require 'nokogiri'
require 'date'
require 'time'
require 'happymapper/anonymous_mapper'

module HappyMapper
  class Boolean; end
  class XmlContent; end

  extend AnonymousMapper

  DEFAULT_NS = "happymapper"

  def self.included(base)
    if !(base.superclass <= HappyMapper)
      base.instance_eval do
        @attributes = {}
        @elements = {}
        @registered_namespaces = {}
        @wrapper_anonymous_classes = {}
      end
    else
      base.instance_eval do
        @attributes =
            superclass.instance_variable_get(:@attributes).dup
        @elements =
            superclass.instance_variable_get(:@elements).dup
        @registered_namespaces =
            superclass.instance_variable_get(:@registered_namespaces).dup
        @wrapper_anonymous_classes =
            superclass.instance_variable_get(:@wrapper_anonymous_classes).dup
      end
    end

    base.extend ClassMethods
  end

  module ClassMethods

    #
    # The xml has the following attributes defined.
    #
    # @example
    #
    #     "<country code='de'>Germany</country>"
    #
    #     # definition of the 'code' attribute within the class
    #     attribute :code, String
    #
    # @param [Symbol] name the name of the accessor that is created
    # @param [String,Class] type the class name of the name of the class whcih
    #     the object will be converted upon parsing
    # @param [Hash] options additional parameters to send to the relationship
    #
    def attribute(name, type, options={})
      attribute = Attribute.new(name, type, options)
      @attributes[name] = attribute
      attr_accessor attribute.method_name.intern
    end

    #
    # The elements defined through {#attribute}.
    #
    # @return [Array<Attribute>] a list of the attributes defined for this class;
    #     an empty array is returned when there have been no attributes defined.
    #
    def attributes
      @attributes.values
    end

    #
    # Register a namespace that is used to persist the object namespace back to
    # XML.
    #
    # @example
    #
    #     register_namespace 'prefix', 'http://www.unicornland.com/prefix'
    #
    #     # the output will contain the namespace defined
    #
    #     "<outputXML xmlns:prefix="http://www.unicornland.com/prefix">
    #     ...
    #     </outputXML>"
    #
    # @param [String] namespace the xml prefix
    # @param [String] ns url for the xml namespace
    #
    def register_namespace(namespace, ns)
      @registered_namespaces.merge!({namespace => ns})
    end

    #
    # An element defined in the XML that is parsed.
    #
    # @example
    #
    #     "<address location='home'>
    #        <city>Oldenburg</city>
    #      </address>"
    #
    #     # definition of the 'city' element within the class
    #
    #     element :city, String
    #
    # @param [Symbol] name the name of the accessor that is created
    # @param [String,Class] type the class name of the name of the class whcih
    #     the object will be converted upon parsing
    # @param [Hash] options additional parameters to send to the relationship
    #
    def element(name, type, options={})
      element = Element.new(name, type, options)
      @elements[name] = element
      attr_accessor element.method_name.intern
    end

    #
    # The elements defined through {#element}, {#has_one}, and {#has_many}.
    #
    # @return [Array<Element>] a list of the elements contained defined for this
    #     class; an empty array is returned when there have been no elements
    #     defined.
    #
    def elements
      @elements.values
    end

    #
    # The value stored in the text node of the current element.
    #
    # @example
    #
    #     "<firstName>Michael Jackson</firstName>"
    #
    #     # definition of the 'firstName' text node within the class
    #
    #     content :first_name, String
    #
    # @param [Symbol] name the name of the accessor that is created
    # @param [String,Class] type the class name of the name of the class whcih
    #     the object will be converted upon parsing. By Default String class will be taken.
    # @param [Hash] options additional parameters to send to the relationship
    #
    def content(name, type=String, options={})
      @content = TextNode.new(name, type, options)
      attr_accessor @content.method_name.intern
    end

    #
    # Sets the object to have xml content, this will assign the XML contents
    # that are parsed to the attribute accessor xml_content. The object will
    # respond to the method #xml_content and will return the XML data that
    # it has parsed.
    #
    def has_xml_content
      attr_accessor :xml_content
    end

