Merge pull request #80 from megaport/feat/json-logging

feat: add option to log response body

client.go

@@ -75,6 +75,8 @@ type Client struct {
 	accessToken string    // Access Token for client
 	tokenExpiry time.Time // Token Expiration
 
+	LogResponseBody bool // Log Response Body of HTTP Requests
+
 	// Optional function called after every successful request made to the API
 	onRequestCompleted RequestCompletionCallback
 
@@ -93,6 +95,41 @@ type AccessTokenResponse struct {
 	Error        string `json:"error"`
 }
 
+// Custom Handler with Log Filtering
+type LevelFilterHandler struct {
+	level   slog.Level
+	handler slog.Handler
+}
+
+func NewLevelFilterHandler(level slog.Level, handler slog.Handler) *LevelFilterHandler {
+	return &LevelFilterHandler{level: level, handler: handler}
+}
+
+func (h *LevelFilterHandler) Handle(ctx context.Context, r slog.Record) error {
+	if r.Level >= h.level {
+		return h.handler.Handle(ctx, r)
+	}
+	return nil
+}
+
+func (h *LevelFilterHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return &LevelFilterHandler{
+		level:   h.level,
+		handler: h.handler.WithAttrs(attrs),
+	}
+}
+
+func (h *LevelFilterHandler) WithGroup(name string) slog.Handler {
+	return &LevelFilterHandler{
+		level:   h.level,
+		handler: h.handler.WithGroup(name),
+	}
+}
+
+func (h *LevelFilterHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	return level >= h.level
+}
+
 // RequestCompletionCallback defines the type of the request callback function
 type RequestCompletionCallback func(*http.Request, *http.Response)
 
@@ -211,6 +248,14 @@ func WithEnvironment(e Environment) ClientOpt {
 	}
 }
 
+// WithLogResponseBody is a client option for setting the log response body flag
+func WithLogResponseBody() ClientOpt {
+	return func(c *Client) error {
+		c.LogResponseBody = true
+		return nil
+	}
+}
+
 // NewRequest creates an API request. A relative URL can be provided in urlStr, which will be resolved to the
 // BaseURL of the Client. Relative URLS should always be specified without a preceding slash. If specified, the
 // value pointed to by body is JSON encoded and included in as the request body.
@@ -279,14 +324,31 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*htt
 	}
 	reqTime := time.Since(reqStart)
 
-	c.Logger.DebugContext(ctx, "completed API request",
-		slog.Duration("duration", reqTime),
+	respBody := resp.Body
+
+	attrs := []slog.Attr{slog.Duration("duration", reqTime),
 		slog.Int("status_code", resp.StatusCode),
 		slog.String("path", req.URL.EscapedPath()),
 		slog.String("api_host", c.BaseURL.Host),
 		slog.String("method", req.Method),
-		slog.String("trace_id", resp.Header.Get(headerTraceId)),
-	)
+		slog.String("trace_id", resp.Header.Get(headerTraceId))}
+
+	if c.LogResponseBody {
+		b, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+
+		// Base64 encode the response body
+		encodedBody := base64.StdEncoding.EncodeToString(b)
+
+		// Create new reader for the later code
+		respBody = io.NopCloser(bytes.NewReader(b))
+
+		attrs = append(attrs, slog.String("response_body_base_64", encodedBody))
+	}
+
+	c.Logger.DebugContext(ctx, "completed api request", slog.Any("api_request", attrs))
 
 	err = CheckResponse(resp)
 	if err != nil {
@@ -295,7 +357,7 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*htt
 
 	if resp.StatusCode != http.StatusNoContent && v != nil {
 		if w, ok := v.(io.Writer); ok {
-			_, err = io.Copy(w, resp.Body)
+			_, err = io.Copy(w, respBody)
 			if err != nil {
 				return nil, err
 			}

client_test.go

@@ -1,8 +1,11 @@
 package megaport
 
 import (
+	"bytes"
 	"context"
 	"fmt"
+	"io"
+	"log/slog"
 	"net/http"
 	"net/http/httptest"
 	"net/http/httputil"
@@ -138,6 +141,41 @@ func (suite *ClientTestSuite) TestNewRequest_withCustomUserAgent() {
 	}
 }
 
+// TestNewRequest_withResponseLogging tests if the NewRequest function returns a request with response logging.
+func (suite *ClientTestSuite) TestNewRequest_withResponseLogging() {
+	// for debugging - capture logs
+	logCapture := &bytes.Buffer{}
+	levelFilterHandler := NewLevelFilterHandler(slog.LevelDebug, slog.NewJSONHandler(io.Writer(logCapture), nil))
+
+	c, err := New(nil, WithLogResponseBody(), WithLogHandler(levelFilterHandler))
+	if err != nil {
+		suite.FailNowf("unexpected error", "New() unexpected error: %v", err.Error())
+	}
+	suite.client = c
+	url, _ := url.Parse(suite.server.URL)
+	suite.client.BaseURL = url
+
+	suite.mux.HandleFunc("/a", func(w http.ResponseWriter, r *http.Request) {
+		if m := http.MethodGet; m != r.Method {
+			suite.FailNowf("Incorrect request method", "Request method = %v, expected %v", r.Method, m)
+		}
+		fmt.Fprint(w, `{"A":"a"}`)
+	})
+
+	req, _ := suite.client.NewRequest(ctx, http.MethodGet, "/a", nil)
+	_, err = suite.client.Do(ctx, req, nil)
+	if err != nil {
+		suite.FailNowf("Unexpected error: Do()", "Unexpected error: Do(): %v", err.Error())
+	}
+
+	// Check the log output for the expected base64 encoded response body
+	expectedBase64 := "eyJBIjoiYSJ9" // base64 encoded {"A":"a"}
+	logOutput := logCapture.String()
+	if !strings.Contains(logOutput, expectedBase64) {
+		suite.FailNowf("Log output does not contain expected base64", "Log output: %s", logOutput)
+	}
+}
+
 // TestNewRequest_withCustomHeaders tests if the NewRequest function returns a request with custom headers.
 func (suite *ClientTestSuite) TestNewRequest_withCustomHeaders() {
 	expectedIdentity := "identity"