refactor: restructure project

cfg/cfg.go

@@ -1,45 +1,64 @@
 package cfg
 
 import (
-	"fmt"
+	"errors"
+	"time"
 
 	"github.com/alecthomas/kong"
 )
 
+var ErrInvalidDataURL = errors.New("invalid data url, must not be blank")
+
 type AppSettings 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"`
+	ServerAddress     string
+	DataFile          string
+	DataURL           string
+	CacheTTL          time.Duration
+	ReadHeaderTimeout time.Duration
 }
 
-func NewAppSettings() *AppSettings {
-	return &AppSettings{}
+//nolint:lll // ignore line length
+type CLI 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"`
+	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}"`
 }
 
-func (s *AppSettings) Parse() error {
-	ctx := kong.Parse(
-		s,
+func (c *CLI) Parse() (*AppSettings, error) {
+	_ = kong.Parse(
+		c,
 		kong.Vars{
-			"default_address":   ":8080",
-			"default_file_path": "./data.csv",
+			"default_address":             ":8080",
+			"default_file_path":           "./data.csv",
+			"default_cache_ttl":           "2m",
+			"default_read_header_timeout": "3s",
 		},
 		kong.Name("country_geo_locations"),
 		kong.Description("🚀 Start a simple web server for GeoIP data"),
 		kong.UsageOnError(),
 	)
 
-	err := validateFlags(*s)
+	cacheTTL, err := time.ParseDuration(c.CacheTTL)
 	if err != nil {
-		ctx.PrintUsage(false)
-		fmt.Println()
-		return err
+		return nil, err
 	}
-	return nil
-}
 
-func validateFlags(settings AppSettings) error {
-	if settings.DataURL == "" {
-		return fmt.Errorf("error: invalid data url, must not be blank")
+	readHeaderTimeout, err := time.ParseDuration(c.ReadHeaderTimeout)
+	if err != nil {
+		return nil, err
 	}
-	return nil
+
+	if c.DataURL == "" {
+		return nil, ErrInvalidDataURL
+	}
+
+	return &AppSettings{
+		ServerAddress:     c.ServerAddress,
+		DataFile:          c.DataFile,
+		DataURL:           c.DataURL,
+		CacheTTL:          cacheTTL,
+		ReadHeaderTimeout: readHeaderTimeout,
+	}, nil
 }