"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { motion } from "framer-motion";
import { usePathname } from "next/navigation";

import { MusicIcon, PauseIcon, PlayIcon, XIcon } from "@/components/icons";
import { aeroMusicEnabled, dismissAeroMusic } from "@/lib/aero-music";
import { useI18n } from "@/lib/i18n";
import { useTheme } from "@/lib/theme";
import { cn } from "@/lib/utils";

/**
 * Frutiger Aero's soundtrack. The theme is the opt-in: selecting it starts a
 * random track from the Frutiger Aero playlist (Bigblamboii's set on
 * SoundCloud) and every later track is drawn at random too, so the playlist
 * shuffles itself.
 *
 * Collapsed it is a glass circle with a note; expanded it becomes the credit
 * bar from the mock — pause, the track's own title, and "SoundCloud · artist".
 * The embed is only ever created while Aero is on and the listener has not
 * turned it off (see lib/aero-music); the player pauses, it never resumes on
 * its own after a reload, because browsers require a gesture for that.
 */

const PLAYLIST_URL = "https://soundcloud.com/rustie-gamer/sets/frutiger-aero";
const API_SRC = "https://w.soundcloud.com/player/api.js";
/** Fallbacks until the widget reports the first track (the playlist's own). */
const FALLBACK_TITLE = "Frutiger Aero";
const FALLBACK_ARTIST = "SoundCloud · Bigblamboii";
/** Background music, not a concert. */
const VOLUME = 45;

type SoundCloudSound = { title?: string; user?: { username?: string } };

type SoundCloudWidget = {
  bind: (event: string, handler: () => void) => void;
  getSounds: (handler: (sounds: SoundCloudSound[]) => void) => void;
  getCurrentSound: (handler: (sound: SoundCloudSound | null) => void) => void;
  skip: (index: number) => void;
  play: () => void;
  pause: () => void;
  setVolume: (volume: number) => void;
};

type SoundCloudApi = {
  Widget: {
    (element: HTMLIFrameElement, options?: Record<string, unknown>): SoundCloudWidget;
    Events: { READY: string; PLAY: string; PAUSE: string; FINISH: string };
  };
};

declare global {
  interface Window {
    SC?: SoundCloudApi;
  }
}

let apiPromise: Promise<SoundCloudApi | null> | null = null;

/** The widget API script, fetched once per page and shared by every mount. */
function loadSoundCloudApi(): Promise<SoundCloudApi | null> {
  if (typeof window === "undefined") return Promise.resolve(null);
  if (window.SC) return Promise.resolve(window.SC);
  apiPromise ??= new Promise<SoundCloudApi | null>((resolve) => {
    const script = document.createElement("script");
    script.src = API_SRC;
    script.async = true;
    script.onload = () => resolve(window.SC ?? null);
    /* No network (offline, blocked): the player just never becomes ready. */
    script.onerror = () => resolve(null);
    document.head.appendChild(script);
  });
  return apiPromise;
}

export function AeroMusic() {
  const { t } = useI18n();
  const { theme } = useTheme();
  const pathname = usePathname();
  const iframe = useRef<HTMLIFrameElement>(null);
  const widget = useRef<SoundCloudWidget | null>(null);
  const trackCount = useRef(0);
  const [allowed, setAllowed] = useState(false);
  const [expanded, setExpanded] = useState(false);
  const [playing, setPlaying] = useState(false);
  const [ready, setReady] = useState(false);
  const [track, setTrack] = useState<{ title: string; artist: string } | null>(null);

  useEffect(() => {
    if (theme === "aero") setAllowed(aeroMusicEnabled());
  }, [theme]);

  const show = theme === "aero" && allowed;

  /** A random index of the playlist, so no two runs open on the same song. */
  const randomIndex = () => Math.floor(Math.random() * Math.max(1, trackCount.current));

  const refreshTrack = useCallback(() => {
    widget.current?.getCurrentSound((sound) => {
      if (!sound) return;
      setTrack({
        title: sound.title ?? FALLBACK_TITLE,
        artist: `SoundCloud · ${sound.user?.username ?? "Bigblamboii"}`,
      });
    });
  }, []);

  const playRandom = useCallback(
    (index?: number) => {
      const target = index ?? randomIndex();
      widget.current?.skip(target);
      widget.current?.play();
      refreshTrack();
    },
    [refreshTrack],
  );

