/* Encrypts input where each byte is XOR'd with the previous encrypted byte.
 * @alias  module:tplink-smarthome-crypto.encrypt
 * @param  {(Buffer|string)} input           Buffer/string to encrypt
 * @param  {number} [firstKey=0xAB]
 * @return {Buffer}                 encrypted buffer
 */
export const encrypt = (input, firstKey = 0xab) => {
	const buf = Buffer.from(input);
	let key = firstKey;
	for (let i = 0; i < buf.length; i++) {
		buf[i] = buf[i] ^ key;
		key = buf[i];
	}
	return buf;
};

/**
 * Decrypts input where each byte is XOR'd with the previous encrypted byte.
 * @alias  module:tplink-smarthome-crypto.decrypt
 * @param  {Buffer} input           encrypted Buffer
 * @param  {number} [firstKey=0xAB]
 * @return {Buffer}                 decrypted buffer
 */
export function decrypt(input, firstKey = 0xab) {
	const buf = Buffer.from(input);
	let key = firstKey;
	let nextKey;
	for (let i = 0; i < buf.length; i++) {
		nextKey = buf[i];
		buf[i] = buf[i] ^ key;
		key = nextKey;
	}
	return buf;
}