From edc81bb380d8b7348d998eb9ad5762f3cd91e87b Mon Sep 17 00:00:00 2001
From: Alexander Skvortsov <38059171+askvortsov1@users.noreply.github.com>
Date: Fri, 26 Feb 2021 16:17:05 -0500
Subject: [PATCH] Editor Driver Abstraction (#2594)

This will allow drop-in replacements of the editor with a more advanced WYSIWYG solution such as ProseMirror
---
 framework/core/js/package-lock.json           |   5 +
 framework/core/js/package.json                |   1 +
 framework/core/js/src/common/compat.js        |   2 -
 .../core/js/src/common/utils/SuperTextarea.js | 109 ---------------
 framework/core/js/src/forum/compat.js         |   3 +
 .../core/js/src/forum/components/Composer.js  |   6 +-
 .../js/src/forum/components/TextEditor.js     |  58 +++++---
 .../core/js/src/forum/states/ComposerState.js |   9 +-
 .../js/src/forum/utils/BasicEditorDriver.ts   | 124 ++++++++++++++++++
 .../src/forum/utils/EditorDriverInterface.ts  | 105 +++++++++++++++
 framework/core/less/forum/Composer.less       |   4 +-
 11 files changed, 287 insertions(+), 139 deletions(-)
 delete mode 100644 framework/core/js/src/common/utils/SuperTextarea.js
 create mode 100644 framework/core/js/src/forum/utils/BasicEditorDriver.ts
 create mode 100644 framework/core/js/src/forum/utils/EditorDriverInterface.ts

