Add tree navigation via arrow keys

app/src/actions/visibleTreeTraversal.ts

@@ -0,0 +1,81 @@
+import * as q from '../../../backend/src/Model'
+import { AppState } from '../reducers'
+import { Dispatch } from 'redux'
+import { selectTopic } from './Tree'
+import { SettingsState } from '../reducers/Settings'
+import { sortedNodes } from '../sortedNodes'
+import { TopicViewModel } from '../model/TopicViewModel'
+
+export const moveSelectionUpOrDownwards = (direction: 'next' | 'previous') => (
+  dispatch: Dispatch<any>,
+  getState: () => AppState
+): any => {
+  const state = getState()
+  const selected = state.tree.get('selectedTopic')
+  const tree = state.tree.get('tree')
+  if (!selected || !tree) {
+    if (tree) {
+      dispatch(selectTopic(tree))
+    }
+    return
+  }
+  const nextTreeNode = nextVisibleElementInTree(state.settings, tree, selected, direction)
+  if (nextTreeNode && nextTreeNode.viewModel) {
+    dispatch(selectTopic(nextTreeNode))
+  }
+}
+
+export const moveInward = () => (dispatch: Dispatch<any>, getState: () => AppState): any => {
+  const state = getState()
+  const selected = state.tree.get('selectedTopic')
+  if (!selected || !selected.viewModel) {
+    return
+  }
+
+  if (!selected.viewModel.isExpanded() && selected.edgeCount() > 0) {
+    selected.viewModel.setExpanded(true, true)
+  } else {
+    dispatch(moveSelectionUpOrDownwards('next'))
+  }
+}
+
+export const moveOutward = () => (dispatch: Dispatch<any>, getState: () => AppState): any => {
+  const state = getState()
+  const selected = state.tree.get('selectedTopic')
+  if (!selected || !selected.viewModel) {
+    return
+  }
+
+  if (selected.viewModel.isExpanded() && selected.edgeCount() > 0) {
+    selected.viewModel.setExpanded(false, true)
+  } else {
+    dispatch(moveSelectionUpOrDownwards('previous'))
+  }
+}
+
+function isTreeNodeVisible(treeNode: q.TreeNode<any>) {
+  return Boolean(treeNode.viewModel)
+}
+
+function nextVisibleElementInTree(
+  settings: SettingsState,
+  tree: q.Tree<TopicViewModel>,
+  node: q.TreeNode<TopicViewModel>,
+  direction: 'next' | 'previous'
+): q.TreeNode<TopicViewModel> | undefined {
+  const nodes = flattenVisibleTree(settings, tree)
+  const idx = nodes.findIndex(n => n.path() === node.path())
+  const indexDirection = direction === 'next' ? 1 : -1
+  return nodes[idx + indexDirection]
+}
+
+/** Not very efficient but easy to implement, complexity should not be an issue here  */
+function flattenVisibleTree(
+  settings: SettingsState,
+  treeNode: q.TreeNode<TopicViewModel>
+): Array<q.TreeNode<TopicViewModel>> {
+  return sortedNodes(settings, treeNode)
+    .filter(isTreeNodeVisible)
+    .map(node => [node].concat(flattenVisibleTree(settings, node)))
+    .reduce((a, b) => a.concat(b), [])
+}