Added LinkTimeline and PreviewCard fetching by id

• Added:
- LinkTimeline and PreviewCard fetching by id

app/javascript/gabsocial/reducers/links.js

@@ -0,0 +1,40 @@
+import {
+  Map as ImmutableMap,
+  List as ImmutableList,
+  fromJS,
+} from 'immutable'
+import {
+  LINK_FETCH_REQUEST,
+  LINK_FETCH_SUCCESS,
+  LINK_FETCH_FAIL,
+} from '../actions/links'
+
+const initialState = ImmutableMap({
+  isFetched: false,
+  isError: false,
+  isLoading: false,
+  items: ImmutableMap(),
+})
+
+export default function links(state = initialState, action) {
+  switch(action.type) {
+  case LINK_FETCH_REQUEST:
+    return state.set('isLoading', true)
+  case LINK_FETCH_SUCCESS:
+    return state.withMutations((mutable) => {
+      mutable.setIn(['items', `${action.card.id}`], fromJS(action.card))
+      mutable.set('isLoading', false)
+      mutable.set('isFetched', false)
+      mutable.set('isError', false)
+    })
+  case LINK_FETCH_FAIL:
+    return state.withMutations((mutable) => {
+      mutable.set('isLoading', false)
+      mutable.set('isFetched', false)
+      mutable.set('isError', true)
+    })
+  default:
+    return state
+  }
+}
+