diff --git a/framework/core/js/package-lock.json b/framework/core/js/package-lock.json
index 609e9e2fa..8a053610c 100644
--- a/framework/core/js/package-lock.json
+++ b/framework/core/js/package-lock.json
@@ -4474,6 +4474,11 @@
         }
       }
     },
+    "textarea-caret": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/textarea-caret/-/textarea-caret-3.1.0.tgz",
+      "integrity": "sha512-cXAvzO9pP5CGa6NKx0WYHl+8CHKZs8byMkt3PCJBCmq2a34YA9pO1NrQET5pzeqnBjBdToF5No4rrmkDUgQC2Q=="
+    },
     "through2": {
       "version": "2.0.5",
       "resolved": "https://registry.npmjs.org/through2/-/through2-2.0.5.tgz",
diff --git a/framework/core/js/package.json b/framework/core/js/package.json
index c6c8aa9b1..770f13ec4 100644
--- a/framework/core/js/package.json
+++ b/framework/core/js/package.json
@@ -16,6 +16,7 @@
     "mithril": "^2.0.4",
     "punycode": "^2.1.1",
     "spin.js": "^3.1.0",
+    "textarea-caret": "^3.1.0",
     "webpack": "^4.43.0",
     "webpack-cli": "^3.3.11",
     "webpack-merge": "^4.1.4"
diff --git a/framework/core/js/src/common/compat.js b/framework/core/js/src/common/compat.js
index 5df365423..6811fa07d 100644
--- a/framework/core/js/src/common/compat.js
+++ b/framework/core/js/src/common/compat.js
@@ -19,7 +19,6 @@ import extract from './utils/extract';
 import ScrollListener from './utils/ScrollListener';
 import stringToColor from './utils/stringToColor';
 import subclassOf from './utils/subclassOf';
-import SuperTextarea from './utils/SuperTextarea';
 import patchMithril from './utils/patchMithril';
 import proxifyCompat from './utils/proxifyCompat';
 import classList from './utils/classList';
@@ -92,7 +91,6 @@ export default {
   'utils/stringToColor': stringToColor,
   'utils/Stream': Stream,
   'utils/subclassOf': subclassOf,
-  'utils/SuperTextarea': SuperTextarea,
   'utils/setRouteWithForcedRefresh': setRouteWithForcedRefresh,
   'utils/patchMithril': patchMithril,
   'utils/proxifyCompat': proxifyCompat,
diff --git a/framework/core/js/src/common/utils/SuperTextarea.js b/framework/core/js/src/common/utils/SuperTextarea.js
deleted file mode 100644
index eebb4c487..000000000
--- a/framework/core/js/src/common/utils/SuperTextarea.js
+++ /dev/null
@@ -1,109 +0,0 @@
-/**
- * A textarea wrapper with powerful helpers for text manipulation.
- *
- * This wraps a <textarea> DOM element and allows directly manipulating its text
- * contents and cursor positions.
- *
- * I apologize for the pretentious name. :)
- */
-export default class SuperTextarea {
-  /**
-   * @param {HTMLTextAreaElement} textarea
-   */
-  constructor(textarea) {
-    this.el = textarea;
-    this.$ = $(textarea);
-  }
-
-  /**
-   * Set the value of the text editor.
-   *
-   * @param {String} value
-   */
-  setValue(value) {
-    this.$.val(value).trigger('input');
-
-    this.el.dispatchEvent(new CustomEvent('input', { bubbles: true, cancelable: true }));
-  }
-
-  /**
-   * Focus the textarea and place the cursor at the given index.
-   *
-   * @param {number} position
-   */
-  moveCursorTo(position) {
-    this.setSelectionRange(position, position);
-  }
-
-  /**
-   * Get the selected range of the textarea.
-   *
-   * @return {Array}
-   */
-  getSelectionRange() {
-    return [this.el.selectionStart, this.el.selectionEnd];
-  }
-
-  /**
-   * Insert content into the textarea at the position of the cursor.
-   *
-   * @param {String} text
-   */
-  insertAtCursor(text) {
-    this.insertAt(this.el.selectionStart, text);
-  }
-
-  /**
-   * Insert content into the textarea at the given position.
-   *
-   * @param {number} pos
-   * @param {String} text
-   */
-  insertAt(pos, text) {
-    this.insertBetween(pos, pos, text);
-  }
-
-  /**
-   * Insert content into the textarea between the given positions.
-   *
-   * If the start and end positions are different, any text between them will be
-   * overwritten.
-   *
-   * @param start
-   * @param end
-   * @param text
-   */
-  insertBetween(start, end, text) {
-    const value = this.el.value;
-
-    const before = value.slice(0, start);
-    const after = value.slice(end);
-
-    this.setValue(`${before}${text}${after}`);
-
-    // Move the textarea cursor to the end of the content we just inserted.
-    this.moveCursorTo(start + text.length);
-  }
-
-  /**
-   * Replace existing content from the start to the current cursor position.
-   *
-   * @param start
-   * @param text
-   */
-  replaceBeforeCursor(start, text) {
-    this.insertBetween(start, this.el.selectionStart, text);
-  }
-
-  /**
-   * Set the selected range of the textarea.
-   *
-   * @param {number} start
-   * @param {number} end
-   * @private
-   */
-  setSelectionRange(start, end) {
-    this.el.setSelectionRange(start, end);
-    this.$.focus();
-  }
-}
diff --git a/framework/core/js/src/forum/compat.js b/framework/core/js/src/forum/compat.js
index cc42fae8f..73a645a63 100644
--- a/framework/core/js/src/forum/compat.js
+++ b/framework/core/js/src/forum/compat.js
@@ -73,6 +73,7 @@ import DiscussionListItem from './components/DiscussionListItem';
 import LoadingPost from './components/LoadingPost';
 import PostsUserPage from './components/PostsUserPage';
 import DiscussionPageResolver from './resolvers/DiscussionPageResolver';
+import BasicEditorDriver from './utils/BasicEditorDriver';
 import routes from './routes';
 import ForumApplication from './ForumApplication';
 
@@ -85,6 +86,8 @@ export default Object.assign(compat, {
   'utils/alertEmailConfirmation': alertEmailConfirmation,
   'utils/UserControls': UserControls,
   'utils/Pane': Pane,
+  'utils/BasicEditorDriver': BasicEditorDriver,
+  'utils/SuperTextarea': BasicEditorDriver, // @deprecated beta 16, remove beta 17
   'states/ComposerState': ComposerState,
   'states/DiscussionListState': DiscussionListState,
   'states/GlobalSearchState': GlobalSearchState,
diff --git a/framework/core/js/src/forum/components/Composer.js b/framework/core/js/src/forum/components/Composer.js
index 7ad257825..360539ae2 100644
--- a/framework/core/js/src/forum/components/Composer.js
+++ b/framework/core/js/src/forum/components/Composer.js
@@ -76,13 +76,13 @@ export default class Composer extends Component {
 
