Show nicer error when version does not exist (#31)

* Show nicer error when version does not exist

* Add very first unit test

* Fix test env

pkg/download/download_test.go

@@ -0,0 +1,23 @@
+package download
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestGetDownloadLocation(t *testing.T) {
+	tempDir := t.TempDir()
+	t.Setenv("HOME", tempDir)
+	downloadLocation := GetDownloadLocation()
+
+	expectedLocation := filepath.Join(tempDir, ".tfversion", "versions")
+	if downloadLocation != expectedLocation {
+		t.Errorf("Expected download location %s, but got %s", expectedLocation, downloadLocation)
+	}
+
+	_, err := os.Stat(downloadLocation)
+	if os.IsNotExist(err) {
+		t.Errorf("Download location directory does not exist: %s", downloadLocation)
+	}
+}

pkg/helpers/helper.go

@@ -24,6 +24,10 @@ func ColoredInstallHelper(version string) string {
 	return color.CyanString(fmt.Sprintf("`tfversion install %s`", version))
 }
 
+func ColoredListHelper() string {
+	return color.CyanString("`tfversion list`")
+}
+
 // ExitWithError prints an error message and exits with status code 1
 func ExitWithError(message string, err error) {
 	fmt.Printf("%s %s: %s\n", color.HiRedString("error:"), message, err)

pkg/install/install.go

@@ -3,6 +3,7 @@ package install
 import (
 	"fmt"
 	"runtime"
+	"slices"
 
 	"github.com/tfversion/tfversion/pkg/download"
 	"github.com/tfversion/tfversion/pkg/helpers"
@@ -16,6 +17,13 @@ func InstallVersion(version string) {
 		helpers.ExitWithError("installing", err)
 	}
 
+	// Check if the version exists
+	availableVersions := list.GetAvailableVersions()
+	if !slices.Contains(availableVersions, version) {
+		err := fmt.Errorf("terraform version %s does not exist, please run %s to check available versions", helpers.ColoredVersion(version), helpers.ColoredListHelper())
+		helpers.ExitWithError("installing", err)
+	}
+
 	// Download the Terraform release
 	zipFile, err := download.Download(version, runtime.GOOS, runtime.GOARCH)
 	if err != nil {