package main

import (
	"crypto/rand"
	"fmt"

	"golang.org/x/crypto/chacha20poly1305"
)

func EncryptSym(key []byte, plaintext []byte) ([]byte, error) {
	aead, err := chacha20poly1305.NewX(key)
	if err != nil {
		return nil, err
	}

	nonce := make([]byte, chacha20poly1305.NonceSizeX)
	if _, err := rand.Read(nonce); err != nil {
		return nil, err
	}

	return aead.Seal(nonce, nonce, plaintext, nil), nil
}

func DecryptSym(key []byte, ciphertext []byte) ([]byte, error) {
	aead, err := chacha20poly1305.NewX(key)
	if err != nil {
		return nil, err
	}

	if len(ciphertext) < aead.NonceSize() {
		return nil, fmt.Errorf("ciphertext too short")
	}
	nonce, ciphertext := ciphertext[:aead.NonceSize()], ciphertext[aead.NonceSize():]

	return aead.Open(nil, nonce, ciphertext, nil)
}