Make logger extensible

examples/logger_examples.go

@@ -0,0 +1,161 @@
+// Example usage patterns for the extensible logger
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/fosrl/newt/logger"
+)
+
+// Example 1: Using the default logger (works exactly as before)
+func exampleDefaultLogger() {
+	logger.Info("Starting application")
+	logger.Debug("Debug information")
+	logger.Warn("Warning message")
+	logger.Error("Error occurred")
+}
+
+// Example 2: Using a custom logger instance with standard writer
+func exampleCustomInstance() {
+	log := logger.NewLogger()
+	log.SetLevel(logger.INFO)
+	log.Info("This is from a custom instance")
+}
+
+// Example 3: Custom writer that adds JSON formatting
+type JSONWriter struct{}
+
+func (w *JSONWriter) Write(level logger.LogLevel, timestamp time.Time, message string) {
+	fmt.Printf("{\"time\":\"%s\",\"level\":\"%s\",\"message\":\"%s\"}\n",
+		timestamp.Format(time.RFC3339),
+		level.String(),
+		message)
+}
+
+func exampleJSONLogger() {
+	jsonWriter := &JSONWriter{}
+	log := logger.NewLoggerWithWriter(jsonWriter)
+	log.Info("This will be logged as JSON")
+}
+
+// Example 4: File writer
+type FileWriter struct {
+	file *os.File
+}
+
+func NewFileWriter(filename string) (*FileWriter, error) {
+	file, err := os.OpenFile(filename, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err != nil {
+		return nil, err
+	}
+	return &FileWriter{file: file}, nil
+}
+
+func (w *FileWriter) Write(level logger.LogLevel, timestamp time.Time, message string) {
+	fmt.Fprintf(w.file, "[%s] %s: %s\n",
+		timestamp.Format("2006-01-02 15:04:05"),
+		level.String(),
+		message)
+}
+
+func (w *FileWriter) Close() error {
+	return w.file.Close()
+}
+
+func exampleFileLogger() {
+	fileWriter, err := NewFileWriter("/tmp/app.log")
+	if err != nil {
+		panic(err)
+	}
+	defer fileWriter.Close()
+
+	log := logger.NewLoggerWithWriter(fileWriter)
+	log.Info("This goes to a file")
+}
+
+// Example 5: Multi-writer to log to multiple destinations
+type MultiWriter struct {
+	writers []logger.LogWriter
+}
+
+func NewMultiWriter(writers ...logger.LogWriter) *MultiWriter {
+	return &MultiWriter{writers: writers}
+}
+
+func (w *MultiWriter) Write(level logger.LogLevel, timestamp time.Time, message string) {
+	for _, writer := range w.writers {
+		writer.Write(level, timestamp, message)
+	}
+}
+
+func exampleMultiWriter() {
+	// Log to both stdout and a file
+	standardWriter := logger.NewStandardWriter()
+	fileWriter, _ := NewFileWriter("/tmp/app.log")
+
+	multiWriter := NewMultiWriter(standardWriter, fileWriter)
+	log := logger.NewLoggerWithWriter(multiWriter)
+
+	log.Info("This goes to both stdout and file!")
+}
+
+// Example 6: Conditional writer (only log errors to a specific destination)
+type ErrorOnlyWriter struct {
+	writer logger.LogWriter
+}
+
+func NewErrorOnlyWriter(writer logger.LogWriter) *ErrorOnlyWriter {
+	return &ErrorOnlyWriter{writer: writer}
+}
+
+func (w *ErrorOnlyWriter) Write(level logger.LogLevel, timestamp time.Time, message string) {
+	if level >= logger.ERROR {
+		w.writer.Write(level, timestamp, message)
+	}
+}
+
+func exampleConditionalWriter() {
+	errorWriter, _ := NewFileWriter("/tmp/errors.log")
+	errorOnlyWriter := NewErrorOnlyWriter(errorWriter)
+
+	log := logger.NewLoggerWithWriter(errorOnlyWriter)
+	log.Info("This won't be logged")
+	log.Error("This will be logged to errors.log")
+}
+
+/* Example 7: OS Log Writer (macOS/iOS only)
+// Uncomment on Darwin platforms
+
+func exampleOSLogWriter() {
+	osWriter := logger.NewOSLogWriter(
+		"net.pangolin.Pangolin.PacketTunnel",
+		"PangolinGo",
+		"MyApp",
+	)
+
+	log := logger.NewLoggerWithWriter(osWriter)
+	log.Info("This goes to os_log and can be viewed with Console.app")
+}
+*/
+
+func main() {
+	fmt.Println("=== Example 1: Default Logger ===")
+	exampleDefaultLogger()
+
+	fmt.Println("\n=== Example 2: Custom Instance ===")
+	exampleCustomInstance()
+
+	fmt.Println("\n=== Example 3: JSON Logger ===")
+	exampleJSONLogger()
+
+	fmt.Println("\n=== Example 4: File Logger ===")
+	exampleFileLogger()
+
+	fmt.Println("\n=== Example 5: Multi-Writer ===")
+	exampleMultiWriter()
+
+	fmt.Println("\n=== Example 6: Conditional Writer ===")
+	exampleConditionalWriter()
+}