polygerrit-ui/app/elements/shared/gr-textarea/gr-textarea.ts - gerrit - Git at Google

 /**
  * @license
  * Copyright 2017 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
 import '../gr-autocomplete-dropdown/gr-autocomplete-dropdown';
 import '../gr-cursor-manager/gr-cursor-manager';
 import '@polymer/iron-autogrow-textarea/iron-autogrow-textarea';
 import '../../../styles/shared-styles';
 import {getAppContext} from '../../../services/app-context';
 import {IronAutogrowTextareaElement} from '@polymer/iron-autogrow-textarea/iron-autogrow-textarea';
 import {
   GrAutocompleteDropdown,
   Item,
   ItemSelectedEventDetail,
 } from '../gr-autocomplete-dropdown/gr-autocomplete-dropdown';
 import {Key} from '../../../utils/dom-util';
 import {ValueChangedEvent} from '../../../types/events';
 import {fire} from '../../../utils/event-util';
 import {LitElement, css, html} from 'lit';
 import {customElement, property, query, state} from 'lit/decorators.js';
 import {sharedStyles} from '../../../styles/shared-styles';
 import {PropertyValues} from 'lit';
 import {classMap} from 'lit/directives/class-map.js';
 import {NumericChangeId, ServerInfo} from '../../../api/rest-api';
 import {subscribe} from '../../lit/subscription-controller';
 import {resolve} from '../../../models/dependency';
 import {changeModelToken} from '../../../models/change/change-model';
 import {assert} from '../../../utils/common-util';
 import {ShortcutController} from '../../lit/shortcut-controller';
 import {getAccountDisplayName} from '../../../utils/display-name-util';
 import {configModelToken} from '../../../models/config/config-model';
 import {formStyles} from '../../../styles/form-styles';

 const MAX_ITEMS_DROPDOWN = 10;

 const ALL_SUGGESTIONS: EmojiSuggestion[] = [
   {value: '😊', match: 'smile :)'},
   {value: '👍', match: 'thumbs up'},
   {value: '😄', match: 'laugh :D'},
   {value: '❤️', match: 'heart <3'},
   {value: '😂', match: "tears :')"},
   {value: '🎉', match: 'party'},
   {value: '😎', match: 'cool |;)'},
   {value: '😞', match: 'sad :('},
   {value: '😐', match: 'neutral :|'},
   {value: '😮', match: 'shock :O'},
   {value: '🙏', match: 'pray'},
   {value: '😕', match: 'confused'},
   {value: '👌', match: 'ok'},
   {value: '🔥', match: 'fire'},
   {value: '💯', match: '100'},
   {value: '✔', match: 'check'},
   {value: '😋', match: 'tongue'},
   {value: '😭', match: "crying :'("},
   {value: '🤓', match: 'glasses'},
   {value: '😢', match: 'tear'},
   {value: '😜', match: 'winking tongue ;)'},
 ];

 export interface EmojiSuggestion extends Item {
   match: string;
 }

 function isEmojiSuggestion(x: EmojiSuggestion | Item): x is EmojiSuggestion {
   return !!x && !!(x as EmojiSuggestion).match;
 }

 declare global {
   interface HTMLElementEventMap {
     'item-selected': CustomEvent<ItemSelectedEventDetail>;
   }
 }

 @customElement('gr-textarea')
 export class GrTextarea extends LitElement {
   /**
    * @event bind-value-changed
    */
   @query('#textarea') textarea?: IronAutogrowTextareaElement;

   @query('#emojiSuggestions') emojiSuggestions?: GrAutocompleteDropdown;

   @query('#mentionsSuggestions') mentionsSuggestions?: GrAutocompleteDropdown;

   @query('#caratSpan', true) caratSpan?: HTMLSpanElement;

   @query('#hiddenText') hiddenText?: HTMLDivElement;

   @property() autocomplete?: string;

   @property({type: Boolean}) disabled?: boolean;

   @property({type: Number}) rows?: number;

   @property({type: Number}) maxRows?: number;

   @property({type: String}) placeholder?: string;

   @property({type: String}) text = '';

   @property({type: Boolean, attribute: 'hide-border'}) hideBorder = false;

   /** Text input should be rendered in monospace font.  */
   @property({type: Boolean}) monospace = false;

   /** Text input should be rendered in code font, which is smaller than the
     standard monospace font. */
   @property({type: Boolean}) code = false;

   @state() suggestions: (Item | EmojiSuggestion)[] = [];

   // Accessed in tests.
   readonly reporting = getAppContext().reportingService;

   private readonly getChangeModel = resolve(this, changeModelToken);

   private readonly restApiService = getAppContext().restApiService;

   private readonly getConfigModel = resolve(this, configModelToken);

   private serverConfig?: ServerInfo;

   private changeNum?: NumericChangeId;

   // Represents the current location of the ':' or '@' that triggered a drop-down.
   // private but used in tests
   specialCharIndex = -1;

