# Copyright (c) 2008 The Kaphan Foundation
#
# Possession of a copy of this file grants no permission or license
# to use, modify, or create derivate works.
# Please contact info@peerworks.org for further information.
#

require 'net/http'

# Just a couple methods form transforming strings
unless defined?(ActiveSupport)
  class String # :nodoc:
    def singularize
      if self =~ /ies$/
        self.sub(/ies$/, 'y')
      else
        self.sub(/s$/, '')
      end
    end
  
    def demodulize
      self.sub(/.*::/, '')
    end
    
    def constantize
      Object.module_eval("::#{self}", __FILE__, __LINE__)
    end
  end
end

module Atom
  module Xml # :nodoc:
    module Parseable # :nodoc:
      def parse(xml, options = {})
        starting_depth = xml.depth
        loop do
          case xml.node_type
          when XML::Reader::TYPE_ELEMENT
            if element_specs.include?(xml.local_name)
              element_specs[xml.local_name].parse(self, xml)
            elsif attributes.any?
              while (xml.move_to_next_attribute == 1)
                if attributes.include?(xml.name)
                  # Support attribute names with namespace prefixes
                  self.send("#{xml.name.sub(/:/, '_')}=", xml.value)
                end
              end
            end
          end
          break unless !options[:once] && xml.next == 1 && xml.depth >= starting_depth
        end
      end
    
      def next_node_is?(xml, element, ns = nil)
        xml.next == 1 && current_node_is?(xml, element, ns)
      end
      
      def current_node_is?(xml, element, ns = nil)
        xml.node_type == XML::Reader::TYPE_ELEMENT && xml.local_name == element && (ns.nil? || ns == xml.namespace_uri)
      end
  
      def Parseable.included(o)
        o.class_eval do
          def o.element_specs;  @element_specs ||= {}; end
          def o.attributes; @attributes ||= []; end
          def element_specs; self.class.element_specs; end
          def attributes; self.class.attributes; end
        end
        o.send(:extend, DeclarationMethods)
      end
      
      def ==(o)
        if self.object_id == o.object_id
          true
        elsif o.instance_of?(self.class)
          self.class.element_specs.values.all? do |spec|
            self.send(spec.attribute) == o.send(spec.attribute)
          end
        else
          false
        end
      end
      
      def to_xml(nodeonly = false, root_name = self.class.name.demodulize.downcase)
        
        node = XML::Node.new(root_name)
        node['xmlns'] = Atom::NAMESPACE unless nodeonly
        
        self.class.element_specs.values.each do |spec|
          if spec.single?
            if attribute = self.send(spec.attribute)
              if attribute.is_a?(Time)
                node << XML::Node.new(spec.name, attribute.xmlschema)
              elsif attribute.respond_to?(:to_xml)
                node << attribute.to_xml(true)
              else
                n =  XML::Node.new(spec.name)
                n << attribute
                node << n
              end
            end
          else
            self.send(spec.attribute).each do |attribute|
              node << attribute.to_xml(true, spec.name.singularize)
            end
          end
        end
        
        self.class.attributes.each do |attribute|
          if value = self.send("#{attribute.sub(/:/, '_')}")
            if value != 0
              node[attribute] = value.to_s
            end
          end
        end
        
        unless nodeonly
          doc = XML::Document.new
          doc.root = node
          doc.to_s
        else
          node
        end
      end
    
      module DeclarationMethods # :nodoc:
        def element(*names)
          options = {:type => :single}
          options.merge!(names.pop) if names.last.is_a?(Hash) 
        
          names.each do |name|
            attr_accessor name          
            self.element_specs[name.to_s] = ParseSpec.new(name, options)
          end
        end
            
        def elements(*names)
          options = {:type => :collection}
          options.merge!(names.pop) if names.last.is_a?(Hash)
        
          names.each do |name|
            attr_accessor name
            self.element_specs[name.to_s.singularize] = ParseSpec.new(name, options)
          end
        end
      
        def attribute(*names)
          names.each do |name|
            attr_accessor name.to_s.sub(/:/, '_').to_sym
            self.attributes << name.to_s
          end
        end
      
        def loadable!(&error_handler)
          class_name = self.name
          (class << self; self; end).instance_eval do
            define_method "load_#{class_name.demodulize.downcase}" do |o|
               xml = nil
                case o
                when String
                  xml = XML::Reader.new(o)
                when IO
                  xml = XML::Reader.new(o.read)
                when URI
                  raise ArgumentError, "#{class_name}.load only handles http URIs" if o.scheme != 'http'
                  xml = XML::Reader.new(Net::HTTP.get_response(o).body)
                else
                  raise ArgumentError, "#{class_name}.load needs String, URI or IO, got #{o.class.name}"
                end

                if error_handler
                  xml.set_error_handler(&error_handler)
                else
                  xml.set_error_handler do |reader, message, severity, base, line|
                    if severity == XML::Reader::SEVERITY_ERROR
                      raise ParseError, "#{message} at #{line}"
                    end
                  end
                end
                
                o = self.new(xml)
                xml.close
                o
            end
          end
        end
        
        def parse(xml)
          new(xml)
        end
      end
    
      # Contains the specification for how an element should be parsed.
      #
      # This should not need to be constructed directly, instead use the
      # element and elements macros in the declaration of the class.
      #
      # See Parseable.
      #
      class ParseSpec # :nodoc:
        attr_reader :name, :options, :attribute
      
        def initialize(name, options = {})
          @name = name.to_s
          @attribute = name.to_s.sub(/:/, '_')
          @options = options
        end
      
        # Parses a chunk of XML according the specification.
        # The data extracted will be assigned to the target object.
        #
        def parse(target, xml)
          case options[:type]
          when :single
            target.send("#{@attribute}=".to_sym, build(target, xml))
          when :collection
            target.send("#{@attribute}") << build(target, xml)
          end
        end
      
        def single?
          options[:type] == :single
        end
        
        private
        # Create a member 
        def build(target, xml)
          if options[:class].is_a?(Class)
            if options[:content_only]
              options[:class].parse(xml.read_string)
            else
              options[:class].parse(xml)
            end
          elsif options[:type] == :single
            xml.read_string
          elsif options[:content_only] 
            xml.read_string
          else
            target_class = target.class.name
            target_class = target_class.sub(/#{target_class.demodulize}$/, name.singularize.capitalize)
            target_class.constantize.parse(xml)
          end
        end
      end
    end
  end
end