1 files changed, 61 insertions, 0 deletions
diff --git a/src/reducers/completion.js b/src/reducers/completion.js
new file mode 100644
index 0000000..a706988
--- /dev/null
+++ b/src/reducers/completion.js
@@ -0,0 +1,61 @@
+import actions from '../actions';
+
+const defaultState = {
+  groupSelection: -1,
+  itemSelection: -1,
+  groups: [],
+};
+
+const nextSelection = (state) => {
+  if (state.groupSelection < 0) {
+    return [0, 0];
+  }
+
+  let group = state.groups[state.groupSelection];
+  if (state.groupSelection + 1 >= state.groups.length &&
+    state.itemSelection + 1 >= group.items.length) {
+    return [-1, -1];
+  }
+  if (state.itemSelection + 1 >= group.items.length) {
+    return [state.groupSelection + 1, 0];
+  }
+  return [state.groupSelection, state.itemSelection + 1];
+};
+
+const prevSelection = (state) => {
+  if (state.groupSelection < 0) {
+    return [0, 0];
+  }
+  if (state.groupSelection === 0 && state.itemSelection === 0) {
+    return [-1, -1];
+  } else if (state.itemSelection === 0) {
+    return [
+      state.groupSelection - 1,
+      state.groups[state.groupSelection - 1].items.length - 1
+    ];
+  }
+  return [state.groupSelection, state.itemSelection - 1];
+};
+
+export default function reducer(state = defaultState, action = {}) {
+  switch (action.type) {
+  case actions.COMPLETION_SET_ITEMS:
+    return Object.assign({}, state, {
+      groups: action.groups
+    });
+  case actions.COMPLETION_SELECT_NEXT: {
+    let next = nextSelection(state);
+    return Object.assign({}, state, {
+      groupSelection: next[0],
+      itemSelection: next[1],
+    });
+  }
+  case actions.COMPLETION_SELECT_PREV: {
+    let next = prevSelection(state);
+    return Object.assign({}, state, {
+      groupSelection: next[0],
+      itemSelection: next[1],
+    });
+  }
+  }
+}