import { browser } from '$app/environment';
import { HUES, accentForHue, gradientForHue } from '$lib/theme/color';
import { extractAccent, type Accent } from '$lib/theme/palette';

export interface PlayerTrack {
	id: string | number;
	title: string;
	artist: string;
	duration: number;
	hue: number;
}

export interface Playlist {
	id: string | number;
	name: string;
	trackIds: (string | number)[];
}

export interface QueueItem {
	id: string | number;
	title: string;
	artist?: string;
}

const RECENT_LIMIT = 15;

const EMPTY: PlayerTrack = { id: '', title: '', artist: '', duration: 0, hue: HUES[0] };

function hueFor(id: string | number): number {
	const text = String(id);
	let hash = 0;
	for (let i = 0; i < text.length; i++) hash = (hash * 31 + text.charCodeAt(i)) >>> 0;
	return HUES[hash % HUES.length];
}

function toTrack(item: QueueItem): PlayerTrack {
	return {
		id: item.id,
		title: item.title,
		artist: item.artist ?? '',
		duration: 0,
		hue: hueFor(item.id)
	};
}

class PlayerState {
	tracks = $state<PlayerTrack[]>([]);
	currentId = $state<string | number | null>(null);
	playing = $state(false);
	progress = $state(0);
	volume = $state(
		browser ? Number(localStorage.getItem("player.volume") ?? 100) : 100
	);
	loading = $state(false);
	error = $state('');
	recentlyPlayed = $state<PlayerTrack[]>([]);
	playlists = $state<Playlist[]>([]);

	accentColor = $state<string | null>(null);
	gradientColor = $state<string | null>(null);

	#audio: HTMLAudioElement | null = null;
	#loadToken = 0;
	#accentCache = new Map<string, Accent>();
	#rafId: number | null = null;

	current = $derived(this.tracks.find((t) => t.id === this.currentId) ?? EMPTY);
	accent = $derived(this.accentColor ?? accentForHue(this.current.hue));
	artGradient = $derived(this.gradientColor ?? gradientForHue(this.current.hue));
	progressPercent = $derived(
		this.current.duration > 0 ? Math.min(100, (this.progress / this.current.duration) * 100) : 0
	);

	get isPlaying() {
		return this.playing;
	}

	#audioEl(): HTMLAudioElement | null {
		if (!browser) return null;
		if (this.#audio) return this.#audio;
		const audio = new Audio();
		audio.preload = 'auto';
		audio.volume = this.volume / 100;
		audio.addEventListener('durationchange', () => this.#syncDuration(audio.duration));
		audio.addEventListener('loadedmetadata', () => this.#syncDuration(audio.duration));
		audio.addEventListener('play', () => {
			this.playing = true;
			this.#startProgressLoop();
		});
		audio.addEventListener('pause', () => {
			this.playing = false;
			this.#stopProgressLoop();
		});
		audio.addEventListener('ended', () => {
			this.#stopProgressLoop();
			this.next();
		});
		audio.addEventListener('error', () => {
			this.#stopProgressLoop();
			this.loading = false;
			this.playing = false;
			this.error = 'No se pudo reproducir la pista.';
		});
		this.#audio = audio;
		return audio;
	}

	#tickProgress = () => {
		const audio = this.#audio;
		if (!audio) return;
		this.progress = audio.currentTime;
		this.#rafId = requestAnimationFrame(this.#tickProgress);
	};

	#startProgressLoop() {
		if (this.#rafId !== null) return;
		this.#rafId = requestAnimationFrame(this.#tickProgress);
	}

	#stopProgressLoop() {
		if (this.#rafId === null) return;
		cancelAnimationFrame(this.#rafId);
		this.#rafId = null;
	}

	#syncDuration(value: number) {
		if (!Number.isFinite(value) || value <= 0) return;
		const id = this.currentId;
		this.tracks = this.tracks.map((t) =>
			t.id === id ? { ...t, duration: Math.round(value) } : t
		);
	}

