package common

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"encoding/hex"
	"time"
)

var CstSh, _ = time.LoadLocation("Asia/Shanghai")

const (
	LocateDateFormat  = "2006-01-02"
	LocateTimeFormat  = "2006-01-02 15:04:05"
	LocateMilliFormat = "2006-01-02 15:04:05.9999"
)

func Date() string {
	return time.Now().In(CstSh).Format(LocateDateFormat)
}

func Now() string {
	return time.Now().In(CstSh).Format(LocateTimeFormat)
}

func NowMilli() string {
	return time.Now().In(CstSh).Format(LocateMilliFormat)
}

func MD5(v []byte) string {
	h := md5.New()
	h.Write(v)
	re := h.Sum(nil)
	return hex.EncodeToString(re)
}

var dbPwKey = []byte("X3O6wVF&6*&lSVk0*504V~q7>\"k]6S'*") // 32 bytes for AES-256
var dbPwNonceHex = "1962a6f6f9999447632c8a34"

func EncryptGCM(key []byte, nonce []byte, plaintext []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

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

	return ciphertext, nil
}

func DecryptGCM(key []byte, nonce []byte, ciphertext []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

	plaintext, err := gcm.Open(nil, nonce, ciphertext, nonce)
	if err != nil {
		return nil, err
	}

	return plaintext, nil
}

func DBPwdEncrypt(ciphertext []byte) ([]byte, error) {
	nonce, _ := hex.DecodeString(dbPwNonceHex)
	return EncryptGCM(dbPwKey, nonce, ciphertext)
}

func DBPwdDecrypt(ciphertext []byte) ([]byte, error) {
	nonce, _ := hex.DecodeString(dbPwNonceHex)
	return DecryptGCM(dbPwKey, nonce, ciphertext)
}