import { PLAYER_COUNT, type Match, type PreviewChunk, type Round } from '$lib/types';
import { listTree, resolveUrl, type FetchOpts } from '$lib/api/hub';
import { fetchParquetRows } from '$lib/api/parquet';

export type FetchOptions = FetchOpts;

let matchesPromise: Promise<Match[]> | null = null;
let roundsPromise: Promise<Round[]> | null = null;
const matchPreviewsCache = new Map<string, Promise<PreviewChunk[]>>();

// The dataset is sharded by upload batch. Index files are named like
// `index/manifest-<shard_id>.parquet` / `index/rounds-<shard_id>.parquet`.
// Discover them at runtime so new shards don't require a code change.
async function listIndexShards(
	prefix: 'manifest' | 'rounds',
	opts: FetchOptions
): Promise<string[]> {
	const entries = await listTree('index', opts);
	return entries
		.filter((e) => e.type === 'file')
		.map((e) => e.path)
		.filter((p) => {
			const name = p.split('/').pop() ?? '';
			return name.startsWith(`${prefix}-`) && name.endsWith('.parquet');
		});
}

type IndexRow = { match_id: number; map_name: string; uploaded_at: string; round?: number };

async function loadShardedIndex<T extends IndexRow>(
	prefix: 'manifest' | 'rounds',
	opts: FetchOptions
): Promise<T[]> {
	const paths = await listIndexShards(prefix, opts);
	if (!paths.length) return [];
	const shards = await Promise.all(paths.map((p) => fetchParquetRows<T>(resolveUrl(p), opts)));
	// A re-rendered batch produces a second shard whose rows collide with the
	// original on (match,map[,round]). Keep the freshest copy per key.
	const keyOf =
		prefix === 'manifest'
			? (r: T) => `${r.match_id}|${r.map_name}`
			: (r: T) => `${r.match_id}|${r.map_name}|${r.round}`;
	const latest = new Map<string, T>();
	for (const r of shards.flat()) {
		const k = keyOf(r);
		const cur = latest.get(k);
		if (!cur || r.uploaded_at > cur.uploaded_at) latest.set(k, r);
	}
	return Array.from(latest.values());
}

export function listMatches(opts: FetchOptions = {}): Promise<Match[]> {
	if (matchesPromise) return matchesPromise;
	matchesPromise = loadShardedIndex<Match>('manifest', opts)
		.then((rows) => {
			rows.sort(
				(a, b) =>
					new Date(b.match_date).getTime() - new Date(a.match_date).getTime() ||
					(a.map_index ?? 0) - (b.map_index ?? 0)
			);
			return rows;
		})
		.catch((err) => {
			matchesPromise = null;
			throw err;
		});
	return matchesPromise;
}

export async function listAllRounds(opts: FetchOptions = {}): Promise<Round[]> {
	if (!roundsPromise) {
		roundsPromise = loadShardedIndex<Round>('rounds', opts).catch((err) => {
			roundsPromise = null;
			throw err;
		});
	}
	return roundsPromise;
}

export async function listRounds(
	matchId: number,
	mapName: string,
	opts: FetchOptions = {}
): Promise<Round[]> {
	const all = await listAllRounds(opts);
	return all
		.filter((r) => r.match_id === matchId && r.map_name === mapName)
		.sort((a, b) => a.round - b.round);
}

/**
 * Fetch all preview rows for every player on this (match, map) in parallel.
 * The shard_id from the match's manifest row is enough to construct each
 * player's parquet URL — no tree-API discovery needed.
 */
async function loadMatchPreviews(
	matchId: number,
	mapName: string,
	opts: FetchOptions
): Promise<PreviewChunk[]> {
	const key = `${matchId}/${mapName}`;
	const cached = matchPreviewsCache.get(key);
	if (cached) return cached;

	const promise = (async () => {
		const matches = await listMatches(opts);
		const match = matches.find((m) => m.match_id === matchId && m.map_name === mapName);
		if (!match) return [];

		const players = Array.from({ length: PLAYER_COUNT }, (_, i) => i);
		const results = await Promise.all(
			players.map(async (player) => {
				const dir = `data/match_id=${matchId}/map_name=${mapName}/player=${player}`;
				try {
					const rows = await fetchParquetRows<PreviewChunk>(
						resolveUrl(`${dir}/chunks-preview-${match.shard_id}.parquet`),
						opts
					);
					for (const r of rows) r.preview_video = { src: resolveUrl(`${dir}/${r.preview_path}`) };
					return rows;
				} catch {
					return [] as PreviewChunk[];
				}
			})
		);
		return results.flat();
	})().catch((err) => {
		matchPreviewsCache.delete(key);
		throw err;
	});

	matchPreviewsCache.set(key, promise);
	return promise;
}

export async function listRoundPreviews(
	matchId: number,
	mapName: string,
	round: number,
	opts: FetchOptions = {}
): Promise<PreviewChunk[]> {
	const all = await loadMatchPreviews(matchId, mapName, opts);
	return all
		.filter((p) => p.round === round)
		.sort((a, b) => a.player - b.player || a.chunk_index - b.chunk_index);
}