From a1c93811f8d2ef891540474be0fd198aaa4b0082 Mon Sep 17 00:00:00 2001
From: Alex Kocharin <alex@kocharin.ru>
Date: Fri, 12 Jul 2019 17:25:57 +0300
Subject: [PATCH] Fix incorrect level recalculation in text_collapse

close #466
---
 lib/rules_block/state_block.js    |  4 ++--
 lib/rules_inline/state_inline.js  |  4 ++--
 lib/rules_inline/text_collapse.js | 14 +++++++++++---
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/lib/rules_block/state_block.js b/lib/rules_block/state_block.js
index 1b21483..e42cb4b 100644
--- a/lib/rules_block/state_block.js
+++ b/lib/rules_block/state_block.js
@@ -111,9 +111,9 @@ StateBlock.prototype.push = function (type, tag, nesting) {
   var token = new Token(type, tag, nesting);
   token.block = true;
 
-  if (nesting < 0) { this.level--; }
+  if (nesting < 0) this.level--; // closing tag
   token.level = this.level;
-  if (nesting > 0) { this.level++; }
+  if (nesting > 0) this.level++; // opening tag
 
   this.tokens.push(token);
   return token;
diff --git a/lib/rules_inline/state_inline.js b/lib/rules_inline/state_inline.js
index 2847496..acf0ddc 100644
--- a/lib/rules_inline/state_inline.js
+++ b/lib/rules_inline/state_inline.js
@@ -50,9 +50,9 @@ StateInline.prototype.push = function (type, tag, nesting) {
 
   var token = new Token(type, tag, nesting);
 
-  if (nesting < 0) { this.level--; }
+  if (nesting < 0) this.level--; // closing tag
   token.level = this.level;
-  if (nesting > 0) { this.level++; }
+  if (nesting > 0) this.level++; // opening tag
 
   this.pendingLevel = this.level;
   this.tokens.push(token);
diff --git a/lib/rules_inline/text_collapse.js b/lib/rules_inline/text_collapse.js
index 3104c0c..390b0fe 100644
--- a/lib/rules_inline/text_collapse.js
+++ b/lib/rules_inline/text_collapse.js
@@ -1,4 +1,10 @@
-// Merge adjacent text nodes into one, and re-calculate all token levels
+// Clean up tokens after emphasis and strikethrough postprocessing:
+// merge adjacent text nodes into one and re-calculate all token levels
+//
+// This is necessary because initially emphasis delimiter markers (*, _, ~)
+// are treated as their own separate text tokens. Then emphasis rule either
+// leaves them as text (needed to merge with adjacent text) or turns them
+// into opening/closing tags (which messes up levels inside).
 //
 'use strict';
 
@@ -10,9 +16,11 @@ module.exports = function text_collapse(state) {
       max = state.tokens.length;
 
   for (curr = last = 0; curr < max; curr++) {
-    // re-calculate levels
-    level += tokens[curr].nesting;
+    // re-calculate levels after emphasis/strikethrough turns some text nodes
+    // into opening/closing tags
+    if (tokens[curr].nesting < 0) level--; // closing tag
     tokens[curr].level = level;
+    if (tokens[curr].nesting > 0) level++; // opening tag
 
     if (tokens[curr].type === 'text' &&
         curr + 1 < max &&