/*
Copyright © 2024 Brian Buller <brian@bullercodeworks.com>
*/
package util

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

func GenTodayKey() string {
	key := []byte(time.Now().Format(fmt.Sprintf("%s%s%s  ", time.DateOnly, time.DateOnly, time.DateOnly)))
	return hex.EncodeToString(key) //convert to string for saving
}

func Encrypt(key, input string) (string, error) {
	btKey, _ := hex.DecodeString(key)
	plaintext := []byte(input)

	// Create a new Cipher Block from the key
	block, err := aes.NewCipher(btKey)
	if err != nil {
		return "", err
	}

	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
	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:], plaintext)

	// Convert to base64
	return base64.URLEncoding.EncodeToString(ciphertext), nil
}

func Decrypt(key, input string) (string, error) {
	btKey, _ := hex.DecodeString(key)
	ciphertext, _ := base64.URLEncoding.DecodeString(input)

	block, err := aes.NewCipher(btKey)
	if err != nil {
		return "", err
	}

	if len(ciphertext) < aes.BlockSize {
		return "", errors.New("ciphertext is too short")
	}
	iv := ciphertext[:aes.BlockSize]
	ciphertext = ciphertext[aes.BlockSize:]

	stream := cipher.NewCFBDecrypter(block, iv)

	// XORKeyStream can work in-place if the two arguments are the same.
	stream.XORKeyStream(ciphertext, ciphertext)

	return fmt.Sprintf("%s", ciphertext), nil
}