Add "check" command to validate UUIDs (#12)

* introduce the new check command

README.md

@@ -15,4 +15,5 @@ Run the following command
 
 ### Commands:
  - uuid v4
+ - uuid check
 

cmd/check.go

@@ -0,0 +1,39 @@
+package cmd
+
+import (
+	"fmt"
+	"regexp"
+
+	"github.com/spf13/cobra"
+)
+
+// check represents a command validating whether the provided input is a valid UUID
+var check = &cobra.Command{
+	Use:   "check",
+	Short: "Checks whether each of the provided arguments is a valid UUID",
+	Long: `Checks whether each of the provided arguments is a valid UUID,
+while using regular expression pattern matching.
+you can pass one or more UUIDs to be checked:
+
+example usage: 
+uuid check d50cddd9-71f3-47f0-a407-1bf7581874fc`,
+	Args: cobra.MinimumNArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		for _, arg := range args {
+			if Check(arg) {
+				fmt.Printf("%s is a valid UUID\n", arg)
+			} else {
+				fmt.Printf("%s is not a valid UUID\n", arg)
+			}
+		}
+	},
+}
+
+func Check(uuid string) bool {
+	uuidPattern := "^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$"
+	re := regexp.MustCompile(uuidPattern)
+	if re.MatchString(uuid) {
+		return true
+	}
+	return false
+}

cmd/check_test.go

@@ -0,0 +1,25 @@
+package cmd
+
+import "testing"
+
+func TestCheck(t *testing.T) {
+
+	t.Run("should return true", func(t *testing.T) {
+		input := "c923d13a-cee4-4182-af57-438f8b032fb6" // valid UUID
+		got := Check(input)
+		expect := true
+		if got != expect {
+			t.Errorf("expected %s to be %t but got %t", input, expect, got)
+		}
+	})
+
+	t.Run("should return false", func(t *testing.T) {
+		input := "c93a-cee4-4182-af57-438f2fb6" // not a valid UUID
+		got := Check(input)
+		expect := false
+		if got != expect {
+			t.Errorf("expected %s to be %t but got %t", input, expect, got)
+		}
+	})
+
+}

cmd/root.go

@@ -52,6 +52,7 @@ func init() {
 
 	rootCmd.AddCommand(v4Cmd)
 	rootCmd.AddCommand(empty)
+	rootCmd.AddCommand(check)
 
 	cobra.OnInitialize(initConfig)