beginning the reducer

superset-frontend/src/views/CRUD/data/dataset/DatasetPage/index.tsx

@@ -17,13 +17,57 @@
  * under the License.
  */
 import React from 'react';
+// import React, { useReducer, Reducer } from 'react';
 import Header from './Header';
 import DatasetPanel from './DatasetPanel';
 import LeftPanel from './LeftPanel';
 import RightPanel from './RightPanel';
 import Footer from './Footer';
+import { DatasetActionType, DatasetObject, DSReducerActionType } from './types';
+
+export function datasetReducer(
+  state: Partial<DatasetObject> | null,
+  action: DSReducerActionType,
+): Partial<DatasetObject> | null {
+  const trimmedState = {
+    ...(state || {}),
+  };
+  switch (action.type) {
+    case DatasetActionType.selectDatabase:
+      return {
+        ...trimmedState,
+        ...action.payload,
+        schema: null,
+        table_name: null,
+      };
+    case DatasetActionType.selectSchema:
+      return {
+        ...trimmedState,
+        ...action.payload,
+        table_name: null,
+      };
+    case DatasetActionType.selectTable:
+      return {
+        ...trimmedState,
+        ...action.payload,
+      };
+    case DatasetActionType.changeDataset:
+      return {
+        ...trimmedState,
+        [action.payload.name]: action.payload.value,
+      };
+    default:
+      return null;
+  }
+}
 
 export default function DatasetPage() {
+  // this is commented out for now, but can be commented in as the component
+  // is built up. Uncomment the useReducer in imports too
+  // const [dataset, setDataset] = useReducer<
+  //   Reducer<Partial<DatasetObject> | null, DSReducerActionType>
+  // >(datasetReducer, null);
+
   return (
     <div>
       <Header />

superset-frontend/src/views/CRUD/data/dataset/DatasetPage/types.tsx

@@ -0,0 +1,53 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 enum DatasetActionType {
+  selectDatabase,
+  selectSchema,
+  selectTable,
+  changeDataset,
+}
+
+export interface DatasetObject {
+  database: {
+    id: string;
+    database_name: string;
+  };
+  owners: number[];
+  schema?: string | null;
+  dataset_name: string;
+  table_name?: string | null;
+}
+
+interface DatasetReducerPayloadType {
+  name: string;
+  value?: string;
+}
+
+export type DSReducerActionType =
+  | {
+      type:
+        | DatasetActionType.selectDatabase
+        | DatasetActionType.selectSchema
+        | DatasetActionType.selectTable;
+      payload: Partial<DatasetObject>;
+    }
+  | {
+      type: DatasetActionType.changeDataset;
+      payload: DatasetReducerPayloadType;
+    };