From 1346a11cb40b96b8f3db6bea8a8addaea28b2389 Mon Sep 17 00:00:00 2001
From: nicovalencia <hello@nico.io>
Date: Wed, 8 Jan 2014 15:34:54 -0700
Subject: [PATCH] Prepending header ids with `section` and adding unique
 identifier to header ids.

closes #82
- Modified header id function to prepend `section` to each id
- Modified header id function to track duplicate count and append a unique numerical-id
---
 src/showdown.js                            | 42 +++++++++++++++-------
 test/cases/anchors-by-reference.html       |  2 +-
 test/cases/blockquote-nested-markdown.html |  2 +-
 test/cases/h1-with-double-hash.html        |  2 +-
 test/cases/h1-with-equals.html             |  2 +-
 test/cases/h1-with-single-hash.html        |  2 +-
 test/cases/h2-with-dashes.html             |  2 +-
 test/cases/h2-with-double-hash.html        |  2 +-
 test/cases/h2-with-single-hash.html        |  2 +-
 test/cases/h3-with-double-hash.html        |  2 +-
 test/cases/h3-with-single-hash.html        |  2 +-
 test/cases/h4-with-single-hash.html        |  2 +-
 test/cases/h5-with-single-hash.html        |  2 +-
 test/cases/h6-with-single-hash.html        |  2 +-
 14 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/src/showdown.js b/src/showdown.js
index ebbd8a7..24835e0 100644
--- a/src/showdown.js
+++ b/src/showdown.js
@@ -767,6 +767,26 @@ Showdown.converter = function(converter_options) {
 
   var _DoHeaders = function(text) {
 
+    // Keep track of ids used for headers for hash-linking. If any duplicates
+    // are used, append a unique string based on the count of identical ids.
+    // This prevents the result of having duplicate ids if a user creates
+    // similar headers.
+    var hashLinkCounts = {};
+    function headerId(m) {
+      var title,
+          escapedId = m.replace(/[^\w]/g, '').toLowerCase();
+
+      if (hashLinkCounts[escapedId]) {
+        title = escapedId + "-" + (hashLinkCounts[escapedId]++);
+      } else {
+        title = escapedId;
+        hashLinkCounts[escapedId] = 1;
+      }
+
+      // Prefix id to prevent causing inadverntent pre-existing style matches.
+      return "section-" + title;
+    }
+
     // Setext-style headers:
     //      Header 1
     //      ========
@@ -774,11 +794,13 @@ Showdown.converter = function(converter_options) {
     //      Header 2
     //      --------
     //
-    text = text.replace(/^(.+)[ \t]*\n=+[ \t]*\n+/gm,
-        function(wholeMatch,m1){return hashBlock('<h1 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h1>");});
+    text = text.replace(/^(.+)[ \t]*\n=+[ \t]*\n+/gm, function(wholeMatch,m1){
+      return hashBlock('<h1 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h1>");
+    });
 
-    text = text.replace(/^(.+)[ \t]*\n-+[ \t]*\n+/gm,
-        function(matchFound,m1){return hashBlock('<h2 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h2>");});
+    text = text.replace(/^(.+)[ \t]*\n-+[ \t]*\n+/gm, function(matchFound,m1){
+      return hashBlock('<h2 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h2>");
+    });
 
     // atx-style headers:
     //  # Header 1
@@ -799,15 +821,11 @@ Showdown.converter = function(converter_options) {
        /gm, function() {...});
        */
 
-    text = text.replace(/^(\#{1,6})[ \t]*(.+?)[ \t]*\#*\n+/gm,
-        function(wholeMatch,m1,m2) {
-          var h_level = m1.length;
-          return hashBlock("<h" + h_level + ' id="' + headerId(m2) + '">' + _RunSpanGamut(m2) + "</h" + h_level + ">");
-        });
+    text = text.replace(/^(\#{1,6})[ \t]*(.+?)[ \t]*\#*\n+/gm, function(wholeMatch,m1,m2) {
+      var h_level = m1.length;
+      return hashBlock("<h" + h_level + ' id="' + headerId(m2) + '">' + _RunSpanGamut(m2) + "</h" + h_level + ">");
+    });
 
-    function headerId(m) {
-      return m.replace(/[^\w]/g, '').toLowerCase();
-    }
     return text;
   };
 
diff --git a/test/cases/anchors-by-reference.html b/test/cases/anchors-by-reference.html
index 9265274..99c15e3 100644
--- a/test/cases/anchors-by-reference.html
+++ b/test/cases/anchors-by-reference.html
@@ -2,4 +2,4 @@
 <p>This is <a href="http://example.com/" title="Optional Title Here">an example</a> reference-style link.
 This is <a href="http://example.com/" title="Optional Title Here">another</a> reference-style link.
 This is <a href="http://example.com/" title="Optional Title Here">a third</a> reference-style link.
-This is <a href="http://example.com/" title="Optional Title Here">a fourth</a> reference-style link.</p>
\ No newline at end of file
+This is <a href="http://example.com/" title="Optional Title Here">a fourth</a> reference-style link.</p>
diff --git a/test/cases/blockquote-nested-markdown.html b/test/cases/blockquote-nested-markdown.html
index 25800d7..afae8f8 100644
--- a/test/cases/blockquote-nested-markdown.html
+++ b/test/cases/blockquote-nested-markdown.html
@@ -1,5 +1,5 @@
 <blockquote>
-    <h2 id="thisisaheader">This is a header.</h2>
+    <h2 id="section-thisisaheader">This is a header.</h2>
 
