From 3b785a0bfadf4ea1201d83fe40ab107f312fd77a Mon Sep 17 00:00:00 2001
From: Alex Kocharin <alex@kocharin.ru>
Date: Wed, 29 Oct 2014 05:00:05 +0300
Subject: [PATCH] Add subscript and superscript

---
 lib/parser_inline.js    |  4 ++-
 lib/renderer.js         | 14 +++++++++
 lib/rules_inline/sub.js | 68 +++++++++++++++++++++++++++++++++++++++++
 lib/rules_inline/sup.js | 68 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 153 insertions(+), 1 deletion(-)
 create mode 100644 lib/rules_inline/sub.js
 create mode 100644 lib/rules_inline/sup.js

diff --git a/lib/parser_inline.js b/lib/parser_inline.js
index 6c03305..889cb62 100644
--- a/lib/parser_inline.js
+++ b/lib/parser_inline.js
@@ -19,6 +19,8 @@ _rules.push(require('./rules_inline/del'));
 _rules.push(require('./rules_inline/ins'));
 _rules.push(require('./rules_inline/mark'));
 _rules.push(require('./rules_inline/emphasis'));
+_rules.push(require('./rules_inline/sub'));
+_rules.push(require('./rules_inline/sup'));
 _rules.push(require('./rules_inline/links'));
 _rules.push(require('./rules_inline/autolink'));
 _rules.push(require('./rules_inline/htmltag'));
@@ -49,7 +51,7 @@ function ParserInline() {
 
   // Rule to skip pure text
   // - '{}$%@+=:' reserved for extentions
-  this.textMatch = /[\n\\`*_\[\]!&<{}$%@~+=:]/;
+  this.textMatch = /[\n\\`*_^\[\]!&<{}$%@~+=:]/;
 
   // By default CommonMark allows too much in links
   // If you need to restrict it - override this with your validator.
diff --git a/lib/renderer.js b/lib/renderer.js
index 078b45c..3e742fe 100644
--- a/lib/renderer.js
+++ b/lib/renderer.js
@@ -240,6 +240,20 @@ rules.mark_close = function(/*tokens, idx, options*/) {
 };
 
 
+rules.sub_open = function(/*tokens, idx, options*/) {
+  return '<sub>';
+};
+rules.sub_close = function(/*tokens, idx, options*/) {
+  return '</sub>';
+};
+rules.sup_open = function(/*tokens, idx, options*/) {
+  return '<sup>';
+};
+rules.sup_close = function(/*tokens, idx, options*/) {
+  return '</sup>';
+};
+
+
 rules.hardbreak = function (tokens, idx, options) {
   return options.xhtmlOut ? '<br />\n' : '<br>\n';
 };
diff --git a/lib/rules_inline/sub.js b/lib/rules_inline/sub.js
new file mode 100644
index 0000000..f89eb7b
--- /dev/null
+++ b/lib/rules_inline/sub.js
@@ -0,0 +1,68 @@
+// Process ~subscript~
+
+'use strict';
+
+module.exports = function sub(state, silent) {
+  var found,
+      stack,
+      max = state.posMax,
+      start = state.pos,
+      lastChar,
+      nextChar;
+
+  if (state.src.charCodeAt(start) !== 0x7E/* ~ */) { return false; }
+  if (start + 2 >= max) { return false; }
+  if (state.level >= state.options.maxNesting) { return false; }
+
+  lastChar = start > 0 ? state.src.charCodeAt(start - 1) : -1;
+  nextChar = state.src.charCodeAt(start + 2);
+
+  if (nextChar === 0x20 || nextChar === 0x0A) { return false; }
+
+  state.pos = start + 1;
+  stack = 1;
+
+  while (state.pos < max) {
+    if (state.src.charCodeAt(state.pos) === 0x7E/* ~ */) {
+      lastChar = state.src.charCodeAt(state.pos - 1);
+      nextChar = state.pos + 1 < max ? state.src.charCodeAt(state.pos + 1) : -1;
+      if (nextChar !== 0x7E/* ~ */ && lastChar !== 0x7E/* ~ */) {
+        if (lastChar !== 0x20 && lastChar !== 0x0A) {
+          // closing '~'
+          stack--;
+        } else if (nextChar !== 0x20 && nextChar !== 0x0A) {
+          // opening '~'
+          stack++;
+        } // else {
+          //  // standalone ' ~ ' indented with spaces
+          //}
+        if (stack <= 0) {
+          found = true;
+          break;
+        }
+      }
+    }
+
+    state.parser.skipToken(state);
+  }
+
+  if (!found) {
+    // parser failed to find ending tag, so it's not valid emphasis
+    state.pos = start;
+    return false;
+  }
+
+  // found!
+  state.posMax = state.pos;
+  state.pos = start + 1;
+
+  if (!silent) {
+    state.push({ type: 'sub_open', level: state.level++ });
+    state.parser.tokenize(state);
+    state.push({ type: 'sub_close', level: --state.level });
+  }
+
+  state.pos = state.posMax + 1;
+  state.posMax = max;
+  return true;
+};
diff --git a/lib/rules_inline/sup.js b/lib/rules_inline/sup.js
new file mode 100644
index 0000000..e78a431
--- /dev/null
+++ b/lib/rules_inline/sup.js
@@ -0,0 +1,68 @@
+// Process ~superscript~
+
+'use strict';
+
+module.exports = function sup(state, silent) {
+  var found,
+      stack,
+      max = state.posMax,
+      start = state.pos,
+      lastChar,
+      nextChar;
+
+  if (state.src.charCodeAt(start) !== 0x5E/* ^ */) { return false; }
+  if (start + 2 >= max) { return false; }
+  if (state.level >= state.options.maxNesting) { return false; }
+
+  lastChar = start > 0 ? state.src.charCodeAt(start - 1) : -1;
+  nextChar = state.src.charCodeAt(start + 2);
+
+  if (nextChar === 0x20 || nextChar === 0x0A) { return false; }
+
+  state.pos = start + 1;
+  stack = 1;
+
+  while (state.pos < max) {
+    if (state.src.charCodeAt(state.pos) === 0x5E/* ^ */) {
+      lastChar = state.src.charCodeAt(state.pos - 1);
+      nextChar = state.pos + 1 < max ? state.src.charCodeAt(state.pos + 1) : -1;
+      if (nextChar !== 0x5E/* ^ */ && lastChar !== 0x5E/* ^ */) {
+        if (lastChar !== 0x20 && lastChar !== 0x0A) {
+          // closing '^'
+          stack--;
+        } else if (nextChar !== 0x20 && nextChar !== 0x0A) {
+          // opening '^'
+          stack++;
+        } // else {
+          //  // standalone ' ^ ' indented with spaces
+          //}
+        if (stack <= 0) {
+          found = true;
+          break;
+        }
+      }
+    }
+
+    state.parser.skipToken(state);
+  }
+
+  if (!found) {
+    // parser failed to find ending tag, so it's not valid emphasis
+    state.pos = start;
+    return false;
+  }
+
+  // found!
+  state.posMax = state.pos;
+  state.pos = start + 1;
+
+  if (!silent) {
+    state.push({ type: 'sub_open', level: state.level++ });
+    state.parser.tokenize(state);
+    state.push({ type: 'sub_close', level: --state.level });
+  }
+
+  state.pos = state.posMax + 1;
+  state.posMax = max;
+  return true;
+};