import { createHmac } from "node:crypto";
import { toHex } from "$lib/markup/paths";
import { signableTarget } from "$lib/server/camotarget";
import { getConfig } from "$lib/server/config";

// null when camo cannot carry the target: no secret configured, or a host the
// worker must not be aimed at
export const camoUrl = (target: string): string | null => {
	let parsed: URL;
	try {
		parsed = new URL(target);
	} catch {
		return null;
	}
	if (parsed.protocol !== "http:" && parsed.protocol !== "https:") return null;
	if (!signableTarget(parsed)) return null;

	const { camoUrl: origin, camoSecret } = getConfig();
	if (!camoSecret) return null;

	const signature = createHmac("sha256", camoSecret).update(target).digest("hex");
	return `${origin}/${signature}/${toHex(target)}`;
};