// phone.go
package crypto

import (
	"crypto/aes"
	"crypto/cipher"
	"encoding/base64"
	"errors"
	"strings"
)

var (
	aesKey = []byte("FSMTjRoFVOzugwDJgxTPlVIEEqUYqyhJ")
	// 使用固定的 IV
	iv = []byte("0123456789abcdef")
)

type PhoneEncryptionService struct {
}

func NewPhoneEncryptionService() *PhoneEncryptionService {
	return &PhoneEncryptionService{}
}

// Encrypt 使用 AES-CBC 加密手机号
func (s *PhoneEncryptionService) Encrypt(phone string) (string, error) {
	if phone == "" {
		return "", nil
	}

	// 创建 AES cipher
	block, err := aes.NewCipher(aesKey)
	if err != nil {
		return "", err
	}

	// 创建 CBC 加密器
	mode := cipher.NewCBCEncrypter(block, iv)

	// 填充数据
	plaintext := []byte(phone)
	padding := aes.BlockSize - len(plaintext)%aes.BlockSize
	padtext := make([]byte, len(plaintext)+padding)
	copy(padtext, plaintext)
	for i := len(plaintext); i < len(padtext); i++ {
		padtext[i] = byte(padding)
	}

	// 加密
	ciphertext := make([]byte, len(padtext))
	mode.CryptBlocks(ciphertext, padtext)

	// Base64编码
	encoded := base64.StdEncoding.EncodeToString(ciphertext)
	return encoded, nil
}

// Decrypt 解密手机号
func (s *PhoneEncryptionService) Decrypt(encryptedPhone string) (string, error) {
	if encryptedPhone == "" {
		return "", nil
	}

	// Base64解码
	ciphertext, err := base64.StdEncoding.DecodeString(encryptedPhone)
	if err != nil {
		return "", err
	}

	// 创建 AES cipher
	block, err := aes.NewCipher(aesKey)
	if err != nil {
		return "", err
	}

	// 创建 CBC 解密器
	mode := cipher.NewCBCDecrypter(block, iv)

	// 解密
	plaintext := make([]byte, len(ciphertext))
	mode.CryptBlocks(plaintext, ciphertext)

	// 去除填充
	padding := int(plaintext[len(plaintext)-1])
	if padding > aes.BlockSize || padding == 0 {
		return "", errors.New("无效的填充")
	}
	for i := len(plaintext) - padding; i < len(plaintext); i++ {
		if int(plaintext[i]) != padding {
			return "", errors.New("无效的填充")
		}
	}

	return string(plaintext[:len(plaintext)-padding]), nil
}

func (s *PhoneEncryptionService) StringPhone(encryptedPhone string) (string, error) {
	p, err := s.Decrypt(encryptedPhone)
	if err != nil {
		return "", err
	}
	a := strings.Join(strings.Split(p, "")[:3], "") + "****" + strings.Join(strings.Split(p, "")[7:], "")
	return a, nil
}