feat(scheduler): ScheduleTargetInput (aws#25663)

This PR contains implementation of ScheduleTargetInput. While a schedule is the main resource in Amazon EventBridge Scheduler, this PR adds ScheduleTargetInput on which ScheduleTargetBase depends.

Every Schedule has a target that determines what extra information is sent to the target when the schedule is triggered. Also 4 ContextAttributes can be used that will be resolved at trigger-time.

To be able to create sensible unit tests, also the a start is made to add the `Schedule` and the `LambdaInvoke` target as described in the RFC.

Implementation is based on RFC: https://github.com/aws/aws-cdk-rfcs/blob/master/text/0474-event-bridge-scheduler-l2.md

Also added a small fix to 2 of the unit tests of the previous PR for this module.

Advances aws#23394

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-scheduler-alpha/README.md

@@ -37,7 +37,15 @@ This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aw
 
 ## Defining a schedule 
 
-TODO: Schedule is not yet implemented. See section in [L2 Event Bridge Scheduler RFC](https://github.com/aws/aws-cdk-rfcs/blob/master/text/0474-event-bridge-scheduler-l2.md)
+TODO: Schedule is not yet fully implemented. See section in [L2 Event Bridge Scheduler RFC](https://github.com/aws/aws-cdk-rfcs/blob/master/text/0474-event-bridge-scheduler-l2.md)
+
+[comment]: <> (TODO: change for each PR that implements more functionality)
+
+Only an L2 class is created that wraps the L1 class and handles the following properties:
+
+- schedule
+- target (only LambdaInvoke is supported for now)
+- flexibleTimeWindow will be set to `{ mode: 'OFF' }`
 
 ### Schedule Expressions
 
@@ -95,10 +103,31 @@ TODO: Group is not yet implemented. See section in [L2 Event Bridge Scheduler RF
 
 TODO: Scheduler Targets Module is not yet implemented. See section in [L2 Event Bridge Scheduler RFC](https://github.com/aws/aws-cdk-rfcs/blob/master/text/0474-event-bridge-scheduler-l2.md)
 
+Only LambdaInvoke target is added for now.
+
 ### Input 
 
-TODO: Target Input is not yet implemented. See section in [L2 Event Bridge Scheduler RFC](https://github.com/aws/aws-cdk-rfcs/blob/master/text/0474-event-bridge-scheduler-l2.md)
+Target can be invoked with a custom input. Class `ScheduleTargetInput` supports free form text input and JSON-formatted object input:
+
+```ts
+const input = ScheduleTargetInput.fromObject({
+    'QueueName': 'MyQueue'
+});
+```
+
+You can include context attributes in your target payload. EventBridge Scheduler will replace each keyword with
+its respective value and deliver it to the target. See
+[full list of supported context attributes](https://docs.aws.amazon.com/scheduler/latest/UserGuide/managing-schedule-context-attributes.html):
 
+1. `ContextAttribute.scheduleArn()` – The ARN of the schedule.
+2. `ContextAttribute.scheduledTime()` – The time you specified for the schedule to invoke its target, for example, 2022-03-22T18:59:43Z.
+3. `ContextAttribute.executionId()` – The unique ID that EventBridge Scheduler assigns for each attempted invocation of a target, for example, d32c5kddcf5bb8c3.
+4. `ContextAttribute.attemptNumber()` – A counter that identifies the attempt number for the current invocation, for example, 1.
+
+```ts
+const text = `Attempt number: ${ContextAttribute.attemptNumber}`;
+const input = ScheduleTargetInput.fromText(text);
+```
 
 ### Specifying Execution Role 
 

packages/@aws-cdk/aws-scheduler-alpha/lib/index.ts

@@ -1 +1,3 @@
-export * from './schedule-expression';
+export * from './schedule-expression';
+export * from './input';
+export * from './schedule';

