package ncrypt

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/des"
	"crypto/rand"
	"errors"
	"io"
)

// ErrUnPadding error
var ErrUnPadding = errors.New("un-padding decrypted data fail")

func GenerateAesKey(key []byte, size int) []byte {
	genKey := make([]byte, size)
	copy(genKey, key)
	for i := size; i < len(key); {
		for j := 0; j < size && i < len(key); j, i = j+1, i+1 {
			genKey[j] ^= key[i]
		}
	}
	return genKey
}

func GenerateDesKey(key []byte) []byte {
	genKey := make([]byte, 8)
	copy(genKey, key)
	for i := 8; i < len(key); {
		for j := 0; j < 8 && i < len(key); j, i = j+1, i+1 {
			genKey[j] ^= key[i]
		}
	}
	return genKey
}

// PKCS5Padding input data
func PKCS5Padding(src []byte, blockSize int) []byte {
	padding := blockSize - len(src)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(src, padText...)
}

// PKCS5UnPadding input data
func PKCS5UnPadding(src []byte) ([]byte, error) {
	length := len(src)
	delLen := int(src[length-1])

	if delLen > length {
		return nil, ErrUnPadding
	}

	// fix: 检查删除的填充是否是一样的字符，不一样说明 delLen 值是有问题的，无法解码
	if delLen > 1 && src[length-1] != src[length-2] {
		return nil, ErrUnPadding
	}

	return src[:length-delLen], nil
}

// PKCS7Padding input data
func PKCS7Padding(src []byte, blockSize int) []byte {
	return PKCS5Padding(src, blockSize)
}

// PKCS7UnPadding input data
func PKCS7UnPadding(src []byte) ([]byte, error) {
	return PKCS5UnPadding(src)
}

// AesEcbEncrypt encrypt data with key use AES ECB algorithm
// len(key) should be 16, 24 or 32.
func AesEcbEncrypt(data, key []byte) []byte {
	size := len(key)
	if size != 16 && size != 24 && size != 32 {
		panic("key length shoud be 16 or 24 or 32")
	}

	length := (len(data) + aes.BlockSize) / aes.BlockSize
	plain := make([]byte, length*aes.BlockSize)

	copy(plain, data)

	pad := byte(len(plain) - len(data))
	for i := len(data); i < len(plain); i++ {
		plain[i] = pad
	}

	encrypted := make([]byte, len(plain))
	cipher, _ := aes.NewCipher(GenerateAesKey(key, size))

	for bs, be := 0, cipher.BlockSize(); bs <= len(data); bs, be = bs+cipher.BlockSize(), be+cipher.BlockSize() {
		cipher.Encrypt(encrypted[bs:be], plain[bs:be])
	}

	return encrypted
}

// AesEcbDecrypt decrypt data with key use AES ECB algorithm
// len(key) should be 16, 24 or 32.
func AesEcbDecrypt(encrypted, key []byte) []byte {
	size := len(key)
	if size != 16 && size != 24 && size != 32 {
		panic("key length should be 16 or 24 or 32")
	}
	cipher, _ := aes.NewCipher(GenerateAesKey(key, size))
	decrypted := make([]byte, len(encrypted))

	for bs, be := 0, cipher.BlockSize(); bs < len(encrypted); bs, be = bs+cipher.BlockSize(), be+cipher.BlockSize() {
		cipher.Decrypt(decrypted[bs:be], encrypted[bs:be])
	}

	trim := 0
	if len(decrypted) > 0 {
		trim = len(decrypted) - int(decrypted[len(decrypted)-1])
	}

	return decrypted[:trim]
}

// AesCbcEncrypt encrypt data with key use AES CBC algorithm
// len(key) should be 16, 24 or 32.
func AesCbcEncrypt(data, key []byte) []byte {
	block, _ := aes.NewCipher(key)
	data = PKCS7Padding(data, block.BlockSize())

	encrypted := make([]byte, aes.BlockSize+len(data))
	iv := encrypted[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(encrypted[aes.BlockSize:], data)

