// client starts an interop client to do stress test and a metrics server to report qps.
package main

import (
	"flag"
	"fmt"
	"math/rand"
	"net"
	"strconv"
	"strings"
	"sync"
	"time"

	"golang.org/x/net/context"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/grpclog"
	"google.golang.org/grpc/interop"
	testpb "google.golang.org/grpc/interop/grpc_testing"
	metricspb "google.golang.org/grpc/stress/grpc_testing"
)

var (
	serverAddresses      = flag.String("server_addresses", "localhost:8080", "a list of server addresses")
	testCases            = flag.String("test_cases", "", "a list of test cases along with the relative weights")
	testDurationSecs     = flag.Int("test_duration_secs", -1, "test duration in seconds")
	numChannelsPerServer = flag.Int("num_channels_per_server", 1, "Number of channels (i.e connections) to each server")
	numStubsPerChannel   = flag.Int("num_stubs_per_channel", 1, "Number of client stubs per each connection to server")
	metricsPort          = flag.Int("metrics_port", 8081, "The port at which the stress client exposes QPS metrics")
)

// testCaseWithWeight contains the test case type and its weight.
type testCaseWithWeight struct {
	name   string
	weight int
}

// parseTestCases converts test case string to a list of struct testCaseWithWeight.
func parseTestCases(testCaseString string) ([]testCaseWithWeight, error) {
	testCaseStrings := strings.Split(testCaseString, ",")
	testCases := make([]testCaseWithWeight, len(testCaseStrings))
	for i, str := range testCaseStrings {
		temp := strings.Split(str, ":")
		if len(temp) < 2 {
			return nil, fmt.Errorf("invalid test case with weight: %s", str)
		}
		// Check if test case is supported.
		switch temp[0] {
		case
			"empty_unary",
			"large_unary",
			"client_streaming",
			"server_streaming",
			"empty_stream":
		default:
			return nil, fmt.Errorf("unknown test type: %s", temp[0])
		}
		testCases[i].name = temp[0]
		w, err := strconv.Atoi(temp[1])
		if err != nil {
			return nil, fmt.Errorf("%v", err)
		}
		testCases[i].weight = w
	}
	return testCases, nil
}

// weightedRandomTestSelector defines a weighted random selector for test case types.
type weightedRandomTestSelector struct {
	tests       []testCaseWithWeight
	totalWeight int
}

// newWeightedRandomTestSelector constructs a weightedRandomTestSelector with the given list of testCaseWithWeight.
func newWeightedRandomTestSelector(tests []testCaseWithWeight) *weightedRandomTestSelector {
	var totalWeight int
	for _, t := range tests {
		totalWeight += t.weight
	}
	rand.Seed(time.Now().UnixNano())
	return &weightedRandomTestSelector{tests, totalWeight}
}

func (selector weightedRandomTestSelector) getNextTest() (string, error) {
	random := rand.Intn(selector.totalWeight)
	var weightSofar int
	for _, test := range selector.tests {
		weightSofar += test.weight
		if random < weightSofar {
			return test.name, nil
		}
	}
	return "", fmt.Errorf("no test case selected by weightedRandomTestSelector")
}

// gauge defines type for gauge.
type gauge struct {
	mutex sync.RWMutex
	val   int64
}

// Set updates the gauge value
func (g *gauge) set(v int64) {
	g.mutex.Lock()
	defer g.mutex.Unlock()
	g.val = v
}

func (g *gauge) get() int64 {
	g.mutex.RLock()
	defer g.mutex.RUnlock()
	return g.val
}

// Server implements metrics server functions.
type server struct {
	mutex  sync.RWMutex
	gauges map[string]*gauge
}

// newMetricsServer returns a new metrics server.
func newMetricsServer() *server {
	return &server{gauges: make(map[string]*gauge)}
}

// GetAllGauges returns all gauges.
func (s *server) GetAllGauges(in *metricspb.EmptyMessage, stream metricspb.MetricsService_GetAllGaugesServer) error {
	s.mutex.RLock()
	defer s.mutex.RUnlock()

	for name, gauge := range s.gauges {
		err := stream.Send(&metricspb.GaugeResponse{Name: name, Value: &metricspb.GaugeResponse_LongValue{gauge.get()}})
		if err != nil {
			return err
		}
	}
	return nil
}

// GetGauge returns the gauge for the given name.
func (s *server) GetGauge(ctx context.Context, in *metricspb.GaugeRequest) (*metricspb.GaugeResponse, error) {
	s.mutex.RLock()
	defer s.mutex.RUnlock()

	if g, ok := s.gauges[in.Name]; ok {
		return &metricspb.GaugeResponse{Name: in.Name, Value: &metricspb.GaugeResponse_LongValue{g.get()}}, nil
	}
	return nil, grpc.Errorf(codes.InvalidArgument, "gauge with name %s not found", in.Name)
}

