import { browser } from '$app/environment';
import { SvelteSet, SvelteMap } from 'svelte/reactivity';
import type { StreamSummary } from './types.ts';

const STORAGE_KEY = 'cachedStreams';

export const cached = new SvelteSet<string>(
	browser ? JSON.parse(localStorage.getItem(STORAGE_KEY) || '[]') : []
);
export const downloading = new SvelteMap<string, number>();

if (browser) {
	$effect.root(() => {
		$effect(() => {
			localStorage.setItem(STORAGE_KEY, JSON.stringify([...cached]));
		});
	});
}

export async function download(stream: StreamSummary) {
	const res = await fetch(`/media/tracks/${stream.filename}`);
	if (!res.ok || !res.body) throw new Error('Download failed');

	const total = Number(res.headers.get('content-length') || 0);
	const reader = res.body.getReader();
	const chunks: Uint8Array[] = [];
	let received = 0;

	downloading.set(stream.id, 0);

	while (true) {
		const { done, value } = await reader.read();
		if (done) break;
		chunks.push(value);
		received += value.length;
		if (total) downloading.set(stream.id, Math.round((received / total) * 100));
	}

	const root = await navigator.storage.getDirectory();
	const handle = await root.getFileHandle(stream.id, { create: true });
	const writable = await handle.createWritable();
	await writable.write(new Blob(chunks));
	await writable.close();

	downloading.delete(stream.id);
	cached.add(stream.id);
}

export async function remove(streamId: string) {
	const root = await navigator.storage.getDirectory();
	await root.removeEntry(streamId);
	cached.delete(streamId);
}

export async function getUrl(streamId: string): Promise<string | null> {
	if (!cached.has(streamId)) return null;
	try {
		const root = await navigator.storage.getDirectory();
		const handle = await root.getFileHandle(streamId);
		const file = await handle.getFile();
		return URL.createObjectURL(file);
	} catch {
		cached.delete(streamId);
		return null;
	}
}