1 files changed, 87 insertions, 0 deletions
diff --git a/backend/log/logger.go b/backend/log/logger.go
new file mode 100644
index 0000000..feb79fc
--- /dev/null
+++ b/backend/log/logger.go
@@ -0,0 +1,87 @@
+package log
+
+import (
+	"context"
+	"log"
+	"log/slog"
+	"net/http"
+	"os"
+	"runtime/debug"
+)
+
+const (
+	loggerKey  = "logger"
+	statusCode = "status_code"
+)
+
+func GetLogger(ctx context.Context) *slog.Logger {
+	return ctx.Value(loggerKey).(*slog.Logger)
+}
+
+type customWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (c *customWriter) WriteHeader(statusCode int) {
+	if statusCode == c.statusCode {
+		return
+	}
+	c.statusCode = statusCode
+	c.ResponseWriter.WriteHeader(statusCode)
+}
+
+func GetStatusCode(ctx context.Context) func() int {
+	return ctx.Value(statusCode).(func() int)
+}
+
+func newLogger(l *slog.Logger, r *http.Request) *slog.Logger {
+	return l.With("uri", r.RequestURI, "method", r.Method)
+}
+
+func SetContextLogger(ctx context.Context, l *slog.Logger, r *http.Request) context.Context {
+	return context.WithValue(ctx, loggerKey, newLogger(l, r))
+}
+
+func SetLogger(l *slog.Logger) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			logger := newLogger(l, r)
+			ww := &customWriter{ResponseWriter: w, statusCode: http.StatusOK}
+			ctx := context.WithValue(r.Context(), statusCode, func() int {
+				return ww.statusCode
+			})
+			ctx = context.WithValue(ctx, loggerKey, logger)
+			defer func(logger *slog.Logger) {
+				rec := recover()
+				if rec == nil {
+					return
+				}
+				if rec == http.ErrAbortHandler {
+					panic(rec)
+				}
+				logger.Error("crashed, recovered", "error", rec, "status", http.StatusInternalServerError)
+				log.New(os.Stderr, "", 0).Printf("%s\n", debug.Stack())
+				http.Error(ww, "internal error", http.StatusInternalServerError)
+			}(logger)
+
+			next.ServeHTTP(ww, r.WithContext(ctx))
+
+			if ww.statusCode == http.StatusNotFound || ww.statusCode == http.StatusTooManyRequests {
+				return
+			}
+			var lvl slog.Level
+			switch {
+			case ww.statusCode >= 500:
+				lvl = slog.LevelError
+			case ww.statusCode >= 400:
+				lvl = slog.LevelWarn
+			case ww.statusCode >= 300:
+				return
+			default:
+				lvl = slog.LevelInfo
+			}
+			logger.Log(context.Background(), lvl, "handled", "status", ww.statusCode)
+		})
+	}
+}