"use client";

import { useEffect, useRef, useState } from "react";
import { createLocalTracks, Track, type LocalTrack } from "livekit-client";

function describeDeviceError(error: unknown): string {
  const name = error instanceof Error ? error.name : "";

  if (name === "NotAllowedError" || name === "SecurityError") {
    return "Der Browser blockiert Kamera oder Mikrofon. Erlaube beide über das Schloss-Symbol neben der Adresse und versuche es danach erneut.";
  }
  if (name === "NotFoundError") {
    return "Es wurde keine Kamera oder kein Mikrofon gefunden. Prüfe, ob beide Geräte angeschlossen und in den Systemeinstellungen freigegeben sind.";
  }
  if (name === "NotReadableError" || name === "TrackStartError") {
    return "Kamera oder Mikrofon werden gerade von einer anderen App verwendet. Schließe zum Beispiel Zoom, Teams oder eine andere Browser-Registerkarte und versuche es erneut.";
  }

  return "Kamera oder Mikrofon konnten nicht gestartet werden. Du kannst dem Meeting trotzdem ohne sie beitreten.";
}

export function PreJoinScreen({ onContinue }: { onContinue: (tracks: LocalTrack[]) => void }) {
  const [tracks, setTracks] = useState<LocalTrack[]>([]);
  const [error, setError] = useState<string | null>(null);
  const [micOn, setMicOn] = useState(true);
  const [cameraOn, setCameraOn] = useState(true);
  const [speakerTested, setSpeakerTested] = useState(false);
  const [requestingDevices, setRequestingDevices] = useState(false);
  const videoRef = useRef<HTMLVideoElement>(null);
  const handedOffRef = useRef(false);

  const videoTrack = tracks.find((track) => track.kind === Track.Kind.Video);
  const audioTrack = tracks.find((track) => track.kind === Track.Kind.Audio);

  useEffect(() => {
    const videoElement = videoRef.current;
    if (!videoElement || !videoTrack) return;
    videoTrack.attach(videoElement);
    return () => {
      videoTrack.detach(videoElement);
    };
  }, [videoTrack]);

  useEffect(() => {
    return () => {
      if (!handedOffRef.current) tracks.forEach((track) => track.stop());
    };
  }, [tracks]);

  async function requestDevices() {
    if (requestingDevices) return;
    setError(null);
    setRequestingDevices(true);
    try {
      // This must originate from the button click. Some privacy-focused
      // browsers deliberately ignore a getUserMedia request from useEffect.
      const nextTracks = await createLocalTracks({ audio: true, video: true });
      tracks.forEach((track) => track.stop());
      setTracks(nextTracks);
      setMicOn(true);
      setCameraOn(true);
    } catch (requestError) {
      setError(describeDeviceError(requestError));
    } finally {
      setRequestingDevices(false);
    }
  }

  async function toggleMic() {
    if (!audioTrack) return;
    if (micOn) await audioTrack.mute();
    else await audioTrack.unmute();
    setMicOn(!micOn);
  }

  async function toggleCamera() {
    if (!videoTrack) return;
    if (cameraOn) await videoTrack.mute();
    else await videoTrack.unmute();
    setCameraOn(!cameraOn);
  }

  function testSpeaker() {
    const AudioContextClass = window.AudioContext || (window as Window & { webkitAudioContext?: typeof AudioContext }).webkitAudioContext;
    if (!AudioContextClass) return;
    const context = new AudioContextClass();
    const oscillator = context.createOscillator();
    const gain = context.createGain();
    oscillator.frequency.value = 660;
    gain.gain.value = 0.08;
    oscillator.connect(gain).connect(context.destination);
    oscillator.start();
    oscillator.stop(context.currentTime + 0.25);
    oscillator.addEventListener("ended", () => void context.close());
    setSpeakerTested(true);
  }

  function continueToCall() {
    handedOffRef.current = true;
    onContinue(tracks);
  }

  return (
    <main className="flex min-h-screen items-center justify-center bg-neutral-950 px-5 py-10 text-white">
      <section className="w-full max-w-3xl rounded-[2rem] border border-white/10 bg-neutral-900 p-6 shadow-2xl sm:p-8">
        <p className="text-xs font-medium uppercase tracking-[0.18em] text-white/50">Vorbereitung</p>
        <h1 className="mt-2 font-serif text-3xl">Prüfe deine Geräte</h1>
        <p className="mt-2 max-w-xl text-sm leading-relaxed text-white/65">
          Erlaube Kamera und Mikrofon, teste kurz den Ton und tritt dann dem geschützten Meeting bei.
        </p>

