ""}`}
                >
                  <span>{day.getDate()}</span>
                  {dayMarkers.length > 0 && (
                    <span className="mt-0.5 flex gap-0.5">
                      {dayMarkers.slice(0, 3).map((m, k) => (
                        <span
                          key={k}
                          className={`h-1.5 w-1.5 rounded-full ${isSelected ? "bg-white" : markerColor[m.status]}`}
                        />
                      ))}
                    </span>
                  )}
                </button>
              );
            })}
          </div>
        ))}
      </div>
    </div>
  );
}