     // Whenever any of the inputs inside the composer are have focus, we want to
     // add a class to the composer to draw attention to it.
-    this.$().on('focus blur', ':input', (e) => {
+    this.$().on('focus blur', ':input,.TextEditor-editorContainer', (e) => {
       this.active = e.type === 'focusin';
       m.redraw();
     });
 
     // When the escape key is pressed on any inputs, close the composer.
-    this.$().on('keydown', ':input', 'esc', () => this.state.close());
+    this.$().on('keydown', ':input,.TextEditor-editorContainer', 'esc', () => this.state.close());
 
     this.handlers = {};
 
@@ -157,7 +157,7 @@ export default class Composer extends Component {
    * Draw focus to the first focusable content element (the text editor).
    */
   focus() {
-    this.$('.Composer-content :input:enabled:visible:first').focus();
+    this.$('.Composer-content :input:enabled:visible, .TextEditor-editor').first().focus();
   }
 
   /**
diff --git a/framework/core/js/src/forum/components/TextEditor.js b/framework/core/js/src/forum/components/TextEditor.js
index 10329295f..5ee970d1c 100644
--- a/framework/core/js/src/forum/components/TextEditor.js
+++ b/framework/core/js/src/forum/components/TextEditor.js
@@ -1,9 +1,10 @@
 import Component from '../../common/Component';
 import ItemList from '../../common/utils/ItemList';
-import SuperTextarea from '../../common/utils/SuperTextarea';
 import listItems from '../../common/helpers/listItems';
 import Button from '../../common/components/Button';
 
+import BasicEditorDriver from '../utils/BasicEditorDriver';
+
 /**
  * The `TextEditor` component displays a textarea with controls, including a
  * submit button.
@@ -22,25 +23,22 @@ export default class TextEditor extends Component {
     super.oninit(vnode);
 
     /**
-     * The value of the textarea.
+     * The value of the editor.
      *
      * @type {String}
      */
     this.value = this.attrs.value || '';
+
+    /**
+     * Whether the editor is disabled.
+     */
+    this.disabled = !!this.attrs.disabled;
   }
 
   view() {
     return (
       <div className="TextEditor">
-        <textarea
-          className="FormControl Composer-flexible"
-          oninput={(e) => {
-            this.oninput(e.target.value, e);
-          }}
-          placeholder={this.attrs.placeholder || ''}
-          disabled={!!this.attrs.disabled}
-          value={this.value}
-        />
+        <div className="TextEditor-editorContainer"></div>
 
         <ul className="TextEditor-controls Composer-footer">
           {listItems(this.controlItems().toArray())}
@@ -53,15 +51,35 @@ export default class TextEditor extends Component {
   oncreate(vnode) {
     super.oncreate(vnode);
 
-    const handler = () => {
-      this.onsubmit();
-      m.redraw();
+    this.attrs.composer.editor = this.buildEditor(this.$('.TextEditor-editorContainer')[0]);
+  }
+
+  onupdate() {
+    const newDisabled = !!this.attrs.disabled;
+
+    if (this.disabled !== newDisabled) {
+      this.disabled = newDisabled;
+      this.attrs.composer.editor.disabled(newDisabled);
+    }
+  }
+
+  buildEditorParams() {
+    return {
+      classNames: ['FormControl', 'Composer-flexible', 'TextEditor-editor'],
+      disabled: this.disabled,
+      placeholder: this.attrs.placeholder || '',
+      value: this.value,
+      oninput: this.oninput.bind(this),
+      inputListeners: [],
+      onsubmit: () => {
+        this.onsubmit();
+        m.redraw();
+      },
     };
+  }
 
-    this.$('textarea').bind('keydown', 'meta+return', handler);
-    this.$('textarea').bind('keydown', 'ctrl+return', handler);
-
-    this.attrs.composer.editor = new SuperTextarea(this.$('textarea')[0]);
+  buildEditor(dom) {
+    return new BasicEditorDriver(dom, this.buildEditorParams());
   }
 