   // Represents the current search string being used to query either emoji or mention suggestions.
   // private but used in tests
   currentSearchString?: string;

   private readonly shortcuts = new ShortcutController(this);

   constructor() {
     super();
     subscribe(
       this,
       () => this.getChangeModel().changeNum$,
       x => (this.changeNum = x)
     );
     subscribe(
       this,
       () => this.getConfigModel().serverConfig$,
       config => {
         this.serverConfig = config;
       }
     );
     this.shortcuts.addLocal({key: Key.UP}, e => this.handleUpKey(e), {
       preventDefault: false,
     });
     this.shortcuts.addLocal({key: Key.DOWN}, e => this.handleDownKey(e), {
       preventDefault: false,
     });
     this.shortcuts.addLocal({key: Key.TAB}, e => this.handleTabKey(e), {
       preventDefault: false,
     });
     this.shortcuts.addLocal({key: Key.ENTER}, e => this.handleEnterByKey(e), {
       preventDefault: false,
     });
     this.shortcuts.addLocal({key: Key.ESC}, e => this.handleEscKey(e), {
       preventDefault: false,
     });
   }

   override disconnectedCallback() {
     super.disconnectedCallback();
   }

   override connectedCallback() {
     super.connectedCallback();
     if (this.monospace) {
       this.classList.add('monospace');
     }
     if (this.code) {
       this.classList.add('code');
     }
   }

   static override get styles() {
     return [
       formStyles,
       sharedStyles,
       css`
         :host {
           display: flex;
           position: relative;
         }
         :host(.monospace) {
           font-family: var(--monospace-font-family);
           font-size: var(--font-size-mono);
           line-height: var(--line-height-mono);
           font-weight: var(--font-weight-normal);
         }
         :host(.code) {
           font-family: var(--monospace-font-family);
           font-size: var(--font-size-code);
           /* usually 16px = 12px + 4px */
           line-height: calc(var(--font-size-code) + var(--spacing-s));
           font-weight: var(--font-weight-normal);
         }
         #emojiSuggestions {
           font-family: var(--font-family);
         }
         #textarea {
           background-color: var(--view-background-color);
           width: 100%;
         }
         #hiddenText #emojiSuggestions {
           visibility: visible;
           white-space: normal;
         }
         iron-autogrow-textarea {
           position: relative;
         }
         #textarea.noBorder {
           border: none;
         }
         #hiddenText {
           display: block;
           float: left;
           position: absolute;
           visibility: hidden;
           width: 100%;
           white-space: pre-wrap;
         }
       `,
     ];
   }

   override render() {
     return html`
       <div id="hiddenText"></div>
       <!-- When the autocomplete is open, the span is moved at the end of
       hiddenText in order to correctly position the dropdown. After being moved,
       it is set as the positionTarget for the emojiSuggestions dropdown. -->
       <span id="caratSpan"></span>
       ${this.renderEmojiDropdown()} ${this.renderMentionsDropdown()}
       <iron-autogrow-textarea
         id="textarea"
         class=${classMap({noBorder: this.hideBorder})}
         .autocomplete=${this.autocomplete}
         .placeholder=${this.placeholder}
         ?disabled=${this.disabled}
         .rows=${this.rows}
         .maxRows=${this.maxRows}
         .value=${this.text}
         @value-changed=${(e: ValueChangedEvent) => {
           this.text = e.detail.value;
         }}
       ></iron-autogrow-textarea>
     `;
   }

   private renderEmojiDropdown() {
     return html`
       <gr-autocomplete-dropdown
         id="emojiSuggestions"
         .suggestions=${this.suggestions}
         .horizontalOffset=${20}
         .verticalOffset=${20}
         @dropdown-closed=${this.resetDropdown}
         @item-selected=${this.handleDropdownItemSelect}
       >
       </gr-autocomplete-dropdown>
     `;
   }

   private renderMentionsDropdown() {
     return html` <gr-autocomplete-dropdown
       id="mentionsSuggestions"
       .suggestions=${this.suggestions}
       @dropdown-closed=${this.resetDropdown}
       @item-selected=${this.handleDropdownItemSelect}
       .horizontalOffset=${20}
       .verticalOffset=${20}
       role="listbox"
     ></gr-autocomplete-dropdown>`;
   }

   override updated(changedProperties: PropertyValues) {
     if (changedProperties.has('text')) {
       this.fireChangedEvents();
       // Add to updated because we want this.textarea.selectionStart and
       // this.textarea is null in the willUpdate lifecycle
       this.computeIndexAndSearchString();
       this.handleTextChanged();
     }
   }

   // private but used in test
   closeDropdown() {
     this.mentionsSuggestions?.close();
     this.emojiSuggestions?.close();
   }

   getNativeTextarea() {
     return this.textarea!.textarea;
   }

   override focus() {
     // Note that this may not work as intended, because the textarea is not
     // rendered yet.
     this.textarea?.textarea.focus();
   }

   putCursorAtEnd() {
     const textarea = this.getNativeTextarea();
     // Put the cursor at the end always.
     textarea.selectionStart = textarea.value.length;
     textarea.selectionEnd = textarea.selectionStart;
     textarea.focus();
   }

   private getVisibleDropdown() {
     if (this.emojiSuggestions && !this.emojiSuggestions.isHidden)
       return this.emojiSuggestions;
     if (this.mentionsSuggestions && !this.mentionsSuggestions.isHidden)
       return this.mentionsSuggestions;
     throw new Error('no dropdown visible');
   }

