chore: Move private packages to internal (#1664)

internal/log/logger.go

@@ -0,0 +1,69 @@
+package log
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+
+	"github.com/prometheus-community/windows_exporter/internal/log/eventlog"
+	"github.com/prometheus/common/promslog"
+	"golang.org/x/sys/windows"
+)
+
+// AllowedFile is a settable identifier for the output file that the logger can have.
+type AllowedFile struct {
+	s string
+	w io.Writer
+}
+
+func (f *AllowedFile) String() string {
+	return f.s
+}
+
+// Set updates the value of the allowed format.
+func (f *AllowedFile) Set(s string) error {
+	f.s = s
+
+	switch s {
+	case "stdout":
+		f.w = os.Stdout
+	case "stderr":
+		f.w = os.Stderr
+	case "eventlog":
+		handle, err := windows.RegisterEventSource(nil, windows.StringToUTF16Ptr("windows_exporter"))
+		if err != nil {
+			return fmt.Errorf("failed to open event log: %w", err)
+		}
+
+		f.w = eventlog.NewEventLogWriter(handle)
+	default:
+		file, err := os.OpenFile(s, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0o200)
+		if err != nil {
+			return fmt.Errorf("failed to open log file: %w", err)
+		}
+
+		f.w = file
+	}
+
+	return nil
+}
+
+// Config is a struct containing configurable settings for the logger.
+type Config struct {
+	*promslog.Config
+
+	File *AllowedFile
+}
+
+func New(config *Config) (*slog.Logger, error) {
+	if config.File == nil {
+		return nil, errors.New("log file undefined")
+	}
+
+	config.Config.Writer = config.File.w
+	config.Config.Style = promslog.GoKitStyle
+
+	return promslog.New(config.Config), nil
+}