Refactoring of autocomplete and tag inputs

assets/js/autocomplete.ts

@@ -15,17 +15,21 @@ import {
   TermSuggestion,
 } from './utils/suggestions';
 
-type InputFieldElement = HTMLInputElement | HTMLTextAreaElement;
+type AcEnabledInputElement = HTMLInputElement | HTMLTextAreaElement;
 
-let inputField: InputFieldElement | null = null,
-  originalTerm: string | undefined,
-  originalQuery: string | undefined,
-  selectedTerm: TermContext | null = null;
+function hasAcEnabled(element: unknown): element is AcEnabledInputElement {
+  return (element instanceof HTMLInputElement || element instanceof HTMLTextAreaElement) && Boolean(element.dataset.ac);
+}
+
+let inputField: AcEnabledInputElement | null = null;
+let originalTerm: string | undefined;
+let originalQuery: string | undefined;
+let selectedTerm: TermContext | null = null;
 
 const popup = new SuggestionsPopup();
 
 function isSearchField(targetInput: HTMLElement): boolean {
-  return targetInput && targetInput.dataset.acMode === 'search';
+  return targetInput.dataset.acMode === 'search';
 }
 
 function restoreOriginalValue() {
@@ -113,7 +117,7 @@ function keydownHandler(event: KeyboardEvent) {
   }
 }
 
-function findSelectedTerm(targetInput: InputFieldElement, searchQuery: string): TermContext | null {
+function findSelectedTerm(targetInput: AcEnabledInputElement, searchQuery: string): TermContext | null {
   if (targetInput.selectionStart === null || targetInput.selectionEnd === null) return null;
 
   const selectionIndex = Math.min(targetInput.selectionStart, targetInput.selectionEnd);
@@ -139,10 +143,15 @@ function findSelectedTerm(targetInput: InputFieldElement, searchQuery: string):
   return term;
 }
 
-function toggleSearchAutocomplete() {
+/**
+ * Our custom autocomplete isn't compatible with the native browser autocomplete,
+ * so we have to turn it off if our autocomplete is enabled, or turn it back on
+ * if it's disabled.
+ */
+function toggleSearchNativeAutocomplete() {
   const enable = store.get('enable_search_ac');
 
-  for (const searchField of $$<InputFieldElement>(':is(input, textarea)[data-ac-mode=search]')) {
+  for (const searchField of $$<AcEnabledInputElement>(':is(input, textarea)[data-ac][data-ac-mode=search]')) {
     if (enable) {
       searchField.autocomplete = 'off';
     } else {
@@ -156,11 +165,15 @@ function trimPrefixes(targetTerm: string): string {
   return targetTerm.trim().replace(/^-/, '');
 }
 
-function listenAutocomplete() {
+/**
+ * We control the autocomplete with `data-ac*` attributes in HTML, and subscribe
+ * event listeners to the `document`. This pattern is described in more detail
+ * here: https://javascript.info/event-delegation
+ */
+export function listenAutocomplete() {
   let serverSideSuggestionsTimeout: number | undefined;
 
   let localAc: LocalAutocompleter | null = null;
-  let isLocalLoading = false;
 
   document.addEventListener('focusin', loadAutocompleteFromEvent);
 
@@ -169,12 +182,10 @@ function listenAutocomplete() {
     loadAutocompleteFromEvent(event);
     window.clearTimeout(serverSideSuggestionsTimeout);
 
-    if (!(event.target instanceof HTMLInputElement) && !(event.target instanceof HTMLTextAreaElement)) return;
+    if (!hasAcEnabled(event.target)) return;
 
     const targetedInput = event.target;
 
-    if (!targetedInput.dataset.ac) return;
-
     targetedInput.addEventListener('keydown', keydownHandler as EventListener);
 
     if (localAc !== null) {
@@ -193,7 +204,7 @@ function listenAutocomplete() {
 
         originalTerm = selectedTerm[1].toLowerCase();
       } else {
-        originalTerm = `${inputField.value}`.toLowerCase();
+        originalTerm = inputField.value.toLowerCase();
       }
 
       const suggestions = localAc
@@ -236,19 +247,19 @@ function listenAutocomplete() {
     }
   });
 
-  function loadAutocompleteFromEvent(event: Event) {
-    if (!(event.target instanceof HTMLInputElement) && !(event.target instanceof HTMLTextAreaElement)) return;
+  // Lazy-load the local AC index from the server only once.
+  let localAcFetchInitiated = false;
 
-    if (!isLocalLoading && event.target.dataset.ac) {
-      isLocalLoading = true;
-
-      fetchLocalAutocomplete().then(autocomplete => {
-        localAc = autocomplete;
-      });
-    }
+  async function loadAutocompleteFromEvent(event: Event) {
+    if (!hasAcEnabled(event.target) || localAcFetchInitiated) {
+      return;
     }
 