   private isDropdownVisible() {
     return (
       (this.emojiSuggestions && !this.emojiSuggestions.isHidden) ||
       (this.mentionsSuggestions && !this.mentionsSuggestions.isHidden)
     );
   }

   private handleEscKey(e: KeyboardEvent) {
     if (!this.isDropdownVisible()) {
       return;
     }
     e.preventDefault();
     e.stopPropagation();
     this.resetDropdown();
   }

   private handleUpKey(e: KeyboardEvent) {
     if (!this.isDropdownVisible()) {
       return;
     }
     e.preventDefault();
     e.stopPropagation();
     this.getVisibleDropdown().cursorUp();
     this.focus();
   }

   private handleDownKey(e: KeyboardEvent) {
     if (!this.isDropdownVisible()) {
       return;
     }
     e.preventDefault();
     e.stopPropagation();
     this.getVisibleDropdown().cursorDown();
     this.focus();
   }

   private handleTabKey(e: KeyboardEvent) {
     // Tab should have normal behavior if the picker is closed.
     if (!this.isDropdownVisible()) {
       return;
     }
     e.preventDefault();
     e.stopPropagation();
     this.setValue(this.getVisibleDropdown().getCurrentText());
   }

   // private but used in test
   handleEnterByKey(e: KeyboardEvent) {
     // Enter should have newline behavior if the picker is closed. Also make
     // sure that shortcuts aren't clobbered.
     if (!this.isDropdownVisible()) {
       this.indent(e);
       return;
     }

     const selection = this.getVisibleDropdown().getCurrentText();
     if (selection === '') {
       // Nothing was selected, so treat this like a newline and reset the dropdown.
       this.indent(e);
       this.resetDropdown();
       return;
     }
     e.preventDefault();
     e.stopPropagation();
     this.setValue(this.getVisibleDropdown().getCurrentText());
   }

   // private but used in test
   handleDropdownItemSelect(e: CustomEvent<ItemSelectedEventDetail>) {
     if (e.detail.selected?.dataset['value']) {
       this.setValue(e.detail.selected?.dataset['value']);
     }
   }

   private async setValue(text: string) {
     if (this.specialCharIndex === -1) {
       return;
     }
     const specialCharIndex = this.specialCharIndex;
     let move = 0;
     if (this.isEmojiDropdownActive()) {
       this.text = this.addValueToText(text);
       this.reporting.reportInteraction('select-emoji', {type: text});
     } else {
       this.text = this.addValueToText('@' + text);
       this.reporting.reportInteraction('select-mention', {type: text});
       move = 1;
     }
     // iron-autogrow-textarea unfortunately sets the cursor at the end when
     // it's value is changed, which means the setting of selectionStart
     // below needs to happen after iron-autogrow-textarea has set the
     // incorrect value.
     await this.updateComplete;
     this.textarea!.selectionStart = specialCharIndex + text.length + move;
     this.textarea!.selectionEnd = specialCharIndex + text.length + move;
     this.resetDropdown();
   }

   private addValueToText(value: string) {
     if (!this.text) return '';
     const specialCharIndex = this.specialCharIndex ?? 0;
     const beforeSearchString = this.text.substring(0, specialCharIndex);
     const afterSearchString = this.text.substring(
       specialCharIndex + 1 + (this.currentSearchString?.length ?? 0)
     );
     return beforeSearchString + value + afterSearchString;
   }

   /**
    * Uses a hidden element with the same width and styling of the textarea and
    * the text up until the point of interest. Then caratSpan element is added
    * to the end and is set to be the positionTarget for the dropdown. Together
    * this allows the dropdown to appear near where the user is typing.
    * private but used in test
    */
   updateCaratPosition() {
     if (typeof this.textarea!.value === 'string') {
       this.hiddenText!.textContent = this.textarea!.value.substring(
         0,
         this.textarea!.selectionStart
       );
     }

     const caratSpan = this.caratSpan!;
     this.hiddenText!.appendChild(caratSpan);
     return caratSpan;
   }

   private shouldResetDropdown(text: string, charIndex: number, char?: string) {
     // Under any of the following conditions, close and reset the dropdown:
     // - The cursor is no longer at the end of the current search string
     // - The search string is an space or new line
     // - The colon has been removed
     // - There are no suggestions that match the search string
     return (
       this.textarea!.selectionStart !==
         (this.currentSearchString ?? '').length + charIndex + 1 ||
       this.currentSearchString === ' ' ||
       this.currentSearchString === '\n' ||
       !(text[charIndex] === char)
     );
   }

   private async computeSuggestions() {
     this.suggestions = [];
     if (this.currentSearchString === undefined) {
       return;
     }
     const searchString = this.currentSearchString;
     let suggestions: (Item | EmojiSuggestion)[] = [];
     if (this.isEmojiDropdownActive()) {
       suggestions = this.computeEmojiSuggestions(this.currentSearchString);
     } else if (this.isMentionsDropdownActive()) {
       suggestions = await this.computeReviewerSuggestions();
     }
     if (searchString === this.currentSearchString) {
       this.suggestions = suggestions;
     }
   }

