package utils

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"io"
)

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

func HashWithPassphrase(data []byte, key string) string {
	h := hmac.New(sha256.New, []byte(key))
	h.Write([]byte(data))
	return hex.EncodeToString(h.Sum(nil))
}

func ASCEncrypt(data []byte, passphrase string) (string, error) {
	block, _ := aes.NewCipher([]byte(GeneratePassphrase(passphrase)))
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	ciphertext := gcm.Seal(nonce, nonce, data, nil)
	return base64.StdEncoding.EncodeToString(ciphertext), nil
}

func ASCDecrypt(msg, passphrase string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(msg)
	key := []byte(GeneratePassphrase(passphrase))
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonceSize := gcm.NonceSize()
	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return "", err
	}
	return string(plaintext), nil
}