From 000049971884e958e92cbfd14331ab88ff2b5e1f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Chalifour?= <francois.chalifour@gmail.com>
Date: Fri, 14 Feb 2020 14:29:44 +0100
Subject: [PATCH] feat(core): allow input pause in keyboard navigation

---
 packages/autocomplete-core/completion.ts   |  6 +--
 packages/autocomplete-core/defaultProps.ts |  4 +-
 packages/autocomplete-core/onKeyDown.ts    |  6 +--
 packages/autocomplete-core/propGetters.ts  |  4 +-
 packages/autocomplete-core/stateReducer.ts | 16 ++++----
 packages/autocomplete-core/types/api.ts    |  6 +--
 packages/autocomplete-core/types/state.ts  |  2 +-
 packages/autocomplete-core/utils.ts        | 45 ++++++++++++----------
 stories/react.stories.tsx                  |  4 +-
 9 files changed, 49 insertions(+), 44 deletions(-)

diff --git a/packages/autocomplete-core/completion.ts b/packages/autocomplete-core/completion.ts
index 3173d085e..cda7b95f3 100644
--- a/packages/autocomplete-core/completion.ts
+++ b/packages/autocomplete-core/completion.ts
@@ -11,9 +11,9 @@ export function getCompletion<TItem>({
   props,
 }: GetCompletionProps<TItem>): string | null {
   if (
-    !props.showCompletion ||
-    state.highlightedIndex < 0 ||
-    !state.isOpen ||
+    props.showCompletion === false ||
+    state.isOpen === false ||
+    state.highlightedIndex === null ||
     state.status === 'stalled'
   ) {
     return null;
diff --git a/packages/autocomplete-core/defaultProps.ts b/packages/autocomplete-core/defaultProps.ts
index df700b061..2dbb2cd62 100644
--- a/packages/autocomplete-core/defaultProps.ts
+++ b/packages/autocomplete-core/defaultProps.ts
@@ -18,7 +18,7 @@ export function getDefaultProps<TItem>(
     minLength: 1,
     placeholder: '',
     autoFocus: false,
-    defaultHighlightedIndex: 0,
+    defaultHighlightedIndex: null,
     showCompletion: false,
     stallThreshold: 300,
     environment,
@@ -31,7 +31,7 @@ export function getDefaultProps<TItem>(
     id: props.id ?? generateAutocompleteId(),
     // The following props need to be deeply defaulted.
     initialState: {
-      highlightedIndex: 0,
+      highlightedIndex: null,
       query: '',
       suggestions: [],
       isOpen: false,
diff --git a/packages/autocomplete-core/onKeyDown.ts b/packages/autocomplete-core/onKeyDown.ts
index fd12f153c..441c7fe10 100644
--- a/packages/autocomplete-core/onKeyDown.ts
+++ b/packages/autocomplete-core/onKeyDown.ts
@@ -48,7 +48,7 @@ export function onKeyDown<TItem>({
     );
     nodeItem?.scrollIntoView(false);
 
-    if (store.getState().highlightedIndex >= 0) {
+    if (store.getState().highlightedIndex !== null) {
       const { item, itemValue, itemUrl, source } = getHighlightedItem({
         state: store.getState(),
       });
@@ -76,7 +76,7 @@ export function onKeyDown<TItem>({
         (event.target as HTMLInputElement).selectionStart ===
           store.getState().query.length)) &&
     props.showCompletion &&
-    store.getState().highlightedIndex >= 0
+    store.getState().highlightedIndex !== null
   ) {
     event.preventDefault();
 
@@ -117,7 +117,7 @@ export function onKeyDown<TItem>({
   } else if (event.key === 'Enter') {
     // No item is selected, so we let the browser handle the native `onSubmit`
     // form event.
-    if (store.getState().highlightedIndex < 0) {
+    if (store.getState().highlightedIndex === null) {
       return;
     }
 
diff --git a/packages/autocomplete-core/propGetters.ts b/packages/autocomplete-core/propGetters.ts
index 10374c636..51183782c 100644
--- a/packages/autocomplete-core/propGetters.ts
+++ b/packages/autocomplete-core/propGetters.ts
@@ -127,7 +127,7 @@ export function getPropGetters<TItem>({
     return {
       'aria-autocomplete': props.showCompletion ? 'both' : 'list',
       'aria-activedescendant':
-        store.getState().isOpen && store.getState().highlightedIndex >= 0
+        store.getState().isOpen && store.getState().highlightedIndex !== null
           ? `${props.id}-item-${store.getState().highlightedIndex}`
           : null,
       'aria-controls': store.getState().isOpen ? `${props.id}-menu` : null,
@@ -228,7 +228,7 @@ export function getPropGetters<TItem>({
         );
         props.onStateChange({ state: store.getState() });
 
