Reduce Args() complexity for 'config write' command (#11)

cmd/mydyndns/cli/config.go

@@ -59,22 +59,7 @@ useful for generating config file templates).`,
 			if err := cobra.MinimumNArgs(1)(cmd, args); err != nil {
 				return err
 			}
-
-			supportedExts := internal.NewStringCollection(viper.SupportedExts...)
-			for _, arg := range args {
-				ext := filepath.Ext(arg)
-				if len(ext) == 0 {
-					ext = arg
-				} else {
-					ext = ext[1:]
-				}
-
-				if !supportedExts.Contains(ext) {
-					return viper.UnsupportedConfigError(ext)
-				}
-			}
-
-			return nil
+			return validateConfigFileNames(args)
 		},
 		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 			seenArgs := internal.NewStringCollection(args...)
@@ -104,7 +89,8 @@ useful for generating config file templates).`,
 		},
 		PreRunE: func(cmd *cobra.Command, args []string) error {
 			if viper.GetBool("validate") {
-				return firstValidationError(cmd, validateAPIKey, validateBaseURL, validatePollInterval)
+				return firstValidationError(cmd,
+					validateAPIKey, validateBaseURL, validatePollInterval)
 			}
 			return nil
 		},
@@ -279,7 +265,8 @@ func newConfigValidateCmd() *cobra.Command {
 		Long: `The validate subcommand isolates the configuration checks executed when the mydyndns agent starts. Use this to
 check whether the agent would fail to start due to invalid configuration, without actually running the agent.`,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			return firstValidationError(cmd, validateAPIKey, validateBaseURL, validatePollInterval)
+			return firstValidationError(cmd,
+				validateAPIKey, validateBaseURL, validatePollInterval)
 		},
 	}
 }

cmd/mydyndns/cli/validation.go

@@ -2,8 +2,10 @@ package cli
 
 import (
 	"fmt"
+	"path/filepath"
 	"strings"
 
+	"github.com/TylerHendrickson/mydyndns/internal"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 )
@@ -39,3 +41,22 @@ func firstValidationError(cmd *cobra.Command, validators ...func(*cobra.Command)
 	}
 	return nil
 }
+
+// validateConfigFileNames ensures that all strings represent a valid Viper extension.
+// Each string must be a supported extension ("json") or end in a supported extension ("foo.json").
+// The first value encountered that does not represent a valid Viper extension returns
+// viper.UnsupportedConfigError.
+func validateConfigFileNames(s []string) error {
+	supportedExts := internal.NewStringCollection(viper.SupportedExts...)
+	for _, toValidate := range s {
+		if ext := filepath.Ext(toValidate); len(ext) > 0 {
+			toValidate = ext[1:]
+		}
+
+		if !supportedExts.Contains(toValidate) {
+			return viper.UnsupportedConfigError(toValidate)
+		}
+	}
+
+	return nil
+}