chore(toolkit): add proposed initial interfaces (#32643)

### Issue

Close #32567 

### Reason for this change

Add proposed interfaces and stub classes to the `@aws-cdk/toolkit` package according to RFC 300, so integrators can start designing their own solution.

### Describe any new or updated permissions being added

n/a

### Description of how you validated changes

n/a unused stub interfaces

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

packages/@aws-cdk/toolkit/lib/actions/deploy.ts

@@ -0,0 +1,228 @@
+import { StackSelector } from '../types';
+
+export type DeploymentMethod = DirectDeploymentMethod | ChangeSetDeploymentMethod;
+
+export interface DirectDeploymentMethod {
+  /**
+   * Use stack APIs to the deploy stack changes
+   */
+  readonly method: 'direct';
+}
+
+export interface ChangeSetDeploymentMethod {
+  /**
+   * Use change-set APIS to deploy a stack changes
+   */
+  readonly method: 'change-set';
+
+  /**
+   * Whether to execute the changeset or leave it in review.
+   *
+   * @default true
+   */
+  readonly execute?: boolean;
+
+  /**
+   * Optional name to use for the CloudFormation change set.
+   * If not provided, a name will be generated automatically.
+   */
+  readonly changeSetName?: string;
+}
+
+/**
+ * When to build assets
+ */
+export enum AssetBuildTime {
+  /**
+   * Build all assets before deploying the first stack
+   *
+   * This is intended for expensive Docker image builds; so that if the Docker image build
+   * fails, no stacks are unnecessarily deployed (with the attendant wait time).
+   */
+  ALL_BEFORE_DEPLOY = 'all-before-deploy',
+
+  /**
+   * Build assets just-in-time, before publishing
+   */
+  JUST_IN_TIME = 'just-in-time',
+}
+
+export interface Tag {
+  readonly Key: string;
+  readonly Value: string;
+}
+
+export enum RequireApproval {
+  NEVER = 'never',
+  ANY_CHANGE = 'any-change',
+  BROADENING = 'broadening',
+}
+
+export enum HotswapMode {
+  /**
+   * Will fall back to CloudFormation when a non-hotswappable change is detected
+   */
+  FALL_BACK = 'fall-back',
+
+  /**
+   * Will not fall back to CloudFormation when a non-hotswappable change is detected
+   */
+  HOTSWAP_ONLY = 'hotswap-only',
+
+  /**
+   * Will not attempt to hotswap anything and instead go straight to CloudFormation
+   */
+  FULL_DEPLOYMENT = 'full-deployment',
+}
+
+export class StackParameters {
+  /**
+   * Use only existing parameters on the stack.
+   */
+  public static onlyExisting() {
+    return new StackParameters({}, true);
+  };
+
+  /**
+   * Use exactly these parameters and remove any other existing parameters from the stack.
+   */
+  public static exactly(params: { [name: string]: string | undefined }) {
+    return new StackParameters(params, false);
+  };
+
+  /**
+   * Define additional parameters for the stack, while keeping existing parameters for unspecified values.
+   */
+  public static withExisting(params: { [name: string]: string | undefined }) {
+    return new StackParameters(params, true);
+  };
+
+  public readonly parameters: Map<string, string | undefined>;
+  public readonly keepExistingParameters: boolean;
+
+  private constructor(params: { [name: string]: string | undefined }, usePreviousParameters = true) {
+    this.keepExistingParameters = usePreviousParameters;
+    this.parameters = new Map(Object.entries(params));
+  }
+}
+
+export interface BaseDeployOptions {
+  /**
+   * Criteria for selecting stacks to deploy
+   */
+  readonly stacks: StackSelector;
+
+  /**
+   * Name of the toolkit stack to use/deploy
+   *
+   * @default CDKToolkit
+   */
+  readonly toolkitStackName?: string;
+
+  /**
+   * Role to pass to CloudFormation for deployment
+   */
+  readonly roleArn?: string;
+
+  /**
+   * @TODO can this be part of `DeploymentMethod`
+   *
+   * Always deploy, even if templates are identical.
+   *
+   * @default false
+   */
+  readonly force?: boolean;
+
+  /**
+   * Deployment method
+   */
+  readonly deploymentMethod?: DeploymentMethod;
+
+  /**
+   * @TODO can this be part of `DeploymentMethod`
+   *
+   * Whether to perform a 'hotswap' deployment.
+   * A 'hotswap' deployment will attempt to short-circuit CloudFormation
+   * and update the affected resources like Lambda functions directly.
+   *
+   * @default - `HotswapMode.FALL_BACK` for regular deployments, `HotswapMode.HOTSWAP_ONLY` for 'watch' deployments
+   */
+  readonly hotswap: HotswapMode;
+
+  /**
+   * Rollback failed deployments
+   *
+   * @default true
+   */
+  readonly rollback?: boolean;
+
+  /**
+   * Reuse the assets with the given asset IDs
+   */
+  readonly reuseAssets?: string[];
+
+  /**
+   * Maximum number of simultaneous deployments (dependency permitting) to execute.
+   * The default is '1', which executes all deployments serially.
+   *
+   * @default 1
+   */
+  readonly concurrency?: number;
+}
+
+export interface DeployOptions extends BaseDeployOptions {
+  /**
+   * ARNs of SNS topics that CloudFormation will notify with stack related events
+   */
+  readonly notificationArns?: string[];
+
+  /**
+   * What kind of security changes require approval
+   *
+   * @default RequireApproval.Broadening
+   */
+  readonly requireApproval?: RequireApproval;
+
+  /**
+   * Tags to pass to CloudFormation for deployment
+   */
+  readonly tags?: Tag[];
+
+  /**
+   * Stack parameters for CloudFormation used at deploy time
+   * @default StackParameters.onlyExisting()
+   */
+  readonly parameters?: StackParameters;
+
+  /**
+   * Path to file where stack outputs will be written after a successful deploy as JSON
+   * @default - Outputs are not written to any file
+   */
+  readonly outputsFile?: string;
+
+  /**
+   * Whether to show logs from all CloudWatch log groups in the template
+   * locally in the users terminal
+   *
+   * @default - false
+   */
+  readonly traceLogs?: boolean;
+
+  /**
+   * Build/publish assets for a single stack in parallel
+   *
+   * Independent of whether stacks are being done in parallel or no.
+   *
+   * @default true
+   */
+  readonly assetParallelism?: boolean;
+
+  /**
+   * When to build assets
+   *
+   * The default is the Docker-friendly default.
+   *
+   * @default AssetBuildTime.ALL_BEFORE_DEPLOY
+   */
+  readonly assetBuildTime?: AssetBuildTime;
+}