-        if (store.getState().highlightedIndex >= 0) {
+        if (store.getState().highlightedIndex !== null) {
           const { item, itemValue, itemUrl, source } = getHighlightedItem({
             state: store.getState(),
           });
diff --git a/packages/autocomplete-core/stateReducer.ts b/packages/autocomplete-core/stateReducer.ts
index d380e105b..7bfe52b0d 100644
--- a/packages/autocomplete-core/stateReducer.ts
+++ b/packages/autocomplete-core/stateReducer.ts
@@ -81,9 +81,10 @@ export const stateReducer = <TItem>(
       return {
         ...state,
         highlightedIndex: getNextHighlightedIndex(
-          action.value.shiftKey ? 5 : 1,
+          1,
           state.highlightedIndex,
-          getItemsCount(state)
+          getItemsCount(state),
+          props.defaultHighlightedIndex
         ),
       };
     }
@@ -92,9 +93,10 @@ export const stateReducer = <TItem>(
       return {
         ...state,
         highlightedIndex: getNextHighlightedIndex(
-          action.value.shiftKey ? -5 : -1,
+          -1,
           state.highlightedIndex,
-          getItemsCount(state)
+          getItemsCount(state),
+          props.defaultHighlightedIndex
         ),
       };
     }
@@ -119,7 +121,7 @@ export const stateReducer = <TItem>(
     case 'submit': {
       return {
         ...state,
-        highlightedIndex: -1,
+        highlightedIndex: null,
         isOpen: false,
         status: 'idle',
         statusContext: {},
@@ -129,7 +131,7 @@ export const stateReducer = <TItem>(
     case 'reset': {
       return {
         ...state,
-        highlightedIndex: -1,
+        highlightedIndex: null,
         isOpen: false,
         status: 'idle',
         statusContext: {},
@@ -151,7 +153,7 @@ export const stateReducer = <TItem>(
       return {
         ...state,
         isOpen: __DEV__ ? state.isOpen : false,
-        highlightedIndex: -1,
+        highlightedIndex: null,
       };
     }
 
diff --git a/packages/autocomplete-core/types/api.ts b/packages/autocomplete-core/types/api.ts
index cce9ed114..6b627d44d 100644
--- a/packages/autocomplete-core/types/api.ts
+++ b/packages/autocomplete-core/types/api.ts
@@ -155,9 +155,9 @@ export interface PublicAutocompleteOptions<TItem> {
   /**
    * The default item index to pre-select.
    *
-   * @default 0
+   * @default null
    */
-  defaultHighlightedIndex?: number;
+  defaultHighlightedIndex?: number | null;
   /**
    * Whether to show the highlighted suggestion as completion in the input.
    *
@@ -217,7 +217,7 @@ export interface AutocompleteOptions<TItem> {
   onStateChange<TItem>(props: { state: AutocompleteState<TItem> }): void;
   placeholder: string;
   autoFocus: boolean;
-  defaultHighlightedIndex: number;
+  defaultHighlightedIndex: number | null;
   showCompletion: boolean;
   minLength: number;
   stallThreshold: number;
diff --git a/packages/autocomplete-core/types/state.ts b/packages/autocomplete-core/types/state.ts
index 43270678e..12bed6e58 100644
--- a/packages/autocomplete-core/types/state.ts
+++ b/packages/autocomplete-core/types/state.ts
@@ -1,7 +1,7 @@
 import { AutocompleteSuggestion } from './api';
 
 export interface AutocompleteState<TItem> {
-  highlightedIndex: number;
+  highlightedIndex: number | null;
   query: string;
   suggestions: Array<AutocompleteSuggestion<TItem>>;
   isOpen: boolean;
diff --git a/packages/autocomplete-core/utils.ts b/packages/autocomplete-core/utils.ts
index 4ff626a23..2a4710af3 100644
--- a/packages/autocomplete-core/utils.ts
+++ b/packages/autocomplete-core/utils.ts
@@ -5,6 +5,7 @@ import {
   AutocompleteSource,
   GetSources,
   AutocompleteSuggestion,
+  AutocompleteOptions,
 } from './types';
 
 export const noop = () => {};
@@ -70,30 +71,34 @@ export function normalizeGetSources<TItem>(
   };
 }
 