   private openOrResetDropdown() {
     let activeDropdown: GrAutocompleteDropdown;
     let activate: () => void;
     if (this.isEmojiDropdownActive()) {
       activeDropdown = this.emojiSuggestions!;
       activate = () => this.openEmojiDropdown();
     } else if (this.isMentionsDropdownActive()) {
       activeDropdown = this.mentionsSuggestions!;
       activate = () => this.openMentionsDropdown();
     } else {
       this.resetDropdown();
       return;
     }

     if (
       this.shouldResetDropdown(
         this.text,
         this.specialCharIndex,
         this.text[this.specialCharIndex]
       )
     ) {
       this.resetDropdown();
     } else if (activeDropdown!.isHidden && this.textarea!.focused) {
       // Otherwise open the dropdown and set the position to be just below the
       // cursor.
       // Do not open dropdown if textarea is not focused
       activeDropdown.setPositionTarget(this.updateCaratPosition());
       activate();
     }
   }

   private isMentionsDropdownActive() {
     return (
       this.specialCharIndex !== -1 && this.text[this.specialCharIndex] === '@'
     );
   }

   private isEmojiDropdownActive() {
     return (
       this.specialCharIndex !== -1 && this.text[this.specialCharIndex] === ':'
     );
   }

   private computeIndexAndSearchString() {
     const currentCarat = this.textarea?.selectionStart ?? this.text.length;
     const m = this.text
       .substring(0, currentCarat)
       .match(/(?:^|\s)([:@][\S]*)$/);
     if (!m) {
       this.specialCharIndex = -1;
       this.currentSearchString = undefined;
       return;
     }
     this.currentSearchString = m[1].substring(1);
     if (this.specialCharIndex !== -1) return;

     this.specialCharIndex = currentCarat - m[1].length;
   }

   // Private but used in tests.
   async handleTextChanged() {
     await this.computeSuggestions();
     this.openOrResetDropdown();
     this.focus();
   }

   private openEmojiDropdown() {
     this.emojiSuggestions!.open();
     this.reporting.reportInteraction('open-emoji-dropdown');
   }

   private openMentionsDropdown() {
     this.mentionsSuggestions!.open();
     this.reporting.reportInteraction('open-mentions-dropdown');
   }

   // private but used in test
   formatSuggestions(matchedSuggestions: EmojiSuggestion[]): EmojiSuggestion[] {
     const suggestions = [];
     for (const suggestion of matchedSuggestions) {
       assert(isEmojiSuggestion(suggestion), 'malformed suggestion');
       suggestion.dataValue = suggestion.value;
       suggestion.text = `${suggestion.value} ${suggestion.match}`;
       suggestions.push(suggestion);
     }
     return suggestions;
   }

   // private but used in test
   computeEmojiSuggestions(suggestionsText?: string): EmojiSuggestion[] {
     if (suggestionsText === undefined) {
       return [];
     }
     if (!suggestionsText.length) {
       return this.formatSuggestions(ALL_SUGGESTIONS);
     } else {
       const matches = ALL_SUGGESTIONS.filter(suggestion =>
         suggestion.match.includes(suggestionsText)
       ).slice(0, MAX_ITEMS_DROPDOWN);
       return this.formatSuggestions(matches);
     }
   }

   // TODO(dhruvsri): merge with getAccountSuggestions in account-util
   async computeReviewerSuggestions(): Promise<Item[]> {
     return (
       (await this.restApiService.getSuggestedAccounts(
         this.currentSearchString ?? '',
         /* number= */ 15,
         this.changeNum,
         /* filterActive= */ true
       )) ?? []
     )
       .filter(account => account.email)
       .map(account => {
         return {
           text: `${getAccountDisplayName(this.serverConfig, account)}`,
           dataValue: account.email,
         };
       });
   }

   // private but used in test
   resetDropdown() {
     // hide and reset the autocomplete dropdown.
     this.requestUpdate();
     this.currentSearchString = '';
     this.closeDropdown();
     this.specialCharIndex = -1;
     this.focus();
   }

   private fireChangedEvents() {
     fire(this, 'text-changed', {value: this.text});
   }

   private indent(e: KeyboardEvent): void {
     if (!document.queryCommandSupported('insertText')) {
       return;
     }
     // When nothing is selected, selectionStart is the caret position. We want
     // the indentation level of the current line, not the end of the text which
     // may be different.
     const currentLine = this.textarea!.textarea.value.substring(
       0,
       this.textarea!.selectionStart
     )
       .split('\n')
       .pop();
     const currentLineIndentation = currentLine?.match(/^\s*/)?.[0];
     if (!currentLineIndentation) {
       return;
     }

     // Stops the normal newline being added afterwards since we are adding it
     // ourselves.
     e.preventDefault();

