Added a helper function to get referenced plugins by type (kubernetes-sigs#1091)

* Added a helper function to get referenced plugins by type

Signed-off-by: Shmuel Kallner <[email protected]>

* Added a function comment

Signed-off-by: Shmuel Kallner <[email protected]>

* Update from review comment

Signed-off-by: Shmuel Kallner <[email protected]>

* Updates from review comments

Signed-off-by: Shmuel Kallner <[email protected]>

---------

Signed-off-by: Shmuel Kallner <[email protected]>

Author: shmuelk

pkg/epp/plugins/plugins.go

@@ -16,7 +16,10 @@ limitations under the License.
 
 package plugins
 
-import "context"
+import (
+	"context"
+	"fmt"
+)
 
 // Plugin defines the interface for a plugin.
 // This interface should be embedded in all plugins across the code.
@@ -50,3 +53,18 @@ type HandlePlugins interface {
 	// GetAllPluginsWithNames returns all of the known plugins with their names
 	GetAllPluginsWithNames() map[string]Plugin
 }
+
+// PluginByType retrieves the specified plugin by name and verifies its type
+func PluginByType[P Plugin](handlePlugins HandlePlugins, name string) (P, error) {
+	var zero P
+
+	rawPlugin := handlePlugins.Plugin(name)
+	if rawPlugin == nil {
+		return zero, fmt.Errorf("there is no plugin with the name '%s' defined", name)
+	}
+	thePlugin, ok := rawPlugin.(P)
+	if !ok {
+		return zero, fmt.Errorf("the plugin with the name '%s' is not an instance of %T", name, zero)
+	}
+	return thePlugin, nil
+}