package tdesx

import (
	"bytes"
	"crypto/cipher"
	"crypto/des"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"strings"
)

// 3DES-ECB 加密,返回大写的十六进制字符串
func EncryptECBHex(input, key string) (string, error) {
	// 创建3DES加密器
	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", err
	}

	// 对输入数据进行PKCS7填充
	paddedInput := PKCS7Padding([]byte(input), block.BlockSize())

	// ECB模式加密
	encrypted := make([]byte, len(paddedInput))
	for i := 0; i < len(paddedInput); i += des.BlockSize {
		block.Encrypt(encrypted[i:i+des.BlockSize], paddedInput[i:i+des.BlockSize])
	}

	// 转换为十六进制并大写
	result := hex.EncodeToString(encrypted)
	return strings.ToUpper(result), nil
}

// 3DES-ECB 解密,输入大写的十六进制字符串
func DecryptECBHex(encryptedHex, key string) (string, error) {
	encrypted, err := hex.DecodeString(encryptedHex)
	if err != nil {
		return "", fmt.Errorf("hex解码失败: %v", err)
	}

	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", fmt.Errorf("创建3DES解密器失败: %v", err)
	}

	// ECB模式解密
	decrypted := make([]byte, len(encrypted))
	for i := 0; i < len(encrypted); i += des.BlockSize {
		block.Decrypt(decrypted[i:i+des.BlockSize], encrypted[i:i+des.BlockSize])
	}

	// 去除PKCS7填充
	unpaddedData, err := PKCS7UnPadding(decrypted)
	if err != nil {
		return "", fmt.Errorf("去除填充失败: %v", err)
	}
	return string(unpaddedData), nil
}

// 3DES-CBC 加密
func EncryptCBCHex(plaintext, key string) (string, error) {
	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", err
	}
	blockSize := block.BlockSize()
	plainBytes := PKCS7Padding([]byte(plaintext), blockSize)

	// 创建密文字节切片，包含IV空间
	cipherbyte := make([]byte, des.BlockSize+len(plainBytes))

	// 生成随机IV
	iv := cipherbyte[:des.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return "", err
	}

	// 创建CBC模式加密器
	blockMode := cipher.NewCBCEncrypter(block, iv)

	// 加密数据
	blockMode.CryptBlocks(cipherbyte[des.BlockSize:], plainBytes)

	// 转换为十六进制并大写
	result := hex.EncodeToString(cipherbyte)
	return strings.ToUpper(result), nil
}

// 3DES-CBC 解密
func DecryptCBCHex(encryptedHex, key string) (string, error) {
	cipherbyte, err := hex.DecodeString(encryptedHex)
	if err != nil {
		return "", fmt.Errorf("hex解码失败: %v", err)
	}

	if len(cipherbyte) < des.BlockSize {
		return "", errors.New("ciphertext too short")
	}

	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", err
	}

	iv := cipherbyte[:des.BlockSize]
	cipherbyte = cipherbyte[des.BlockSize:]
	if len(cipherbyte)%des.BlockSize != 0 {
		return "", errors.New("ciphertext is not a multiple of the block size")
	}

	blockMode := cipher.NewCBCDecrypter(block, iv)
	origData := make([]byte, len(cipherbyte))
	blockMode.CryptBlocks(origData, cipherbyte)
	origBy, err := PKCS7UnPadding(origData)
	if err != nil {
		return "", err
	}
	return string(origBy), nil
}

// 3DES-CFB 加密
func EncryptCFBHex(plaintext, key string) (string, error) {
	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", err
	}

	// 创建密文字节切片，包含IV空间
	cipherbyte := make([]byte, des.BlockSize+len(plaintext))

	// 生成随机IV
	iv := cipherbyte[:des.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return "", err
	}

	// 创建CFB模式加密器
	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(cipherbyte[des.BlockSize:], []byte(plaintext))

	// 转换为十六进制并大写
	result := hex.EncodeToString(cipherbyte)
	return strings.ToUpper(result), nil
}

// 3DES-CFB 解密
func DecryptCFBHex(encryptedHex, key string) (string, error) {
	cipherbyte, err := hex.DecodeString(encryptedHex)
	if err != nil {
		return "", fmt.Errorf("hex解码失败: %v", err)
	}

	if len(cipherbyte) < des.BlockSize {
		return "", errors.New("ciphertext too short")
	}

	block, err := des.NewTripleDESCipher([]byte(key))
	if err != nil {
		return "", err
	}

	// 获取IV
	iv := cipherbyte[:des.BlockSize]
	cipherbyte = cipherbyte[des.BlockSize:]

	// 创建CFB模式解密器
	stream := cipher.NewCFBDecrypter(block, iv)
	stream.XORKeyStream(cipherbyte, cipherbyte)

	return string(cipherbyte), nil
}

// PKCS7补码
func PKCS7Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}

// 去除PKCS7补码
func PKCS7UnPadding(data []byte) ([]byte, error) {
	length := len(data)
	if length == 0 {
		return nil, errors.New("ciphertext is empty")
	}

	unpadding := int(data[length-1])
	if unpadding > length || unpadding == 0 {
		return nil, errors.New("unpadding size is invalid")
	}

	// 检查填充是否正确
	for i := length - unpadding; i < length; i++ {
		if data[i] != byte(unpadding) {
			return nil, errors.New("invalid padding")
		}
	}

	return data[:(length - unpadding)], nil
}