	return encrypted
}

// AesCbcDecrypt decrypt data with key use AES CBC algorithm
// len(key) should be 16, 24 or 32.
func AesCbcDecrypt(encrypted, key []byte) ([]byte, error) {
	block, _ := aes.NewCipher(key)

	iv := encrypted[:aes.BlockSize]
	encrypted = encrypted[aes.BlockSize:]

	mode := cipher.NewCBCDecrypter(block, iv)
	mode.CryptBlocks(encrypted, encrypted)

	return PKCS7UnPadding(encrypted)
}

// AesCtrCrypt encrypt data with key use AES CTR algorithm
// len(key) should be 16, 24 or 32.
func AesCtrCrypt(data, key []byte) []byte {
	block, _ := aes.NewCipher(key)

	iv := bytes.Repeat([]byte("1"), block.BlockSize())
	stream := cipher.NewCTR(block, iv)

	dst := make([]byte, len(data))
	stream.XORKeyStream(dst, data)

	return dst
}

// AesCfbEncrypt encrypt data with key use AES CFB algorithm
// len(key) should be 16, 24 or 32.
func AesCfbEncrypt(data, key []byte) []byte {
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	encrypted := make([]byte, aes.BlockSize+len(data))
	iv := encrypted[:aes.BlockSize]

	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(encrypted[aes.BlockSize:], data)

	return encrypted
}

// AesCfbDecrypt decrypt data with key use AES CFB algorithm
// len(encrypted) should be greater than 16, len(key) should be 16, 24 or 32.
func AesCfbDecrypt(encrypted, key []byte) []byte {
	if len(encrypted) < aes.BlockSize {
		panic("encrypted data is too short")
	}

	block, _ := aes.NewCipher(key)
	iv := encrypted[:aes.BlockSize]
	encrypted = encrypted[aes.BlockSize:]

	stream := cipher.NewCFBDecrypter(block, iv)

	stream.XORKeyStream(encrypted, encrypted)

	return encrypted
}

// AesOfbEncrypt encrypt data with key use AES OFB algorithm
// len(key) should be 16, 24 or 32.
func AesOfbEncrypt(data, key []byte) []byte {
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	data = PKCS7Padding(data, aes.BlockSize)
	encrypted := make([]byte, aes.BlockSize+len(data))
	iv := encrypted[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	stream := cipher.NewOFB(block, iv)
	stream.XORKeyStream(encrypted[aes.BlockSize:], data)

	return encrypted
}

// AesOfbDecrypt decrypt data with key use AES OFB algorithm
// len(key) should be 16, 24 or 32.
func AesOfbDecrypt(data, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	iv := data[:aes.BlockSize]
	data = data[aes.BlockSize:]
	if len(data)%aes.BlockSize != 0 {
		return nil, errors.New("data must % 16")
	}

	decrypted := make([]byte, len(data))
	mode := cipher.NewOFB(block, iv)
	mode.XORKeyStream(decrypted, data)

	return PKCS7UnPadding(decrypted)
}

// DesEcbEncrypt encrypt data with key use DES ECB algorithm
// len(key) should be 8.
func DesEcbEncrypt(data, key []byte) []byte {
	length := (len(data) + des.BlockSize) / des.BlockSize
	plain := make([]byte, length*des.BlockSize)
	copy(plain, data)

	pad := byte(len(plain) - len(data))
	for i := len(data); i < len(plain); i++ {
		plain[i] = pad
	}

	encrypted := make([]byte, len(plain))
	cipher, _ := des.NewCipher(GenerateDesKey(key))

	for bs, be := 0, cipher.BlockSize(); bs <= len(data); bs, be = bs+cipher.BlockSize(), be+cipher.BlockSize() {
		cipher.Encrypt(encrypted[bs:be], plain[bs:be])
	}

	return encrypted
}

// DesEcbDecrypt decrypt data with key use DES ECB algorithm
// len(key) should be 8.
func DesEcbDecrypt(encrypted, key []byte) []byte {
	cipher, _ := des.NewCipher(GenerateDesKey(key))
	decrypted := make([]byte, len(encrypted))

