chore: Move private packages to internal (#1664)

internal/log/eventlog/eventlog.go

@@ -0,0 +1,53 @@
+//go:build windows
+
+// Package eventlog provides a Logger that writes to Windows Event Log.
+package eventlog
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"golang.org/x/sys/windows"
+)
+
+const (
+	// NeLogOemCode is a generic error log entry for OEMs to use to
+	// elog errors from OEM value added services.
+	// See: https://github.com/microsoft/win32metadata/blob/2f3c5282ce1024a712aeccd90d3aa50bf7a49e27/generation/WinSDK/RecompiledIdlHeaders/um/LMErrlog.h#L824-L845
+	neLogOemCode = uint32(3299)
+)
+
+// Interface guard.
+var _ io.Writer = (*Writer)(nil)
+
+type Writer struct {
+	handle windows.Handle
+}
+
+// NewEventLogWriter returns a new Writer which writes to Windows EventLog.
+func NewEventLogWriter(handle windows.Handle) *Writer {
+	return &Writer{handle: handle}
+}
+
+func (w *Writer) Write(p []byte) (int, error) {
+	var eType uint16
+
+	switch {
+	case bytes.Contains(p, []byte(" level=error")) || bytes.Contains(p, []byte(`"level":"error"`)):
+		eType = windows.EVENTLOG_ERROR_TYPE
+	case bytes.Contains(p, []byte(" level=warn")) || bytes.Contains(p, []byte(`"level":"warn"`)):
+		eType = windows.EVENTLOG_WARNING_TYPE
+	default:
+		eType = windows.EVENTLOG_INFORMATION_TYPE
+	}
+
+	msg, err := windows.UTF16PtrFromString(string(p))
+	if err != nil {
+		return 0, fmt.Errorf("error convert string to UTF-16: %w", err)
+	}
+
+	ss := []*uint16{msg, nil, nil, nil, nil, nil, nil, nil, nil}
+
+	return len(p), windows.ReportEvent(w.handle, eType, 0, neLogOemCode, 0, 9, 0, &ss[0], nil)
+}

internal/log/flag/flag.go

@@ -0,0 +1,37 @@
+// Copyright 2017 The Prometheus Authors
+// 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 flag
+
+import (
+	"github.com/alecthomas/kingpin/v2"
+	"github.com/prometheus-community/windows_exporter/internal/log"
+	"github.com/prometheus/common/promslog"
+	"github.com/prometheus/common/promslog/flag"
+)
+
+// FileFlagName is the canonical flag name to configure the log file.
+const FileFlagName = "log.file"
+
+// FileFlagHelp is the help description for the log.file flag.
+const FileFlagHelp = "Output file of log messages. One of [stdout, stderr, eventlog, <path to log file>]"
+
+// AddFlags adds the flags used by this package to the Kingpin application.
+// To use the default Kingpin application, call AddFlags(kingpin.CommandLine).
+func AddFlags(a *kingpin.Application, config *log.Config) {
+	config.Config = new(promslog.Config)
+	flag.AddFlags(a, config.Config)
+
+	config.File = &log.AllowedFile{}
+	a.Flag(FileFlagName, FileFlagHelp).Default("stderr").SetValue(config.File)
+}

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
+}