    #
    # The object has one of these elements in the XML. If there are multiple,
    # the last one will be set to this value.
    #
    # @param [Symbol] name the name of the accessor that is created
    # @param [String,Class] type the class name of the name of the class whcih
    #     the object will be converted upon parsing
    # @param [Hash] options additional parameters to send to the relationship
    #
    # @see #element
    #
    def has_one(name, type, options={})
      element name, type, {:single => true}.merge(options)
    end

    #
    # The object has many of these elements in the XML.
    #
    # @param [Symbol] name the name of accessor that is created
    # @param [String,Class] type the class name or the name of the class which
    #     the object will be converted upon parsing.
    # @param [Hash] options additional parameters to send to the relationship
    #
    # @see #element
    #
    def has_many(name, type, options={})
      element name, type, {:single => false}.merge(options)
    end

    #
    # Specify a namespace if a node and all its children are all namespaced
    # elements. This is simpler than passing the :namespace option to each
    # defined element.
    #
    # @param [String] namespace the namespace to set as default for the class
    #     element.
    #
    def namespace(namespace = nil)
      @namespace = namespace if namespace
      @namespace
    end

    #
    # @param [String] new_tag_name the name for the tag
    #
    def tag(new_tag_name)
      @tag_name = new_tag_name.to_s unless new_tag_name.nil? || new_tag_name.to_s.empty?
    end

    #
    # The name of the tag
    #
    # @return [String] the name of the tag as a string, downcased
    #
    def tag_name
      @tag_name ||= to_s.split('::')[-1].downcase
    end

    # There is an XML tag that needs to be known for parsing and should be generated
    # during a to_xml.  But it doesn't need to be a class and the contained elements should
    # be made available on the parent class
    #
    # @param [String] name the name of the element that is just a place holder
    # @param [Proc] blk the element definitions inside the place holder tag
    #
    def wrap(name, &blk)
      # Get an anonymous HappyMapper that has 'name' as its tag and defined
      # in '&blk'.  Then save that to a class instance variable for later use
      wrapper = AnonymousWrapperClassFactory.get(name, &blk)
      @wrapper_anonymous_classes[wrapper.inspect] = wrapper

      # Create getter/setter for each element and attribute defined on the anonymous HappyMapper
      # onto this class. They get/set the value by passing thru to the anonymous class.
      passthrus = wrapper.attributes + wrapper.elements
      passthrus.each do |item|
        class_eval %{
          def #{item.method_name}
            @#{name} ||= self.class.instance_variable_get('@wrapper_anonymous_classes')['#{wrapper.inspect}'].new
            @#{name}.#{item.method_name}
          end
          def #{item.method_name}=(value)
            @#{name} ||= self.class.instance_variable_get('@wrapper_anonymous_classes')['#{wrapper.inspect}'].new
            @#{name}.#{item.method_name} = value
          end
        }
      end

      has_one name, wrapper
    end

    # The callback defined through {.with_nokogiri_config}.
    #
    # @return [Proc] the proc to pass to Nokogiri to setup parse options. nil if empty.
    #
    def nokogiri_config_callback
      @nokogiri_config_callback
    end

    # Register a config callback according to the block Nokogori expects when calling Nokogiri::XML::Document.parse().
    # See http://nokogiri.org/Nokogiri/XML/Document.html#method-c-parse
    #
    # @param [Proc] the proc to pass to Nokogiri to setup parse options
    #
    def with_nokogiri_config(&blk)
      @nokogiri_config_callback = blk
    end

    #
    # @param [Nokogiri::XML::Node,Nokogiri:XML::Document,String] xml the XML
    #     contents to convert into Object.
    # @param [Hash] options additional information for parsing. :single => true
    #     if requesting a single object, otherwise it defaults to retuning an
    #     array of multiple items. :xpath information where to start the parsing
    #     :namespace is the namespace to use for additional information.
    #
    def parse(xml, options = {})

      # create a local copy of the objects namespace value for this parse execution
      namespace = @namespace

      # If the XML specified is an Node then we have what we need.
      if xml.is_a?(Nokogiri::XML::Node) && !xml.is_a?(Nokogiri::XML::Document)
        node = xml
      else

        # If xml is an XML document select the root node of the document
        if xml.is_a?(Nokogiri::XML::Document)
          node = xml.root
        else

          # Attempt to parse the xml value with Nokogiri XML as a document
          # and select the root element
          xml = Nokogiri::XML(
            xml, nil, nil,
            Nokogiri::XML::ParseOptions::STRICT,
            &nokogiri_config_callback
          )
          node = xml.root
        end

