itex Endpoint

Add a Rack Metal itex endpoint.
Add an itex tool to SVG-Edit.
Disable the foreignObject tool
(at least, for now) as it doesn't
currently play nice with the itex tool.

app/metal/itex.rb

@@ -0,0 +1,36 @@
+# Allow the metal piece to run in isolation
+require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)
+
+require 'stringsupport'
+
+class Itex
+  def self.call(env)
+    if env["PATH_INFO"] =~ /^\/itex/
+      [200, {"Content-Type" => "application/xml"}, [response(env)]]
+    else
+      [404, {"Content-Type" => "text/html"}, ["Not Found"]]
+    end
+  end
+  
+  private
+  
+  def self.response(env)
+    @params = Rack::Request.new(env).params
+    tex = @params['tex'].purify
+    display = @params['display'] || 'inline'
+    filter = (display  + '_filter').to_sym
+    estart = "<math xmlns='http://www.w3.org/1998/Math/MathML' display='inline'><merror><mtext>"
+    eend = "</mtext></merror></math>"
+    begin
+      require 'itextomml'
+      itex2mml_parser =  Itex2MML::Parser.new
+      itex2mml_parser.send(filter, tex).to_utf8
+    rescue LoadError
+      estart + "Please install the itex2MML Ruby bindings." + eend  
+    rescue Itex2MML::Error => e
+      estart + e.to_s + eend
+    rescue
+      estart + "Unknown Error" + eend
+    end
+  end
+end