import type { Keypair } from "@atproto/crypto";

type SignatureHeaders = { authorization: string; "signature-input": string; signature: string; "atproto-space-audience"?: string };

export async function spaceSignatureHeaders(key: Keypair, authorization: string, audience?: string) {
	const parameters = audience === undefined
		? `("authorization");keyid="${key.did()}"`
		: '("authorization" "atproto-space-audience")';
	const lines = [`"authorization": ${authorization}`];
	if (audience !== undefined) lines.push(`"atproto-space-audience": ${audience}`);
	lines.push(`"@signature-params": ${parameters}`);
	const signature = await key.sign(new TextEncoder().encode(lines.join("\n")));
	const headers: SignatureHeaders = {
		authorization,
		"signature-input": `atproto-space=${parameters}`,
		signature: `atproto-space=:${btoa(String.fromCharCode(...signature))}:`,
	};
	if (audience !== undefined) headers["atproto-space-audience"] = audience;
	return headers;
}