io-exporter/cmd/config.go

package cmd

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

	flag "github.com/spf13/pflag"

	"github.com/knadh/koanf/providers/posflag"
	koanf "github.com/knadh/koanf/v2"
)

const (
	Version = `v0.0.1`
	SLEEP   = 5
	Usage   = `io-exporter [options] <file>
Options:
-t --timeout <int>          When should the operation timeout in seconds
-l --label   <label=value>  Add label to exported metric
-h --help                   Show help
-v --version                Show program version`
)

// config via commandline flags
type Config struct {
	Showversion bool     `koanf:"version"` // -v
	Showhelp    bool     `koanf:"help"`    // -h
	Label       []string `koanf:"label"`   // -v
	Timeout     int      `koanf:"timeout"` // -t
	Port        int      `koanf:"port"`    // -p

	File   string
	Labels []Label
}

func InitConfig(output io.Writer) (*Config, error) {
	var kloader = koanf.New(".")

	// setup custom usage
	flagset := flag.NewFlagSet("config", flag.ContinueOnError)
	flagset.Usage = func() {
		_, err := fmt.Fprintln(output, Usage)
		if err != nil {
			log.Fatalf("failed to print to output: %s", err)
		}
	}

	// parse commandline flags
	flagset.BoolP("version", "v", false, "show program version")
	flagset.BoolP("help", "h", false, "show help")
	flagset.StringArrayP("label", "l", nil, "additional labels")
	flagset.IntP("timeout", "t", 1, "timeout for file operation in seconds")
	flagset.IntP("port", "p", 9187, "prometheus metrics port to listen to")

	if err := flagset.Parse(os.Args[1:]); err != nil {
		return nil, fmt.Errorf("failed to parse program arguments: %w", err)
	}

	// command line setup
	if err := kloader.Load(posflag.Provider(flagset, ".", kloader), nil); err != nil {
		return nil, fmt.Errorf("error loading flags: %w", err)
	}

	// fetch values
	conf := &Config{}
	if err := kloader.Unmarshal("", &conf); err != nil {
		return nil, fmt.Errorf("error unmarshalling: %w", err)
	}

	// arg is the file under test
	if len(flagset.Args()) > 0 {
		conf.File = flagset.Args()[0]
	} else {
		if !conf.Showversion {
			flagset.Usage()
			os.Exit(1)
		}
	}

	for _, label := range conf.Label {
		if len(label) == 0 {
			continue
		}

		parts := strings.Split(label, "=")
		if len(parts) != 2 {
			return nil, errors.New("invalid label spec: " + label + ", expected label=value")
		}

		conf.Labels = append(conf.Labels, Label{Name: parts[0], Value: parts[1]})
	}

	return conf, nil
}