package utils

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
)

// 将整数转换为固定长度的字符串
func intToFixedLengthString(num int, length int) string {
	return fmt.Sprintf("%0*d", length, num)
}

// 加密函数
func IDEncrypt(plainText, key string) (string, error) {
	block, err := aes.NewCipher([]byte(key))
	if err != nil {
		return "", err
	}

	plainTextBytes := []byte(plainText)
	cipherText := make([]byte, aes.BlockSize+len(plainTextBytes))
	iv := cipherText[:aes.BlockSize]

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

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

	// 使用URL安全的Base64编码
	encrypted := base64.URLEncoding.EncodeToString(cipherText)
	return encrypted, nil
}

// 解密函数
func IDDecrypt(encryptedText, key string) (string, error) {
	cipherText, err := base64.URLEncoding.DecodeString(encryptedText)
	if err != nil {
		return "", err
	}

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

	if len(cipherText) < aes.BlockSize {
		return "", errors.New("cipherText too short")
	}

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

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

	return string(cipherText), nil
}