✨ Created LogFmt middleware

internal/middleware/logfmt.go

@@ -0,0 +1,130 @@
+package middleware
+
+import (
+	"io"
+	"log/slog"
+	"net/http"
+	"os"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+type (
+	LogFmtConfig struct {
+		// Skipper defines a function to skip middleware.
+		Skipper Skipper
+
+		// Output is a writer where logs in JSON format are written.
+		// Optional. Default value os.Stdout.
+		Output io.Writer
+	}
+
+	logFmtResponse struct {
+		http.ResponseWriter
+		error          error
+		start          time.Time
+		end            time.Time
+		statusCode     int
+		responseLength int
+		id             uint64
+	}
+)
+
+//nolint:gochecknoglobals // default configuration
+var DefaultLogFmtConfig = LogFmtConfig{
+	Skipper: DefaultSkipper,
+	Output:  os.Stdout,
+}
+
+//nolint:gochecknoglobals
+var globalConnID uint64
+
+func LogFmt() Interceptor {
+	c := DefaultLogFmtConfig
+
+	return LogFmtWithConfig(c)
+}
+
+func LogFmtWithConfig(config LogFmtConfig) Interceptor {
+	if config.Skipper == nil {
+		config.Skipper = DefaultLogFmtConfig.Skipper
+	}
+
+	if config.Output == nil {
+		config.Output = DefaultLogFmtConfig.Output
+	}
+
+	encoder := slog.New(slog.NewTextHandler(config.Output, nil))
+
+	return func(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+		tx := &logFmtResponse{
+			id:             nextConnID(),
+			responseLength: 0,
+			ResponseWriter: w,
+			start:          time.Now().UTC(),
+			statusCode:     0,
+		}
+
+		next(tx, r)
+
+		tx.end = time.Now().UTC()
+		payload := []any{
+			slog.Int64("bytes_in", r.ContentLength),
+			slog.Int("bytes_out", tx.responseLength),
+			slog.Any("error", tx.error),
+			slog.String("host", r.Host),
+			slog.Uint64("id", tx.id),
+			slog.Int64("latency", tx.end.Sub(tx.start).Nanoseconds()),
+			slog.String("latency_human", tx.end.Sub(tx.start).String()),
+			slog.String("method", r.Method),
+			slog.String("path", r.URL.Path),
+			slog.String("protocol", r.Proto),
+			slog.String("referer", r.Referer()),
+			slog.String("remote_ip", r.RemoteAddr),
+			slog.Int("status", tx.statusCode),
+			slog.String("time_rfc3339", tx.start.Format(time.RFC3339)),
+			slog.String("time_rfc3339_nano", tx.start.Format(time.RFC3339Nano)),
+			slog.Int64("time_unix", tx.start.Unix()),
+			slog.Int64("time_unix_nano", tx.start.UnixNano()),
+			slog.String("uri", r.RequestURI),
+			slog.String("user_agent", r.UserAgent()),
+		}
+
+		for name, src := range map[string]map[string][]string{
+			"form":   r.PostForm,
+			"header": r.Header,
+			"query":  r.URL.Query(),
+		} {
+			values := make([]any, 0)
+
+			for k, v := range src {
+				values = append(values, slog.String(strings.ReplaceAll(strings.ToLower(k), " ", "_"),
+					strings.Join(v, " ")))
+			}
+
+			payload = append(payload, slog.Group(name, values...))
+		}
+
+		encoder.Log(r.Context(), slog.LevelInfo, "" /* msg */, payload...)
+	}
+}
+
+func (r *logFmtResponse) WriteHeader(status int) {
+	r.statusCode = status
+
+	r.ResponseWriter.WriteHeader(status)
+}
+
+func (r *logFmtResponse) Write(src []byte) (int, error) {
+	var length int
+
+	length, r.error = r.ResponseWriter.Write(src)
+	r.responseLength += length
+
+	return length, r.error
+}
+
+func nextConnID() uint64 {
+	return atomic.AddUint64(&globalConnID, 1)
+}