package crypt

import (
	"crypto/cipher"
	"crypto/rand"
	"log"

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

type Crypt struct {
	key  []byte
	ads  []byte
	aead cipher.AEAD
}

func NewChacha20poly1305Key() []byte {
	k := make([]byte, chacha20poly1305.KeySize)
	if _, err := rand.Read(k); err != nil {
		panic(err)
	}
	return k
}

func NewCrypt(key []byte, ads []byte) *Crypt {
	if len(key) == 0 {
		// log.Printf(" == GENERATE NEW KEY ==\n")
		key = NewChacha20poly1305Key()
	}
	aead, err := chacha20poly1305.New(key)
	if err != nil {
		panic(err)
	}
	return &Crypt{key: key, ads: ads, aead: aead}
}

func (c *Crypt) GenNonce(length int) []byte {
	nonce := make([]byte, c.aead.NonceSize(), c.aead.NonceSize()+length+c.aead.Overhead())
	if _, err := rand.Read(nonce); err != nil {
		panic(err)
	}
	return nonce
}

func (c *Crypt) Encrypt(msg []byte) []byte {
	nonce := c.GenNonce(len(msg))
	encryptedMsg := c.aead.Seal(nonce, nonce, msg, c.ads)
	return encryptedMsg
}

func (c *Crypt) Decrypt(encrypted []byte) ([]byte, bool) {
	done := true
	nonce, ciphertext := encrypted[:c.aead.NonceSize()], encrypted[c.aead.NonceSize():]
	plaintext, err := c.aead.Open(nil, nonce, ciphertext, c.ads)
	if err != nil {
		done = false
		log.Printf(" error decrypt data : %v\n", err)
	}
	return plaintext, done
}