package ext

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/gob"
	"errors"
	"io"
)

type Token struct {
	UserID   uint
	Username string
}

func ReadToken(data []byte, key []byte) (*Token, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		panic(err.Error())
	}

	nonceSize := aesgcm.NonceSize()
	if len(data) < nonceSize {
		return nil, errors.New("nonce size greater than data's size")
	}

	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
	plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return nil, err
	}

	r := bytes.NewReader(plaintext)
	var token Token
	dec := gob.NewDecoder(r)
	if err = dec.Decode(&token); err != nil {
		return nil, err
	}
	return &token, nil
}

func WriteToken(token *Token, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

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

	var buffer bytes.Buffer
	enc := gob.NewEncoder(&buffer)
	if err := enc.Encode(token); err != nil {
		return nil, err
	}
	nonce := make([]byte, aesgcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}

	ciphertext := aesgcm.Seal(nonce, nonce, buffer.Bytes(), nil)
	return ciphertext, nil
}