Add support for tabs

Tabs are represented by tab characters in Mobiledoc, ala \t, and in
rendered DOM are represened as an emspace: \u2003

Additionally fix an issue with white-space only markers being the first
thing in a section. They were disregarded by the renderer, errantly.

src/js/editor/editor.js

@@ -36,6 +36,7 @@ import {
   setClipboardCopyData
 } from '../utils/paste-utils';
 import { DIRECTION } from 'mobiledoc-kit/utils/key';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 
 export const EDITOR_ELEMENT_CLASS_NAME = '__mobiledoc-editor';
 
@@ -598,8 +599,7 @@ class Editor {
       this._insertEmptyMarkupSectionAtCursor();
     }
 
-    const key = Key.fromEvent(event);
-
+    let key = Key.fromEvent(event);
     let range, nextPosition;
 
     switch(true) {
@@ -630,11 +630,24 @@ class Editor {
         this.handleNewline(event);
         break;
       case key.isPrintable():
-        let range = this.cursor.offsets;
-        if (this.cursor.hasSelection()) {
-          let nextPosition = this.run(postEditor => postEditor.deleteRange(range));
+        let { offsets: range } = this.cursor;
+        let { isCollapsed } = range;
+        let nextPosition = range.head;
+        this.run(postEditor => {
+          if (!isCollapsed) {
+            nextPosition = postEditor.deleteRange(range);
+          }
+          if (key.isTab() && !range.head.section.isCardSection) {
+            nextPosition = postEditor.insertText(nextPosition, TAB);
+          }
+        });
+        if (nextPosition !== range.head) {
           this.cursor.moveToPosition(nextPosition);
-        } else if (range.head.section.isCardSection) {
+        }
+        if (
+          (isCollapsed && range.head.section.isCardSection) ||
+          key.isTab()
+        ) {
           event.preventDefault();
         }
         break;

src/js/editor/post.js

@@ -674,6 +674,29 @@ class PostEditor {
     return this.moveSectionBefore(collection, renderedSection, beforeSection);
   }
 
+  insertText(position, text) {
+    let section = position.section;
+    if (!section.isMarkerable) {
+      return;
+    }
+
+    let {marker,offset} = position.markerPosition;
+    let nextPosition = position;
+    if (!marker) {
+      marker = this.builder.createMarker(text);
+      section.markers.append(marker);
+      this._markDirty(section);
+      nextPosition = new Position(section, 1);
+    } else if (marker) {
+      let markerHead = marker.value.slice(0, offset);
+      let markerTail = marker.value.slice(offset, marker.length);
+      marker.value = `${markerHead}${text}${markerTail}`;
+      this._markDirty(marker);
+      nextPosition = position.moveRight();
+    }
+    return nextPosition;
+  }
+
   _replaceSection(section, newSections) {
     let nextSection = section.next;
     let collection = section.parent.sections;

src/js/models/marker.js

@@ -4,10 +4,6 @@ import { normalizeTagName } from '../utils/dom-utils';
 import { detect, commonItemLength, forEach, filter } from '../utils/array-utils';
 import LinkedItem from '../utils/linked-item';
 
-function trim(str) {
-  return str.replace(/^\s+/, '').replace(/\s+$/, '');
-}
-
 const Marker = class Marker extends LinkedItem {
   constructor(value='', markups=[]) {
     super();
@@ -27,7 +23,7 @@ const Marker = class Marker extends LinkedItem {
   }
 
   get isBlank() {
-    return trim(this.value).length === 0;
+    return this.value.length === 0;
   }
 
   get length() {

src/js/parsers/dom.js

@@ -1,4 +1,7 @@
-import { NO_BREAK_SPACE } from '../renderers/editor-dom';
+import {
+  NO_BREAK_SPACE,
+  TAB_CHARACTER
+} from '../renderers/editor-dom';
 import {
   MARKUP_SECTION_TYPE,
   LIST_SECTION_TYPE,
@@ -12,6 +15,7 @@ import {
   detect,
   forEach,
 } from '../utils/array-utils';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 
 import SectionParser from 'mobiledoc-kit/parsers/section';
 import { getAttributes, walkTextNodes } from '../utils/dom-utils';
@@ -20,9 +24,11 @@ import Markup from 'mobiledoc-kit/models/markup';
 const GOOGLE_DOCS_CONTAINER_ID_REGEX = /^docs\-internal\-guid/;
 
 const NO_BREAK_SPACE_REGEX = new RegExp(NO_BREAK_SPACE, 'g');
+const TAB_CHARACTER_REGEX = new RegExp(TAB_CHARACTER, 'g');
 export function transformHTMLText(textContent) {
   let text = textContent;
   text = text.replace(NO_BREAK_SPACE_REGEX, ' ');
+  text = text.replace(TAB_CHARACTER_REGEX, TAB);
   return text;
 }
 
@@ -54,6 +60,10 @@ function remapTagName(tagName) {
   return remapped || normalized;
 }
 
