// Copyright (c) Mysten Labs, Inc.
// SPDX-License-Identifier: Apache-2.0
export type DescriptorInput = {
	data: Buffer;
	signature: Buffer;
};

function buildTLV(tag: Buffer, value: Buffer): Buffer {
	const length = value.length;

	if (length > 0xff) {
		throw new Error('Value length exceeds 255 bytes');
	}

	return Buffer.concat([tag, new Uint8Array([length]), value]);
}

export function buildDescriptor({ data, signature }: DescriptorInput): Buffer {
	const SIGNATURE_TAG = Buffer.from(new Uint8Array([0x08]));
	const descriptor = Buffer.concat([data, buildTLV(SIGNATURE_TAG, signature)]);
	const descriptorLength = Buffer.from(new Uint16Array([descriptor.length]).buffer);
	return Buffer.concat([descriptorLength, descriptor]);
}