/*
 *
 * Copyright 2020 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 use the credential reloading feature in
// advancedtls to make a mTLS connection to the server.
package main

import (
	"context"
	"flag"
	"log"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/tls/certprovider/pemfile"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
	"google.golang.org/grpc/security/advancedtls"
	"google.golang.org/grpc/security/advancedtls/testdata"
)

var address = "localhost:50051"

const (
	// Default timeout for normal connections.
	defaultTimeout = 2 * time.Second
	// Intervals that set to monitor the credential updates.
	credRefreshingInterval = 500 * time.Millisecond
)

func main() {
	tmpKeyFile := flag.String("key", "", "temporary key file path")
	tmpCertFile := flag.String("cert", "", "temporary cert file path")
	flag.Parse()

	if tmpKeyFile == nil || *tmpKeyFile == "" {
		log.Fatalf("tmpKeyFile is nil or empty.")
	}
	if tmpCertFile == nil || *tmpCertFile == "" {
		log.Fatalf("tmpCertFile is nil or empty.")
	}

	// Initialize credential struct using reloading API.
	identityOptions := pemfile.Options{
		CertFile:        *tmpCertFile,
		KeyFile:         *tmpKeyFile,
		RefreshDuration: credRefreshingInterval,
	}
	identityProvider, err := pemfile.NewProvider(identityOptions)
	if err != nil {
		log.Fatalf("pemfile.NewProvider(%v) failed: %v", identityOptions, err)
	}
	rootOptions := pemfile.Options{
		RootFile:        testdata.Path("client_trust_cert_1.pem"),
		RefreshDuration: credRefreshingInterval,
	}
	rootProvider, err := pemfile.NewProvider(rootOptions)
	if err != nil {
		log.Fatalf("pemfile.NewProvider(%v) failed: %v", rootOptions, err)
	}
	options := &advancedtls.Options{
		IdentityOptions: advancedtls.IdentityCertificateOptions{
			IdentityProvider: identityProvider,
		},
		AdditionalPeerVerification: func(*advancedtls.HandshakeVerificationInfo) (*advancedtls.PostHandshakeVerificationResults, error) {
			return &advancedtls.PostHandshakeVerificationResults{}, nil
		},
		RootOptions: advancedtls.RootCertificateOptions{
			RootProvider: rootProvider,
		},
		VerificationType: advancedtls.CertVerification,
	}
	clientTLSCreds, err := advancedtls.NewClientCreds(options)
	if err != nil {
		log.Fatalf("advancedtls.NewClientCreds(%v) failed: %v", options, err)
	}

	// Make a connection using the credentials.
	conn, err := grpc.NewClient(address, grpc.WithTransportCredentials(clientTLSCreds))
	if err != nil {
		log.Fatalf("grpc.NewClient to %s failed: %v", address, err)
	}
	client := pb.NewGreeterClient(conn)

	// Send the requests every 0.5s. The credential is expected to be changed in
	// the bash script. We don't cancel the context nor call conn.Close() here,
	// since the bash script is expected to close the client goroutine.
	for {
		ctx, cancel := context.WithTimeout(context.Background(), defaultTimeout)
		_, err = client.SayHello(ctx, &pb.HelloRequest{Name: "gRPC"}, grpc.WaitForReady(true))
		if err != nil {
			log.Fatalf("client.SayHello failed: %v", err)
		}
		cancel()
		time.Sleep(500 * time.Millisecond)
	}
}