+function trim(str) {
+  return str.replace(/^\s+/, '').replace(/\s+$/, '');
+}
+
 /**
  * Parses DOM element -> Post
  */
@@ -80,7 +90,7 @@ export default class DOMParser {
   }
 
   appendSection(post, section) {
-    if (section.isBlank) {
+    if (section.isBlank || (section.isMarkerable && trim(section.text) === '')) {
       return;
     }
 

src/js/renderers/editor-dom.js

@@ -13,9 +13,11 @@ import { startsWith, endsWith } from '../utils/string-utils';
 import { addClassName } from '../utils/dom-utils';
 import { MARKUP_SECTION_ELEMENT_NAMES } from '../models/markup-section';
 import assert from '../utils/assert';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 
 const CARD_ELEMENT_CLASS_NAME = '__mobiledoc-card';
 export const NO_BREAK_SPACE = '\u00A0';
+export const TAB_CHARACTER = '\u2003';
 export const SPACE = ' ';
 
 function createElementFromMarkup(doc, markup) {
@@ -40,9 +42,8 @@ function renderHTMLText(marker) {
   } else if ((!marker.prev || endsWith(marker.prev.value, SPACE)) && startsWith(text, SPACE)) {
     text = NO_BREAK_SPACE + text.substr(1);
   }
-  text = text.replace(/ ( )/g, () => {
-    return ' '+NO_BREAK_SPACE;
-  });
+  text = text.replace(/ ( )/g, ' '+NO_BREAK_SPACE);
+  text = text.replace(new RegExp(TAB, 'g'), TAB_CHARACTER);
   return text;
 }
 

src/js/utils/characters.js

@@ -0,0 +1 @@
+export const TAB = '\t';

src/js/utils/key.js

@@ -108,6 +108,10 @@ const Key = class Key {
     return this.keyCode === Keycodes.SPACE;
   }
 
+  isTab() {
+    return this.keyCode === Keycodes.TAB;
+  }
+
   isEnter() {
     return this.keyCode === Keycodes.ENTER;
   }
@@ -158,6 +162,7 @@ const Key = class Key {
     return (
       (code >= Keycodes['0'] && code <= Keycodes['9']) ||         // number keys
       this.isSpace() ||
+      this.isTab()   ||
       this.isEnter() ||
       (code >= Keycodes.A && code <= Keycodes.Z) ||               // letter keys
       (code >= Keycodes.NUMPAD_0 && code <= Keycodes.NUMPAD_9) || // numpad keys

tests/acceptance/basic-editor-test.js

@@ -1,5 +1,6 @@
 import { Editor } from 'mobiledoc-kit';
 import Helpers from '../test-helpers';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 
 const { test, module } = Helpers;
 
@@ -147,6 +148,32 @@ test('typing when on the start of a card is blocked', (assert) => {
   assert.hasNoElement('#editor div:contains(Y)');
 });
 
+test('typing tab enters a tab character', (assert) => {
+  let done = assert.async();
+  let mobiledoc = Helpers.mobiledoc.build(({post}) => post());
+  editor = new Editor({mobiledoc});
+  editor.render(editorElement);
+
+  assert.hasElement('#editor');
+  assert.hasNoElement('#editor p');
+
+  Helpers.dom.moveCursorTo($('#editor')[0]);
+  Helpers.dom.insertText(editor, TAB);
+  Helpers.dom.insertText(editor, 'Y');
+  window.setTimeout(() => {
+    let editedMobiledoc = editor.serialize();
+    assert.deepEqual(editedMobiledoc.sections, [
+      [],
+      [
+        [1, 'p', [
+          [[], 0, `${TAB}Y`]
+        ]]
+      ]
+    ], 'correctly encoded');
+    done();
+  }, 0);
+});
+
 // see https://github.com/bustlelabs/mobiledoc-kit/issues/215
 test('select-all and type text works ok', (assert) => {
   let done = assert.async();

tests/unit/parsers/dom-test.js

@@ -3,6 +3,7 @@ import PostNodeBuilder from 'mobiledoc-kit/models/post-node-builder';
 import Helpers from '../../test-helpers';
 import { Editor } from 'mobiledoc-kit';
 import { NO_BREAK_SPACE } from 'mobiledoc-kit/renderers/editor-dom';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 
 const {module, test} = Helpers;
 
@@ -61,6 +62,14 @@ test('#parse can parse spaces and breaking spaces', (assert) => {
   assert.equal(s1.markers.head.value, 'some  text   for    you', 'has text');
 });
 
+test('#parse can parse tabs', (assert) => {
+  let element = buildDOM("<p>a\u2003b</p>");
+  let post = parser.parse(element);
+  let s1 = post.sections.head;
+  assert.equal(s1.markers.length, 1, 's1 has 1 marker');
+  assert.equal(s1.markers.head.value, `a${TAB}b`);
+});
+
 test('editor#reparse catches changes to section', (assert) => {
   const mobiledoc = Helpers.mobiledoc.build(({post, markupSection, marker}) =>
     post([

tests/unit/renderers/editor-dom-test.js

@@ -3,6 +3,7 @@ import Renderer from 'mobiledoc-kit/renderers/editor-dom';
 import RenderTree from 'mobiledoc-kit/models/render-tree';
 import Helpers from '../../test-helpers';
 import { NO_BREAK_SPACE } from 'mobiledoc-kit/renderers/editor-dom';
+import { TAB } from 'mobiledoc-kit/utils/characters';
 const { module, test } = Helpers;
 
 const ZWNJ = '\u200c';
@@ -126,6 +127,19 @@ test('renders a post with marker', (assert) => {
   assert.equal(renderTree.rootElement.innerHTML, '<p><strong>Hi</strong></p>');
 });
 
+test('renders a post with marker with a tab', (assert) => {
+  let post = Helpers.postAbstract.build(({post, markupSection, marker}) => {
+    return post([
+      markupSection('p', [marker(`a${TAB}b`)])
+    ]);
+  });
+
+  const renderTree = new RenderTree(post);
+  render(renderTree);
+  assert.equal(renderTree.rootElement.innerHTML, '<p>a\u2003b</p>',
+               'HTML for a tab character is correct');
+});
+
 test('renders a post with markup empty section', (assert) => {
   let post = builder.createPost();
   let section = builder.createMarkupSection('P');