adding exercise for step 5

step2-05/demo/src/reducers/index.ts

@@ -0,0 +1,20 @@
+import { Store } from '../store';
+import { addTodo, remove, complete, clear } from './pureFunctions';
+
+export function reducer(state: Store['todos'], payload: any): Store['todos'] {
+  switch (payload.type) {
+    case 'addTodo':
+      return addTodo(state, payload.id, payload.label);
+
+    case 'remove':
+      return remove(state, payload.id);
+
+    case 'complete':
+      return complete(state, payload.id);
+
+    case 'clear':
+      return clear(state);
+  }
+
+  return state;
+}

step2-05/demo/src/reducers/pureFunctions.spec.ts

@@ -0,0 +1,17 @@
+import { addTodo } from './pureFunctions';
+import { Store } from '../store';
+
+describe('TodoApp reducers', () => {
+  it('can add an item', () => {
+    const state = <Store['todos']>{};
+
+    const newState = addTodo(state, '0', 'item1');
+
+    const keys = Object.keys(newState);
+
+    expect(newState).not.toBe(state);
+    expect(keys.length).toBe(1);
+    expect(newState[keys[0]].label).toBe('item1');
+    expect(newState[keys[0]].completed).toBeFalsy();
+  });
+});

step2-05/demo/src/reducers/pureFunctions.ts

@@ -0,0 +1,32 @@
+import { Store, FilterTypes } from '../store';
+
+export function addTodo(state: Store['todos'], id: string, label: string): Store['todos'] {
+  return { ...state, [id]: { label, completed: false } };
+}
+
+export function remove(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+
+  delete newTodos[id];
+
+  return newTodos;
+}
+
+export function complete(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+  newTodos[id].completed = !newTodos[id].completed;
+
+  return newTodos;
+}
+
+export function clear(state: Store['todos']) {
+  const newTodos = { ...state };
+
+  Object.keys(state.todos).forEach(key => {
+    if (state.todos[key].completed) {
+      delete newTodos[key];
+    }
+  });
+
+  return newTodos;
+}