Fix #463 - Fetch and display previews of URLs using OpenGraph tags

app/assets/javascripts/components/reducers/cards.jsx

@@ -0,0 +1,14 @@
+import { STATUS_CARD_FETCH_SUCCESS } from '../actions/cards';
+
+import Immutable from 'immutable';
+
+const initialState = Immutable.Map();
+
+export default function cards(state = initialState, action) {
+  switch(action.type) {
+  case STATUS_CARD_FETCH_SUCCESS:
+    return state.set(action.id, Immutable.fromJS(action.card));
+  default:
+    return state;
+  }
+};