        <div className="mt-7 grid gap-5 lg:grid-cols-[1.35fr_1fr]">
          <div className="relative aspect-video overflow-hidden rounded-3xl bg-neutral-800">
            {videoTrack && cameraOn ? (
              <video ref={videoRef} autoPlay muted playsInline className="h-full w-full object-cover [transform:scaleX(-1)]" />
            ) : requestingDevices ? (
              <div className="flex h-full flex-col items-center justify-center gap-3 text-sm text-white/65">
                <span className="h-8 w-8 animate-spin rounded-full border-2 border-white/20 border-t-white" aria-hidden="true" />
                Berechtigungsfenster wird geöffnet …
              </div>
            ) : (
              <div className="flex h-full flex-col items-center justify-center gap-2 px-6 text-center text-sm text-white/55">
                <span className="flex h-12 w-12 items-center justify-center rounded-full bg-white/10" aria-hidden="true">▣</span>
                {error ? "Kameravorschau nicht verfügbar" : "Kamera noch nicht aktiviert"}
              </div>
            )}
            {tracks.length > 0 && (
              <span className="absolute bottom-3 left-3 rounded-full bg-black/50 px-3 py-1 text-xs text-white/80">
                {micOn ? "Mikrofon an" : "Mikrofon aus"}
              </span>
            )}
          </div>

          <div className="flex flex-col justify-center gap-3">
            <button
              type="button"
              onClick={() => void requestDevices()}
              disabled={requestingDevices}
              className="rounded-full bg-white px-5 py-3 text-sm font-medium text-neutral-900 transition-all duration-200 hover:-translate-y-0.5 hover:bg-white/85 hover:shadow-lg hover:shadow-white/10 active:translate-y-0 active:scale-[0.98] disabled:cursor-wait disabled:opacity-75"
            >
              {requestingDevices ? "Browser-Anfrage ist offen …" : tracks.length > 0 ? "Kamera & Mikrofon erneut prüfen" : "Kamera & Mikrofon aktivieren"}
            </button>
            <div className="grid grid-cols-2 gap-3">
              <button type="button" onClick={() => void toggleMic()} disabled={!audioTrack} className={`rounded-2xl px-4 py-3 text-xs transition-all duration-200 hover:-translate-y-0.5 active:translate-y-0 active:scale-[0.98] disabled:opacity-40 ${micOn ? "bg-white/10 hover:bg-white/15" : "bg-red-500/85 hover:bg-red-500"}`}>
                {micOn ? "Mikrofon aus" : "Mikrofon an"}
              </button>
              <button type="button" onClick={() => void toggleCamera()} disabled={!videoTrack} className={`rounded-2xl px-4 py-3 text-xs transition-all duration-200 hover:-translate-y-0.5 active:translate-y-0 active:scale-[0.98] disabled:opacity-40 ${cameraOn ? "bg-white/10 hover:bg-white/15" : "bg-red-500/85 hover:bg-red-500"}`}>
                {cameraOn ? "Kamera aus" : "Kamera an"}
              </button>
            </div>
            <button type="button" onClick={testSpeaker} className="rounded-2xl border border-white/15 px-4 py-3 text-left text-xs text-white/80 hover:bg-white/10">
              {speakerTested ? "✓ Lautsprecher getestet" : "Lautsprecher testen"}
            </button>
            {error && <p role="alert" className="rounded-2xl border border-amber-200/20 bg-amber-200/10 p-3 text-xs leading-relaxed text-amber-100">{error}</p>}
            <button type="button" onClick={continueToCall} disabled={requestingDevices} className="mt-2 rounded-full bg-anouma-mauve-dark px-5 py-3.5 text-sm font-medium transition-all duration-200 hover:-translate-y-0.5 hover:bg-anouma-plum hover:shadow-lg hover:shadow-anouma-mauve-dark/20 active:translate-y-0 active:scale-[0.98] disabled:cursor-wait disabled:opacity-60">
              Meeting beitreten
            </button>
          </div>
        </div>
      </section>
    </main>
  );
}