-export function getNextHighlightedIndex(
+export function getNextHighlightedIndex<TItem>(
   moveAmount: number,
-  baseIndex: number,
-  itemCount: number
-) {
-  const itemsLastIndex = itemCount - 1;
-
-  if (
-    typeof baseIndex !== 'number' ||
-    baseIndex < 0 ||
-    baseIndex >= itemCount
-  ) {
-    baseIndex = moveAmount > 0 ? -1 : itemsLastIndex + 1;
+  baseIndex: number | null,
+  itemCount: number,
+  defaultHighlightedIndex: AutocompleteOptions<TItem>['defaultHighlightedIndex']
+): number | null {
+  // We allow circular keyboard navigation from the base index.
+  // The base index can either be `null` (nothing is highlighted) or `0`
+  // (the first item is highlighted).
+  // The base index is allowed to get assigned `null` only if
+  // `props.defaultHighlightedIndex` is `null`. This pattern allows to "stop"
+  // by the actual query before navigating to other suggestions as seen on
+  // Google or Amazon.
+  if (baseIndex === null && moveAmount < 0) {
+    return itemCount - 1;
   }
 
-  let newIndex = baseIndex + moveAmount;
+  if (defaultHighlightedIndex !== null && baseIndex === 0 && moveAmount < 0) {
+    return itemCount - 1;
+  }
+
+  const numericIndex = (baseIndex === null ? -1 : baseIndex) + moveAmount;
 
-  if (newIndex < 0) {
-    newIndex = itemsLastIndex;
-  } else if (newIndex > itemsLastIndex) {
-    newIndex = 0;
+  if (numericIndex <= -1 || numericIndex >= itemCount) {
+    return defaultHighlightedIndex === null ? null : 0;
   }
 
-  return newIndex;
+  return numericIndex;
 }
 
 // We don't have access to the autocomplete source when we call `onKeyDown`
@@ -120,7 +125,7 @@ function getSuggestionFromHighlightedIndex<TItem>({
 
   // Based on the accumulated counts, we can infer the index of the suggestion.
   const suggestionIndex = accumulatedSuggestionsCount.reduce((acc, current) => {
-    if (current <= state.highlightedIndex) {
+    if (current <= state.highlightedIndex!) {
       return acc + 1;
     }
 
@@ -164,7 +169,7 @@ function getRelativeHighlightedIndex<TItem>({
     counter++;
   }
 
-  return state.highlightedIndex - previousItemsOffset;
+  return state.highlightedIndex! - previousItemsOffset;
 }
 
 export function getHighlightedItem<TItem>({
diff --git a/stories/react.stories.tsx b/stories/react.stories.tsx
index 3b4516aa4..e20a24c69 100644
--- a/stories/react.stories.tsx
+++ b/stories/react.stories.tsx
@@ -21,8 +21,8 @@ storiesOf('React', module)
         <Autocomplete
           placeholder="Search items…"
           showCompletion={true}
-          defaultHighlightedIndex={-1}
           dropdownContainer={dropdownContainer}
+          defaultHighlightedIndex={null}
           getSources={() => {
             return [
               {
@@ -60,7 +60,6 @@ storiesOf('React', module)
         <Autocomplete
           placeholder="Search items…"
           showCompletion={true}
-          defaultHighlightedIndex={-1}
           dropdownContainer={dropdownContainer}
           getSources={() => {
             return [
@@ -101,7 +100,6 @@ storiesOf('React', module)
       render(
         <Autocomplete
           placeholder="Search items…"
-          defaultHighlightedIndex={-1}
           dropdownContainer={dropdownContainer}
           getSources={() => {
             return [