feat(context-providers) Enable arguments to be passed as property object

packages/@aws-cdk/aws-ec2/lib/machine-image.ts

@@ -25,10 +25,11 @@ export class WindowsImage implements IMachineImageSource  {
    * Return the image to use in the given context
    */
   public getImage(parent: Construct): MachineImage {
-    const ssmProvider = new SSMParameterProvider(parent);
+    const ssmProvider = new SSMParameterProvider(parent, {
+      parameterName: this.imageParameterName(this.version),
+    });
 
-    const parameterName = this.imageParameterName(this.version);
-    const ami = ssmProvider.getString(parameterName);
+    const ami = ssmProvider.parameterValue();
     return new MachineImage(ami, new WindowsOS());
   }
 
@@ -98,8 +99,10 @@ export class AmazonLinuxImage implements IMachineImageSource {
 
     const parameterName = '/aws/service/ami-amazon-linux-latest/' + parts.join('-');
 
-    const ssmProvider = new SSMParameterProvider(parent);
-    const ami = ssmProvider.getString(parameterName);
+    const ssmProvider = new SSMParameterProvider(parent, {
+      parameterName,
+    });
+    const ami = ssmProvider.parameterValue();
     return new MachineImage(ami, new LinuxOS());
   }
 }

packages/@aws-cdk/aws-route53/lib/hosted-zone-provider.ts

@@ -0,0 +1,57 @@
+import cdk = require('@aws-cdk/cdk');
+import { HostedZoneRefProps } from './hosted-zone-ref';
+
+export interface HostedZoneProviderProps {
+  domainName: string;
+  privateZone?: boolean;
+  vpcId?: string;
+}
+
+const HOSTED_ZONE_PROVIDER = 'hosted-zone';
+
+const DEFAULT_HOSTED_ZONE: HostedZoneRefProps = {
+  hostedZoneId: '/hostedzone/DUMMY',
+  zoneName: 'example.com',
+};
+
+interface AwsHostedZone {
+  Id: string;
+  Name: string;
+}
+
+/**
+ * Context provider that will lookup the Hosted Zone ID for the given arguments
+ */
+export class HostedZoneProvider {
+  private provider: cdk.ContextProvider;
+  constructor(context: cdk.Construct, props: HostedZoneProviderProps) {
+    this.provider = new cdk.ContextProvider(context, HOSTED_ZONE_PROVIDER, props);
+  }
+  /**
+   * Return the hosted zone meeting the filter
+   */
+  public findHostedZone(): HostedZoneRefProps {
+    const zone =  this.provider.getValue(DEFAULT_HOSTED_ZONE);
+    if (zone === DEFAULT_HOSTED_ZONE) {
+      return zone;
+    }
+    if (!this.isAwsHostedZone(zone)) {
+      throw new Error(`Expected an AWS Hosted Zone received ${JSON.stringify(zone)}`);
+    } else {
+      const actualZone = zone as AwsHostedZone;
+      // CDK handles the '.' at the end, so remove it here
+      if (actualZone.Name.endsWith('.')) {
+        actualZone.Name = actualZone.Name.substring(0, actualZone.Name.length - 1);
+      }
+      return {
+        hostedZoneId: actualZone.Id,
+        zoneName: actualZone.Name,
+      };
+    }
+  }
+
+  private isAwsHostedZone(zone: AwsHostedZone | any): zone is AwsHostedZone {
+    const candidateZone = zone as AwsHostedZone;
+    return candidateZone.Name !== undefined && candidateZone.Id !== undefined;
+  }
+}

packages/@aws-cdk/aws-route53/lib/index.ts

@@ -1,4 +1,5 @@
 export * from './hosted-zone';
+export * from './hosted-zone-provider';
 export * from './hosted-zone-ref';
 export * from './records';
 

packages/@aws-cdk/aws-route53/test/test.hosted-zone-provider.ts

@@ -0,0 +1,36 @@
+import cdk = require('@aws-cdk/cdk');
+import { Test } from 'nodeunit';
+import { HostedZoneProvider } from '../lib';
+
+export = {
+  'Hosted Zone Provider': {
+    'HostedZoneProvider will return context values if availble'(test: Test) {
+      const stack = new cdk.Stack(undefined, 'TestStack', { env: { account: '12345', region: 'us-east-1' } });
+      const filter = {domainName: 'test.com'};
+      new HostedZoneProvider(stack, filter).findHostedZone();
+      const key = Object.keys(stack.missingContext)[0];
+
+      const fakeZone = {
+        Id: "/hostedzone/11111111111111",
+        Name: "example.com.",
+        CallerReference: "TestLates-PublicZo-OESZPDFV7G6A",
+        Config: {
+          Comment: "CDK created",
+          PrivateZone: false
+        },
+        ResourceRecordSetCount: 3
+      };
+
+      stack.setContext(key, fakeZone);
+
+      const cdkZone = {
+        hostedZoneId: fakeZone.Id,
+        zoneName: 'example.com',
+      };
+
+      const zone = cdk.resolve(new HostedZoneProvider(stack, filter).findHostedZone());
+      test.deepEqual(zone, cdkZone);
+      test.done();
+    },
+  }
+};