  useEffect(() => {
    if (!show) return;
    const element = iframe.current;
    if (!element) return;
    let cancelled = false;
    void loadSoundCloudApi().then((api) => {
      if (cancelled || !api) return;
      const instance = api.Widget(element);
      widget.current = instance;
      const { READY, PLAY, PAUSE, FINISH } = api.Widget.Events;
      instance.bind(READY, () => {
        if (cancelled) return;
        setReady(true);
        instance.setVolume(VOLUME);
        instance.getSounds((sounds) => {
          if (cancelled) return;
          trackCount.current = sounds.length;
          /* A gesture selected the theme, so this usually plays right away;
             if the browser refuses (a reload with no gesture), the circle
             stays paused until the listener taps it. */
          playRandom();
        });
      });
      instance.bind(PLAY, () => {
        setPlaying(true);
        refreshTrack();
      });
      instance.bind(PAUSE, () => setPlaying(false));
      /* Shuffle onward: every track is drawn at random, not in order. */
      instance.bind(FINISH, () => playRandom());
    });
    return () => {
      cancelled = true;
      widget.current = null;
    };
  }, [show, playRandom, refreshTrack]);

  if (!show) return null;

  const title = track?.title ?? FALLBACK_TITLE;
  const artist = track?.artist ?? FALLBACK_ARTIST;

  /* The composer sits at the bottom of the chat screen and the wizard has its
     own action bar; everywhere else the phone tab bar is the only neighbour. */
  const raised = pathname === "/chat" ? "chat" : pathname === "/create" || pathname === "/homework" ? "wizard" : undefined;

  return (
    <div className="aero-music" data-testid="aero-music" data-raised={raised}>
      {/* The embed itself: 1px and inert, it is only the audio engine. */}
      <iframe
        ref={iframe}
        title={t("aero.music")}
        aria-hidden="true"
        tabIndex={-1}
        allow="autoplay; encrypted-media"
        scrolling="no"
        frameBorder="no"
        src={`https://w.soundcloud.com/player/?url=${encodeURIComponent(PLAYLIST_URL)}&auto_play=false&hide_related=true&show_comments=false&show_user=true&show_reposts=false&show_teaser=false&visual=false&color=%2338bdf8`}
        className="pointer-events-none absolute size-px opacity-0"
      />

      {expanded ? (
        <motion.div
          initial={{ opacity: 0, y: 8, scale: 0.96 }}
          animate={{ opacity: 1, y: 0, scale: 1 }}
          transition={{ duration: 0.18, ease: [0.22, 1, 0.36, 1] }}
          className="glass-pill flex max-w-[min(20rem,calc(100vw-1.5rem))] items-center gap-3 rounded-full py-1.5 pl-1.5 pr-1.5"
        >
          <button
            type="button"
            onClick={() => {
              if (playing) {
                widget.current?.pause();
                return;
              }
              /* Resume where it stopped; the random draw is for starts. */
              widget.current?.play();
              refreshTrack();
            }}
            aria-label={playing ? t("aero.musicPause") : t("aero.musicPlay")}
            title={playing ? t("aero.musicPause") : t("aero.musicPlay")}
            className="touch-target grid size-11 shrink-0 place-items-center rounded-full bg-[var(--text)] text-[var(--page)] transition hover:opacity-90"
          >
            {playing ? <PauseIcon className="size-4" /> : <PlayIcon className="size-4" />}
          </button>
          <button
            type="button"
            onClick={() => setExpanded(false)}
            aria-label={t("aero.musicCollapse")}
            title={t("aero.musicCollapse")}
            className="min-w-0 flex-1 py-1 text-left"
          >
            <p className="truncate text-[13px] font-semibold leading-tight text-[var(--text)]">
              {ready ? title : t("aero.musicLoading")}
            </p>
            <p className="truncate text-[11.5px] leading-tight text-[var(--text-muted)]">{artist}</p>
          </button>
          <button
            type="button"
            onClick={() => {
              widget.current?.pause();
              dismissAeroMusic();
              setAllowed(false);
            }}
            aria-label={t("aero.musicClose")}
            title={t("aero.musicClose")}
            className="touch-target grid size-11 shrink-0 place-items-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)] sm:size-8"
          >
            <XIcon className="size-3.5" />
          </button>
        </motion.div>
      ) : (
        <button
          type="button"
          onClick={() => setExpanded(true)}
          aria-label={t("aero.music")}
          title={t("aero.music")}
          className="glass-pill touch-target grid size-11 place-items-center rounded-full"
        >
          <MusicIcon className={cn("size-5", playing ? "text-accent-700 dark:text-accent-200" : "text-[var(--text-muted)]")} />
        </button>
      )}
    </div>
  );
}

/** Exported for the suite: the playlist the widget must point at. */
export const AERO_PLAYLIST_URL = PLAYLIST_URL;