import "server-only";

import { resolveImagerBase } from "@/lib/runtime-asset-config";

export const FIGURE_RE = /^[a-z]{2}-\d+(?:-\d+)*(?:\.[a-z]{2}-\d+(?:-\d+)*)*$/i;
export const FIGURE_MAX_LEN = 512;
export const FIGURE_MAX_PARTS = 24;

const HABBO_PUBLIC_UPSTREAM = "https://www.habbo.com/habbo-imaging/avatarimage";

const PRIMARY_TIMEOUT_MS = 10_000;
const FALLBACK_TIMEOUT_MS = 6_000;

export type ImagerSource = "primary" | "fallback";

export interface ImagerResult {
	body: Uint8Array;
	contentType: string;
	source: ImagerSource;
}

export type AvatarQuery =
	| { ok: true; params: URLSearchParams }
	| { ok: false; message: string };

export class ImagerUnavailableError extends Error {
	constructor(message = "Avatar imager unavailable") {
		super(message);
		this.name = "ImagerUnavailableError";
	}
}

export function parseAvatarQuery(searchParams: URLSearchParams): AvatarQuery {
	const figure = (
		searchParams.get("figure") ??
		searchParams.get("look") ??
		""
	).trim();
	if (!figure) return { ok: false, message: "Missing figure parameter" };
	if (figure.length > FIGURE_MAX_LEN || !FIGURE_RE.test(figure))
		return { ok: false, message: "Invalid figure format" };
	if (figure.split(".").length > FIGURE_MAX_PARTS)
		return { ok: false, message: "Figure has too many parts" };

	const sizeParam = searchParams.get("size");
	const size: "s" | "m" | "l" =
		sizeParam === "s" || sizeParam === "l" ? sizeParam : "m";

	const direction = clampInt(searchParams.get("direction"), 0, 7, 2);
	const headDirection = clampInt(
		searchParams.get("head_direction") ?? searchParams.get("headDirection"),
		0,
		7,
		3,
	);
	const headOnly =
		searchParams.get("headonly") === "1" ||
		searchParams.get("headOnly") === "1";
	const gesture = searchParams.get("gesture") ?? undefined;
	const action = searchParams.get("action") ?? undefined;
	const effect = searchParams.get("effect") ?? undefined;

	const params = new URLSearchParams({
		figure,
		direction: String(direction),
		head_direction: String(headDirection),
		size,
		img_format: "png",
	});
	if (headOnly) params.set("headonly", "1");
	if (gesture) params.set("gesture", gesture);
	if (action) params.set("action", action);
	if (effect) params.set("effect", effect);

	const imgFormat = searchParams.get("img_format");
	if (imgFormat) params.set("img_format", imgFormat);

	return { ok: true, params };
}

export async function fetchAvatarImage(
	origin: string,
	params: URLSearchParams,
): Promise<ImagerResult> {
	const primary = resolveImagerBase(origin);
	const primaryResult = await fetchUpstream(
		primary,
		params,
		PRIMARY_TIMEOUT_MS,
	);
	if (primaryResult) return { ...primaryResult, source: "primary" };

	if (isSameUpstream(primary, HABBO_PUBLIC_UPSTREAM)) {
		throw new ImagerUnavailableError(
			"Configured imager is already the fallback upstream",
		);
	}

	const fallbackResult = await fetchUpstream(
		HABBO_PUBLIC_UPSTREAM,
		buildFallbackParams(params),
		FALLBACK_TIMEOUT_MS,
	);
	if (fallbackResult) return { ...fallbackResult, source: "fallback" };

	throw new ImagerUnavailableError();
}

async function fetchUpstream(
	baseUrl: string,
	params: URLSearchParams,
	timeoutMs: number,
): Promise<Omit<ImagerResult, "source"> | null> {
	const url = new URL(baseUrl);
	for (const [key, value] of params) url.searchParams.set(key, value);

	try {
		const res = await fetch(url, {
			signal: AbortSignal.timeout(timeoutMs),
			cache: "no-store",
			headers: {
				"User-Agent":
					"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36",
			},
		});
		if (!res.ok) return null;
		return {
			body: new Uint8Array(await res.arrayBuffer()),
			contentType: res.headers.get("content-type") || "image/png",
		};
	} catch {
		return null;
	}
}

function buildFallbackParams(params: URLSearchParams): URLSearchParams {
	const fallback = new URLSearchParams(params);
	// The public Habbo renderer has no effect rendering support.
	fallback.delete("effect");
	// The public Habbo renderer emits PNG/GIF, not APNG.
	fallback.set("img_format", "png");
	return fallback;
}

function isSameUpstream(a: string, b: string): boolean {
	const normalize = (value: string) =>
		value.replace(/\/+$/, "").replace(/^https?:/, "");
	return normalize(a) === normalize(b);
}

function clampInt(
	raw: string | null,
	min: number,
	max: number,
	fallback: number,
): number {
	if (raw == null) return fallback;
	const n = Number.parseInt(raw, 10);
	if (Number.isNaN(n) || n < min || n > max) return fallback;
	return n;
}