refactor backend (#116)

Author: SparkYuan

pkg/engine/states/backend.go

@@ -1,6 +1,18 @@
 package states
 
-// TODO: We will refactor this file with StateStorage later
+import "github.com/zclconf/go-cty/cty"
+
+// Backend represent a medium that Kusion will operate on.
+type Backend interface {
+	// ConfigSchema returns a set of attributes that is needed to config this backend
+	ConfigSchema() cty.Type
+
+	// Configure will config this backend with provided configuration
+	Configure(obj cty.Value) error
+
+	// StateStorage return a StateStorage to manage State
+	StateStorage() StateStorage
+}
 
 var Backends = make(map[string]func() StateStorage)
 

pkg/engine/states/state.go

@@ -5,21 +5,11 @@ import (
 
 	"kusionstack.io/kusion/pkg/engine/models"
 
-	"github.com/zclconf/go-cty/cty"
-
 	"kusionstack.io/kusion/pkg/version"
 )
 
-// StateStorage represents the set of methods required for a State backend
+// StateStorage represents the set of methods to manipulate State in a specified storage
 type StateStorage interface {
-	// ConfigSchema returns a description of the expected configuration
-	// structure for the receiving backend.
-	ConfigSchema() cty.Type
-
-	// Configure uses the provided configuration to set configuration fields
-	// within the backend.
-	Configure(obj cty.Value) error
-
 	// GetLatestState return nil if state not exists
 	GetLatestState(query *StateQuery) (*State, error)