package home

import (
	"fmt"
	"path/filepath"
	"runtime"

	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
	"github.com/AdguardTeam/golibs/log"
	"github.com/AdguardTeam/golibs/stringutil"
	"gopkg.in/natefinch/lumberjack.v2"
	"gopkg.in/yaml.v3"
)

// configSyslog is used to indicate that syslog or eventlog (win) should be used
// for logger output.
const configSyslog = "syslog"

// configureLogger configures logger level and output.
func configureLogger(opts options) (err error) {
	ls := getLogSettings(opts)

	// Configure logger level.
	if ls.Verbose {
		log.SetLevel(log.DEBUG)
	}

	// Make sure that we see the microseconds in logs, as networking stuff can
	// happen pretty quickly.
	log.SetFlags(log.LstdFlags | log.Lmicroseconds)

	// Write logs to stdout by default.
	if ls.File == "" {
		return nil
	}

	if ls.File == configSyslog {
		// Use syslog where it is possible and eventlog on Windows.
		err = aghos.ConfigureSyslog(serviceName)
		if err != nil {
			return fmt.Errorf("cannot initialize syslog: %w", err)
		}

		return nil
	}

	logFilePath := ls.File
	if !filepath.IsAbs(logFilePath) {
		logFilePath = filepath.Join(Context.workDir, logFilePath)
	}

	log.SetOutput(&lumberjack.Logger{
		Filename:   logFilePath,
		Compress:   ls.Compress,
		LocalTime:  ls.LocalTime,
		MaxBackups: ls.MaxBackups,
		MaxSize:    ls.MaxSize,
		MaxAge:     ls.MaxAge,
	})

	return nil
}

// getLogSettings returns a log settings object properly initialized from opts.
func getLogSettings(opts options) (ls *logSettings) {
	configLogSettings := config.Log

	ls = readLogSettings()
	if ls == nil {
		// Use default log settings.
		ls = &configLogSettings
	}

	// Command-line arguments can override config settings.
	if opts.verbose {
		ls.Verbose = true
	}

	// TODO(a.garipov): Use cmp.Or in Go 1.22.
	ls.File = stringutil.Coalesce(opts.logFile, ls.File)

	if opts.runningAsService && ls.File == "" && runtime.GOOS == "windows" {
		// When running as a Windows service, use eventlog by default if
		// nothing else is configured.  Otherwise, we'll lose the log output.
		ls.File = configSyslog
	}

	return ls
}

// readLogSettings reads logging settings from the config file.  We do it in a
// separate method in order to configure logger before the actual configuration
// is parsed and applied.
func readLogSettings() (ls *logSettings) {
	conf := &configuration{}

	yamlFile, err := readConfigFile()
	if err != nil {
		return nil
	}

	err = yaml.Unmarshal(yamlFile, conf)
	if err != nil {
		log.Error("Couldn't get logging settings from the configuration: %s", err)
	}

	return &conf.Log
}
