import { ArrowUpRightIcon, MapPinIcon } from "lucide-react";
import type { Metadata } from "next";
import Link from "next/link";
import { CopyLinkCard } from "@/components/landing/CopyLinkCard";
import { dateBlock, describeWhen } from "@/lib/event-display";
import { normaliseUrl } from "@/lib/event-form";
import { API_BASE_URL } from "@/lib/env";
import { fetchUpcomingPublicEvents, googleCalendarUrl, icalUrl, webcalUrl } from "@/lib/public-calendar";
import type { CalendarEvent } from "@/lib/types";

export const metadata: Metadata = {
  title: "Nachklang e.V. – Veranstaltungskalender",
  description: "Abonniere den Kalender von Nachklang e.V. und verpasse keine Veranstaltung mehr.",
};

// Static, refreshed every five minutes - matches the fetch's own revalidate.
export const revalidate = 300;

/**
 * Where the server fetches from. Optional and read at request time, like in
 * nachklang-feedback: it may point at an internal address. The links on the
 * page always use the public URL, since visitors' calendar apps fetch them.
 */
const serverApiBaseUrl = (): string => (process.env.API_BASE_URL || API_BASE_URL).replace(/\/+$/, "");

// Shared by the three subscribe options, so the two links and the copy button look alike.
// A row on phones; icon above text in the three-column grid, where a row would wrap.
const OPTION =
  "flex w-full items-center gap-3 rounded-xl border bg-card p-4 text-left transition-colors sm:flex-col sm:items-start " +
  "hover:bg-muted/50 focus-visible:ring-3 focus-visible:ring-ring/30 focus-visible:outline-none";

/**
 * The public page: how to subscribe, and what is coming up. Same look as the
 * admin area (design system, light, Inter) - one product, one visual language.
 */
export default async function Home() {
  const upcoming = await fetchUpcomingPublicEvents(serverApiBaseUrl(), new Date(), 4);

  return (
    <div className="flex min-h-dvh flex-col">
      <header className="border-b pt-[env(safe-area-inset-top)]">
        <div className="mx-auto flex h-14 w-full max-w-2xl items-center justify-between gap-3 px-4 sm:px-6">
          <span className="flex items-baseline gap-2">
            <span className="font-semibold tracking-tight">Nachklang</span>
            <span className="text-sm text-muted-foreground">Kalender</span>
          </span>
          <Link href="/admin" className="text-sm text-muted-foreground transition-colors hover:text-foreground">
            Verwaltung
          </Link>
        </div>
      </header>

      <main className="mx-auto flex w-full max-w-2xl flex-1 flex-col gap-10 px-4 py-10 sm:px-6 sm:py-14">
        <div className="flex flex-col gap-2">
          <h1 className="text-3xl font-semibold tracking-tight sm:text-4xl">Veranstaltungskalender</h1>
          <p className="text-muted-foreground">
            Abonniere den Kalender von Nachklang e.V. – neue Termine erscheinen dann automatisch in deiner Kalender-App.
          </p>
        </div>

        <section aria-labelledby="abonnieren" className="flex flex-col gap-3">
          <h2 id="abonnieren" className="text-sm font-semibold text-muted-foreground">
            Abonnieren
          </h2>
          <div className="grid gap-3 sm:grid-cols-3">
            <a href={webcalUrl(API_BASE_URL)} className={OPTION}>
              <AppleIcon />
              <OptionText label="Apple Kalender" sub="iPhone, iPad, Mac" />
            </a>
            <a href={googleCalendarUrl(API_BASE_URL)} target="_blank" rel="noopener noreferrer" className={OPTION}>
              <GoogleIcon />
              <OptionText label="Google Kalender" sub="Android, Web" />
            </a>
            <CopyLinkCard url={icalUrl(API_BASE_URL)} className={OPTION} />
          </div>
        </section>

        {upcoming && <UpcomingEvents events={upcoming} />}
      </main>

      <footer className="border-t">
        <div className="mx-auto w-full max-w-2xl px-4 py-6 pb-[max(1.5rem,env(safe-area-inset-bottom))] text-sm text-muted-foreground sm:px-6">
          Nachklang e.V.
        </div>
      </footer>
    </div>
  );
}

function OptionText({ label, sub }: { label: string; sub: string }) {
  return (
    <span className="flex min-w-0 flex-col gap-0.5">
      <span className="font-medium">{label}</span>
      <span className="text-sm text-muted-foreground">{sub}</span>
    </span>
  );
}