   /**
@@ -115,12 +133,10 @@ export default class TextEditor extends Component {
    *
    * @param {String} value
    */
-  oninput(value, e) {
+  oninput(value) {
     this.value = value;
 
     this.attrs.onchange(this.value);
-
-    e.redraw = false;
   }
 
   /**
diff --git a/framework/core/js/src/forum/states/ComposerState.js b/framework/core/js/src/forum/states/ComposerState.js
index dd4ed9645..34b3956f4 100644
--- a/framework/core/js/src/forum/states/ComposerState.js
+++ b/framework/core/js/src/forum/states/ComposerState.js
@@ -1,6 +1,7 @@
 import subclassOf from '../../common/utils/subclassOf';
 import Stream from '../../common/utils/Stream';
 import ReplyComposer from '../components/ReplyComposer';
+import EditorDriverInterface from '../utils/EditorDriverInterface';
 
 class ComposerState {
   constructor() {
@@ -29,7 +30,7 @@ class ComposerState {
     /**
      * A reference to the text editor that allows text manipulation.
      *
-     * @type {SuperTextArea|null}
+     * @type {EditorDriverInterface|null}
      */
     this.editor = null;
 
@@ -66,12 +67,16 @@ class ComposerState {
   clear() {
     this.position = ComposerState.Position.HIDDEN;
     this.body = { attrs: {} };
-    this.editor = null;
     this.onExit = null;
 
     this.fields = {
       content: Stream(''),
     };
+
+    if (this.editor) {
+      this.editor.destroy();
+    }
+    this.editor = null;
   }
 
