import type {
	BeatLeaderFollower,
	BeatLeaderLeaderboard,
	BeatLeaderLeaderboardsByHashResponse,
	BeatLeaderPlayer,
	BeatLeaderScore,
	FriendMode,
} from "./types.ts";

interface BeatLeaderLeaderboardScoresResponse {
	scores?: BeatLeaderScore[];
}

const BASE_URL = "https://api.beatleader.com";
const PAGE_SIZE = 100;
/**
 * `/leaderboard/{id}` uses `page` + `count` like v5 scores. Without `count`, the API default page
 * size is small, so `batch.length < PAGE_SIZE` stopped pagination after the first page.
 * `MAX_LEADERBOARD_SCORE_PAGES` bounds total requests for pathological maps.
 */
const MAX_LEADERBOARD_SCORE_PAGES = 2000;
const USE_RUNTIME_PROXY = typeof document !== "undefined";

function beatleaderUrl(path: string): string {
	if (USE_RUNTIME_PROXY) {
		return `/api/beatleader?path=${encodeURIComponent(path)}`;
	}
	return `${BASE_URL}${path}`;
}

export async function fetchBLLeaderboardsByHash(hash: string): Promise<BeatLeaderLeaderboard[]> {
	const path = `/leaderboards/hash/${encodeURIComponent(hash)}`;
	try {
		const res = await fetch(beatleaderUrl(path));
		if (!res.ok) return [];
		const data = await res.json() as BeatLeaderLeaderboardsByHashResponse | BeatLeaderLeaderboard[];
		return Array.isArray(data)
			? data
			: Array.isArray(data.leaderboards)
			? data.leaderboards
			: [];
	} catch {
		return [];
	}
}

export async function fetchBeatLeaderPlayer(playerId: string): Promise<{ id: string; avatar: string | null } | null> {
	const path = `/player/${encodeURIComponent(playerId)}`;
	try {
		const res = await fetch(beatleaderUrl(path));
		if (!res.ok) return null;
		const data = await res.json() as BeatLeaderPlayer;
		const id = data.id == null ? playerId : String(data.id);
		const avatar = typeof data.avatar === "string" ? data.avatar.trim() || null : null;
		return { id, avatar };
	} catch {
		return null;
	}
}

async function resolveBeatLeaderPlayerId(playerId: string): Promise<string> {
	const p = await fetchBeatLeaderPlayer(playerId);
	return p?.id ?? playerId;
}

async function fetchLeaderboardScoresById(
	leaderboardId: string,
	maxPages = MAX_LEADERBOARD_SCORE_PAGES,
): Promise<BeatLeaderScore[]> {
	const scores: BeatLeaderScore[] = [];
	const pageSize = PAGE_SIZE;
	let page = 1;
	for (;;) {
		if (page > maxPages) break;
		const qs = new URLSearchParams({
			leaderboardContext: "general",
			page: String(page),
			sortBy: "rank",
			order: "desc",
			count: String(pageSize),
		});
		const path = `/leaderboard/${encodeURIComponent(leaderboardId)}?${qs}`;
		const url = beatleaderUrl(path);
		let res: Response;
		try {
			res = await fetch(url);
		} catch {
			break;
		}
		if (!res.ok) break;
		const payload = await res.json() as BeatLeaderLeaderboardScoresResponse;
		const batch = Array.isArray(payload.scores) ? payload.scores : [];
		if (batch.length === 0) break;
		scores.push(...batch);
		if (batch.length < pageSize) break;
		page += 1;
	}
	return scores;
}

export async function fetchAllMapScoresByHash(
	hash: string,
	leaderboards: BeatLeaderLeaderboard[],
	maxPagesPerLeaderboard = MAX_LEADERBOARD_SCORE_PAGES,
): Promise<BeatLeaderScore[]> {
	const requests = leaderboards.map((lb) => {
		const leaderboardId = lb.id == null ? null : String(lb.id);
		if (!leaderboardId) return Promise.resolve<BeatLeaderScore[]>([]);
		return fetchLeaderboardScoresById(leaderboardId, maxPagesPerLeaderboard);
	});
	const batches = await Promise.all(requests);
	return batches.flat();
}

async function fetchFollowersPage(
	playerId: string,
	type: "Followers" | "Following",
	page: number,
	count: number,
): Promise<BeatLeaderFollower[]> {
	const qs = new URLSearchParams({
		type,
		page: String(page),
		count: String(count),
	});
	const path = `/player/${encodeURIComponent(playerId)}/followers?${qs}`;
	const url = beatleaderUrl(path);
	try {
		const response = await fetch(url);
		if (!response.ok) return [];
		const data = await response.json() as BeatLeaderFollower[];
		return Array.isArray(data) ? data : [];
	} catch {
		return [];
	}
}

async function fetchAllFollowers(
	playerId: string,
	type: "Followers" | "Following",
	maxPages = 100,
): Promise<BeatLeaderFollower[]> {
	const all: BeatLeaderFollower[] = [];
	for (let page = 1; page <= maxPages; page += 1) {
		const batch = await fetchFollowersPage(playerId, type, page, PAGE_SIZE);
		if (batch.length === 0) break;
		all.push(...batch);
		if (batch.length < PAGE_SIZE) break;
	}
	return all;
}

function normalizeFollowerEntry(entry: BeatLeaderFollower): BeatLeaderFollower {
	return {
		...entry,
		id: String(entry.id),
	};
}

/** Friend list for the given mode, with `avatar` / `name` from BeatLeader follower payloads. */
export async function fetchFriends(playerId: string, mode: FriendMode, maxPages = 100): Promise<BeatLeaderFollower[]> {
	const canonicalPlayerId = await resolveBeatLeaderPlayerId(playerId);
	const [following, followers] = await Promise.all([
		fetchAllFollowers(canonicalPlayerId, "Following", maxPages),
		fetchAllFollowers(canonicalPlayerId, "Followers", maxPages),
	]);
	const followingIds = new Set(following.map((entry) => String(entry.id)));
	if (mode === "following") {
		return following.map((entry) => normalizeFollowerEntry(entry as BeatLeaderFollower));
	}
	if (mode === "followers") {
		return followers.map((entry) => normalizeFollowerEntry(entry as BeatLeaderFollower));
	}
	return followers
		.filter((entry) => followingIds.has(String(entry.id)))
		.map((entry) => normalizeFollowerEntry(entry as BeatLeaderFollower));
}

export function normalizeAccuracy(value: number | null | undefined): number | null {
	if (typeof value !== "number" || !Number.isFinite(value)) return null;
	return value <= 1 ? value * 100 : value;
}