Fix #3665 - Refactor timelines reducer (#3686)

* Move ancestors/descendants out of timelines reducer

* Refactor timelines reducer

All types of timelines now have a flat structure and use the same
reducer functions and actions

* Reintroduce some missing behaviours

* Fix wrong import in reports

* Fix includes typo

* Fix issue related to "next" pagination in timelines and notifications

* Fix bug with timeline's initial state, expandNotifications

1 files changed, 43 insertions, 0 deletions

diff --git a/app/javascript/mastodon/reducers/contexts.js b/app/javascript/mastodon/reducers/contexts.js
new file mode 100644
index 000000000..8a24f5f7a
--- /dev/null
+++ b/app/javascript/mastodon/reducers/contexts.js
@@ -0,0 +1,43 @@
+import { CONTEXT_FETCH_SUCCESS } from '../actions/statuses';
+import { TIMELINE_DELETE } from '../actions/timelines';
+import Immutable from 'immutable';
+
+const initialState = Immutable.Map({
+  ancestors: Immutable.Map(),
+  descendants: Immutable.Map(),
+});
+
+const normalizeContext = (state, id, ancestors, descendants) => {
+  const ancestorsIds   = ancestors.map(ancestor => ancestor.get('id'));
+  const descendantsIds = descendants.map(descendant => descendant.get('id'));
+
+  return state.withMutations(map => {
+    map.setIn(['ancestors', id], ancestorsIds);
+    map.setIn(['descendants', id], descendantsIds);
+  });
+};
+
+const deleteFromContexts = (state, id) => {
+  state.getIn(['descendants', id], Immutable.List()).forEach(descendantId => {
+    state = state.updateIn(['ancestors', descendantId], Immutable.List(), list => list.filterNot(itemId => itemId === id));
+  });
+
+  state.getIn(['ancestors', id], Immutable.List()).forEach(ancestorId => {
+    state = state.updateIn(['descendants', ancestorId], Immutable.List(), list => list.filterNot(itemId => itemId === id));
+  });
+
+  state = state.deleteIn(['descendants', id]).deleteIn(['ancestors', id]);
+
+  return state;
+};
+
+export default function contexts(state = initialState, action) {
+  switch(action.type) {
+  case CONTEXT_FETCH_SUCCESS:
+    return normalizeContext(state, action.id, Immutable.fromJS(action.ancestors), Immutable.fromJS(action.descendants));
+  case TIMELINE_DELETE:
+    return deleteFromContexts(state, action.id);
+  default:
+    return state;
+  }
+};