feat: Add lifecycle hooks for nitric. (#237)

Co-authored-by: Ryan Cartwright <[email protected]>

Author: tjholm

src/index.ts

@@ -16,3 +16,4 @@ export * from './resources';
 export * from './types';
 export * from './context';
 export * from './handlers';
+export * from './lifecycle';

src/lifecycle/index.ts

@@ -0,0 +1,15 @@
+// Copyright 2021, Nitric Technologies Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+export * from './lifecycle';

src/lifecycle/lifecycle.ts

@@ -0,0 +1,83 @@
+// Copyright 2021, Nitric Technologies Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// The environment variable key that will be used to determine the current Nitric lifecycle/executing environment
+const NITRIC_ENVIRONMENT = 'NITRIC_ENVIRONMENT';
+
+// Possible nitric execution environments
+enum LifecycleStage {
+  // Local development run (using nitric run/start)
+  LocalRun = 'run',
+  // Local development requirements building/collection (using nitric up)
+  Build = 'build',
+  // When the code is running in a deployed environment
+  Cloud = 'cloud',
+}
+
+const getCurrentLifecycle = (): LifecycleStage => {
+  const lifecycle = process.env[NITRIC_ENVIRONMENT];
+  if (
+    !lifecycle ||
+    !Object.values(LifecycleStage).includes(lifecycle as LifecycleStage)
+  ) {
+    throw new Error(
+      `Unable to determine the current Nitric lifecycle, please ensure the ${NITRIC_ENVIRONMENT} environment variable is set`
+    );
+  }
+  return lifecycle as LifecycleStage;
+};
+
+// Check if the current environment is one of the provided stages
+const isInLifecycle = (stage: LifecycleStage[]) => {
+  const currentStage = getCurrentLifecycle();
+  return stage.includes(currentStage);
+};
+
+// If the current environment is one of the provided stages, execute the provided callback
+const whenInLifecycles = <T>(
+  stage: LifecycleStage[],
+  callback: Lifecycle<T>
+): T | undefined => {
+  if (isInLifecycle(stage)) {
+    return callback();
+  }
+};
+
+const whenRunning = <T>(callback: Lifecycle<T>) =>
+  whenInLifecycles([LifecycleStage.LocalRun, LifecycleStage.Cloud], callback);
+
+const whenCollecting = <T>(callback: Lifecycle<T>) =>
+  whenInLifecycles([LifecycleStage.Build], callback);
+
+const isRunning = () =>
+  isInLifecycle([LifecycleStage.LocalRun, LifecycleStage.Cloud]);
+
+const isCollecting = () => isInLifecycle([LifecycleStage.Build]);
+
+type Lifecycle<T> = () => T;
+
+export const Lifecycle = {
+  // Check if the current environment is one of the provided stages
+  is: isInLifecycle,
+  // Check if the current lifecycle is collecting application requirements
+  isCollecting,
+  // Check if the current lifecycle is running the app
+  isRunning,
+  // If the current environment is one of the provided stages, execute the provided callback
+  when: whenInLifecycles,
+  // If the current environment is collecting application requirements
+  whenCollecting,
+  // If the current environment is a cloud environment, execute the provided callback
+  whenRunning,
+};