feat: implemented getParameter function

Author: dreamorosi

Diff for: packages/parameters/src/BaseProvider.ts

@@ -8,6 +8,9 @@ import type { BaseProviderInterface, GetMultipleOptionsInterface, GetOptionsInte
 import { isSSMGetOptionsInterface } from './types/SSMProvider';
 import type { SSMGetOptionsInterface } from './types/SSMProvider';
 
+// These providers will be dynamically initialized on first use of the helper functions
+const DEFAULT_PROVIDERS: { [key: string]: BaseProvider } = {};
+
 abstract class BaseProvider implements BaseProviderInterface {
   protected store: Map<string, ExpirableValue>;
 
@@ -175,4 +178,5 @@ export {
   BaseProvider,
   ExpirableValue,
   transformValue,
+  DEFAULT_PROVIDERS,
 };

Diff for: packages/parameters/src/SSMProvider.ts

@@ -1,6 +1,7 @@
-import { BaseProvider } from './BaseProvider';
+import { BaseProvider, DEFAULT_PROVIDERS } from './BaseProvider';
 import { SSMClient, GetParameterCommand } from '@aws-sdk/client-ssm';
 import type { SSMClientConfig, GetParameterCommandInput } from '@aws-sdk/client-ssm';
+import type { SSMGetOptionsInterface } from 'types/SSMProvider';
 
 class SSMProvider extends BaseProvider {
   public client: SSMClient;
@@ -27,6 +28,15 @@ class SSMProvider extends BaseProvider {
   }
 }
 
+const getParameter = (name: string, options?: SSMGetOptionsInterface): Promise<undefined | string | Record<string, unknown>> => {
+  if (!DEFAULT_PROVIDERS.hasOwnProperty('ssm')) {
+    DEFAULT_PROVIDERS.ssm = new SSMProvider();
+  }
+
+  return DEFAULT_PROVIDERS.ssm.get(name, options);
+};
+
 export {
-  SSMProvider
+  SSMProvider,
+  getParameter,
 };

Diff for: packages/parameters/tests/unit/SSMProvider.test.ts

@@ -1,7 +1,7 @@
 /**
   * Test SSMProvider class
  *
- * @group unit/idempotency/all
+ * @group unit/parameters/SSMProvider/class
  */
 import { SSMProvider } from '../../src/SSMProvider';
 import { SSMClient, GetParameterCommand } from '@aws-sdk/client-ssm';

Diff for: packages/parameters/tests/unit/getParameter.test.ts

@@ -0,0 +1,65 @@
+/**
+  * Test getParameter function
+ *
+ * @group unit/parameters/SSMProvider/getParameter/function
+ */
+import { DEFAULT_PROVIDERS } from '../../src/BaseProvider';
+import { SSMProvider, getParameter } from '../../src/SSMProvider';
+import { SSMClient, GetParameterCommand } from '@aws-sdk/client-ssm';
+import { mockClient } from 'aws-sdk-client-mock';
+import 'aws-sdk-client-mock-jest';
+
+describe('Function: getParameter', () => {
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  test('when called and a default provider doesn\'t exist, it instantiates one and returns the value', async () => {
+
+    // Prepare
+    const parameterName = 'foo';
+    const parameterValue = 'foo';
+    const client = mockClient(SSMClient).on(GetParameterCommand).resolves({
+      Parameter: {
+        Value: parameterValue,
+      },
+    });
+
+    // Act
+    const value = await getParameter(parameterName);
+
+    // Assess
+    expect(client).toReceiveCommandWith(GetParameterCommand, {
+      Name: parameterName,
+    });
+    expect(value).toBe(parameterValue);
+
+  });
+  
+  test('when called and a default provider exists, it uses it and returns the value', async () => {
+
+    // Prepare
+    const provider = new SSMProvider();
+    DEFAULT_PROVIDERS.ssm = provider;
+    const parameterName = 'foo';
+    const parameterValue = 'foo';
+    const client = mockClient(SSMClient).on(GetParameterCommand).resolves({
+      Parameter: {
+        Value: parameterValue,
+      },
+    });
+
+    // Act
+    const value = await getParameter(parameterName);
+
+    // Assess
+    expect(client).toReceiveCommandWith(GetParameterCommand, {
+      Name: parameterName,
+    });
+    expect(value).toBe(parameterValue);
+    expect(DEFAULT_PROVIDERS.ssm).toBe(provider);
+
+  });
+
+});