Output debug logs for API access

atom/client.go

@@ -5,7 +5,13 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
+	"log"
+	"log/slog"
 	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
 )
 
 // Client wrapped *http.Client and some methods for accessing atom feed are added
@@ -88,13 +94,70 @@ func entryBody(e *Entry) (*bytes.Buffer, error) {
 	return body, nil
 }
 
-func (c *Client) http(method, url string, body io.Reader) (*http.Response, error) {
+var blogsyncDebug = os.Getenv("BLOGSYNC_DEBUG") != ""
+
+var debugLogger = sync.OnceValue(func() *slog.Logger {
+	var w io.Writer = os.Stderr
+	cached, err := os.UserCacheDir()
+	if err == nil {
+		logf := filepath.Join(cached, "blogsync", "tracedump.log")
+		if err := os.MkdirAll(filepath.Dir(logf), 0755); err == nil {
+			if f, err := os.OpenFile(logf, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644); err == nil {
+				log.Printf("trace dumps are output to %s\n", logf)
+				w = f
+			}
+		}
+	}
+	return slog.New(slog.NewJSONHandler(w, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+})
+
+type traceDump struct {
+	Request  string `json:"request,omitempty"`
+	Response string `json:"response,omitempty"`
+	Method   string `json:"method"`
+	URL      string `json:"url"`
+	Status   int    `json:"status"`
+}
+
+func (c *Client) http(method, url string, body io.Reader) (resp *http.Response, err error) {
+	if blogsyncDebug {
+		td := traceDump{
+			Method: method,
+			URL:    url,
+		}
+		if body != nil {
+			bb, err := io.ReadAll(body)
+			if err != nil {
+				return nil, err
+			}
+			td.Request = string(bb)
+			body = strings.NewReader(td.Request)
+		}
+		defer func() {
+			if err != nil {
+				return
+			}
+			bb, rerr := io.ReadAll(resp.Body)
+			if rerr != nil {
+				err = rerr
+				resp.Body.Close()
+				return
+			}
+			td.Response = string(bb)
+			td.Status = resp.StatusCode
+			debugLogger().Debug("traceDump", "data", td)
+			resp.Body = io.NopCloser(strings.NewReader(td.Response))
+		}()
+	}
+
 	req, err := http.NewRequest(method, url, body)
 	if err != nil {
 		return nil, err
 	}
 
-	resp, err := c.Client.Do(req)
+	resp, err = c.Client.Do(req)
 	if err != nil {
 		return nil, err
 	}