country-geo-locations/internal/cmd/cli.go

package cmd

import (
	"errors"
	"time"

	"github.com/alecthomas/kong"
)

var ErrInvalidDataURL = errors.New("invalid data url, must not be blank")

type AppSettings struct {
	ServerAddress     string
	DataFile          string
	DataURL           string
	CacheTTL          time.Duration
	ReadHeaderTimeout time.Duration
	EnableExporter    bool
	ExporterAddress   string
}

//nolint:lll // ignore line length
type CLI struct {
	ServerAddress     string `name:"listen-address" env:"GEOIP_LISTEN_ADDRESS" help:"Address to use for the api server" default:"${default_address}"`
	DataFile          string `name:"data-file" env:"GEOIP_DATA_FILE" help:"path to data file" default:"${default_file_path}"`
	DataURL           string `name:"data-url" env:"GEOIP_DATA_URL" help:"url to data file"`
	CacheTTL          string `name:"cache-ttl" env:"GEOIP_CACHE_TTL" help:"ttl for response cache" default:"${default_cache_ttl}"`
	ReadHeaderTimeout string `name:"read-header-timeout" env:"GEOIP_READ_HEADER_TIMEOUT" help:"timeout for reading http header" default:"${default_read_header_timeout}"`
	EnableExporter    bool   `name:"enable-exporter" env:"GEOIP_ENABLE_EXPORTER" help:"enable prometheus exporter" default:"${default_enable_exporter}"`
	ExporterAddress   string `name:"exporter-address" env:"GEOIP_EXPORTER_ADDRESS" help:"Address to use for the prometheus metrics server" default:"${default_exporter_address}"`
}

func (c *CLI) Parse() (*AppSettings, error) {
	_ = kong.Parse(
		c,
		kong.Vars{
			"default_address":             ":8080",
			"default_file_path":           "./data.csv",
			"default_cache_ttl":           "2m",
			"default_read_header_timeout": "3s",
			"default_enable_exporter":     "false",
			"default_exporter_address":    ":9191",
		},
		kong.Name("country-geo-locations"),
		kong.Description("🚀 Start a simple web server for GeoIP data"),
		kong.UsageOnError(),
	)

	cacheTTL, err := time.ParseDuration(c.CacheTTL)
	if err != nil {
		return nil, err
	}

	readHeaderTimeout, err := time.ParseDuration(c.ReadHeaderTimeout)
	if err != nil {
		return nil, err
	}

	if c.DataURL == "" {
		return nil, ErrInvalidDataURL
	}

	return &AppSettings{
		ServerAddress:     c.ServerAddress,
		DataFile:          c.DataFile,
		DataURL:           c.DataURL,
		CacheTTL:          cacheTTL,
		ReadHeaderTimeout: readHeaderTimeout,
		EnableExporter:    c.EnableExporter,
		ExporterAddress:   c.ExporterAddress,
	}, nil
}