	#index() {
		return this.tracks.findIndex((t) => t.id === this.currentId);
	}

	#pushRecent(track: PlayerTrack) {
		if (!track.id) return;
		this.recentlyPlayed = [track, ...this.recentlyPlayed.filter((t) => t.id !== track.id)].slice(
			0,
			RECENT_LIMIT
		);
	}

	async #applyAccent(id: string | number) {
		const key = String(id);
		const cached = this.#accentCache.get(key);
		if (cached) {
			this.accentColor = cached.accent;
			this.gradientColor = cached.gradient;
			return;
		}
		const result = await extractAccent(`/api/tracks/${id}/cover?size=small`);
		if (this.currentId !== id) return;
		if (result) {
			this.#accentCache.set(key, result);
			this.accentColor = result.accent;
			this.gradientColor = result.gradient;
		} else {
			this.accentColor = null;
			this.gradientColor = null;
		}
	}

	async #loadCurrent() {
		const audio = this.#audioEl();
		if (!audio || this.currentId === null) return;
		const id = this.currentId;
		this.#applyAccent(id);
		const token = ++this.#loadToken;
		this.loading = true;
		this.error = '';
		this.progress = 0;
		try {
			const res = await fetch(`/api/tracks/${id}/stream`);
			if (!res.ok) throw new Error(String(res.status));
			const { manifestUrl, ticket } = (await res.json()) as {
				manifestUrl: string;
				ticket: string;
			};
			if (token !== this.#loadToken) return;
			const sep = manifestUrl.includes('?') ? '&' : '?';
			audio.src = ticket ? `${manifestUrl}${sep}t=${encodeURIComponent(ticket)}` : manifestUrl;
			audio.volume = this.volume / 100;
			await audio.play();
			this.loading = false;
			this.#pushRecent(this.current);
		} catch {
			if (token !== this.#loadToken) return;
			this.loading = false;
			this.playing = false;
			this.error = 'No se pudo reproducir la pista.';
		}
	}

	playlistTracks(ids: (string | number)[]): PlayerTrack[] {
		return ids
			.map((id) => this.tracks.find((t) => t.id === id))
			.filter((t): t is PlayerTrack => Boolean(t));
	}

	mosaicFor(ids: (string | number)[]): string[] {
		const gradients = this.playlistTracks(ids)
			.slice(0, 4)
			.map((t) => gradientForHue(t.hue));
		while (gradients.length < 4) gradients.push('var(--mf-surface)');
		return gradients;
	}

	playQueue(list: QueueItem[], startIndex = 0) {
		if (list.length === 0) return;
		this.tracks = list.map(toTrack);
		const start = this.tracks[startIndex] ?? this.tracks[0];
		this.currentId = start.id;
		this.#loadCurrent();
	}

	playTrack(id: string | number) {
		if (this.currentId === id) {
			this.toggle();
			return;
		}
		const known =
			this.tracks.find((t) => t.id === id) ?? this.recentlyPlayed.find((t) => t.id === id);
		if (known && !this.tracks.some((t) => t.id === id)) {
			this.tracks = [known];
		}
		if (!this.tracks.some((t) => t.id === id)) return;
		this.currentId = id;
		this.#loadCurrent();
	}

	playPlaylist(id: string | number) {
		const playlist = this.playlists.find((p) => p.id === id);
		if (!playlist) return;
		const items = this.playlistTracks(playlist.trackIds);
		if (items.length > 0) this.playQueue(items, 0);
	}

	toggle() {
		const audio = this.#audioEl();
		if (!audio || this.currentId === null) return;
		if (audio.paused) audio.play().catch(() => {});
		else audio.pause();
	}

	next() {
		if (this.tracks.length === 0) return;
		const idx = this.#index();
		this.currentId = this.tracks[(idx + 1) % this.tracks.length].id;
		this.#loadCurrent();
	}

	previous() {
		if (this.tracks.length === 0) return;
		const audio = this.#audioEl();
		if (audio && audio.currentTime > 3) {
			audio.currentTime = 0;
			return;
		}
		const idx = this.#index();
		this.currentId = this.tracks[(idx - 1 + this.tracks.length) % this.tracks.length].id;
		this.#loadCurrent();
	}

	seekFraction(fraction: number) {
		const audio = this.#audioEl();
		const clamped = Math.min(1, Math.max(0, fraction));
		const target = clamped * this.current.duration;
		this.progress = target;
		if (audio && Number.isFinite(audio.duration)) audio.currentTime = target;
	}

	setVolume(value: number) {
		this.volume = Math.min(100, Math.max(0, Math.round(value)));
		const audio = this.#audioEl();
		if (audio) {
			audio.volume = this.volume / 100;
			localStorage.setItem("player.volume", String(this.volume));
		}
	}
}

export const player = new PlayerState();