Improve smartquotes handling

Use implementation similar to the new emphasis one.

lib/rules_core/smartquotes.js

@@ -3,18 +3,14 @@
 'use strict';
 
 
+var isWhiteSpace   = require('../common/utils').isWhiteSpace;
+var isPunctChar    = require('../common/utils').isPunctChar;
+var isMdAsciiPunct = require('../common/utils').isMdAsciiPunct;
+
 var QUOTE_TEST_RE = /['"]/;
 var QUOTE_RE = /['"]/g;
-var PUNCT_RE = /[-\s()\[\]]/;
 var APOSTROPHE = '\u2019'; /* ’ */
 
-// This function returns true if the character at `pos`
-// could be inside a word.
-function isLetter(str, pos) {
-  if (pos < 0 || pos >= str.length) { return false; }
-  return !PUNCT_RE.test(str[pos]);
-}
-
 
 function replaceAt(str, index, ch) {
   return str.substr(0, index) + ch + str.substr(index + 1);
@@ -23,9 +19,9 @@ function replaceAt(str, index, ch) {
 
 module.exports = function smartquotes(state) {
   /*eslint max-depth:0*/
-  var i, token, text, t, pos, max, thisLevel, lastSpace, nextSpace, item,
-      canOpen, canClose, j, isSingle, blkIdx, tokens,
-      stack;
+  var i, token, text, t, pos, max, thisLevel, item, lastChar, nextChar,
+      isLastPunctChar, isNextPunctChar, isLastWhiteSpace, isNextWhiteSpace,
+      canOpen, canClose, j, isSingle, blkIdx, tokens, stack;
 
   if (!state.md.options.typographer) { return; }
 
@@ -61,12 +57,51 @@ module.exports = function smartquotes(state) {
         t = QUOTE_RE.exec(text);
         if (!t) { break; }
 
-        lastSpace = !isLetter(text, t.index - 1);
+        canOpen = canClose = true;
         pos = t.index + 1;
         isSingle = (t[0] === "'");
-        nextSpace = !isLetter(text, pos);
 
-        if (!nextSpace && !lastSpace) {
+        lastChar = t.index - 1 >= 0 ? text.charCodeAt(t.index - 1) : -1;
+        nextChar = pos < max ? text.charCodeAt(pos) : -1;
+
+        isLastPunctChar = lastChar >= 0 &&
+          (isMdAsciiPunct(lastChar) || isPunctChar(String.fromCharCode(lastChar)));
+        isNextPunctChar = nextChar >= 0 &&
+          (isMdAsciiPunct(nextChar) || isPunctChar(String.fromCharCode(nextChar)));
+
+        // begin/end of the line counts as a whitespace too
+        isLastWhiteSpace = lastChar < 0 || isWhiteSpace(lastChar);
+        isNextWhiteSpace = nextChar < 0 || isWhiteSpace(nextChar);
+
+        if (isNextWhiteSpace) {
+          canOpen = false;
+        } else if (isNextPunctChar) {
+          if (!(isLastWhiteSpace || isLastPunctChar)) {
+            canOpen = false;
+          }
+        }
+
+        if (isLastWhiteSpace) {
+          canClose = false;
+        } else if (isLastPunctChar) {
+          if (!(isNextWhiteSpace || isNextPunctChar)) {
+            canClose = false;
+          }
+        }
+
+        if (nextChar === 0x22 /* " */ && t[0] === '"') {
+          if (lastChar >= 0x30 /* 0 */ && lastChar <= 0x39 /* 9 */) {
+            // special case: 1"" - count first quote as an inch
+            canClose = canOpen = false;
+          }
+        }
+
+        if (canOpen && canClose) {
+          // treat this as the middle of the word
+          canOpen = canClose = false;
+        }
+
+        if (!canOpen && !canClose) {
           // middle of word
           if (isSingle) {
             token.content = replaceAt(token.content, t.index, APOSTROPHE);
@@ -74,9 +109,6 @@ module.exports = function smartquotes(state) {
           continue;
         }
 
-        canOpen = !nextSpace;
-        canClose = !lastSpace;
-
         if (canClose) {
           // this could be a closing quote, rewind the stack to get a match
           for (j = stack.length - 1; j >= 0; j--) {

test/fixtures/markdown-it/smartquotes.txt

@@ -31,6 +31,19 @@ Should match quotes on the same level:
 .
 
 
+Should handle adjacent nested quotes:
+
+.
+'"double in single"'
+
+"'single in double'"
+.
+<p>‘“double in single”’</p>
+<p>“‘single in double’”</p>
+.
+
+
+
 Should not match quotes on different levels:
 
 .