/*
 *
 * Copyright 2018 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

// The client demonstrates how to supply an OAuth2 token for every RPC.
package main

import (
	"crypto/tls"
	"log"
	"time"

	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/credentials/oauth"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
)

func main() {
	perRPC := oauth.NewOauthAccess(fetchToken())
	opts := []grpc.DialOption{
		// In addition to the following grpc.DialOption, callers may also use
		// the grpc.CallOption grpc.PerRPCCredentials with the RPC invocation
		// itself.
		// See: https://godoc.org/google.golang.org/grpc#PerRPCCredentials
		grpc.WithPerRPCCredentials(perRPC),
		// oauth.NewOauthAccess requires the configuration of transport
		// credentials.
		grpc.WithTransportCredentials(
			credentials.NewTLS(&tls.Config{InsecureSkipVerify: true}),
		),
	}
	conn, err := grpc.Dial(":8080", opts...)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	c := pb.NewGreeterClient(conn)

	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: "authenticated-client"})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %s", r.Message)
}

// fetchToken simulates a token lookup and omits the details of proper token
// acquisition. For examples of how to acquire an OAuth2 token, see:
// https://godoc.org/golang.org/x/oauth2
func fetchToken() *oauth2.Token {
	return &oauth2.Token{
		AccessToken: "some-secret-token",
	}
}