package crypto

import "crypto/aes"

// PKCS7UnPadding removes PKCS#7 padding.
func PKCS7UnPadding(encrypt []byte) []byte {
	length := len(encrypt)
	if length == 0 {
		return encrypt
	}
	unPadding := int(encrypt[length-1])
	if unPadding <= 0 || unPadding > length {
		return encrypt
	}
	return encrypt[:length-unPadding]
}

// DecryptAES128ECB decrypts data with AES-128 ECB (block size 16).
func DecryptAES128ECB(data, key []byte) []byte {
	cipher, err := aes.NewCipher(key)
	if err != nil {
		return nil
	}
	decrypted := make([]byte, len(data))
	size := aes.BlockSize
	for bs, be := 0, size; bs < len(data); bs, be = bs+size, be+size {
		if be > len(data) {
			break
		}
		cipher.Decrypt(decrypted[bs:be], data[bs:be])
	}
	return decrypted
}