        # if the node name is equal to the tag name then the we are parsing the
        # root element and that is important to record so that we can apply
        # the correct xpath on the elements of this document.

        root = node.name == tag_name
      end

      # if any namespaces have been provied then we should capture those and then
      # merge them with any namespaces found on the xml node and merge all that
      # with any namespaces that have been registered on the object

      namespaces = options[:namespaces] || {}
      namespaces = namespaces.merge(xml.collect_namespaces) if xml.respond_to?(:collect_namespaces)
      namespaces = namespaces.merge(@registered_namespaces)

      # if a namespace has been provided then set the current namespace to it
      # or set the default namespace to the one defined under 'xmlns'
      # or set the default namespace to the namespace that matches 'happymapper's

      if options[:namespace]
        namespace = options[:namespace]
      elsif namespaces.has_key?("xmlns")
        namespace ||= DEFAULT_NS
        namespaces[DEFAULT_NS] = namespaces.delete("xmlns")
      elsif namespaces.has_key?(DEFAULT_NS)
        namespace ||= DEFAULT_NS
      end

      # from the options grab any nodes present and if none are present then
      # perform the following to find the nodes for the given class

      nodes = options.fetch(:nodes) do

        # when at the root use the xpath '/' otherwise use a more gready './/'
        # unless an xpath has been specified, which should overwrite default
        # and finally attach the current namespace if one has been defined
        #

        xpath  = (root ? '/' : './/')
        xpath  = options[:xpath].to_s.sub(/([^\/])$/, '\1/') if options[:xpath]
        xpath += "#{namespace}:" if namespace

        nodes = []

        # when finding nodes, do it in this order:
        # 1. specified tag if one has been provided
        # 2. name of element
        # 3. tag_name (derived from class name by default)

        # If a tag has been provided we need to search for it.

        if options.key?(:tag)
          begin
            nodes = node.xpath(xpath + options[:tag].to_s, namespaces)
          rescue
            # This exception takes place when the namespace is often not found
            # and we should continue on with the empty array of nodes.
          end
        else

          # This is the default case when no tag value is provided.
          # First we use the name of the element `items` in `has_many items`
          # Second we use the tag name which is the name of the class cleaned up

          [options[:name], tag_name].compact.each do |xpath_ext|
            begin
              nodes = node.xpath(xpath + xpath_ext.to_s, namespaces)
            rescue
              break
              # This exception takes place when the namespace is often not found
              # and we should continue with the empty array of nodes or keep looking
            end
            break if nodes && !nodes.empty?
          end

        end

        nodes
      end

      # Nothing matching found, we can go ahead and return
      return ( ( options[:single] || root ) ? nil : [] ) if nodes.size == 0

      # If the :limit option has been specified then we are going to slice
      # our node results by that amount to allow us the ability to deal with
      # a large result set of data.

      limit = options[:in_groups_of] || nodes.size

      # If the limit of 0 has been specified then the user obviously wants
      # none of the nodes that we are serving within this batch of nodes.

      return [] if limit == 0

      collection = []

      nodes.each_slice(limit) do |slice|

        part = slice.map do |n|

          # If an existing HappyMapper object is provided, update it with the
          # values from the xml being parsed.  Otherwise, create a new object

          obj = options[:update] ? options[:update] : new

          attributes.each do |attr|
            value = attr.from_xml_node(n, namespace, namespaces)
            value = attr.default if value.nil?
            obj.send("#{attr.method_name}=", value)
          end

          elements.each do |elem|
            obj.send("#{elem.method_name}=",elem.from_xml_node(n, namespace, namespaces))
          end

          if @content
            obj.send("#{@content.method_name}=",@content.from_xml_node(n, namespace, namespaces))
          end

          # If the HappyMapper class has the method #xml_value=,
          # attr_writer :xml_value, or attr_accessor :xml_value then we want to
          # assign the current xml that we just parsed to the xml_value

          if obj.respond_to?('xml_value=')
            n.namespaces.each {|name,path| n[name] = path }
            obj.xml_value = n.to_xml
          end

          # If the HappyMapper class has the method #xml_content=,
          # attr_write :xml_content, or attr_accessor :xml_content then we want to
          # assign the child xml that we just parsed to the xml_content

          if obj.respond_to?('xml_content=')
            n = n.children if n.respond_to?(:children)
            obj.xml_content = n.to_xml
          end

