package crypto

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"fmt"
	"io"
)

// AESEncryptor AES-GCM加密器
type AESEncryptor struct {
	key []byte
}

// NewAESEncryptor 创建AES加密器
func NewAESEncryptor(key string) (*AESEncryptor, error) {
	// 使用SHA256生成32字节密钥
	hash := sha256.Sum256([]byte(key))
	return &AESEncryptor{key: hash[:]}, nil
}

func (e *AESEncryptor) Encrypt(plaintext []byte) ([]byte, error) {
	block, err := aes.NewCipher(e.key)
	if err != nil {
		return nil, fmt.Errorf("创建cipher失败: %w", err)
	}

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, fmt.Errorf("创建GCM失败: %w", err)
	}

	nonce := make([]byte, gcm.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, fmt.Errorf("生成nonce失败: %w", err)
	}

	ciphertext := gcm.Seal(nonce, nonce, plaintext, nil)
	return ciphertext, nil
}

func (e *AESEncryptor) Decrypt(ciphertext []byte) ([]byte, error) {
	block, err := aes.NewCipher(e.key)
	if err != nil {
		return nil, fmt.Errorf("创建cipher失败: %w", err)
	}

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, fmt.Errorf("创建GCM失败: %w", err)
	}

	nonceSize := gcm.NonceSize()
	if len(ciphertext) < nonceSize {
		return nil, fmt.Errorf("密文长度不足")
	}

	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return nil, fmt.Errorf("解密失败: %w", err)
	}

	return plaintext, nil
}

func (e *AESEncryptor) Name() string {
	return "AES-GCM-256"
}