adding exercise for step 5

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

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+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/exercise/src/reducers/pureFunctions.spec.ts

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+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();
+  });
+
+  // test remove, complete and clear
+});

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

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+import { Store, FilterTypes } from '../store';
+
+export function addTodo(state: Store['todos'], id: string, label: string): Store['todos'] {
+  // Write code to clone the state object while inserting a new TodoItem inside
+  // - the new object must be of the type TodoItem
+  // - the new state should be cloned using the spread syntax
+  // - return the new state
+
+  return state;
+}
+
+export function remove(state: Store['todos'], id: string) {
+  // Write code:
+  // - to clone the state object into new state object
+  // - remove and item from the new state by using the "delete" keyword
+  // - return the new state
+
+  return state;
+}
+
+export function complete(state: Store['todos'], id: string) {
+  // Write code:
+  // - to clone the state object into new state object
+  // - create a clone of the state[id] into a new item object
+  // - modify new state and set the id key to the value of the new item object
+
+  return state;
+}
+
+export function clear(state: Store['todos']) {
+  // Write code:
+  // - to clone the state object into new state object
+  // - loop through the keys of the new state object
+  // - remove those items inside that new state if the item is completed using the "delete" keyword
+  // - return the new state
+
+  return state;
+}