Add toc link when enable set to true.

README.md

@@ -57,7 +57,7 @@ Markd.to_html(markdown, options)
 | prettyprint | `Bool` | false         | if **true**, code tags generated by code blocks will have a `prettyprint` class added to them, to be used by [Google code-prettify](https://github.com/google/code-prettify).   |
 | gfm         | `Bool` | false         | **Partial support**                                                                                                                                                         |
 | autolink    | `Bool` | false         | if **true**, more autolinks are detected, like bare email addresses or http links. Requires `gfm` be set to `true`                                  |
-| toc         | `Bool` | false         | **Not supported for now**                                                                                                                                                         |
+| toc         | `Bool` | false         | **Partial support**, if **true**, show only a anchor text to the beginning of the head tag(as github markdown does) for now.                                                                                                                                                       |
 | base_url    | `URI?` | nil           | if not **nil**, relative URLs of links are resolved against this `URI`. It act's like HTML's `<base href="base_url">` in the context of a Markdown document.                    |
 
 ## Advanced

spec/markd_spec.cr

@@ -25,4 +25,55 @@
 
     Markd.to_html(raw).should eq(html)
   end
+
+  it "should add a anchor text to the beginning of the head tag" do
+    raw = <<-'HEREDOC'
+## foo
+## bar
+### 标题1
+### 标题2
+HEREDOC
+
+    options = Markd::Options.new(toc: true)
+
+    html = <<-'HEREDOC'
+<h2><a id="anchor-f" class="anchor" href="#anchor-f">§ </a>foo</h2>
+<h2><a id="anchor-bar" class="anchor" href="#anchor-bar">§ </a>bar</h2>
+<h3><a id="anchor-%E6%A0%87%E9%A2%981" class="anchor" href="#anchor-%E6%A0%87%E9%A2%981">§ </a>标题1</h3>
+<h3><a id="anchor-%E6%A0%87%E9%A2%982" class="anchor" href="#anchor-%E6%A0%87%E9%A2%982">§ </a>标题2</h3>
+
+HEREDOC
+
+    Markd.to_html(raw, options).should eq(html)
+
+    options = Markd::Options.new(toc: "@")
+
+    html = <<-'HEREDOC'
+<h2><a id="anchor-f" class="anchor" href="#anchor-f">@ </a>foo</h2>
+<h2><a id="anchor-bar" class="anchor" href="#anchor-bar">@ </a>bar</h2>
+<h3><a id="anchor-%E6%A0%87%E9%A2%981" class="anchor" href="#anchor-%E6%A0%87%E9%A2%981">@ </a>标题1</h3>
+<h3><a id="anchor-%E6%A0%87%E9%A2%982" class="anchor" href="#anchor-%E6%A0%87%E9%A2%982">@ </a>标题2</h3>
+
+HEREDOC
+
+    Markd.to_html(raw, options).should eq(html)
+  end
+
+  it "should generate a correct anchor on the beginning of the head tag" do
+    raw = <<-'HEREDOC'
+# h1
+# h2
+# hh3
+HEREDOC
+
+    options = Markd::Options.new(toc: true)
+
+    html = <<-'HEREDOC'
+<h1><a id="anchor-h1" class="anchor" href="#anchor-h1">§ </a>h1</h1>
+<h2><a id="anchor-h2" class="anchor" href="#anchor-h2">§ </a>h2</h2>
+<h2><a id="anchor-hh3" class="anchor" href="#anchor-hh3">§ </a>hh3</h2>
+HEREDOC
+
+    Markd.to_html(raw, options).should eq(html)
+  end
 end

src/markd/options.cr

@@ -3,7 +3,11 @@ require "uri"
 module Markd
   # Markdown rendering options.
   class Options
-    property time, gfm, toc
+    property time, gfm
+
+    # if `true', show a anchor text to the beginning of the head tag
+    # You can specify a String as the anchor text to this option too.
+    property toc : String | Bool
 
     # If `true`:
     # - straight quotes will be made curly

src/markd/renderers/html_renderer.cr

@@ -11,10 +11,17 @@ module Markd
 
     def heading(node : Node, entering : Bool) : Nil
       tag_name = HEADINGS[node.data["level"].as(Int32) - 1]
+      toc = @options.toc
+
       if entering
         newline
         tag(tag_name, attrs(node))
-        toc(node) if @options.toc
+        case toc
+        when String
+          toc(node, toc)
+        when true
+          toc(node)
+        end
       else
         tag(tag_name, end_tag: true)
         newline
@@ -308,16 +315,16 @@ module Markd
       url.match(Rule::UNSAFE_PROTOCOL) && !url.match(Rule::UNSAFE_DATA_PROTOCOL)
     end
 
-    private def toc(node : Node)
+    private def toc(node : Node, anchor_text = "§")
       return unless node.type.heading?
 
-      {% if compare_versions(Crystal::VERSION, "1.2.0") < 0 %}
-        title = URI.encode(node.first_child.text)
-        @output_io << %(<a id="anchor-) << title << %(" class="anchor" href="#anchor-) << title << %("></a>)
-      {% else %}
-        title = URI.encode_path(node.first_child.text)
-        @output_io << %(<a id="anchor-) << title << %(" class="anchor" href="#anchor-) << title << %("></a>)
-      {% end %}
+      title = {% if compare_versions(Crystal::VERSION, "1.2.0") < 0 %}
+                URI.encode(node.first_child.text)
+              {% else %}
+                URI.encode_path(node.first_child.text)
+              {% end %}
+
+      @output_io << %(<a id="anchor-) << title << %(" class="anchor" href="#anchor-) << title << %(">) << anchor_text << %( </a>)
       @last_output = ">"
     end