// Creates a configuration with the Auth0 information
secret, _ := base64.URLEncoding.DecodeString(os.Getenv("AUTH0_CLIENT_SECRET"))
secretProvider := auth0.NewKeyProvider(secret)
audience := os.Getenv("AUTH0_CLIENT_ID")

configuration := auth0.NewConfiguration(secretProvider, []string{audience}, "https://mydomain.eu.auth0.com/", jose.HS256)
validator := auth0.NewValidator(configuration, nil)

token, err := validator.ValidateRequest(r)

if err != nil {
    fmt.Println("Token is not valid:", token)
}

// Extracted from https://github.com/square/go-jose/blob/master/utils.go
// LoadPublicKey loads a public key from PEM/DER-encoded data.
// You can download the Auth0 pem file from `applications -> your_app -> scroll down -> Advanced Settings -> certificates -> download`
func LoadPublicKey(data []byte) (interface{}, error) {
	input := data

	block, _ := pem.Decode(data)
	if block != nil {
		input = block.Bytes
	}

	// Try to load SubjectPublicKeyInfo
	pub, err0 := x509.ParsePKIXPublicKey(input)
	if err0 == nil {
		return pub, nil
	}

	cert, err1 := x509.ParseCertificate(input)
	if err1 == nil {
		return cert.PublicKey, nil
	}

	return nil, fmt.Errorf("square/go-jose: parse error, got '%s' and '%s'", err0, err1)
}
// Create a configuration with the Auth0 information
pem, err := ioutil.ReadFile("path/to/your/cert.pem")
if err != nil {
	panic(err)
}
secret, err := LoadPublicKey(sharedKey)
if err != nil {
	panic(err)
}
secretProvider := auth0.NewKeyProvider(secret)
audience := os.Getenv("AUTH0_CLIENT_ID")

configuration := auth0.NewConfiguration(secretProvider, []string{audience}, "https://mydomain.eu.auth0.com/", jose.RS256)
validator := auth0.NewValidator(configuration, nil)

token, err := validator.ValidateRequest(r)

if err != nil {
    fmt.Println("Token is not valid:", token)
}

client := NewJWKClient(JWKClientOptions{URI: "https://mydomain.eu.auth0.com/.well-known/jwks.json"}, nil)
audience := os.Getenv("AUTH0_CLIENT_ID")
configuration := NewConfiguration(client, []string{audience}, "https://mydomain.eu.auth0.com/", jose.RS256)
validator := NewValidator(configuration, nil)

token, err := validator.ValidateRequest(r)

if err != nil {
    fmt.Println("Token is not valid:", token)
}

opts := JWKClientOptions{URI: "https://mydomain.eu.auth0.com/.well-known/jwks.json"}
// Creating key cacher with max age of 100sec and max size of 5 entries.
// Defaults to persistent key cacher if not specified when creating a client.
keyCacher := NewMemoryKeyCacher(time.Duration(100) * time.Second, 5)
client := NewJWKClientWithCache(opts, nil, keyCacher)

searchedKey, err := client.GetKey("KEY_ID")

if err != nil {
	fmt.Println("Cannot get key because of", err)
}

var auth.AdminGroup string = "my_admin_group"

// Access Control Helper function.
func shouldAccess(wantedGroups []string, groups []interface{}) bool {
 /* Fill depending on your needs */
}

// Wrapping a Gin endpoint with Auth0 Groups.
func Auth0Groups(wantedGroups ...string) gin.HandlerFunc {

	return gin.HandlerFunc(func(c *gin.Context) {

		tok, err := validator.ValidateRequest(c.Request)
		if err != nil {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
			c.Abort()
			log.Println("Invalid token:", err)
			return
		}

		claims := map[string]interface{}{}
		err = validator.Claims(c.Request, tok, &claims)
		if err != nil {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid claims"})
			c.Abort()
			log.Println("Invalid claims:", err)
			return
		}

		metadata, okMetadata := claims["app_metadata"].(map[string]interface{})
		authorization, okAuthorization := metadata["authorization"].(map[string]interface{})
		groups, hasGroups := authorization["groups"].([]interface{})
		if !okMetadata || !okAuthorization || !hasGroups || !shouldAccess(wantedGroups, groups) {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "need more privileges"})
			c.Abort()
			log.Println("Need more provileges")
			return
		}
		c.Next()
	})
}

// Use it
r.PUT("/news", auth.Auth0Groups(auth.AdminGroup), api.GetNews)