feat: initial implementation

Author: riywo

API.md

@@ -1,5 +1,85 @@
-export class Hello {
-  public sayHello() {
-    return 'hello, world!';
+import { Stack } from 'aws-cdk-lib';
+import { CfnDataSource, CfnGraphQLSchema, CfnResolver } from 'aws-cdk-lib/aws-appsync';
+import { PolicyStatement, Role, ServicePrincipal } from 'aws-cdk-lib/aws-iam';
+import { StateMachine, StateMachineType } from 'aws-cdk-lib/aws-stepfunctions';
+import { Construct } from 'constructs';
+
+export interface AppSyncDataSourceStepFunctionsExpressProps {
+  readonly apiId: string;
+}
+
+export interface AddStateMachineResolverProps {
+  readonly stateMachine: StateMachine;
+  readonly schema: CfnGraphQLSchema;
+  readonly typeName: string;
+  readonly fieldName: string;
+}
+
+export class AppSyncDataSourceStepFunctionsExpress extends Construct {
+  readonly role: Role;
+  readonly dataSource: CfnDataSource;
+
+  constructor(scope: Construct, id: string, props: AppSyncDataSourceStepFunctionsExpressProps) {
+    super(scope, id);
+    this.role = new Role(this, 'ServiceRole', {
+      assumedBy: new ServicePrincipal('appsync.amazonaws.com'),
+    });
+    this.role.addToPolicy(new PolicyStatement({
+      resources: ['*'],
+      actions: ['states:StartSyncExecution'],
+    }));
+    const region = Stack.of(this).region;
+    this.dataSource = new CfnDataSource(this, 'SyncStatesApi', {
+      apiId: props.apiId,
+      name: 'SyncStatesApi',
+      type: 'HTTP',
+      httpConfig: {
+        endpoint: `https://sync-states.${region}.amazonaws.com`,
+        authorizationConfig: {
+          authorizationType: 'AWS_IAM',
+          awsIamConfig: {
+            signingRegion: region,
+            signingServiceName: 'states',
+          },
+        },
+      },
+      serviceRoleArn: this.role.roleArn,
+    });
+  }
+
+  addStateMachineResolver(id: string, props: AddStateMachineResolverProps) {
+    const { stateMachine, schema, typeName, fieldName } = props;
+    if (stateMachine.stateMachineType !== StateMachineType.EXPRESS) {
+      throw new Error(`stateMachine must be EXPRESS type. (${stateMachine.stateMachineName} is ${stateMachine.stateMachineType})`);
+    }
+    const resolver = new CfnResolver(this, id, {
+      apiId: this.dataSource.apiId,
+      typeName,
+      fieldName,
+      dataSourceName: this.dataSource.name,
+      kind: 'UNIT',
+      requestMappingTemplate: `
+        {
+          "version": "2018-05-29",
+          "method": "POST",
+          "resourcePath": "/",
+          "params": {
+            "headers": {
+              "X-Amz-Target": "AWSStepFunctions.StartSyncExecution",
+              "Content-Type": "application/x-amz-json-1.0"
+            },
+            "body": $util.toJson({
+              "stateMachineArn": "${stateMachine.stateMachineArn}",
+              "input": $util.toJson($ctx.args)
+            })
+          }
+        }
+      `,
+      responseMappingTemplate: `
+        $util.parseJson($ctx.result.body).output
+      `,
+    });
+    resolver.addDependsOn(schema);
+    return resolver;
   }
 }