	for bs, be := 0, cipher.BlockSize(); bs < len(encrypted); bs, be = bs+cipher.BlockSize(), be+cipher.BlockSize() {
		cipher.Decrypt(decrypted[bs:be], encrypted[bs:be])
	}

	trim := 0
	if len(decrypted) > 0 {
		trim = len(decrypted) - int(decrypted[len(decrypted)-1])
	}

	return decrypted[:trim]
}

// DesCbcEncrypt encrypt data with key use DES CBC algorithm
// len(key) should be 8.
func DesCbcEncrypt(data, key []byte) []byte {
	block, _ := des.NewCipher(key)
	data = PKCS7Padding(data, block.BlockSize())

	encrypted := make([]byte, des.BlockSize+len(data))
	iv := encrypted[:des.BlockSize]

	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(encrypted[des.BlockSize:], data)

	return encrypted
}

// DesCbcDecrypt decrypt data with key use DES CBC algorithm
// len(key) should be 8.
func DesCbcDecrypt(encrypted, key []byte) ([]byte, error) {
	block, _ := des.NewCipher(key)

	iv := encrypted[:des.BlockSize]
	encrypted = encrypted[des.BlockSize:]

	mode := cipher.NewCBCDecrypter(block, iv)
	mode.CryptBlocks(encrypted, encrypted)

	return PKCS7UnPadding(encrypted)
}

// DesCtrCrypt encrypt data with key use DES CTR algorithm
// len(key) should be 8.
func DesCtrCrypt(data, key []byte) []byte {
	block, _ := des.NewCipher(key)

	iv := bytes.Repeat([]byte("1"), block.BlockSize())
	stream := cipher.NewCTR(block, iv)

	dst := make([]byte, len(data))
	stream.XORKeyStream(dst, data)

	return dst
}

// DesCfbEncrypt encrypt data with key use DES CFB algorithm
// len(key) should be 8.
func DesCfbEncrypt(data, key []byte) []byte {
	block, err := des.NewCipher(key)
	if err != nil {
		panic(err)
	}

	encrypted := make([]byte, des.BlockSize+len(data))
	iv := encrypted[:des.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(encrypted[des.BlockSize:], data)

	return encrypted
}

// DesCfbDecrypt decrypt data with key use DES CFB algorithm
// len(encrypted) should be greater than 16, len(key) should be 8.
func DesCfbDecrypt(encrypted, key []byte) []byte {
	block, _ := des.NewCipher(key)
	if len(encrypted) < des.BlockSize {
		panic("encrypted data is too short")
	}
	iv := encrypted[:des.BlockSize]
	encrypted = encrypted[des.BlockSize:]

	stream := cipher.NewCFBDecrypter(block, iv)
	stream.XORKeyStream(encrypted, encrypted)

	return encrypted
}

// DesOfbEncrypt encrypt data with key use DES OFB algorithm
// len(key) should be 16, 24 or 32.
func DesOfbEncrypt(data, key []byte) []byte {
	block, err := des.NewCipher(key)
	if err != nil {
		panic(err)
	}
	data = PKCS7Padding(data, des.BlockSize)
	encrypted := make([]byte, des.BlockSize+len(data))
	iv := encrypted[:des.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	stream := cipher.NewOFB(block, iv)
	stream.XORKeyStream(encrypted[des.BlockSize:], data)

	return encrypted
}

// DesOfbDecrypt decrypt data with key use DES OFB algorithm
// len(key) should be 8.
func DesOfbDecrypt(data, key []byte) ([]byte, error) {
	block, err := des.NewCipher(key)
	if err != nil {
		panic(err)
	}

	iv := data[:des.BlockSize]
	data = data[des.BlockSize:]
	if len(data)%des.BlockSize != 0 {
		return nil, errors.New("data must % 16")
	}

	decrypted := make([]byte, len(data))
	mode := cipher.NewOFB(block, iv)
	mode.XORKeyStream(decrypted, data)

	return PKCS7UnPadding(decrypted)
}