     // MDN says that execCommand is deprecated, but the replacements are still
     // WIP (Input Events Level 2). The queryCommandSupported check should ensure
     // that entering newlines will work even if this indent feature breaks.
     // Directly replacing the text is possible, but would destroy the undo/redo
     // queue.
     document.execCommand('insertText', false, '\n' + currentLineIndentation);
   }
 }

 declare global {
   interface HTMLElementTagNameMap {
     'gr-textarea': GrTextarea;
   }
 }
	/**
	* @license
	* Copyright 2017 Google LLC
	* SPDX-License-Identifier: Apache-2.0
	*/
	import '../gr-autocomplete-dropdown/gr-autocomplete-dropdown';
	import '../gr-cursor-manager/gr-cursor-manager';
	import '@polymer/iron-autogrow-textarea/iron-autogrow-textarea';
	import '../../../styles/shared-styles';
	import {getAppContext} from '../../../services/app-context';
	import {IronAutogrowTextareaElement} from '@polymer/iron-autogrow-textarea/iron-autogrow-textarea';
	import {
	GrAutocompleteDropdown,
	Item,
	ItemSelectedEventDetail,
	} from '../gr-autocomplete-dropdown/gr-autocomplete-dropdown';
	import {Key} from '../../../utils/dom-util';
	import {ValueChangedEvent} from '../../../types/events';
	import {fire} from '../../../utils/event-util';
	import {LitElement, css, html} from 'lit';
	import {customElement, property, query, state} from 'lit/decorators.js';
	import {sharedStyles} from '../../../styles/shared-styles';
	import {PropertyValues} from 'lit';
	import {classMap} from 'lit/directives/class-map.js';
	import {NumericChangeId, ServerInfo} from '../../../api/rest-api';
	import {subscribe} from '../../lit/subscription-controller';
	import {resolve} from '../../../models/dependency';
	import {changeModelToken} from '../../../models/change/change-model';
	import {assert} from '../../../utils/common-util';
	import {ShortcutController} from '../../lit/shortcut-controller';
	import {getAccountDisplayName} from '../../../utils/display-name-util';
	import {configModelToken} from '../../../models/config/config-model';
	import {formStyles} from '../../../styles/form-styles';

	const MAX_ITEMS_DROPDOWN = 10;

	const ALL_SUGGESTIONS: EmojiSuggestion[] = [
	{value: '😊', match: 'smile :)'},
	{value: '👍', match: 'thumbs up'},
	{value: '😄', match: 'laugh :D'},
	{value: '❤️', match: 'heart <3'},
	{value: '😂', match: "tears :')"},
	{value: '🎉', match: 'party'},
	{value: '😎', match: 'cool \|;)'},
	{value: '😞', match: 'sad :('},
	{value: '😐', match: 'neutral :\|'},
	{value: '😮', match: 'shock :O'},
	{value: '🙏', match: 'pray'},
	{value: '😕', match: 'confused'},
	{value: '👌', match: 'ok'},
	{value: '🔥', match: 'fire'},
	{value: '💯', match: '100'},
	{value: '✔', match: 'check'},
	{value: '😋', match: 'tongue'},
	{value: '😭', match: "crying :'("},
	{value: '🤓', match: 'glasses'},
	{value: '😢', match: 'tear'},
	{value: '😜', match: 'winking tongue ;)'},
	];

	export interface EmojiSuggestion extends Item {
	match: string;
	}

	function isEmojiSuggestion(x: EmojiSuggestion \| Item): x is EmojiSuggestion {
	return !!x && !!(x as EmojiSuggestion).match;
	}

	declare global {
	interface HTMLElementEventMap {
	'item-selected': CustomEvent<ItemSelectedEventDetail>;
	}
	}

	@customElement('gr-textarea')
	export class GrTextarea extends LitElement {
	/**
	* @event bind-value-changed
	*/
	@query('#textarea') textarea?: IronAutogrowTextareaElement;

	@query('#emojiSuggestions') emojiSuggestions?: GrAutocompleteDropdown;

	@query('#mentionsSuggestions') mentionsSuggestions?: GrAutocompleteDropdown;

	@query('#caratSpan', true) caratSpan?: HTMLSpanElement;

	@query('#hiddenText') hiddenText?: HTMLDivElement;

	@property() autocomplete?: string;

	@property({type: Boolean}) disabled?: boolean;

	@property({type: Number}) rows?: number;

	@property({type: Number}) maxRows?: number;

	@property({type: String}) placeholder?: string;

	@property({type: String}) text = '';

	@property({type: Boolean, attribute: 'hide-border'}) hideBorder = false;

	/** Text input should be rendered in monospace font. */
	@property({type: Boolean}) monospace = false;

	/** Text input should be rendered in code font, which is smaller than the
	standard monospace font. */
	@property({type: Boolean}) code = false;

	@state() suggestions: (Item \| EmojiSuggestion)[] = [];

	// Accessed in tests.
	readonly reporting = getAppContext().reportingService;

	private readonly getChangeModel = resolve(this, changeModelToken);

	private readonly restApiService = getAppContext().restApiService;

	private readonly getConfigModel = resolve(this, configModelToken);

	private serverConfig?: ServerInfo;

	private changeNum?: NumericChangeId;

	// Represents the current location of the ':' or '@' that triggered a drop-down.
	// private but used in tests
	specialCharIndex = -1;