packages/@aws-cdk/aws-scheduler-alpha/lib/input.ts

@@ -0,0 +1,122 @@
+import { DefaultTokenResolver, IResolveContext, Stack, StringConcat, Token, Tokenization } from 'aws-cdk-lib';
+import { ISchedule } from './schedule';
+
+/**
+ * The text, or well-formed JSON, passed to the target of the schedule.
+ */
+export abstract class ScheduleTargetInput {
+  /**
+   * Pass text to the target, it is possible to embed `ContextAttributes`
+   * that will be resolved to actual values while the CloudFormation is
+   * deployed or cdk Tokens that will be resolved when the CloudFormation
+   * templates are generated by CDK.
+   *
+   * The target input value will be a single string that you pass.
+   * For passing complex values like JSON object to a target use method
+   * `ScheduleTargetInput.fromObject()` instead.
+   *
+   * @param text Text to use as the input for the target
+   */
+  public static fromText(text: string): ScheduleTargetInput {
+    return new FieldAwareEventInput(text);
+  }
+
+  /**
+   * Pass a JSON object to the target, it is possible to embed `ContextAttributes` and other
+   * cdk references.
+   *
+   * @param obj object to use to convert to JSON to use as input for the target
+   */
+  public static fromObject(obj: any): ScheduleTargetInput {
+    return new FieldAwareEventInput(obj);
+  }
+
+  protected constructor() {
+  }
+
+  /**
+   * Return the input properties for this input object
+   */
+  public abstract bind(schedule: ISchedule): string;
+}
+
+class FieldAwareEventInput extends ScheduleTargetInput {
+  constructor(private readonly input: any) {
+    super();
+  }
+
+  public bind(schedule: ISchedule): string {
+    class Replacer extends DefaultTokenResolver {
+      constructor() {
+        super(new StringConcat());
+      }
+
+      public resolveToken(t: Token, _context: IResolveContext) {
+        return Token.asString(t);
+      }
+    }
+
+    const stack = Stack.of(schedule);
+    return stack.toJsonString(Tokenization.resolve(this.input, {
+      scope: schedule,
+      resolver: new Replacer(),
+    }));
+  }
+}
+
+/**
+ * Represents a field in the event pattern
+ *
+ * @see https://docs.aws.amazon.com/scheduler/latest/UserGuide/managing-schedule-context-attributes.html
+ */
+export class ContextAttribute {
+  /**
+   * The ARN of the schedule.
+   */
+  public static get scheduleArn(): string {
+    return this.fromName('schedule-arn');
+  }
+
+  /**
+   * The time you specified for the schedule to invoke its target, for example,
+   * 2022-03-22T18:59:43Z.
+   */
+  public static get scheduledTime(): string {
+    return this.fromName('scheduled-time');
+  }
+
+  /**
+   * The unique ID that EventBridge Scheduler assigns for each attempted invocation of
+   * a target, for example, d32c5kddcf5bb8c3.
+   */
+  public static get executionId(): string {
+    return this.fromName('execution-id');
+  }
+
+  /**
+   * A counter that identifies the attempt number for the current invocation, for
+   * example, 1.
+   */
+  public static get attemptNumber(): string {
+    return this.fromName('attempt-number');
+  }
+
+  /**
+   * Escape hatch for other ContextAttribute that might be resolved in future.
+   *
+   * @param name - name will replace xxx in <aws.scheduler.xxx>
+   */
+  public static fromName(name: string): string {
+    return new ContextAttribute(name).toString();
+  }
+
+  private constructor(public readonly name: string) {
+  }
+
+  /**
+   * Convert the path to the field in the event pattern to JSON
+   */
+  public toString() {
+    return `<aws.scheduler.${this.name}>`;
+  }
+}

packages/@aws-cdk/aws-scheduler-alpha/lib/private/index.ts

@@ -0,0 +1,2 @@
+export * from './schedule';
+export * from './targets';