     <ol>
         <li>This is the first list item.</li>
diff --git a/test/cases/h1-with-double-hash.html b/test/cases/h1-with-double-hash.html
index 2cecc38..749011b 100644
--- a/test/cases/h1-with-double-hash.html
+++ b/test/cases/h1-with-double-hash.html
@@ -1 +1 @@
-<h1 id="thisisanh1">This is an H1</h1>
\ No newline at end of file
+<h1 id="section-thisisanh1">This is an H1</h1>
diff --git a/test/cases/h1-with-equals.html b/test/cases/h1-with-equals.html
index 2cecc38..749011b 100644
--- a/test/cases/h1-with-equals.html
+++ b/test/cases/h1-with-equals.html
@@ -1 +1 @@
-<h1 id="thisisanh1">This is an H1</h1>
\ No newline at end of file
+<h1 id="section-thisisanh1">This is an H1</h1>
diff --git a/test/cases/h1-with-single-hash.html b/test/cases/h1-with-single-hash.html
index 2cecc38..749011b 100644
--- a/test/cases/h1-with-single-hash.html
+++ b/test/cases/h1-with-single-hash.html
@@ -1 +1 @@
-<h1 id="thisisanh1">This is an H1</h1>
\ No newline at end of file
+<h1 id="section-thisisanh1">This is an H1</h1>
diff --git a/test/cases/h2-with-dashes.html b/test/cases/h2-with-dashes.html
index d040d75..2fc6b0b 100644
--- a/test/cases/h2-with-dashes.html
+++ b/test/cases/h2-with-dashes.html
@@ -1 +1 @@
-<h2 id="thisisanh2">This is an H2</h2>
\ No newline at end of file
+<h2 id="section-thisisanh2">This is an H2</h2>
diff --git a/test/cases/h2-with-double-hash.html b/test/cases/h2-with-double-hash.html
index d040d75..2fc6b0b 100644
--- a/test/cases/h2-with-double-hash.html
+++ b/test/cases/h2-with-double-hash.html
@@ -1 +1 @@
-<h2 id="thisisanh2">This is an H2</h2>
\ No newline at end of file
+<h2 id="section-thisisanh2">This is an H2</h2>
diff --git a/test/cases/h2-with-single-hash.html b/test/cases/h2-with-single-hash.html
index d040d75..2fc6b0b 100644
--- a/test/cases/h2-with-single-hash.html
+++ b/test/cases/h2-with-single-hash.html
@@ -1 +1 @@
-<h2 id="thisisanh2">This is an H2</h2>
\ No newline at end of file
+<h2 id="section-thisisanh2">This is an H2</h2>
diff --git a/test/cases/h3-with-double-hash.html b/test/cases/h3-with-double-hash.html
index 082318e..92a7399 100644
--- a/test/cases/h3-with-double-hash.html
+++ b/test/cases/h3-with-double-hash.html
@@ -1 +1 @@
-<h3 id="thisisanh3">This is an H3</h3>
\ No newline at end of file
+<h3 id="section-thisisanh3">This is an H3</h3>
diff --git a/test/cases/h3-with-single-hash.html b/test/cases/h3-with-single-hash.html
index 082318e..92a7399 100644
--- a/test/cases/h3-with-single-hash.html
+++ b/test/cases/h3-with-single-hash.html
@@ -1 +1 @@
-<h3 id="thisisanh3">This is an H3</h3>
\ No newline at end of file
+<h3 id="section-thisisanh3">This is an H3</h3>
diff --git a/test/cases/h4-with-single-hash.html b/test/cases/h4-with-single-hash.html
index cc32aa1..605e93a 100644
--- a/test/cases/h4-with-single-hash.html
+++ b/test/cases/h4-with-single-hash.html
@@ -1 +1 @@
-<h4 id="thisisanh4">This is an H4</h4>
\ No newline at end of file
+<h4 id="section-thisisanh4">This is an H4</h4>
diff --git a/test/cases/h5-with-single-hash.html b/test/cases/h5-with-single-hash.html
index 96dca78..ae3a75d 100644
--- a/test/cases/h5-with-single-hash.html
+++ b/test/cases/h5-with-single-hash.html
@@ -1 +1 @@
-<h5 id="thisisanh5">This is an H5</h5>
\ No newline at end of file
+<h5 id="section-thisisanh5">This is an H5</h5>
diff --git a/test/cases/h6-with-single-hash.html b/test/cases/h6-with-single-hash.html
index 10de690..a93ba51 100644
--- a/test/cases/h6-with-single-hash.html
+++ b/test/cases/h6-with-single-hash.html
@@ -1 +1 @@
-<h6 id="thisisanh6">This is an H6</h6>
\ No newline at end of file
+<h6 id="section-thisisanh6">This is an H6</h6>