From 8e89ec504f804f805452a9e006db962f44a260b0 Mon Sep 17 00:00:00 2001
From: Arran Cudbard-Bell <arran.cudbard-bell@hp.com>
Date: Fri, 3 Jun 2011 23:21:59 -0700
Subject: [PATCH] Initial commit of Nokogiri based TOC generator

---
 lib/extensions/toc.rb | 132 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 lib/extensions/toc.rb

diff --git a/lib/extensions/toc.rb b/lib/extensions/toc.rb
new file mode 100644
index 00000000..ab1889f3
--- /dev/null
+++ b/lib/extensions/toc.rb
@@ -0,0 +1,132 @@
+module Gollum::Extensions
+  class Toc_gen
+    attr_accessor :header_tags
+    
+    NODE_CONTENT = 0
+    NODE_ORDER   = 1
+    
+    def initialize (doc, settings = {})
+      @doc = doc
+      @header_tags = ['title','h1','h2','h3','h4','h5','h6']
+    end
+    
+    # Generates a table of contents for @doc using headers
+    #
+    # Returns Nokogiri::XML::Node if there were headers to parse, or nil if none were found
+    def generate
+      return unless (headings = find_headings).count > 0
+      
+      node_count = 0
+      lvl = 0
+      @lvls = [].fill(0..@header_tags.count) {[]}
+      
+      headings.each do |h|
+        node_count += 1
+        lvl_new = heading_to_lvl h
+
+        @lvls[lvl_new].push [build_toc_node(h), node_count]
+        
+        # Pass in the highest level prior to flattening for efficiency
+        flatten_to_lvl(lvl, lvl_new) if lvl_new < lvl
+        
+        lvl = lvl_new
+      end
+      
+      flatten_to_lvl(lvl, 0)
+    end
+    
+    # Escape title string for use in ID attribute
+    #
+    # title - Title string
+    #
+    # Returns string  
+    def insert_anchors
+      find_headings.each do |h|
+        rep_h = Nokogiri::XML::Node.new('a', @doc)
+        rep_h['name'] = anchor_id(h.content)
+        rep_h.add_child(h.clone)
+        h.replace(rep_h)
+      end
+    end
+    
+    # Escape title string for use in ID attribute
+    #
+    # title - Title string
+    #
+    # Returns string  
+    def anchor_id (title)
+      CGI::escape(title)
+    end
+    
+    # Convert heading into list element
+    #
+    # heading - Nokogiri::XML::Node representing a single heading
+    #
+    # Returns string
+    def build_toc_node(heading)
+      xml_node = Nokogiri::XML::Node.new('li', @doc)
+      xml_node.add_child("<a href='#" + anchor_id(heading.content) + "'>" + heading.content + "</a>")
+      xml_node
+    end
+    
+    # Search the current @doc for headings
+    #
+    # Returns Nokogiri::XML::NodeSet
+    def find_headings
+      @doc.css(@header_tags.join ' ,')
+    end
+    
+    # Convert specified heading to integer level
+    #
+    # heading - Nokogiri::XML::Node representing a single heading
+    #
+    # Returns int
+    def heading_to_lvl(heading)
+      heading.name.gsub('h','').to_i
+    end
+
+    # Convert Nokogiri::XML:Nodes higher in the level array than the specified low_idx
+    # into a node tree, and either append or prepend the tree to the level specified
+    # by low_idx.
+    #
+    # low_idx - The level in the array to flatten to
+    # high  - The highest level to flatten from
+    #
+    # Returns Nokogiri::XML::Nodes if low_idx is 0, else nil
+    def flatten_to_lvl(high_idx, low_idx = 0)
+      lvl = high_idx + 1 
+      lvl_up = nil
+      
+      @lvls[low_idx..high_idx].reverse_each do |lvl_children|
+        lvl -= 1
+        next if lvl_children.count() == 0 || !lvl_up && (lvl_up = lvl)
+        
+        flatten_lvl(lvl_up,lvl)     
+        lvl_up = lvl   
+      end
+      
+      # Level 0 flattens all levels, and returns an XML node containing the TOC data
+      flatten_lvl(lvl_up, 0).first[NODE_CONTENT] if lvl == 0 && lvl_up
+    end
+
+    # Insert all Nokogiri::XML::Nodes at lvl_src into a new ul XML::Node as children.
+    # Then either append or prepend the ul node, depending on whether the first child
+    # at the src_level appeared before or after the node in the dst_level in @doc
+    #
+    # lvl_src - The level in the array to src li XML::Nodes from
+    # lvl_dst - The level in the array to insert resulting ul XML::Node
+    #
+    # Returns array of Nokogiri::XML::Nodes @ lvl_dst
+    def flatten_lvl(lvl_src, lvl_dst)
+      lvl_sib = Nokogiri::XML::Node.new('ul', @doc)
+      src_pos = @lvls[lvl_src].first[NODE_ORDER]
+      @lvls[lvl_src].each {|lvl_child| lvl_sib.add_child(lvl_child[NODE_CONTENT])}
+      @lvls[lvl_src] = []
+      
+      lvl_dst > 0 && src_pos < @lvls[lvl_dst].last[NODE_ORDER] ?
+        @lvls[lvl_dst].insert(-2,[lvl_sib, src_pos]) :
+        @lvls[lvl_dst].push([lvl_sib, src_pos])
+      @lvls[lvl_dst]
+    end
+  end
+end
\ No newline at end of file