	// Represents the current search string being used to query either emoji or mention suggestions.
	// private but used in tests
	currentSearchString?: string;

	private readonly shortcuts = new ShortcutController(this);

	constructor() {
	super();
	subscribe(
	this,
	() => this.getChangeModel().changeNum$,
	x => (this.changeNum = x)
	);
	subscribe(
	this,
	() => this.getConfigModel().serverConfig$,
	config => {
	this.serverConfig = config;
	}
	);
	this.shortcuts.addLocal({key: Key.UP}, e => this.handleUpKey(e), {
	preventDefault: false,
	});
	this.shortcuts.addLocal({key: Key.DOWN}, e => this.handleDownKey(e), {
	preventDefault: false,
	});
	this.shortcuts.addLocal({key: Key.TAB}, e => this.handleTabKey(e), {
	preventDefault: false,
	});
	this.shortcuts.addLocal({key: Key.ENTER}, e => this.handleEnterByKey(e), {
	preventDefault: false,
	});
	this.shortcuts.addLocal({key: Key.ESC}, e => this.handleEscKey(e), {
	preventDefault: false,
	});
	}

	override disconnectedCallback() {
	super.disconnectedCallback();
	}

	override connectedCallback() {
	super.connectedCallback();
	if (this.monospace) {
	this.classList.add('monospace');
	}
	if (this.code) {
	this.classList.add('code');
	}
	}

	static override get styles() {
	return [
	formStyles,
	sharedStyles,
	css`
	:host {
	display: flex;
	position: relative;
	}
	:host(.monospace) {
	font-family: var(--monospace-font-family);
	font-size: var(--font-size-mono);
	line-height: var(--line-height-mono);
	font-weight: var(--font-weight-normal);
	}
	:host(.code) {
	font-family: var(--monospace-font-family);
	font-size: var(--font-size-code);
	/* usually 16px = 12px + 4px */
	line-height: calc(var(--font-size-code) + var(--spacing-s));
	font-weight: var(--font-weight-normal);
	}
	#emojiSuggestions {
	font-family: var(--font-family);
	}
	#textarea {
	background-color: var(--view-background-color);
	width: 100%;
	}
	#hiddenText #emojiSuggestions {
	visibility: visible;
	white-space: normal;
	}
	iron-autogrow-textarea {
	position: relative;
	}
	#textarea.noBorder {
	border: none;
	}
	#hiddenText {
	display: block;
	float: left;
	position: absolute;
	visibility: hidden;
	width: 100%;
	white-space: pre-wrap;
	}
	`,
	];
	}

	override render() {
	return html`
	<div id="hiddenText"></div>
	<!-- When the autocomplete is open, the span is moved at the end of
	hiddenText in order to correctly position the dropdown. After being moved,
	it is set as the positionTarget for the emojiSuggestions dropdown. -->
	<span id="caratSpan"></span>
	${this.renderEmojiDropdown()} ${this.renderMentionsDropdown()}
	<iron-autogrow-textarea
	id="textarea"
	class=${classMap({noBorder: this.hideBorder})}
	.autocomplete=${this.autocomplete}
	.placeholder=${this.placeholder}
	?disabled=${this.disabled}
	.rows=${this.rows}
	.maxRows=${this.maxRows}
	.value=${this.text}
	@value-changed=${(e: ValueChangedEvent) => {
	this.text = e.detail.value;
	}}
	></iron-autogrow-textarea>
	`;
	}

	private renderEmojiDropdown() {
	return html`
	<gr-autocomplete-dropdown
	id="emojiSuggestions"
	.suggestions=${this.suggestions}
	.horizontalOffset=${20}
	.verticalOffset=${20}
	@dropdown-closed=${this.resetDropdown}
	@item-selected=${this.handleDropdownItemSelect}
	>
	</gr-autocomplete-dropdown>
	`;
	}

	private renderMentionsDropdown() {
	return html` <gr-autocomplete-dropdown
	id="mentionsSuggestions"
	.suggestions=${this.suggestions}
	@dropdown-closed=${this.resetDropdown}
	@item-selected=${this.handleDropdownItemSelect}
	.horizontalOffset=${20}
	.verticalOffset=${20}
	role="listbox"
	></gr-autocomplete-dropdown>`;
	}

	override updated(changedProperties: PropertyValues) {
	if (changedProperties.has('text')) {
	this.fireChangedEvents();
	// Add to updated because we want this.textarea.selectionStart and
	// this.textarea is null in the willUpdate lifecycle
	this.computeIndexAndSearchString();
	this.handleTextChanged();
	}
	}

	// private but used in test
	closeDropdown() {
	this.mentionsSuggestions?.close();
	this.emojiSuggestions?.close();
	}

	getNativeTextarea() {
	return this.textarea!.textarea;
	}

	override focus() {
	// Note that this may not work as intended, because the textarea is not
	// rendered yet.
	this.textarea?.textarea.focus();
	}

	putCursorAtEnd() {
	const textarea = this.getNativeTextarea();
	// Put the cursor at the end always.
	textarea.selectionStart = textarea.value.length;
	textarea.selectionEnd = textarea.selectionStart;
	textarea.focus();
	}

	private getVisibleDropdown() {
	if (this.emojiSuggestions && !this.emojiSuggestions.isHidden)
	return this.emojiSuggestions;
	if (this.mentionsSuggestions && !this.mentionsSuggestions.isHidden)
	return this.mentionsSuggestions;
	throw new Error('no dropdown visible');
	}

