/*
 *
 * 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 (
	"context"
	"flag"
	"fmt"
	"log"
	"time"

	"golang.org/x/oauth2"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/credentials/oauth"
	ecpb "google.golang.org/grpc/examples/features/proto/echo"
	"google.golang.org/grpc/testdata"
)

var addr = flag.String("addr", "localhost:50051", "the address to connect to")

func callUnaryEcho(client ecpb.EchoClient, message string) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	resp, err := client.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message})
	if err != nil {
		log.Fatalf("client.UnaryEcho(_) = _, %v: ", err)
	}
	fmt.Println("UnaryEcho: ", resp.Message)
}

func main() {
	flag.Parse()

	// Set up the credentials for the connection.
	perRPC := oauth.NewOauthAccess(fetchToken())
	creds, err := credentials.NewClientTLSFromFile(testdata.Path("ca.pem"), "x.test.youtube.com")
	if err != nil {
		log.Fatalf("failed to load credentials: %v", err)
	}
	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(creds),
	}

	conn, err := grpc.Dial(*addr, opts...)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	rgc := ecpb.NewEchoClient(conn)

	callUnaryEcho(rgc, "hello world")
}

// 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",
	}
}