packages/@aws-cdk/toolkit/lib/actions/destroy.ts

@@ -0,0 +1,13 @@
+import { StackSelector } from '../types';
+
+export interface DestroyOptions {
+  /**
+   * Criteria for selecting stacks to deploy
+   */
+  readonly stacks: StackSelector;
+
+  /**
+   * The arn of the IAM role to use
+   */
+  readonly roleArn?: string;
+}

packages/@aws-cdk/toolkit/lib/actions/import.ts

@@ -0,0 +1,24 @@
+import { BaseDeployOptions } from './deploy';
+
+export interface ImportOptions extends Omit<BaseDeployOptions, 'reuseAssets' | 'hotswap'> {
+  /**
+   * Build a physical resource mapping and write it to the given file, without performing the actual import operation
+   *
+   * @default - No file
+   */
+  readonly recordResourceMapping?: string;
+
+  /**
+   * Path to a file with the physical resource mapping to CDK constructs in JSON format
+   *
+   * @default - No mapping file
+   */
+  readonly resourceMappingFile?: string;
+
+  /**
+   * Allow non-addition changes to the template
+   *
+   * @default false
+   */
+  readonly force?: boolean;
+}

packages/@aws-cdk/toolkit/lib/actions/synth.ts

@@ -0,0 +1,14 @@
+import { StackSelector } from '../types';
+
+export interface SynthOptions {
+  /**
+   * Select the stacks
+   */
+  readonly stacks: StackSelector;
+
+  /**
+   * After synthesis, validate stacks with the "validateOnSynth" attribute set (can also be controlled with CDK_VALIDATION)
+   * @default true
+   */
+  readonly validateStacks?: boolean;
+}

packages/@aws-cdk/toolkit/lib/actions/watch.ts

@@ -0,0 +1,11 @@
+import { BaseDeployOptions } from './deploy';
+
+export interface WatchOptions extends BaseDeployOptions {
+  /**
+   * Whether to show CloudWatch logs for hotswapped resources
+   * locally in the users terminal
+   *
+   * @default - false
+   */
+  readonly traceLogs?: boolean;
+}

packages/@aws-cdk/toolkit/lib/cloud-assembly-source.ts

@@ -0,0 +1,72 @@
+import { CloudAssembly } from '@aws-cdk/cx-api';
+
+export interface ICloudAssemblySource {
+  /**
+   * produce
+   */
+  produce(): Promise<CloudAssembly>;
+}
+
+/**
+ * Configuration for creating a CLI from an AWS CDK App directory
+ */
+export interface CdkAppDirectoryProps {
+  /**
+   * Command-line for executing your app or a cloud assembly directory
+   * e.g. "node bin/my-app.js"
+   * or
+   * "cdk.out"
+   *
+   * @default - read from cdk.json
+   */
+  readonly app?: string;
+
+  /**
+   * Emits the synthesized cloud assembly into a directory
+   *
+   * @default cdk.out
+   */
+  readonly output?: string;
+}
+
+export class CloudAssemblySource implements ICloudAssemblySource {
+  /**
+   * Use a directory containing an AWS CDK app as source.
+   * @param directory the directory of the AWS CDK app. Defaults to the current working directory.
+   * @param props additional configuration properties
+   * @returns an instance of `AwsCdkCli`
+   */
+  public static fromCdkAppDirectory(_directory?: string, _props: CdkAppDirectoryProps = {}) {}
+
+  /**
+   * Create the CLI from a Cloud Assembly builder function.
+   */
+  public static fromAssemblyBuilder(_builder: (context: Record<string, any>) => Promise<CloudAssembly>) {}
+
+  public produce(): Promise<CloudAssembly> {
+    throw new Error('Method not implemented.');
+  }
+}
+
+/**
+ * A CloudAssemblySource that is caching its result once produced.
+ *
+ * Most Toolkit interactions should use a cached source.
+ * Not caching is relevant when the source changes frequently
+ * and it is to expensive to predict if the source has changed.
+ */
+export class CachedCloudAssemblySource implements ICloudAssemblySource {
+  private source: ICloudAssemblySource;
+  private cloudAssembly: CloudAssembly | undefined;
+
+  public constructor(source: ICloudAssemblySource) {
+    this.source = source;
+  }
+
+  public async produce(): Promise<CloudAssembly> {
+    if (!this.cloudAssembly) {
+      this.cloudAssembly = await this.source.produce();
+    }
+    return this.cloudAssembly;
+  }
+}

packages/@aws-cdk/toolkit/lib/index.ts

@@ -1 +1,10 @@
-export class Toolkit {}
+export * from './toolkit';
+export * from './cloud-assembly-source';
+export * from './actions/deploy';
+export * from './actions/destroy';
+export * from './actions/import';
+export * from './actions/synth';
+export * from './actions/watch';
+
+export * from './io-host';
+export * from './types';