packages/@aws-cdk/aws-scheduler-alpha/lib/private/schedule.ts

@@ -0,0 +1,57 @@
+import { Resource } from 'aws-cdk-lib';
+import { CfnSchedule } from 'aws-cdk-lib/aws-scheduler';
+import { Construct } from 'constructs';
+import { ISchedule } from '../schedule';
+import { ScheduleExpression } from '../schedule-expression';
+
+/**
+ * DISCLAIMER: WORK IN PROGRESS, INTERFACE MIGHT CHANGE
+ *
+ * This unit is not yet finished. Only rudimentary Schedule is implemented in order
+ * to be able to create some sensible unit tests
+ */
+
+export interface IScheduleTarget {
+  bind(_schedule: ISchedule): CfnSchedule.TargetProperty;
+}
+
+/**
+ * Construction properties for `Schedule`.
+ */
+export interface ScheduleProps {
+  /**
+   * The expression that defines when the schedule runs. Can be either a `at`, `rate`
+   * or `cron` expression.
+   */
+  readonly schedule: ScheduleExpression;
+
+  /**
+   * The schedule's target details.
+   */
+  readonly target: IScheduleTarget;
+
+  /**
+   * The description you specify for the schedule.
+   *
+   * @default - no value
+   */
+  readonly description?: string;
+}
+
+/**
+ * An EventBridge Schedule
+ */
+export class Schedule extends Resource implements ISchedule {
+  constructor(scope: Construct, id: string, props: ScheduleProps) {
+    super(scope, id);
+
+    new CfnSchedule(this, 'Resource', {
+      flexibleTimeWindow: { mode: 'OFF' },
+      scheduleExpression: props.schedule.expressionString,
+      scheduleExpressionTimezone: props.schedule.timeZone?.timezoneName,
+      target: {
+        ...props.target.bind(this),
+      },
+    });
+  }
+}

packages/@aws-cdk/aws-scheduler-alpha/lib/private/targets.ts

@@ -0,0 +1,58 @@
+import * as iam from 'aws-cdk-lib/aws-iam';
+import * as lambda from 'aws-cdk-lib/aws-lambda';
+import { CfnSchedule } from 'aws-cdk-lib/aws-scheduler';
+import { ScheduleTargetInput } from '../input';
+import { ISchedule } from '../schedule';
+
+/**
+ * DISCLAIMER: WORK IN PROGRESS, INTERFACE MIGHT CHANGE
+ *
+ * This unit is not yet finished. The LambaInvoke target is only implemented to be able
+ * to create some sensible unit tests.
+ */
+
+export namespace targets {
+  export interface ScheduleTargetBaseProps {
+    readonly role?: iam.IRole;
+    readonly input?: ScheduleTargetInput;
+  }
+
+  abstract class ScheduleTargetBase {
+    constructor(
+      private readonly baseProps: ScheduleTargetBaseProps,
+      protected readonly targetArn: string,
+    ) {
+    }
+
+    protected abstract addTargetActionToRole(role: iam.IRole): void;
+
+    protected bindBaseTargetConfig(_schedule: ISchedule): CfnSchedule.TargetProperty {
+      if (typeof this.baseProps.role === undefined) {
+        throw Error('A role is needed (for now)');
+      }
+      this.addTargetActionToRole(this.baseProps.role!);
+      return {
+        arn: this.targetArn,
+        roleArn: this.baseProps.role!.roleArn,
+        input: this.baseProps.input?.bind(_schedule),
+      };
+    }
+
+    bind(schedule: ISchedule): CfnSchedule.TargetProperty {
+      return this.bindBaseTargetConfig(schedule);
+    }
+  }
+
+  export class LambdaInvoke extends ScheduleTargetBase {
+    constructor(
+      baseProps: ScheduleTargetBaseProps,
+      private readonly func: lambda.IFunction,
+    ) {
+      super(baseProps, func.functionArn);
+    }
+
+    protected addTargetActionToRole(role: iam.IRole): void {
+      this.func.grantInvoke(role);
+    }
+  }
+}

packages/@aws-cdk/aws-scheduler-alpha/lib/schedule.ts

@@ -0,0 +1,8 @@
+import { IResource } from 'aws-cdk-lib';
+
+/**
+ * Interface representing a created or an imported `Schedule`.
+ */
+export interface ISchedule extends IResource {
+
+}

packages/@aws-cdk/aws-scheduler-alpha/rosetta/default.ts-fixture

@@ -7,7 +7,7 @@ import * as kms from 'aws-cdk-lib/aws-kms';
 import * as sqs from 'aws-cdk-lib/aws-sqs';
 import * as cloudwatch from 'aws-cdk-lib/aws-cloudwatch';
 import { App, Stack, TimeZone, Duration } from 'aws-cdk-lib';
-import { ScheduleExpression } from '@aws-cdk/aws-scheduler-alpha';
+import { ScheduleExpression, ScheduleTargetInput, ContextAttribute } from '@aws-cdk/aws-scheduler-alpha';
 
 class Fixture extends cdk.Stack {
   constructor(scope: Construct, id: string) {