config/config.go

package config

import (
	"errors"
	"fmt"
	"log"
	"os"
	"strings"

	"github.com/Masterminds/semver"

	"github.com/spf13/afero"
	"github.com/spf13/pflag"
	"github.com/spf13/viper"
)

var (
	Config             = viper.GetViper()
	autoHelpAndVersion = true
	configFS           = afero.NewOsFs()
)

func init() {
	SetConfigFile("config", "yaml")
}

func SetConfigFile(name string, format string) {
	viper.SetDefault("Config.filename", name)
	viper.SetDefault("Config.format", format)
}

func AddHelpAndVersion(helpRequested *bool, versionRequested *bool) {
	if autoHelpAndVersion {
		if !viper.IsSet("help") {
			pflag.BoolVarP(helpRequested, "help", "h", false, "This message")
		}

		if !viper.IsSet("version") {
			pflag.BoolVarP(versionRequested, "version", "v", false, "Get Program Version")
		}
	}
}

func DefineConfigItem(key string, short string, def interface{}, helpString string) {
	switch t := def.(type) {
	case bool:
		viper.SetDefault(key, t)
		pflag.BoolP(key, short, viper.GetBool(key), helpString)
	case float64:
		viper.SetDefault(key, t)
		pflag.Float64P(key, short, viper.GetFloat64(key), helpString)
	case int:
		viper.SetDefault(key, t)
		pflag.IntP(key, short, viper.GetInt(key), helpString)
	case string:
		viper.SetDefault(key, t)
		pflag.StringP(key, short, viper.GetString(key), helpString)
	default:
		log.Fatalln("Config Type Unsupported")
	}
}

func SetAppName(appName, appPrefix string) {
	viper.SetDefault("app.name", appName)
	viper.SetDefault("app.prefix", appPrefix)
}

func SetAppVersion(verStr string) {
	var appVersion *semver.Version
	var err error

	appVersion, err = semver.NewVersion(verStr)
	if err != nil {
		log.Fatalln("Error setting app version")
	}

	viper.SetDefault("app.version", appVersion)
}

func GetConfigs() {
	var helpRequested bool
	var versionRequested bool

	viper.SetFs(configFS)

	viper.SetConfigName(viper.GetString("Config.filename"))
	viper.SetConfigType(viper.GetString("Config.format"))

	viper.AddConfigPath(fmt.Sprintf("/etc/%s/", viper.GetString("app.prefix")))
	viper.AddConfigPath(fmt.Sprintf("$HOME/.%s/", viper.GetString("app.prefix")))
	viper.AddConfigPath("./etc/")
	viper.WatchConfig()

	viper.SetEnvPrefix(viper.GetString("app.prefix"))
	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	viper.AutomaticEnv()

	if autoHelpAndVersion {
		AddHelpAndVersion(&helpRequested, &versionRequested)
		autoHelpAndVersion = false // insure you do not add these twice, or you will experience a failure
	}

	if err := viper.ReadInConfig(); err != nil {
		var configFileNotFoundError viper.ConfigFileNotFoundError

		if errors.As(err, &configFileNotFoundError) {
		} else {
			log.Fatal("invalid Config file format", err)
		}
	}

	pflag.Parse()
	_ = viper.BindPFlags(pflag.CommandLine)

	if helpRequested {
		fmt.Printf("Usage: %s:\n", os.Args[0])
		pflag.PrintDefaults()

		os.Exit(0)
	}
	if versionRequested {
		fmt.Printf("%s: %s\n", os.Args[0], viper.Get("app.version"))

		os.Exit(0)
	}
}