   /**
diff --git a/framework/core/js/src/forum/utils/BasicEditorDriver.ts b/framework/core/js/src/forum/utils/BasicEditorDriver.ts
new file mode 100644
index 000000000..9cb6100b7
--- /dev/null
+++ b/framework/core/js/src/forum/utils/BasicEditorDriver.ts
@@ -0,0 +1,124 @@
+import getCaretCoordinates from 'textarea-caret';
+import EditorDriverInterface, { EditorDriverParams } from './EditorDriverInterface';
+
+export default class BasicEditorDriver implements EditorDriverInterface {
+  el: HTMLTextAreaElement;
+
+  constructor(dom: HTMLElement, params: EditorDriverParams) {
+    this.el = document.createElement('textarea');
+
+    this.build(dom, params);
+  }
+
+  build(dom: HTMLElement, params: EditorDriverParams) {
+    this.el.className = params.classNames.join(' ');
+    this.el.disabled = params.disabled;
+    this.el.placeholder = params.placeholder;
+    this.el.value = params.value;
+
+    const callInputListeners = (e) => {
+      params.inputListeners.forEach((listener) => {
+        listener();
+      });
+
+      e.redraw = false;
+    };
+
+    this.el.oninput = (e) => {
+      params.oninput(this.el.value);
+      callInputListeners(e);
+    };
+
+    this.el.onclick = callInputListeners;
+    this.el.onkeyup = callInputListeners;
+
+    this.el.addEventListener('keydown', function (e) {
+      if ((e.metaKey || e.ctrlKey) && e.key === 'Enter') {
+        params.onsubmit();
+      }
+    });
+
+    dom.append(this.el);
+  }
+
+  protected setValue(value: string) {
+    $(this.el).val(value).trigger('input');
+
+    this.el.dispatchEvent(new CustomEvent('input', { bubbles: true, cancelable: true }));
+  }
+
+  moveCursorTo(position: number) {
+    this.setSelectionRange(position, position);
+  }
+
+  getSelectionRange(): Array<number> {
+    return [this.el.selectionStart, this.el.selectionEnd];
+  }
+
+  getLastNChars(n: number): string {
+    const value = this.el.value;
+
+    return value.slice(Math.max(0, this.el.selectionStart - n), this.el.selectionStart);
+  }
+
+  insertAtCursor(text: string) {
+    this.insertAt(this.el.selectionStart, text);
+  }
+
+  insertAt(pos: number, text: string) {
+    this.insertBetween(pos, pos, text);
+  }
+
+  insertBetween(start: number, end: number, text: string) {
+    const value = this.el.value;
+
+    const before = value.slice(0, start);
+    const after = value.slice(end);
+
+    this.setValue(`${before}${text}${after}`);
+
+    // Move the textarea cursor to the end of the content we just inserted.
+    this.moveCursorTo(start + text.length);
+  }
+
+  replaceBeforeCursor(start: number, text: string) {
+    this.insertBetween(start, this.el.selectionStart, text);
+  }
+
+  protected setSelectionRange(start: number, end: number) {
+    this.el.setSelectionRange(start, end);
+    this.focus();
+  }
+
+  getCaretCoordinates(position: number) {
+    const relCoords = getCaretCoordinates(this.el, position);
+
+    return {
+      top: relCoords.top - this.el.scrollTop,
+      left: relCoords.left,
+    };
+  }
+
+  // DOM Interactions
+
+  /**
+   * Set the disabled status of the editor.
+   */
+  disabled(disabled: boolean) {
+    this.el.disabled = disabled;
+  }
+
+  /**
+   * Focus on the editor.
+   */
+  focus() {
+    this.el.focus();
+  }
+
+  /**
+   * Destroy the editor
+   */
+  destroy() {
+    this.el.remove();
+  }
+}
diff --git a/framework/core/js/src/forum/utils/EditorDriverInterface.ts b/framework/core/js/src/forum/utils/EditorDriverInterface.ts
new file mode 100644
index 000000000..1f53dceb5
--- /dev/null
+++ b/framework/core/js/src/forum/utils/EditorDriverInterface.ts
@@ -0,0 +1,105 @@
+export interface EditorDriverParams {
+  /**
+   * An array of HTML class names to apply to the editor's main DOM element.
+   */
+  classNames: string[];
+
+  /**
+   * Whether the editor should be initially disabled.
+   */
+  disabled: boolean;
+
+  /**
+   * An optional placeholder for the editor.
+   */
+  placeholder: string;
+
+  /**
+   * An optional initial value for the editor.
+   */
+  value: string;
+
+  /**
+   * This is separate from inputListeners since the full serialized content will be passed to it.
+   * It is considered private API, and should not be used/modified by extensions not implementing
+   * EditorDriverInterface.
+   */
+  oninput: Function;
+
+  /**
+   * Each of these functions will be called on click, input, and keyup.
+   * No arguments will be passed.
+   */
+  inputListeners: Function[];
+
+  /**
+   * This function will be called if submission is triggered programmatically via keybind.
+   * No arguments should be passed.
+   */
+  onsubmit: Function;
+}
+
+export default interface EditorDriverInterface {
+  /**
+   * Focus the editor and place the cursor at the given position.
+   */
+  moveCursorTo(position: number): void;
+
+  /**
+   * Get the selected range of the editor.
+   */
+  getSelectionRange(): Array<number>;
+
+  /**
+   * Get the last N characters from the current "text block".
+   *
+   * A textarea-based driver would just return the last N characters,
+   * but more advanced implementations might restrict to the current block.
+   *
+   * This is useful for monitoring recent user input to trigger autocomplete.
+   */
+  getLastNChars(n: number): string;
+
+  /**
+   * Insert content into the editor at the position of the cursor.
+   */
+  insertAtCursor(text: string, escape: boolean): void;
+
+  /**
+   * Insert content into the editor at the given position.
+   */
+  insertAt(pos: number, text: string, escape: boolean): void;
+
+  /**
+   * Insert content into the editor between the given positions.
+   *
+   * If the start and end positions are different, any text between them will be
+   * overwritten.
+   */
+  insertBetween(start: number, end: number, text: string, escape: boolean): void;
+
+  /**
+   * Replace existing content from the start to the current cursor position.
+   */
+  replaceBeforeCursor(start: number, text: string, escape: boolean): void;
+
+  /**
+   * Get left and top coordinates of the caret relative to the editor viewport.
+   */
+  getCaretCoordinates(position: number): { left: number; top: number };
+
+  /**
+   * Set the disabled status of the editor.
+   */
+  disabled(disabled: boolean): void;
+
+  /**
+   * Focus on the editor.
+   */
+  focus(): void;
+
+  /**
+   * Destroy the editor
+   */
+  destroy(): void;
+}
diff --git a/framework/core/less/forum/Composer.less b/framework/core/less/forum/Composer.less
index 1b52fabc9..d58d15a67 100644
--- a/framework/core/less/forum/Composer.less
+++ b/framework/core/less/forum/Composer.less
@@ -293,7 +293,7 @@
     }
   }
   .ComposerBody-editor {
-    .fullScreen & textarea {
+    .fullScreen & .TextEditor-editor {
       font-size: 16px;
     }
   }
@@ -323,7 +323,7 @@
 // ------------------------------------
 // Text Editor
 
-.TextEditor textarea {
+.TextEditor .TextEditor-editor {
   border-radius: 0;
   padding: 0 0 10px;
   border: 0;