"use client";

import { startTransition, useEffect, useState } from "react";
import NumberFlow, { NumberFlowGroup } from "@number-flow/react";
import { CalendarDays, Clock3 } from "lucide-react";

const TERCIH_BASLANGICI = new Date("2026-07-29T00:00:00+03:00").getTime();
const TERCIH_BITISI = new Date("2026-08-10T23:59:59+03:00").getTime();

type GeriSayim = {
  asama: "baslamadi" | "devam-ediyor" | "sona-erdi";
  gun: number;
  saat: number;
  dakika: number;
  saniye: number;
};

function geriSayimiHesapla(simdi: number): GeriSayim {
  const asama =
    simdi < TERCIH_BASLANGICI
      ? "baslamadi"
      : simdi <= TERCIH_BITISI
        ? "devam-ediyor"
        : "sona-erdi";

  const hedef =
    asama === "baslamadi" ? TERCIH_BASLANGICI : TERCIH_BITISI;
  const kalan = Math.max(0, hedef - simdi);

  return {
    asama,
    gun: Math.floor(kalan / 86_400_000),
    saat: Math.floor((kalan % 86_400_000) / 3_600_000),
    dakika: Math.floor((kalan % 3_600_000) / 60_000),
    saniye: Math.floor((kalan % 60_000) / 1_000),
  };
}

const BIRIMLER = [
  { anahtar: "gun", etiket: "gün" },
  { anahtar: "saat", etiket: "sa" },
  { anahtar: "dakika", etiket: "dk" },
  { anahtar: "saniye", etiket: "sn" },
] as const;

export function SiteTopBanner() {
  const [geriSayim, setGeriSayim] = useState<GeriSayim | null>(null);

  useEffect(() => {
    // Saniyelik tik acil değil — layout'ta her sayfada monte; urgent şeritten çık
    const guncelle = () =>
      startTransition(() => setGeriSayim(geriSayimiHesapla(Date.now())));

    guncelle();
    const zamanlayici = window.setInterval(guncelle, 1_000);

    return () => window.clearInterval(zamanlayici);
  }, []);

  const asamaMetni =
    geriSayim?.asama === "baslamadi"
      ? "Başlamasına"
      : geriSayim?.asama === "sona-erdi"
        ? "Tercih dönemi sona erdi"
        : "Sona ermesine";

  return (
    <section
      aria-label="2026 YKS tercih dönemi"
      className="relative z-50 border-b border-primary-foreground/15 bg-primary text-primary-foreground print:hidden"
    >
      <div className="mx-auto flex min-h-12 max-w-6xl flex-wrap items-center justify-center gap-x-5 gap-y-1.5 px-4 py-2 sm:justify-between">
        <div className="flex min-w-0 items-center gap-2.5">
          <CalendarDays className="size-4 shrink-0 opacity-80" aria-hidden />
          <p className="truncate text-sm font-semibold tracking-[-0.01em]">
            <span className="hidden sm:inline">2026 YKS tercih dönemi · </span>
            <time dateTime="2026-07-29">29 Temmuz</time>
            <span aria-hidden> – </span>
            <time dateTime="2026-08-10">10 Ağustos 2026</time>
          </p>
        </div>

        <div className="flex items-center gap-2.5" role="timer">
          <div className="flex items-center gap-1.5 text-xs font-medium opacity-85">
            <Clock3 className="size-3.5" aria-hidden />
            <span>{asamaMetni}</span>
          </div>

          {geriSayim?.asama !== "sona-erdi" ? (
            <dl
              className="flex items-baseline gap-1 font-mono text-xs tabular-nums"
              aria-label={
                geriSayim
                  ? `${geriSayim.gun} gün, ${geriSayim.saat} saat, ${geriSayim.dakika} dakika, ${geriSayim.saniye} saniye`
                  : "Geri sayım yükleniyor"
              }
            >
              <NumberFlowGroup>
                {BIRIMLER.map(({ anahtar, etiket }) => (
                  <div className="flex items-baseline gap-0.5" key={anahtar}>
                    <dt className="sr-only">{etiket}</dt>
                    <dd className="font-semibold">
                      {geriSayim ? (
                        <NumberFlow
                          value={geriSayim[anahtar]}
                          trend={-1}
                          format={{
                            minimumIntegerDigits: 2,
                            useGrouping: false,
                          }}
                          transformTiming={{
                            duration: 280,
                            easing: "cubic-bezier(0.23, 1, 0.32, 1)",
                          }}
                          spinTiming={{
                            duration: 280,
                            easing: "cubic-bezier(0.23, 1, 0.32, 1)",
                          }}
                          opacityTiming={{
                            duration: 180,
                            easing: "ease-out",
                          }}
                          willChange={anahtar === "saniye"}
                          className="inline-block min-w-[2ch] text-right"
                          aria-hidden
                        />
                      ) : (
                        "--"
                      )}
                      <span className="ml-0.5 text-[10px] font-medium opacity-70">
                        {etiket}
                      </span>
                    </dd>
                  </div>
                ))}
              </NumberFlowGroup>
            </dl>
          ) : null}
        </div>
      </div>
    </section>
  );
}