	private isDropdownVisible() {
	return (
	(this.emojiSuggestions && !this.emojiSuggestions.isHidden) \|\|
	(this.mentionsSuggestions && !this.mentionsSuggestions.isHidden)
	);
	}

	private handleEscKey(e: KeyboardEvent) {
	if (!this.isDropdownVisible()) {
	return;
	}
	e.preventDefault();
	e.stopPropagation();
	this.resetDropdown();
	}

	private handleUpKey(e: KeyboardEvent) {
	if (!this.isDropdownVisible()) {
	return;
	}
	e.preventDefault();
	e.stopPropagation();
	this.getVisibleDropdown().cursorUp();
	this.focus();
	}

	private handleDownKey(e: KeyboardEvent) {
	if (!this.isDropdownVisible()) {
	return;
	}
	e.preventDefault();
	e.stopPropagation();
	this.getVisibleDropdown().cursorDown();
	this.focus();
	}

	private handleTabKey(e: KeyboardEvent) {
	// Tab should have normal behavior if the picker is closed.
	if (!this.isDropdownVisible()) {
	return;
	}
	e.preventDefault();
	e.stopPropagation();
	this.setValue(this.getVisibleDropdown().getCurrentText());
	}

	// private but used in test
	handleEnterByKey(e: KeyboardEvent) {
	// Enter should have newline behavior if the picker is closed. Also make
	// sure that shortcuts aren't clobbered.
	if (!this.isDropdownVisible()) {
	this.indent(e);
	return;
	}

	const selection = this.getVisibleDropdown().getCurrentText();
	if (selection === '') {
	// Nothing was selected, so treat this like a newline and reset the dropdown.
	this.indent(e);
	this.resetDropdown();
	return;
	}
	e.preventDefault();
	e.stopPropagation();
	this.setValue(this.getVisibleDropdown().getCurrentText());
	}

	// private but used in test
	handleDropdownItemSelect(e: CustomEvent<ItemSelectedEventDetail>) {
	if (e.detail.selected?.dataset['value']) {
	this.setValue(e.detail.selected?.dataset['value']);
	}
	}

	private async setValue(text: string) {
	if (this.specialCharIndex === -1) {
	return;
	}
	const specialCharIndex = this.specialCharIndex;
	let move = 0;
	if (this.isEmojiDropdownActive()) {
	this.text = this.addValueToText(text);
	this.reporting.reportInteraction('select-emoji', {type: text});
	} else {
	this.text = this.addValueToText('@' + text);
	this.reporting.reportInteraction('select-mention', {type: text});
	move = 1;
	}
	// iron-autogrow-textarea unfortunately sets the cursor at the end when
	// it's value is changed, which means the setting of selectionStart
	// below needs to happen after iron-autogrow-textarea has set the
	// incorrect value.
	await this.updateComplete;
	this.textarea!.selectionStart = specialCharIndex + text.length + move;
	this.textarea!.selectionEnd = specialCharIndex + text.length + move;
	this.resetDropdown();
	}

	private addValueToText(value: string) {
	if (!this.text) return '';
	const specialCharIndex = this.specialCharIndex ?? 0;
	const beforeSearchString = this.text.substring(0, specialCharIndex);
	const afterSearchString = this.text.substring(
	specialCharIndex + 1 + (this.currentSearchString?.length ?? 0)
	);
	return beforeSearchString + value + afterSearchString;
	}

	/**
	* Uses a hidden element with the same width and styling of the textarea and
	* the text up until the point of interest. Then caratSpan element is added
	* to the end and is set to be the positionTarget for the dropdown. Together
	* this allows the dropdown to appear near where the user is typing.
	* private but used in test
	*/
	updateCaratPosition() {
	if (typeof this.textarea!.value === 'string') {
	this.hiddenText!.textContent = this.textarea!.value.substring(
	0,
	this.textarea!.selectionStart
	);
	}

	const caratSpan = this.caratSpan!;
	this.hiddenText!.appendChild(caratSpan);
	return caratSpan;
	}

	private shouldResetDropdown(text: string, charIndex: number, char?: string) {
	// Under any of the following conditions, close and reset the dropdown:
	// - The cursor is no longer at the end of the current search string
	// - The search string is an space or new line
	// - The colon has been removed
	// - There are no suggestions that match the search string
	return (
	this.textarea!.selectionStart !==
	(this.currentSearchString ?? '').length + charIndex + 1 \|\|
	this.currentSearchString === ' ' \|\|
	this.currentSearchString === '\n' \|\|
	!(text[charIndex] === char)
	);
	}

	private async computeSuggestions() {
	this.suggestions = [];
	if (this.currentSearchString === undefined) {
	return;
	}
	const searchString = this.currentSearchString;
	let suggestions: (Item \| EmojiSuggestion)[] = [];
	if (this.isEmojiDropdownActive()) {
	suggestions = this.computeEmojiSuggestions(this.currentSearchString);
	} else if (this.isMentionsDropdownActive()) {
	suggestions = await this.computeReviewerSuggestions();
	}
	if (searchString === this.currentSearchString) {
	this.suggestions = suggestions;
	}
	}

