Added photos reducer.

redux/photos/photos.reducer.js

@@ -0,0 +1,44 @@
+import PhotosActionTypes from "./photos.types";
+
+const INITIAL_STATE = {
+  photos: [],
+  uploadInProgress: false,
+  uploadError: null,
+};
+
+const photosReducer = (state = INITIAL_STATE, action) => {
+  switch (action.type) {
+    case PhotosActionTypes.ADD_PHOTO:
+      return {
+        ...state,
+        photos: [...state.photos, action.payload],
+      };
+    case PhotosActionTypes.REMOVE_ALL_PHOTOS:
+      return {
+        ...state,
+        photos: [],
+      };
+    case PhotosActionTypes.REMOVE_PHOTOS:
+      return {
+        ...state,
+        photos: state.photos.filter((p) => !action.payload.includes(p.id)),
+      };
+    case PhotosActionTypes.UPLOAD_PHOTO_FAILURE:
+      return {
+        ...state,
+        uploadInProgress: false,
+        uploadError: action.payload,
+      };
+    case PhotosActionTypes.UPLOAD_ALL_PHOTOS_START:
+    case PhotosActionTypes.UPLOAD_SELECTED_PHOTOS_START:
+      return {
+        ...state,
+        uploadInProgress: true,
+        uploadError: null,
+      };
+    default:
+      return state;
+  }
+};
+
+export default photosReducer;