import Link from "next/link";
import type { Metadata } from "next";
import { requireUser } from "@/lib/auth";
import { getSettings } from "@/lib/settings";
import { getUpcomingEpisodes } from "@/lib/stats";
import { AppShell } from "@/components/AppShell";
import { CalendarMonth } from "@/components/CalendarMonth";
import { episodeCode, formatDateLong } from "@/lib/labels";

export const metadata: Metadata = { title: "Kalender" };

/** Monatsangabe aus der URL („2026-09") oder der laufende Monat. */
function parseMonth(value: string | undefined): Date {
  const match = value?.match(/^(\d{4})-(\d{2})$/);
  if (match) {
    const year = Number(match[1]);
    const month = Number(match[2]) - 1;
    if (year >= 1900 && year <= 2200 && month >= 0 && month <= 11) {
      return new Date(year, month, 1);
    }
  }
  const now = new Date();
  return new Date(now.getFullYear(), now.getMonth(), 1);
}

function monthParam(date: Date): string {
  return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, "0")}`;
}

export default async function CalendarPage({
  searchParams,
}: {
  searchParams: Promise<{ monat?: string }>;
}) {
  const user = await requireUser("/kalender");
  const settings = await getSettings();
  const params = await searchParams;

  const month = parseMonth(params.monat);
  const from = new Date(month.getFullYear(), month.getMonth(), 1);
  // Das Raster reicht in den Vor- und Folgemonat hinein — die Termine auch.
  const gridFrom = new Date(from.getTime() - 7 * 86_400_000);
  const gridTo = new Date(from.getFullYear(), from.getMonth() + 1, 7);

  const episodes = await getUpcomingEpisodes(user.id, gridFrom, gridTo);
  const inMonth = episodes.filter((episode) => episode.airDate.getMonth() === month.getMonth());

  const previous = new Date(month.getFullYear(), month.getMonth() - 1, 1);
  const next = new Date(month.getFullYear(), month.getMonth() + 1, 1);

  return (
    <AppShell user={user} instanceName={settings.instanceName}>
      <header className="mb-5 flex flex-wrap items-end justify-between gap-3">
        <div>
          <h1 className="text-2xl font-semibold tracking-tight sm:text-3xl">Kalender</h1>
          <p className="mt-1 text-sm text-[var(--fl-muted)]">
            Ausstrahlungstermine der Serien in deiner Bibliothek.
          </p>
        </div>

        <nav className="flex items-center gap-2" aria-label="Monat wechseln">
          <Link
            href={`/kalender?monat=${monthParam(previous)}`}
            className="fl-btn fl-btn-ghost px-3 py-1.5 text-sm"
            aria-label={`Zum ${previous.toLocaleDateString("de-DE", { month: "long", year: "numeric" })}`}
          >
            ←
          </Link>
          <span className="min-w-40 text-center font-medium">
            {month.toLocaleDateString("de-DE", { month: "long", year: "numeric" })}
          </span>
          <Link
            href={`/kalender?monat=${monthParam(next)}`}
            className="fl-btn fl-btn-ghost px-3 py-1.5 text-sm"
            aria-label={`Zum ${next.toLocaleDateString("de-DE", { month: "long", year: "numeric" })}`}
          >
            →
          </Link>
          <Link href="/kalender" className="ml-1 text-sm text-[var(--fl-faint)] hover:text-[var(--fl-text)]">
            Heute
          </Link>
        </nav>
      </header>

      <div className="fl-card overflow-x-auto p-3 sm:p-4">
        <div className="min-w-[44rem]">
          <CalendarMonth month={month} episodes={episodes} />
        </div>
      </div>

      <section className="mt-6" aria-labelledby="liste">
        <h2 id="liste" className="mb-3 text-lg font-semibold">
          Termine im {month.toLocaleDateString("de-DE", { month: "long" })}
        </h2>

        {inMonth.length === 0 ? (
          <div className="fl-card p-6 text-center text-sm text-[var(--fl-muted)]">
            In diesem Monat läuft nichts aus deiner Bibliothek.
          </div>
        ) : (
          <ol className="fl-card divide-y divide-[var(--fl-border)]">
            {inMonth.map((episode) => (
              <li key={episode.episodeId} className="flex flex-wrap items-center gap-x-3 gap-y-1 px-4 py-3">
                <span className="w-52 shrink-0 text-sm text-[var(--fl-faint)]">
                  {formatDateLong(episode.airDate)}
                </span>
                <Link
                  href={`/titel/${episode.titleId}`}
                  className="min-w-0 flex-1 text-sm hover:text-[var(--fl-accent)]"
                >
                  <span className="font-medium">{episode.title}</span>
                  <span className="ml-2 font-mono text-xs text-[var(--fl-faint)]">
                    {episodeCode(episode.seasonNumber, episode.episodeNumber)}
                  </span>
                  <span className="ml-2 text-[var(--fl-muted)]">{episode.name}</span>
                </Link>
                {episode.runtime && (
                  <span className="shrink-0 text-xs text-[var(--fl-faint)]">{episode.runtime} min</span>
                )}
              </li>
            ))}
          </ol>
        )}
      </section>
    </AppShell>
  );
}