Forking glitch theme

app/javascript/themes/glitch/reducers/contexts.js

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+import { CONTEXT_FETCH_SUCCESS } from 'themes/glitch/actions/statuses';
+import { TIMELINE_DELETE, TIMELINE_CONTEXT_UPDATE } from 'themes/glitch/actions/timelines';
+import { Map as ImmutableMap, List as ImmutableList } from 'immutable';
+
+const initialState = ImmutableMap({
+  ancestors: ImmutableMap(),
+  descendants: ImmutableMap(),
+});
+
+const normalizeContext = (state, id, ancestors, descendants) => {
+  const ancestorsIds   = ImmutableList(ancestors.map(ancestor => ancestor.id));
+  const descendantsIds = ImmutableList(descendants.map(descendant => descendant.id));
+
+  return state.withMutations(map => {
+    map.setIn(['ancestors', id], ancestorsIds);
+    map.setIn(['descendants', id], descendantsIds);
+  });
+};
+
+const deleteFromContexts = (state, id) => {
+  state.getIn(['descendants', id], ImmutableList()).forEach(descendantId => {
+    state = state.updateIn(['ancestors', descendantId], ImmutableList(), list => list.filterNot(itemId => itemId === id));
+  });
+
+  state.getIn(['ancestors', id], ImmutableList()).forEach(ancestorId => {
+    state = state.updateIn(['descendants', ancestorId], ImmutableList(), list => list.filterNot(itemId => itemId === id));
+  });
+
+  state = state.deleteIn(['descendants', id]).deleteIn(['ancestors', id]);
+
+  return state;
+};
+
+const updateContext = (state, status, references) => {
+  return state.update('descendants', map => {
+    references.forEach(parentId => {
+      map = map.update(parentId, ImmutableList(), list => {
+        if (list.includes(status.id)) {
+          return list;
+        }
+
+        return list.push(status.id);
+      });
+    });
+
+    return map;
+  });
+};
+
+export default function contexts(state = initialState, action) {
+  switch(action.type) {
+  case CONTEXT_FETCH_SUCCESS:
+    return normalizeContext(state, action.id, action.ancestors, action.descendants);
+  case TIMELINE_DELETE:
+    return deleteFromContexts(state, action.id);
+  case TIMELINE_CONTEXT_UPDATE:
+    return updateContext(state, action.status, action.references);
+  default:
+    return state;
+  }
+};