package xutils

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"crypto/sha1"
	"encoding/base64"
	"encoding/hex"
	"hash/crc32"
	"io/ioutil"
	"os"
)

// Md5 md5()
func Md5(str string) string {
	hash := md5.New()
	hash.Write([]byte(str))
	return hex.EncodeToString(hash.Sum(nil))
}

// Md5File md5_file()
func Md5File(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()

	fi, err := f.Stat()
	if err != nil {
		return "", err
	}

	var size int64 = 1048576 // 1M
	hash := md5.New()

	if fi.Size() < size {
		data, err := ioutil.ReadFile(path)
		if err != nil {
			return "", err
		}
		hash.Write(data)
	} else {
		b := make([]byte, size)
		for {
			n, err := f.Read(b)
			if err != nil {
				break
			}

			hash.Write(b[:n])
		}
	}

	return hex.EncodeToString(hash.Sum(nil)), nil
}

// Sha1 sha1()
func Sha1(str string) string {
	hash := sha1.New()
	hash.Write([]byte(str))
	return hex.EncodeToString(hash.Sum(nil))
}

// Sha1File sha1_file()
func Sha1File(path string) (string, error) {
	data, err := ioutil.ReadFile(path)
	if err != nil {
		return "", err
	}
	hash := sha1.New()
	hash.Write([]byte(data))
	return hex.EncodeToString(hash.Sum(nil)), nil
}

// Crc32 crc32()
func Crc32(str string) uint32 {
	return crc32.ChecksumIEEE([]byte(str))
}

func Base64Encode(str string) string {
	return base64.StdEncoding.EncodeToString([]byte(str))
}

func Base64Decode(str string) (string, error) {
	b, err := base64.StdEncoding.DecodeString(str)
	if err != nil {
		return "", err
	}
	return string(b), err
}

func AesEncryptCBC(origData []byte, key []byte) (encrypted []byte) {
	// 分组秘钥
	// NewCipher该函数限制了输入k的长度必须为16, 24或者32
	block, _ := aes.NewCipher(key)
	blockSize := block.BlockSize()                              // 获取秘钥块的长度
	origData = pkcs5Padding(origData, blockSize)                // 补全码
	blockMode := cipher.NewCBCEncrypter(block, key[:blockSize]) // 加密模式
	encrypted = make([]byte, len(origData))                     // 创建数组
	blockMode.CryptBlocks(encrypted, origData)                  // 加密
	return encrypted
}

func AesDecryptCBC(encrypted []byte, key []byte) (decrypted []byte) {
	block, _ := aes.NewCipher(key)                              // 分组秘钥
	blockSize := block.BlockSize()                              // 获取秘钥块的长度
	blockMode := cipher.NewCBCDecrypter(block, key[:blockSize]) // 加密模式
	decrypted = make([]byte, len(encrypted))                    // 创建数组
	blockMode.CryptBlocks(decrypted, encrypted)                 // 解密
	decrypted = pkcs5UnPadding(decrypted)                       // 去除补全码
	return decrypted
}

func pkcs5UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}

func pkcs5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}