From d060108afe0902a8c6df8d765dbed15dd584afe7 Mon Sep 17 00:00:00 2001
From: Christopher Allford <christopher.allford@automattic.com>
Date: Thu, 5 Nov 2020 14:13:41 -0800
Subject: [PATCH] Added a custom transformation for models to implement
 specific logic.

---
 .../__tests__/custom-transformation.spec.ts   | 26 +++++++
 .../transformations/custom-transformation.ts  | 75 +++++++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 tests/e2e/api/src/framework/transformations/__tests__/custom-transformation.spec.ts
 create mode 100644 tests/e2e/api/src/framework/transformations/custom-transformation.ts

diff --git a/tests/e2e/api/src/framework/transformations/__tests__/custom-transformation.spec.ts b/tests/e2e/api/src/framework/transformations/__tests__/custom-transformation.spec.ts
new file mode 100644
index 00000000000..1384ae47fe2
--- /dev/null
+++ b/tests/e2e/api/src/framework/transformations/__tests__/custom-transformation.spec.ts
@@ -0,0 +1,26 @@
+import { CustomTransformation } from '../custom-transformation';
+
+describe( 'CustomTransformation', () => {
+	it( 'should do nothing without hooks', () => {
+		const transformation = new CustomTransformation( 0, null, null );
+
+		const expected = { test: 'Test' };
+
+		expect( transformation.toModel( expected ) ).toMatchObject( expected );
+		expect( transformation.fromModel( expected ) ).toMatchObject( expected );
+	} );
+
+	it( 'should execute hooks', () => {
+		const toHook = jest.fn();
+		toHook.mockReturnValue( { toModel: 'Test' } );
+		const fromHook = jest.fn();
+		fromHook.mockReturnValue( { fromModel: 'Test' } );
+
+		const transformation = new CustomTransformation( 0, toHook, fromHook );
+
+		expect( transformation.toModel( { test: 'Test' } ) ).toMatchObject( { toModel: 'Test' } );
+		expect( toHook ).toHaveBeenCalledWith( { test: 'Test' } );
+		expect( transformation.fromModel( { test: 'Test' } ) ).toMatchObject( { fromModel: 'Test' } );
+		expect( fromHook ).toHaveBeenCalledWith( { test: 'Test' } );
+	} );
+} );
diff --git a/tests/e2e/api/src/framework/transformations/custom-transformation.ts b/tests/e2e/api/src/framework/transformations/custom-transformation.ts
new file mode 100644
index 00000000000..511670fbf1e
--- /dev/null
+++ b/tests/e2e/api/src/framework/transformations/custom-transformation.ts
@@ -0,0 +1,75 @@
+import { ModelTransformation } from '../model-transformer';
+
+/**
+ * A callback for transforming model properties.
+ *
+ * @callback TransformationCallback
+ * @param {*} properties The properties to transform.
+ * @return {*} The transformed properties.
+ */
+type TransformationCallback = ( properties: any ) => any;
+
+export class CustomTransformation implements ModelTransformation {
+	public readonly order: number;
+
+	/**
+	 * The hook to run for toModel.
+	 *
+	 * @type {TransformationCallback|null}
+	 * @private
+	 */
+	private readonly toHook: TransformationCallback | null;
+
+	/**
+	 * The hook to run for fromModel.
+	 *
+	 * @type {TransformationCallback|null}
+	 * @private
+	 */
+	private readonly fromHook: TransformationCallback | null;
+
+	/**
+	 * Creates a new transformation.
+	 *
+	 * @param {number} order The order for the transformation. Higher numbers are executed later.
+	 * @param {TransformationCallback|null} toHook The hook to run for toModel.
+	 * @param {TransformationCallback|null} fromHook The hook to run for fromModel.
+	 */
+	public constructor(
+		order: number,
+		toHook: TransformationCallback | null,
+		fromHook: TransformationCallback | null,
+	) {
+		this.order = order;
+		this.toHook = toHook;
+		this.fromHook = fromHook;
+	}
+
+	/**
+	 * Performs a transformation from model properties to raw properties.
+	 *
+	 * @param {*} properties The properties to transform.
+	 * @return {*} The transformed properties.
+	 */
+	public fromModel( properties: any ): any {
+		if ( ! this.fromHook ) {
+			return properties;
+		}
+
+		return this.fromHook( properties );
+	}
+
+	/**
+	 * Performs a transformation from raw properties to model properties.
+	 *
+	 * @param {*} properties The properties to transform.
+	 * @return {*} The transformed properties.
+	 */
+	public toModel( properties: any ): any {
+		if ( ! this.toHook ) {
+			return properties;
+		}
+
+		return this.toHook( properties );
+	}
+}