	private openOrResetDropdown() {
	let activeDropdown: GrAutocompleteDropdown;
	let activate: () => void;
	if (this.isEmojiDropdownActive()) {
	activeDropdown = this.emojiSuggestions!;
	activate = () => this.openEmojiDropdown();
	} else if (this.isMentionsDropdownActive()) {
	activeDropdown = this.mentionsSuggestions!;
	activate = () => this.openMentionsDropdown();
	} else {
	this.resetDropdown();
	return;
	}

	if (
	this.shouldResetDropdown(
	this.text,
	this.specialCharIndex,
	this.text[this.specialCharIndex]
	)
	) {
	this.resetDropdown();
	} else if (activeDropdown!.isHidden && this.textarea!.focused) {
	// Otherwise open the dropdown and set the position to be just below the
	// cursor.
	// Do not open dropdown if textarea is not focused
	activeDropdown.setPositionTarget(this.updateCaratPosition());
	activate();
	}
	}

	private isMentionsDropdownActive() {
	return (
	this.specialCharIndex !== -1 && this.text[this.specialCharIndex] === '@'
	);
	}

	private isEmojiDropdownActive() {
	return (
	this.specialCharIndex !== -1 && this.text[this.specialCharIndex] === ':'
	);
	}

	private computeIndexAndSearchString() {
	const currentCarat = this.textarea?.selectionStart ?? this.text.length;
	const m = this.text
	.substring(0, currentCarat)
	.match(/(?:^\|\s)([:@][\S]*)$/);
	if (!m) {
	this.specialCharIndex = -1;
	this.currentSearchString = undefined;
	return;
	}
	this.currentSearchString = m[1].substring(1);
	if (this.specialCharIndex !== -1) return;

	this.specialCharIndex = currentCarat - m[1].length;
	}

	// Private but used in tests.
	async handleTextChanged() {
	await this.computeSuggestions();
	this.openOrResetDropdown();
	this.focus();
	}

	private openEmojiDropdown() {
	this.emojiSuggestions!.open();
	this.reporting.reportInteraction('open-emoji-dropdown');
	}

	private openMentionsDropdown() {
	this.mentionsSuggestions!.open();
	this.reporting.reportInteraction('open-mentions-dropdown');
	}

	// private but used in test
	formatSuggestions(matchedSuggestions: EmojiSuggestion[]): EmojiSuggestion[] {
	const suggestions = [];
	for (const suggestion of matchedSuggestions) {
	assert(isEmojiSuggestion(suggestion), 'malformed suggestion');
	suggestion.dataValue = suggestion.value;
	suggestion.text = `${suggestion.value} ${suggestion.match}`;
	suggestions.push(suggestion);
	}
	return suggestions;
	}

	// private but used in test
	computeEmojiSuggestions(suggestionsText?: string): EmojiSuggestion[] {
	if (suggestionsText === undefined) {
	return [];
	}
	if (!suggestionsText.length) {
	return this.formatSuggestions(ALL_SUGGESTIONS);
	} else {
	const matches = ALL_SUGGESTIONS.filter(suggestion =>
	suggestion.match.includes(suggestionsText)
	).slice(0, MAX_ITEMS_DROPDOWN);
	return this.formatSuggestions(matches);
	}
	}

	// TODO(dhruvsri): merge with getAccountSuggestions in account-util
	async computeReviewerSuggestions(): Promise<Item[]> {
	return (
	(await this.restApiService.getSuggestedAccounts(
	this.currentSearchString ?? '',
	/* number= */ 15,
	this.changeNum,
	/* filterActive= */ true
	)) ?? []
	)
	.filter(account => account.email)
	.map(account => {
	return {
	text: `${getAccountDisplayName(this.serverConfig, account)}`,
	dataValue: account.email,
	};
	});
	}

	// private but used in test
	resetDropdown() {
	// hide and reset the autocomplete dropdown.
	this.requestUpdate();
	this.currentSearchString = '';
	this.closeDropdown();
	this.specialCharIndex = -1;
	this.focus();
	}

	private fireChangedEvents() {
	fire(this, 'text-changed', {value: this.text});
	}

	private indent(e: KeyboardEvent): void {
	if (!document.queryCommandSupported('insertText')) {
	return;
	}
	// When nothing is selected, selectionStart is the caret position. We want
	// the indentation level of the current line, not the end of the text which
	// may be different.
	const currentLine = this.textarea!.textarea.value.substring(
	0,
	this.textarea!.selectionStart
	)
	.split('\n')
	.pop();
	const currentLineIndentation = currentLine?.match(/^\s*/)?.[0];
	if (!currentLineIndentation) {
	return;
	}

	// Stops the normal newline being added afterwards since we are adding it
	// ourselves.
	e.preventDefault();

	// MDN says that execCommand is deprecated, but the replacements are still
	// WIP (Input Events Level 2). The queryCommandSupported check should ensure
	// that entering newlines will work even if this indent feature breaks.
	// Directly replacing the text is possible, but would destroy the undo/redo
	// queue.
	document.execCommand('insertText', false, '\n' + currentLineIndentation);
	}
	}

	declare global {
	interface HTMLElementTagNameMap {
	'gr-textarea': GrTextarea;
	}
	}