package utils

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"io"

	"github.com/authorizerdev/authorizer/server/constants"
	"github.com/authorizerdev/authorizer/server/envstore"
	"golang.org/x/crypto/bcrypt"
)

// EncryptB64 encrypts data into base64 string
func EncryptB64(text string) string {
	return base64.StdEncoding.EncodeToString([]byte(text))
}

// DecryptB64 decrypts from base64 string to readable string
func DecryptB64(s string) (string, error) {
	data, err := base64.StdEncoding.DecodeString(s)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

// EncryptAES encrypts data using AES algorithm
func EncryptAES(text []byte) ([]byte, error) {
	key := []byte(envstore.EnvInMemoryStoreObj.GetStringStoreEnvVariable(constants.EnvKeyEncryptionKey))
	c, err := aes.NewCipher(key)
	var res []byte
	if err != nil {
		return res, err
	}

	// gcm or Galois/Counter Mode, is a mode of operation
	// for symmetric key cryptographic block ciphers
	// - https://en.wikipedia.org/wiki/Galois/Counter_Mode
	gcm, err := cipher.NewGCM(c)
	if err != nil {
		return res, err
	}

	// creates a new byte array the size of the nonce
	// which must be passed to Seal
	nonce := make([]byte, gcm.NonceSize())
	// populates our nonce with a cryptographically secure
	// random sequence
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return res, err
	}

	// here we encrypt our text using the Seal function
	// Seal encrypts and authenticates plaintext, authenticates the
	// additional data and appends the result to dst, returning the updated
	// slice. The nonce must be NonceSize() bytes long and unique for all
	// time, for a given key.
	return gcm.Seal(nonce, nonce, text, nil), nil
}

// DecryptAES decrypts data using AES algorithm
func DecryptAES(ciphertext []byte) ([]byte, error) {
	key := []byte(envstore.EnvInMemoryStoreObj.GetStringStoreEnvVariable(constants.EnvKeyEncryptionKey))
	c, err := aes.NewCipher(key)
	var res []byte
	if err != nil {
		return res, err
	}

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

	nonceSize := gcm.NonceSize()
	if len(ciphertext) < nonceSize {
		return res, err
	}

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

	return plaintext, nil
}

// EncryptEnvData is used to encrypt the env data
func EncryptEnvData(data envstore.Store) (string, error) {
	jsonBytes, err := json.Marshal(data)
	if err != nil {
		return "", err
	}

	envStoreObj := envstore.EnvInMemoryStoreObj.GetEnvStoreClone()

	err = json.Unmarshal(jsonBytes, &envStoreObj)
	if err != nil {
		return "", err
	}

	configData, err := json.Marshal(envStoreObj)
	if err != nil {
		return "", err
	}
	encryptedConfig, err := EncryptAES(configData)
	if err != nil {
		return "", err
	}

	return EncryptB64(string(encryptedConfig)), nil
}

// EncryptPassword is used for encrypting password
func EncryptPassword(password string) (string, error) {
	pw, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}

	return string(pw), nil
}