          # collect the object that we have created

          obj
        end

        # If a block has been provided and the user has requested that the objects
        # be handled in groups then we should yield the slice of the objects to them
        # otherwise continue to lump them together

        if block_given? and options[:in_groups_of]
          yield part
        else
          collection += part
        end

      end

      # per http://libxml.rubyforge.org/rdoc/classes/LibXML/XML/Document.html#M000354
      nodes = nil

      # If the :single option has been specified or we are at the root element
      # then we are going to return the first item in the collection. Otherwise
      # the return response is going to be an entire array of items.

      if options[:single] or root
        collection.first
      else
        collection
      end
    end
  end

  # Set all attributes with a default to their default values
  def initialize
    super
    self.class.attributes.reject {|attr| attr.default.nil?}.each do |attr|
      send("#{attr.method_name}=", attr.default)
    end
  end

  #
  # Create an xml representation of the specified class based on defined
  # HappyMapper elements and attributes. The method is defined in a way
  # that it can be called recursively by classes that are also HappyMapper
  # classes, allowg for the composition of classes.
  #
  # @param [Nokogiri::XML::Builder] builder an instance of the XML builder which
  #     is being used when called recursively.
  # @param [String] default_namespace the name of the namespace which is the
  #     default for the xml being produced; this is specified by the element
  #     declaration when calling #to_xml recursively.
  # @param [String] tag_from_parent the xml tag to use on the element when being
  #     called recursively.  This lets the parent doc define its own structure.
  #     Otherwise the element uses the tag it has defined for itself.  Should only
  #     apply when calling a child HappyMapper element.
  #
  # @return [String,Nokogiri::XML::Builder] return XML representation of the
  #      HappyMapper object; when called recursively this is going to return
  #      and Nokogiri::XML::Builder object.
  #
  def to_xml(builder = nil,default_namespace = nil,tag_from_parent = nil)

    #
    # If to_xml has been called without a passed in builder instance that
    # means we are going to return xml output. When it has been called with
    # a builder instance that means we most likely being called recursively
    # and will return the end product as a builder instance.
    #
    unless builder
      write_out_to_xml = true
      builder = Nokogiri::XML::Builder.new
    end

    #
    # Find the attributes for the class and collect them into an array
    # that will be placed into a Hash structure
    #
    attributes = self.class.attributes.collect do |attribute|

      #
      # If an attribute is marked as read_only then we want to ignore the attribute
      # when it comes to saving the xml document; so we wiill not go into any of
      # the below process
      #
      unless attribute.options[:read_only]

        value = send(attribute.method_name)
        value = nil if value == attribute.default

        #
        # If the attribute defines an on_save lambda/proc or value that maps to
        # a method that the class has defined, then call it with the value as a
        # parameter.
        #
        if on_save_action = attribute.options[:on_save]
          if on_save_action.is_a?(Proc)
            value = on_save_action.call(value)
          elsif respond_to?(on_save_action)
            value = send(on_save_action,value)
          end
        end

        #
        # Attributes that have a nil value should be ignored unless they explicitly
        # state that they should be expressed in the output.
        #
        if not value.nil? || attribute.options[:state_when_nil]
          attribute_namespace = attribute.options[:namespace] || default_namespace
          [ "#{attribute_namespace ? "#{attribute_namespace}:" : ""}#{attribute.tag}", value ]
        else
          []
        end

      else
        []
      end

    end.flatten

    attributes = Hash[ *attributes ]

    #
    # Create a tag in the builder that matches the class's tag name unless a tag was passed
    # in a recursive call from the parent doc.  Then append
    # any attributes to the element that were defined above.
    #
    builder.send("#{tag_from_parent || self.class.tag_name}_",attributes) do |xml|

      #
      # Add all the registered namespaces to the root element.
      # When this is called recurisvely by composed classes the namespaces
      # are still added to the root element
      #
      # However, we do not want to add the namespace if the namespace is 'xmlns'
      # which means that it is the default namesapce of the code.
      #
      if self.class.instance_variable_get('@registered_namespaces') && builder.doc.root
        self.class.instance_variable_get('@registered_namespaces').each_pair do |name,href|
          name = nil if name == "xmlns"
          builder.doc.root.add_namespace(name,href)
        end
      end

