enable passing custom logger

logRequests.go

@@ -1,30 +1,71 @@
 package transport
 
 import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"time"
 
 	"moul.io/http2curl/v2"
 )
 
-func LogRequests(next http.RoundTripper) http.RoundTripper {
-	return RoundTripFunc(func(req *http.Request) (resp *http.Response, err error) {
-		r := CloneRequest(req)
+type RequestLogger interface {
+	LogRequest(req *http.Request, curl *http2curl.CurlCommand)
+	LogResponse(r *http.Request, resp *http.Response, startTime time.Time)
+}
 
-		curlCommand, _ := http2curl.GetCurlCommand(r)
-		log.Printf("%v", curlCommand)
-		log.Printf("request: %s %s", r.Method, r.URL)
+func LogRequests(logger RequestLogger) func(next http.RoundTripper) http.RoundTripper {
+	return func(next http.RoundTripper) http.RoundTripper {
+		return RoundTripFunc(func(req *http.Request) (resp *http.Response, err error) {
+			r := CloneRequest(req)
 
-		startTime := time.Now()
-		defer func() {
-			if resp != nil {
-				log.Printf("response (HTTP %v): %v %s", time.Since(startTime), resp.Status, r.URL)
-			} else {
-				log.Printf("response (<nil>): %v %s", time.Since(startTime), r.URL)
-			}
-		}()
+			curlCommand, _ := http2curl.GetCurlCommand(r)
+
+			logger.LogRequest(req, curlCommand)
+
+			startTime := time.Now()
+			defer func() {
+				logger.LogResponse(r, resp, startTime)
+			}()
+
+			return next.RoundTrip(r)
+		})
+	}
+}
+
+type DefaultLogger struct {
+	PrintResponsePayload bool
+}
 
-		return next.RoundTrip(r)
-	})
+func (d *DefaultLogger) LogRequest(r *http.Request, curl *http2curl.CurlCommand) {
+	log.Printf(curl.String())
+	log.Printf("request: %s %s", r.Method, r.URL)
+}
+
+func (d *DefaultLogger) LogResponse(r *http.Request, resp *http.Response, startTime time.Time) {
+	if resp == nil {
+		log.Printf(fmt.Sprintf("response (<nil>): %v %s", time.Since(startTime), r.URL))
+		return
+	}
+
+	log.Printf("response: %s %s", resp.Status, resp.Request.URL)
+
+	if d.PrintResponsePayload && resp.Header.Get("Content-Type") == "application/json" {
+		var b bytes.Buffer
+
+		tee := io.TeeReader(resp.Body, &b)
+		resp.Body = io.NopCloser(&b)
+
+		payload, err := io.ReadAll(tee)
+		if err == nil {
+			// Pretty print the JSON payload
+			var prettyJSON bytes.Buffer
+			if err := json.Indent(&prettyJSON, payload, "", "    "); err == nil {
+				log.Printf("%s", prettyJSON.String())
+			}
+		}
+	}
 }

setHeaderFunc_test.go

@@ -34,7 +34,7 @@ func TestSetHeaderFunc(t *testing.T) {
 		Transport: transport.Chain(
 			http.DefaultTransport,
 			transport.SetHeaderFunc("Authorization", issueRandomAuthToken),
-			transport.LogRequests,
+			transport.LogRequests(&transport.DefaultLogger{PrintResponsePayload: true}),
 		),
 		Timeout: 15 * time.Second,
 	}

setHeader_test.go

@@ -45,7 +45,7 @@ func TestSetHeader(t *testing.T) {
 			transport.SetHeader("User-Agent", userAgent),
 			transport.SetHeader("Authorization", authHeader),
 			transport.SetHeader("x-extra", "value"),
-			transport.LogRequests,
+			transport.LogRequests(&transport.DefaultLogger{PrintResponsePayload: true}),
 		),
 		Timeout: 15 * time.Second,
 	}

transport_test.go

@@ -24,7 +24,7 @@ func TestChain(t *testing.T) {
 		Transport: Chain(
 			nil,
 			SetHeader("User-Agent", "transport-chain/v1.0.0"),
-			LogRequests,
+			LogRequests(&DefaultLogger{PrintResponsePayload: true}),
 		),
 	}
 
@@ -63,7 +63,7 @@ func TestChainWithRetries(t *testing.T) {
 		Transport: Chain(
 			http.DefaultTransport,
 			Retry(http.DefaultTransport, 5),
-			LogRequests,
+			LogRequests(&DefaultLogger{PrintResponsePayload: true}),
 		),
 	}
 
@@ -103,7 +103,7 @@ func TestChainWithRetryAfter(t *testing.T) {
 		Transport: Chain(
 			http.DefaultTransport,
 			Retry(http.DefaultTransport, 5),
-			LogRequests,
+			LogRequests(&DefaultLogger{PrintResponsePayload: true}),
 		),
 	}