-  toggleSearchAutocomplete();
+    localAcFetchInitiated = true;
+    localAc = await fetchLocalAutocomplete();
+  }
+
+  toggleSearchNativeAutocomplete();
 
   popup.onItemSelected((event: CustomEvent<TermSuggestion>) => {
     if (!event.detail || !inputField) return;
@@ -272,5 +283,3 @@ function listenAutocomplete() {
     );
   });
 }
-
-export { listenAutocomplete };

assets/js/utils/suggestions.ts

@@ -75,6 +75,11 @@ export class SuggestionsPopup {
   }
 
   private watchItem(listItem: HTMLElement, suggestion: TermSuggestion) {
+    // This makes sure the item isn't selected if the mouse pointer happens to
+    // be right on top of the item when the list is rendered. So, the item may
+    // only be selected on the first `mousemove` event occurring on the element.
+    // See more details about this problem in the PR description:
+    // https://github.com/philomena-dev/philomena/pull/350
     mouseMoveThenOver(listItem, () => this.updateSelection(listItem));
 
     listItem.addEventListener('mouseout', () => this.clearSelection());

lib/philomena_web/templates/layout/_header.html.slime

@@ -10,9 +10,22 @@ header.header
           ' Derpibooru
       a.header__link.hide-mobile href="/images/new" title="Upload"
         i.fa.fa-upload
-
     = form_for @conn, ~p"/search", [method: "get", class: "header__search flex flex--no-wrap flex--centered", enforce_utf8: false], fn f ->
-      input.input.header__input.header__input--search#q name="q" title="For terms all required, separate with ',' or 'AND'; also supports 'OR' for optional terms and '-' or 'NOT' for negation. Search with a blank query for more options or click the ? for syntax help." value=@conn.params["q"] placeholder="Search" autocapitalize="none" data-ac="true" data-ac-min-length="3" data-ac-mode="search"
+      - title = \
+        "For terms all required, separate with ',' or 'AND'; also supports 'OR' " <> \
+        "for optional terms and '-' or 'NOT' for negation. Search with a blank " <> \
+        "query for more options or click the ? for syntax help"
+
+      input.input.header__input.header__input--search#q[
+        name="q"
+        title=title
+        value=@conn.params["q"]
+        placeholder="Search"
+        autocapitalize="none"
+        data-ac="true"
+        data-ac-min-length="3"
+        data-ac-mode="search"
+      ]
 
       = if present?(@conn.params["sf"]) do
         input type="hidden" name="sf" value=@conn.params["sf"]

lib/philomena_web/templates/tag/_tag_editor.html.slime

@@ -9,8 +9,28 @@ elixir:
 .js-tag-block class="fancy-tag-#{@type}"
   = textarea @f, @name, html_options
   .js-taginput.input.input--wide.tagsinput.hidden class="js-taginput-fancy" data-click-focus=".js-taginput-input.js-taginput-#{@name}"
-    input.input class="js-taginput-input js-taginput-#{@name}" id="taginput-fancy-#{@name}" type="text" placeholder="add a tag" autocomplete="off" autocapitalize="none" data-ac="true" data-ac-min-length="3" data-ac-source="/autocomplete/tags?term="
-button.button.button--state-primary.button--bold class="js-taginput-show" data-click-show=".js-taginput-fancy,.js-taginput-hide" data-click-hide=".js-taginput-plain,.js-taginput-show" data-click-focus=".js-taginput-input.js-taginput-#{@name}"
-  ' Fancy Editor
-button.hidden.button.button--state-primary.button--bold class="js-taginput-hide" data-click-show=".js-taginput-plain,.js-taginput-show" data-click-hide=".js-taginput-fancy,.js-taginput-hide" data-click-focus=".js-taginput-plain.js-taginput-#{@name}"
-  ' Plain Editor
+    input.input [
+      class="js-taginput-input js-taginput-#{@name}"
+      id="taginput-fancy-#{@name}"
+      type="text"
+      placeholder="add a tag"
+      autocomplete="off"
+      autocapitalize="none"
+      data-ac="true"
+      data-ac-min-length="3"
+      data-ac-source="/autocomplete/tags?term="
+    ]
+button.button.button--state-primary.button--bold[
+  class="js-taginput-show"
+  data-click-show=".js-taginput-fancy,.js-taginput-hide"
+  data-click-hide=".js-taginput-plain,.js-taginput-show"
+  data-click-focus=".js-taginput-input.js-taginput-#{@name}"
+]
+  | Fancy Editor
+button.hidden.button.button--state-primary.button--bold [
+  class="js-taginput-hide"
+  data-click-show=".js-taginput-plain,.js-taginput-show"
+  data-click-hide=".js-taginput-fancy,.js-taginput-hide"
+  data-click-focus=".js-taginput-plain.js-taginput-#{@name}"
+]
+  | Plain Editor