From 254cb9146521945eaa36ce5959ab13ba9c9d9260 Mon Sep 17 00:00:00 2001
From: David Dreher <dredav@users.noreply.github.com>
Date: Thu, 7 Feb 2019 17:20:00 +0100
Subject: [PATCH] Fix for #2782: CodeEditor.handleChange will now update the
 toc if available when a headline was modified

---
 browser/components/CodeEditor.js      | 35 +++++++++++++++++++++++++++
 browser/lib/markdown-toc-generator.js | 17 +++++++------
 2 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/browser/components/CodeEditor.js b/browser/components/CodeEditor.js
index f19fc3f1d..76c7be669 100644
--- a/browser/components/CodeEditor.js
+++ b/browser/components/CodeEditor.js
@@ -22,6 +22,7 @@ const buildEditorContextMenu = require('browser/lib/contextMenuBuilder')
 import TurndownService from 'turndown'
 import {languageMaps} from '../lib/CMLanguageList'
 import snippetManager from '../lib/SnippetManager'
+import {generateInEditor, tocExistsInEditor} from 'browser/lib/markdown-toc-generator'
 
 CodeMirror.modeURL = '../node_modules/codemirror/mode/%N/%N.js'
 
@@ -614,6 +615,34 @@ export default class CodeEditor extends React.Component {
   handleChange (editor, changeObject) {
     spellcheck.handleChange(editor, changeObject)
 
+    // The current note contains an toc. We'll check for changes on headlines.
+    // origin is undefined when markdownTocGenerator replace the old tod
+    if (tocExistsInEditor(editor) && changeObject.origin !== undefined) {
+      let requireTocUpdate
+
+      // Check if one of the changed lines contains a headline
+      for (let line = 0; line < changeObject.text.length; line++) {
+        if (this.linePossibleContainsHeadline(editor.getLine(changeObject.from.line + line))) {
+          requireTocUpdate = true
+          break
+        }
+      }
+
+      if (!requireTocUpdate) {
+        // Check if one of the removed lines contains a headline
+        for (let line = 0; line < changeObject.removed.length; line++) {
+          if (this.linePossibleContainsHeadline(changeObject.removed[line])) {
+            requireTocUpdate = true
+            break
+          }
+        }
+      }
+
+      if (requireTocUpdate) {
+        generateInEditor(editor)
+      }
+    }
+
     this.updateHighlight(editor, changeObject)
 
     this.value = editor.getValue()
@@ -622,6 +651,12 @@ export default class CodeEditor extends React.Component {
     }
   }
 
+  linePossibleContainsHeadline (currentLine) {
+    // We can't check if the line start with # because when some write text before
+    // the # we also need to update the toc
+    return currentLine.includes('# ')
+  }
+
   incrementLines (start, linesAdded, linesRemoved, editor) {
     const highlightedLines = editor.options.linesHighlighted
 
diff --git a/browser/lib/markdown-toc-generator.js b/browser/lib/markdown-toc-generator.js
index af1c833f4..8f027247b 100644
--- a/browser/lib/markdown-toc-generator.js
+++ b/browser/lib/markdown-toc-generator.js
@@ -28,6 +28,8 @@ function linkify (token) {
 const TOC_MARKER_START = '<!-- toc -->'
 const TOC_MARKER_END = '<!-- tocstop -->'
 
+const tocRegex = new RegExp(`${TOC_MARKER_START}[\\s\\S]*?${TOC_MARKER_END}`)
+
 /**
  * Takes care of proper updating given editor with TOC.
  * If TOC doesn't exit in the editor, it's inserted at current caret position.
@@ -35,12 +37,6 @@ const TOC_MARKER_END = '<!-- tocstop -->'
  * @param editor CodeMirror editor to be updated with TOC
  */
 export function generateInEditor (editor) {
-  const tocRegex = new RegExp(`${TOC_MARKER_START}[\\s\\S]*?${TOC_MARKER_END}`)
-
-  function tocExistsInEditor () {
-    return tocRegex.test(editor.getValue())
-  }
-
   function updateExistingToc () {
     const toc = generate(editor.getValue())
     const search = editor.getSearchCursor(tocRegex)
@@ -54,13 +50,17 @@ export function generateInEditor (editor) {
     editor.replaceRange(wrapTocWithEol(toc, editor), editor.getCursor())
   }
 
-  if (tocExistsInEditor()) {
+  if (tocExistsInEditor(editor)) {
     updateExistingToc()
   } else {
     addTocAtCursorPosition()
   }
 }
 
+export function tocExistsInEditor (editor) {
+  return tocRegex.test(editor.getValue())
+}
+
 /**
  * Generates MD TOC based on MD document passed as string.
  * @param markdownText MD document
@@ -94,5 +94,6 @@ function wrapTocWithEol (toc, editor) {
 
 export default {
   generate,
-  generateInEditor
+  generateInEditor,
+  tocExistsInEditor
 }