✨ Create helpers to simplify reducer logic

modules/ppcp-settings/resources/js/data/utils.js

@@ -0,0 +1,75 @@
+/**
+ * Updates an object with new values, filtering based on allowed keys.
+ *
+ * Helper method used by createSetters.
+ *
+ * @param {Object} oldObject   The original object to update.
+ * @param {Object} newValues   The new values to apply.
+ * @param {Object} allowedKeys An object whose keys define the allowed keys to update.
+ * @return {Object} A new object with the allowed updates applied.
+ */
+const updateObject = ( oldObject, newValues, allowedKeys = {} ) => ( {
+	...oldObject,
+	...Object.keys( newValues ).reduce( ( acc, key ) => {
+		if ( key in allowedKeys ) {
+			acc[ key ] = newValues[ key ];
+		}
+		return acc;
+	}, {} ),
+} );
+
+/**
+ * Creates setter functions for updating state.
+ *
+ * Only properties that are present in the "defaultTransient" or "defaultPersistent"
+ * arguments can be updated by the setters. Make sure that the default state defines
+ * ALL possible properties.
+ *
+ * @param {Object} defaultTransient  Object defining initial transient values.
+ * @param {Object} defaultPersistent Object defining initial persistent values.
+ * @return {[Function, Function]} An array containing setTransient and setPersistent functions.
+ */
+export const createSetters = ( defaultTransient, defaultPersistent ) => {
+	const setTransient = ( oldState, newValues ) =>
+		updateObject( oldState, newValues, defaultTransient );
+
+	const setPersistent = ( oldState, newValues ) => ( {
+		...oldState,
+		data: updateObject( oldState.data, newValues, defaultPersistent ),
+	} );
+
+	return [ setTransient, setPersistent ];
+};
+
+/**
+ * Creates a reducer function with predefined action handlers.
+ *
+ * @param {Object} defaultTransient  Object defining initial transient values.
+ * @param {Object} defaultPersistent Object defining initial persistent values.
+ * @param {Object} handlers          An object mapping action types to handler functions.
+ * @return {Function} A reducer function.
+ */
+export const createReducer = (
+	defaultTransient,
+	defaultPersistent,
+	handlers
+) => {
+	if ( Object.hasOwnProperty.call( defaultTransient, 'data' ) ) {
+		throw new Error(
+			'The transient state cannot contain a "data" property.'
+		);
+	}
+
+	const initialState = {
+		...defaultTransient,
+		data: defaultPersistent,
+	};
+
+	return function reducer( state = initialState, action ) {
+		if ( Object.hasOwnProperty.call( handlers, action.type ) ) {
+			return handlers[ action.type ]( state, action.data );
+		}
+
+		return state;
+	};
+};