initial commit

applog.go

@@ -0,0 +1,129 @@
+package applog
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"time"
+
+	"gitea.auvem.com/go-toolkit/app"
+	"github.com/lmittmann/tint"
+	slogmulti "github.com/samber/slog-multi"
+)
+
+// ModuleName is the name of the module provided by applog.
+const ModuleName = "app logger"
+
+var (
+	// logfile is the file handle for the log file, if any.
+	logfile *os.File
+)
+
+// AppLogOpts contains options for configuring the application logger.
+type AppLogOpts struct {
+	// Verbose enables verbose logging, which will use the LogOutput writer
+	// for pretty-printed console output. If false, console output is disabled.
+	Verbose bool
+
+	// LogOutput is the output writer for the pretty-printed slog console
+	// logger that is enabled if Verbose is set to true. If nil, console
+	// output will be disabled.
+	LogOutput io.Writer
+
+	// LogFile is the file where JSON formatted logs will be written. If
+	// empty, log file output will be disabled.
+	LogFile string
+
+	// SetDefault indicates whether to set the logger as the default logger
+	// for slog. Generally not recommended.
+	SetDefault bool
+}
+
+// Module creates a new Module instance.
+func (opts AppLogOpts) Module() *app.Module {
+	return app.NewModule(ModuleName, app.ModuleOpts{
+		Setup: func(m *app.Module) error {
+			if opts.LogFile == "" && (opts.LogOutput == nil || !opts.Verbose) {
+				return fmt.Errorf("no logging output configured")
+			}
+
+			output := opts.LogOutput
+			if !opts.Verbose {
+				output = nil
+			}
+
+			if err := setupLogger(m.Lifecycle(), opts.LogFile, output); err != nil {
+				return fmt.Errorf("failed to set up logger: %w", err)
+			}
+
+			if opts.SetDefault {
+				slog.SetDefault(m.Logger())
+			}
+
+			return nil
+		},
+		Teardown: func(m *app.Module) error {
+			teardownLogger()
+			return nil
+		},
+	})
+}
+
+// Module creates a new Module instance for the application logger with the
+// provided options.
+func Module(opts AppLogOpts) *app.Module {
+	return opts.Module()
+}
+
+// setupLogger initializes the multi logger with a JSON handler for file output
+// and a tint handler for pretty-printed console output. May return an error
+// if the log file cannot be opened. Log file should be created if it does not
+// exist and appended to if it does.
+func setupLogger(lifecycle *app.Lifecycle, logFilePath string, logoutput io.Writer) error {
+	handlers := make([]slog.Handler, 0)
+
+	// If log file is specified, set up JSON file logging
+	if logFilePath != "" {
+		var err error
+		logfile, err = os.OpenFile(logFilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			return err
+		}
+
+		handlers = append(handlers, slog.NewJSONHandler(logfile, &slog.HandlerOptions{}))
+	}
+
+	// If log output is specified, set up pretty-printed console logging
+	if logoutput != nil {
+		handlers = append(handlers, tint.NewHandler(logoutput, &tint.Options{
+			Level:      slog.LevelDebug,
+			TimeFormat: time.Kitchen,
+		}))
+	}
+
+	logger := slog.New(
+		slogmulti.Fanout(handlers...),
+	)
+	lifecycle.WithLogger(logger)
+
+	return nil
+}
+
+// teardownLogger flushes and closes the log file handle.
+func teardownLogger() {
+	// If logfile is nil, nothing to do
+	if logfile == nil {
+		return
+	}
+
+	// Flush the logger to ensure all logs are written
+	if err := logfile.Sync(); err != nil {
+		slog.Error("Error flushing log file", "err", err)
+	}
+
+	// Close log file handle
+	if err := logfile.Close(); err != nil {
+		slog.Error("Error closing log file", "err", err)
+	}
+}