      #
      # If the object we are persisting has a namespace declaration we will want
      # to use that namespace or we will use the default namespace.
      # When neither are specifed we are simply using whatever is default to the
      # builder
      #
      if self.class.respond_to?(:namespace) && self.class.namespace
        xml.parent.namespace = builder.doc.root.namespace_definitions.find { |x| x.prefix == self.class.namespace }
      elsif default_namespace
        xml.parent.namespace = builder.doc.root.namespace_definitions.find { |x| x.prefix == default_namespace }
      end


      #
      # When a content has been defined we add the resulting value
      # the output xml
      #
      if content = self.class.instance_variable_get('@content')

        unless content.options[:read_only]
          text_accessor = content.tag || content.name
          value = send(text_accessor)

          if on_save_action = content.options[:on_save]
            if on_save_action.is_a?(Proc)
              value = on_save_action.call(value)
            elsif respond_to?(on_save_action)
              value = send(on_save_action,value)
            end
          end

          builder.text(value)
        end

      end

      #
      # for every define element (i.e. has_one, has_many, element) we are
      # going to persist each one
      #
      self.class.elements.each do |element|

        #
        # If an element is marked as read only do not consider at all when
        # saving to XML.
        #
        unless element.options[:read_only]

          tag = element.tag || element.name

          #
          # The value to store is the result of the method call to the element,
          # by default this is simply utilizing the attr_accessor defined. However,
          # this allows for this method to be overridden
          #
          value = send(element.name)

          #
          # If the element defines an on_save lambda/proc then we will call that
          # operation on the specified value. This allows for operations to be
          # performed to convert the value to a specific value to be saved to the xml.
          #
          if on_save_action = element.options[:on_save]
            if on_save_action.is_a?(Proc)
              value = on_save_action.call(value)
            elsif respond_to?(on_save_action)
              value = send(on_save_action,value)
            end
          end

          #
          # Normally a nil value would be ignored, however if specified then
          # an empty element will be written to the xml
          #
          if value.nil? && element.options[:single] && element.options[:state_when_nil]
            xml.send("#{tag}_","")
          end

          #
          # To allow for us to treat both groups of items and singular items
          # equally we wrap the value and treat it as an array.
          #
          if value.nil?
            values = []
          elsif value.respond_to?(:to_ary) && !element.options[:single]
            values = value.to_ary
          else
            values = [value]
          end

          values.each do |item|

            if item.is_a?(HappyMapper)

              #
              # Other items are convertable to xml through the xml builder
              # process should have their contents retrieved and attached
              # to the builder structure
              #
              item.to_xml(xml,element.options[:namespace],element.options[:tag] || nil)

            elsif item

              item_namespace = element.options[:namespace] || self.class.namespace || default_namespace

              #
              # When a value exists we should append the value for the tag
              #
              if item_namespace
                xml[item_namespace].send("#{tag}_",item.to_s)
              else
                xml.send("#{tag}_",item.to_s)
              end

            else

              #
              # Normally a nil value would be ignored, however if specified then
              # an empty element will be written to the xml
              #
              xml.send("#{tag}_","") if element.options[:state_when_nil]

            end

          end

        end
      end

    end

    # Write out to XML, this value was set above, based on whether or not an XML
    # builder object was passed to it as a parameter. When there was no parameter
    # we assume we are at the root level of the #to_xml call and want the actual
    # xml generated from the object. If an XML builder instance was specified
    # then we assume that has been called recursively to generate a larger
    # XML document.
    write_out_to_xml ? builder.to_xml : builder

  end

  # Parse the xml and update this instance. This does not update instances
  # of HappyMappers that are children of this object.  New instances will be
  # created for any HappyMapper children of this object.
  #
  # Params and return are the same as the class parse() method above.
  def parse(xml, options = {})
    self.class.parse(xml, options.merge!(:update => self))
  end

  private

  # Factory for creating anonmyous HappyMappers
  class AnonymousWrapperClassFactory
   def self.get(name, &blk)
     Class.new do
       include HappyMapper
       tag name
       instance_eval &blk
     end
   end
  end

end

require 'happymapper/supported_types'
require 'happymapper/item'
require 'happymapper/attribute'
require 'happymapper/element'
require 'happymapper/text_node'