// CreateGauge creates a guage using the given name in metrics server
func (s *server) createGauge(name string) (*gauge, error) {
	s.mutex.Lock()
	defer s.mutex.Unlock()

	grpclog.Printf("create gauge: %s", name)
	if _, ok := s.gauges[name]; ok {
		// gauge already exists.
		return nil, fmt.Errorf("gauge %s already exists", name)
	}
	var g gauge
	s.gauges[name] = &g
	return &g, nil
}

func startServer(server *server, port int) {
	lis, err := net.Listen("tcp", ":"+strconv.Itoa(port))
	if err != nil {
		grpclog.Fatalf("failed to listen: %v", err)
	}

	s := grpc.NewServer()
	metricspb.RegisterMetricsServiceServer(s, server)
	s.Serve(lis)

}

// stressClient defines client for stress test.
type stressClient struct {
	testID        int
	address       string
	selector      *weightedRandomTestSelector
	interopClient testpb.TestServiceClient
	stop          <-chan bool
}

// newStressClient construct a new stressClient.
func newStressClient(id int, addr string, conn *grpc.ClientConn, selector *weightedRandomTestSelector, stop <-chan bool) *stressClient {
	client := testpb.NewTestServiceClient(conn)
	return &stressClient{testID: id, address: addr, selector: selector, interopClient: client, stop: stop}
}

// mainLoop uses weightedRandomTestSelector to select test case and runs the tests.
func (c *stressClient) mainLoop(gauge *gauge) {
	var numCalls int64
	timeStarted := time.Now()
	for {
		done := make(chan bool)
		go func() {
			test, err := c.selector.getNextTest()
			if err != nil {
				grpclog.Printf("%v", err)
				done <- false
			}
			switch test {
			case "empty_unary":
				interop.DoEmptyUnaryCall(c.interopClient)
			case "large_unary":
				interop.DoLargeUnaryCall(c.interopClient)
			case "client_streaming":
				interop.DoClientStreaming(c.interopClient)
			case "server_streaming":
				interop.DoServerStreaming(c.interopClient)
			case "empty_stream":
				interop.DoEmptyStream(c.interopClient)
			default:
				grpclog.Fatalf("Unsupported test case: %d", test)
			}
			done <- true
		}()
		select {
		case <-c.stop:
			return
		case r := <-done:
			if r {
				numCalls++
				gauge.set(int64(float64(numCalls) / time.Since(timeStarted).Seconds()))
			}
		}
	}
}

func logParameterInfo(addresses []string, tests []testCaseWithWeight) {
	grpclog.Printf("server_addresses: %s", *serverAddresses)
	grpclog.Printf("test_cases: %s", *testCases)
	grpclog.Printf("test_duration-secs: %d", *testDurationSecs)
	grpclog.Printf("num_channels_per_server: %d", *numChannelsPerServer)
	grpclog.Printf("num_stubs_per_channel: %d", *numStubsPerChannel)
	grpclog.Printf("metrics_port: %d", *metricsPort)

	grpclog.Println("addresses:")
	for i, addr := range addresses {
		grpclog.Printf("%d. %s\n", i+1, addr)
	}
	grpclog.Println("tests:")
	for i, test := range tests {
		grpclog.Printf("%d. %v\n", i+1, test)
	}
}

func main() {
	flag.Parse()
	addresses := strings.Split(*serverAddresses, ",")
	tests, err := parseTestCases(*testCases)
	if err != nil {
		grpclog.Fatalf("%v\n", err)
	}
	logParameterInfo(addresses, tests)
	testSelector := newWeightedRandomTestSelector(tests)
	metricsServer := newMetricsServer()

	var wg sync.WaitGroup
	wg.Add(len(addresses) * *numChannelsPerServer * *numStubsPerChannel)
	stop := make(chan bool)

	var clientIndex int
	for serverIndex, address := range addresses {
		for connIndex := 0; connIndex < *numChannelsPerServer; connIndex++ {
			conn, err := grpc.Dial(address, grpc.WithInsecure())
			if err != nil {
				grpclog.Fatalf("Fail to dial: %v", err)
			}
			defer conn.Close()
			for stubIndex := 0; stubIndex < *numStubsPerChannel; stubIndex++ {
				clientIndex++
				client := newStressClient(clientIndex, address, conn, testSelector, stop)
				buf := fmt.Sprintf("/stress_test/server_%d/channel_%d/stub_%d/qps", serverIndex+1, connIndex+1, stubIndex+1)
				go func() {
					defer wg.Done()
					if g, err := metricsServer.createGauge(buf); err != nil {
						grpclog.Fatalf("%v", err)
					} else {
						client.mainLoop(g)
					}
				}()
			}

		}
	}
	go startServer(metricsServer, *metricsPort)
	if *testDurationSecs > 0 {
		time.Sleep(time.Duration(*testDurationSecs) * time.Second)
		close(stop)
	}
	wg.Wait()
	grpclog.Printf(" ===== ALL DONE ===== ")

}