chore: add command and describe properties to decommission

Author: Sai Ray

packages/amplify-cli/src/commands/gen2-migration/decommission.ts

@@ -1,12 +1,25 @@
 import { AmplifyMigrationStep } from './_step';
 import { printer } from '@aws-amplify/amplify-prompts';
+import { AmplifyGen2MigrationValidations } from './_validations';
+import {
+  CloudFormationClient,
+  CreateChangeSetCommand,
+  DescribeChangeSetCommand,
+  DeleteChangeSetCommand,
+  DescribeChangeSetOutput,
+  waitUntilChangeSetCreateComplete,
+} from '@aws-sdk/client-cloudformation';
+import { stateManager } from '@aws-amplify/amplify-cli-core';
 
 export class AmplifyMigrationDecommissionStep extends AmplifyMigrationStep {
   readonly command = 'decommission';
-  readonly describe = 'Decommission Gen1 resources';
+  readonly describe = 'Decommission Gen1 resources after migration';
 
   public async validate(): Promise<void> {
-    printer.warn('Not implemented');
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const validations = new AmplifyGen2MigrationValidations({} as any);
+    // eslint-disable-next-line spellcheck/spell-checker
+    await validations.validateStatefulResources(await this.createChangeSet());
   }
 
   public async execute(): Promise<void> {
@@ -16,4 +29,44 @@ export class AmplifyMigrationDecommissionStep extends AmplifyMigrationStep {
   public async rollback(): Promise<void> {
     printer.warn('Not implemented');
   }
+
+  private async createChangeSet(): Promise<DescribeChangeSetOutput> {
+    const meta = stateManager.getMeta();
+    const stackName = meta.providers.awscloudformation.StackName;
+
+    const cfn = new CloudFormationClient({});
+    const changeSetName = `decommission-${Date.now()}`;
+
+    await cfn.send(
+      new CreateChangeSetCommand({
+        StackName: stackName,
+        ChangeSetName: changeSetName,
+        TemplateBody: JSON.stringify({
+          Resources: {
+            DummyResource: {
+              Type: 'AWS::CloudFormation::WaitConditionHandle',
+            },
+          },
+        }),
+      }),
+    );
+
+    await waitUntilChangeSetCreateComplete({ client: cfn, maxWaitTime: 120 }, { StackName: stackName, ChangeSetName: changeSetName });
+
+    const changeSet = await cfn.send(
+      new DescribeChangeSetCommand({
+        StackName: stackName,
+        ChangeSetName: changeSetName,
+      }),
+    );
+
+    await cfn.send(
+      new DeleteChangeSetCommand({
+        StackName: stackName,
+        ChangeSetName: changeSetName,
+      }),
+    );
+
+    return changeSet;
+  }
 }