Gl/avg latency (#1)

* Add IDE files in gitignore

* Add IDE files in gitignore

* Add latency option

* Add random latency algorithm

Author: gudgl

.gitignore

@@ -3,3 +3,6 @@
 /TODO.md
 /stripe-mock
 /dist/
+
+# IDE files
+.idea

main.go

@@ -7,10 +7,12 @@ import (
 	"crypto/tls"
 	"flag"
 	"fmt"
+	"math/rand"
 	"net"
 	"net/http"
 	"os"
 	"strconv"
+	"time"
 
 	"github.com/stripe/stripe-mock/server"
 )
@@ -62,7 +64,11 @@ func main() {
 	flag.BoolVar(&verbose, "verbose", false, "Enable verbose mode")
 	flag.BoolVar(&options.showVersion, "version", false, "Show version and exit")
 
+	flag.IntVar(&options.avgLatency, "avg-latency", -1, "Average response latency for reasonable response time (ms)")
+	flag.Float64Var(&options.stdv, "stdv", 0.5, "Standard deviation for latency, must be in range (0, 1)")
+
 	flag.Parse()
+	rand.Seed(time.Now().UnixNano())
 
 	fmt.Printf("stripe-mock %s\n", version)
 	if options.showVersion || len(flag.Args()) == 1 && flag.Arg(0) == "version" {
@@ -90,7 +96,14 @@ func main() {
 		abort(err.Error())
 	}
 
-	stub, err := server.NewStubServer(fixtures, stripeSpec, options.strictVersionCheck, verbose)
+	stub, err := server.NewStubServer(
+		fixtures,
+		stripeSpec,
+		options.strictVersionCheck,
+		verbose,
+		server.SetAvgLatency(options.avgLatency),
+		server.SetStdv(options.stdv),
+	)
 	if err != nil {
 		abort(fmt.Sprintf("Error initializing router: %v\n", err))
 	}
@@ -166,6 +179,8 @@ func main() {
 		}()
 	}
 
+	fmt.Printf("Average latency: %dms, STDV: %f\n", options.avgLatency, options.stdv)
+
 	// Block forever. The serve Goroutines above will abort the program if
 	// either of them fails.
 	select {}
@@ -196,6 +211,9 @@ type options struct {
 	specPath           string
 	strictVersionCheck bool
 	unixSocket         string
+
+	avgLatency int     // For reasonable response times - in milliseconds
+	stdv       float64 // For reasonable response times - standard deviation in rage (0, 1)
 }
 
 func (o *options) checkConflictingOptions() error {

server/server.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
+	"math/rand"
 	"net/http"
 	"net/url"
 	"path/filepath"
@@ -14,6 +15,7 @@ import (
 	"time"
 
 	"github.com/lestrrat-go/jsval"
+
 	"github.com/stripe/stripe-mock/param"
 	"github.com/stripe/stripe-mock/param/coercer"
 	"github.com/stripe/stripe-mock/spec"
@@ -206,30 +208,72 @@ type StubServer struct {
 	fixtures           *spec.Fixtures
 	routes             map[spec.HTTPVerb][]stubServerRoute
 	spec               *spec.Spec
+	stdv               float64
+	avgLatency         int
+	delayResponses     bool
 	strictVersionCheck bool
 	verbose            bool
 }
 
+type StubServerOption func(s *StubServer)
+
+func SetAvgLatency(avgLatency int) StubServerOption {
+	return func(s *StubServer) {
+		if avgLatency <= 0 {
+			return
+		}
+		s.delayResponses = true
+		s.avgLatency = avgLatency
+	}
+}
+
+func SetStdv(stdv float64) StubServerOption {
+	return func(s *StubServer) {
+		s.stdv = stdv
+	}
+}
+
 // NewStubServer creates a new instance of StubServer
-func NewStubServer(fixtures *spec.Fixtures, spec *spec.Spec, strictVersionCheck, verbose bool) (*StubServer, error) {
+func NewStubServer(fixtures *spec.Fixtures, spec *spec.Spec, strictVersionCheck, verbose bool, opts ...StubServerOption) (*StubServer, error) {
 	s := StubServer{
 		fixtures:           fixtures,
 		spec:               spec,
 		strictVersionCheck: strictVersionCheck,
 		verbose:            verbose,
 	}
+
+	for _, option := range opts {
+		option(&s)
+	}
+
 	err := s.initializeRouter()
 	if err != nil {
 		return nil, err
 	}
 	return &s, nil
 }
 
+func (s *StubServer) delay() {
+	lat := float64(s.avgLatency/1000) + s.stdv*rand.NormFloat64()
+	if lat < 0 {
+		lat = - lat
+	}
+
+	fmt.Printf("Request latency = %f", lat*1000)
+	time.Sleep(time.Duration(lat*1000) * time.Millisecond)
+}
+
 // HandleRequest handes an HTTP request directed at the API stub.
 func (s *StubServer) HandleRequest(w http.ResponseWriter, r *http.Request) {
 	start := time.Now()
 	fmt.Printf("Request: %v %v\n", r.Method, r.URL.Path)
 
+	//
+	// Delaying the response according to acg-latency and stdv
+	//
+
+	s.delay()
+
 	//
 	// Validate headers
 	//