Rework complete project

cfg/cfg.go

@@ -0,0 +1,59 @@
+package cfg
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/alecthomas/kong"
+)
+
+type AppSettings struct {
+	ServerAddress string
+	DataFile      string
+	DataURL       string
+}
+
+var cliStruct struct {
+	ServerAddress string `name:"listen-address" env:"GEOIP_LISTEN_ADDRESS" help:"Address to use for the metrics 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" default:"${default_file_url}"`
+}
+
+func Parse() *AppSettings {
+	ctx := kong.Parse(
+		&cliStruct,
+		kong.Vars{
+			"default_address":   ":8080",
+			"default_file_path": "./data.csv",
+			"default_file_url":  "https://data.neuber.io/data.csv",
+		},
+		kong.Name("country_geo_locations"),
+		kong.Description("🚀 Start a simple web server for GeoIP data"),
+		kong.UsageOnError(),
+	)
+
+	validateFlags(ctx)
+	settings := &AppSettings{
+		ServerAddress: cliStruct.ServerAddress,
+		DataFile:      cliStruct.DataFile,
+		DataURL:       cliStruct.DataURL,
+	}
+	return settings
+}
+
+func validateFlags(cliCtx *kong.Context) {
+	var flagsValid = true
+	var messages = []string{}
+	if cliStruct.ServerAddress == "" {
+		messages = append(messages, "error: invalid server address, must not be blank")
+		flagsValid = false
+	}
+	if !flagsValid {
+		cliCtx.PrintUsage(false)
+		fmt.Println()
+		for i := 0; i < len(messages); i++ {
+			fmt.Println(messages[i])
+		}
+		os.Exit(1)
+	}
+}