/**
 * The next few public events, in the admin list's style. Hidden entirely when
 * the API could not be reached, so the page never shows an error where people
 * come to subscribe.
 */
function UpcomingEvents({ events }: { events: CalendarEvent[] }) {
  const now = new Date();
  return (
    <section aria-labelledby="naechste-termine" className="flex flex-col gap-3">
      <h2 id="naechste-termine" className="text-sm font-semibold text-muted-foreground">
        Nächste Termine
      </h2>
      {events.length === 0 ? (
        <p className="rounded-xl border border-dashed px-4 py-8 text-center text-sm text-muted-foreground">
          Gerade stehen keine öffentlichen Termine an.
        </p>
      ) : (
        <ul className="divide-y overflow-hidden rounded-xl border bg-card">
          {events.map((event) => {
            const block = dateBlock(event.start);
            // Links come from the database, and rows older than this app's URL check were never
            // validated - only an http(s) URL becomes a link on this public page.
            const link = normaliseUrl(event.url);
            const href = link.ok && link.value !== "" ? link.value : null;
            const content = (
              <>
                <span className="flex w-11 shrink-0 flex-col items-center pt-0.5 text-center leading-tight" aria-hidden>
                  <span className="text-[11px] font-medium text-muted-foreground uppercase">{block.weekday}</span>
                  <span className="text-xl font-semibold tabular-nums">{block.day}</span>
                  <span className="text-[11px] text-muted-foreground">{block.month}</span>
                </span>
                <span className="flex min-w-0 flex-1 flex-col gap-1">
                  <span className="font-medium">{event.name}</span>
                  <span className="flex flex-wrap items-center gap-x-3 gap-y-0.5 text-sm text-muted-foreground">
                    <span>{describeWhen(event, now)}</span>
                    {event.location && (
                      <span className="inline-flex min-w-0 items-center gap-1">
                        <MapPinIcon aria-hidden className="size-3.5 shrink-0" />
                        <span className="truncate">{event.location}</span>
                      </span>
                    )}
                  </span>
                </span>
                {href && <ArrowUpRightIcon aria-hidden className="mt-0.5 size-4 shrink-0 text-muted-foreground" />}
              </>
            );
            return (
              <li key={event.eventId}>
                {href ? (
                  <a
                    href={href}
                    target="_blank"
                    rel="noopener noreferrer"
                    className="flex gap-3 px-3 py-3 transition-colors hover:bg-muted/50 focus-visible:bg-muted/50 focus-visible:outline-none sm:gap-4 sm:px-4"
                  >
                    {content}
                  </a>
                ) : (
                  <div className="flex gap-3 px-3 py-3 sm:gap-4 sm:px-4">{content}</div>
                )}
              </li>
            );
          })}
        </ul>
      )}
    </section>
  );
}

function AppleIcon() {
  return (
    <span className="size-10 shrink-0 overflow-hidden rounded-lg ring-1 ring-border">
      <svg viewBox="0 0 48 48" fill="none" aria-hidden className="block size-full">
        <rect width="48" height="48" fill="white" />
        <rect width="48" height="14" fill="#FF3B30" />
        <text x="24" y="41" textAnchor="middle" fontFamily="Helvetica Neue, Helvetica, Arial, sans-serif" fontSize="22" fontWeight="300" fill="#1c1c1e">
          31
        </text>
      </svg>
    </span>
  );
}

function GoogleIcon() {
  return (
    <span className="size-10 shrink-0 overflow-hidden rounded-lg ring-1 ring-border">
      <svg viewBox="0 0 48 48" fill="none" aria-hidden className="block size-full">
        <rect width="48" height="48" fill="white" />
        <rect width="48" height="14" fill="#1a73e8" />
        <rect x="8" y="18" width="14" height="12" rx="1.5" fill="#4285f4" />
        <rect x="26" y="18" width="14" height="12" rx="1.5" fill="#ea4335" />
        <rect x="8" y="34" width="14" height="11" rx="1.5" fill="#34a853" />
        <rect x="26" y="34" width="14" height="11" rx="1.5" fill="#fbbc05" />
      </svg>
    </span>
  );
}