feat: add DefaultLogger (#1648)

Author: hsluoyz

log/default_logger.go

@@ -0,0 +1,139 @@
+// Copyright 2026 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package log
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"time"
+)
+
+// DefaultLogger is the default implementation of the Logger interface.
+type DefaultLogger struct {
+	output      io.Writer
+	eventTypes  map[EventType]bool
+	logCallback func(entry *LogEntry) error
+}
+
+// NewDefaultLogger creates a new DefaultLogger instance.
+// If no output is set via SetOutput, it defaults to os.Stdout.
+func NewDefaultLogger() *DefaultLogger {
+	return &DefaultLogger{
+		output:     os.Stdout,
+		eventTypes: make(map[EventType]bool),
+	}
+}
+
+// SetOutput sets the output destination for the logger.
+// It can be set to a buffer or any io.Writer.
+func (l *DefaultLogger) SetOutput(w io.Writer) {
+	if w != nil {
+		l.output = w
+	}
+}
+
+// SetEventTypes sets the event types that should be logged.
+// Only events matching these types will have IsActive set to true.
+func (l *DefaultLogger) SetEventTypes(eventTypes []EventType) error {
+	l.eventTypes = make(map[EventType]bool)
+	for _, et := range eventTypes {
+		l.eventTypes[et] = true
+	}
+	return nil
+}
+
+// OnBeforeEvent is called before an event occurs.
+// It sets the StartTime and determines if the event should be active based on configured event types.
+func (l *DefaultLogger) OnBeforeEvent(entry *LogEntry) error {
+	if entry == nil {
+		return fmt.Errorf("log entry is nil")
+	}
+
+	entry.StartTime = time.Now()
+
+	// Set IsActive based on whether this event type is enabled
+	// If no event types are configured, all events are considered active
+	if len(l.eventTypes) == 0 {
+		entry.IsActive = true
+	} else {
+		entry.IsActive = l.eventTypes[entry.EventType]
+	}
+
+	return nil
+}
+
+// OnAfterEvent is called after an event completes.
+// It calculates the duration, logs the entry if active, and calls the user callback if set.
+func (l *DefaultLogger) OnAfterEvent(entry *LogEntry) error {
+	if entry == nil {
+		return fmt.Errorf("log entry is nil")
+	}
+
+	entry.EndTime = time.Now()
+	entry.Duration = entry.EndTime.Sub(entry.StartTime)
+
+	// Only log if the event is active
+	if entry.IsActive && l.output != nil {
+		if err := l.writeLog(entry); err != nil {
+			return err
+		}
+	}
+
+	// Call user-provided callback if set
+	if l.logCallback != nil {
+		if err := l.logCallback(entry); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// SetLogCallback sets a user-provided callback function.
+// The callback is called at the end of OnAfterEvent.
+func (l *DefaultLogger) SetLogCallback(callback func(entry *LogEntry) error) error {
+	l.logCallback = callback
+	return nil
+}
+
+// writeLog writes the log entry to the configured output.
+func (l *DefaultLogger) writeLog(entry *LogEntry) error {
+	var logMessage string
+
+	switch entry.EventType {
+	case EventEnforce:
+		logMessage = fmt.Sprintf("[%s] Enforce: subject=%s, object=%s, action=%s, domain=%s, allowed=%v, duration=%v\n",
+			entry.EventType, entry.Subject, entry.Object, entry.Action, entry.Domain, entry.Allowed, entry.Duration)
+	case EventAddPolicy, EventRemovePolicy:
+		logMessage = fmt.Sprintf("[%s] RuleCount=%d, duration=%v\n",
+			entry.EventType, entry.RuleCount, entry.Duration)
+	case EventLoadPolicy, EventSavePolicy:
+		logMessage = fmt.Sprintf("[%s] RuleCount=%d, duration=%v\n",
+			entry.EventType, entry.RuleCount, entry.Duration)
+	default:
+		logMessage = fmt.Sprintf("[%s] duration=%v\n",
+			entry.EventType, entry.Duration)
+	}
+
+	if entry.Error != nil {
+		logMessage = strings.TrimSuffix(logMessage, "\n")
+		logMessage = fmt.Sprintf("%s Error: %v\n", logMessage, entry.Error)
+	}
+
+	_, err := l.output.Write([]byte(logMessage))
+	return err
+}