require 'rubygems'
require 'extensions/enumerable'
require 'extensions/array'
require 'extensions/object'
require 'activesupport'

%w(extensions/array extensions/string options xml).each do |file|
  require File.join(File.dirname(__FILE__), 'roxml', file)
end

module ROXML # :nodoc:
  def self.included(base) # :nodoc:
    base.extend ClassMethods::Declarations
    base.extend ClassMethods::Accessors
    base.extend ClassMethods::Operations
    base.class_eval do
      include InstanceMethods::Accessors
      include InstanceMethods::Conversions
    end
  end

  module InstanceMethods # :nodoc:
    # Instance method equivalents of the Class method accessors
    module Accessors
      # Provides access to ROXML::ClassMethods::Accessors::tag_name directly from an instance of a ROXML class
      def tag_name
        self.class.tag_name
      end

      # Provides access to ROXML::ClassMethods::Accessors::tag_refs directly from an instance of a ROXML class
      def tag_refs
        self.class.tag_refs
      end
    end

    module Conversions
      # Returns a LibXML::XML::Node or a REXML::Element representing this object
      def to_xml(name = nil)
        returning XML::Node.new_element(name || tag_name) do |root|
          tag_refs.each do |ref|
            if v = __send__(ref.accessor)
              ref.update_xml(root, v)
            end
          end
        end
      end
    end
  end

  # This class defines the annotation methods that are mixed into your
  # Ruby classes for XML mapping information and behavior.
  #
  # See xml_name, xml_construct, xml, xml_reader and xml_accessor for
  # available annotations.
  #
  module ClassMethods # :nodoc:
    module Declarations
      # Sets the name of the XML element that represents this class. Use this
      # to override the default lowercase class name.
      #
      # Example:
      #  class BookWithPublisher
      #   xml_name :book
      #  end
      #
      # Without the xml_name annotation, the XML mapped tag would have been "bookwithpublisher".
      #
      def xml_name(name)
        @tag_name = name
      end

      # Declares an accesser to a certain xml element, whether an attribute, a node,
      # or a typed collection of nodes
      #
      # [sym]   Symbol representing the name of the accessor
      #
      # == Type options
      # All type arguments may be used as the type argument to indicate just type,
      # or used as :from, pointing to a xml name to indicate both type and attribute name.
      # Also, any type may be passed via an array to indicate that multiple instances
      # of the object should be returned as an array.
      #
      # === :attr
      # Declare an accessor that represents an XML attribute.
      #
      # Example:
      #  class Book
      #   xml_reader :isbn, :attr => "ISBN" # 'ISBN' is used to specify :from
      #   xml_accessor :title, :attr        # :from defaults to :title
      #  end
      #
      # To map:
      #  <book ISBN="0974514055" title="Programming Ruby: the pragmatic programmers' guide" />
      #
      # === :text
      # The default type, if none is specified. Declares an accessor that
      # represents a text node from XML.
      #
      # Example:
      #  class Book
      #    xml :author, false, :text => 'Author'
      #    xml_accessor :description, :text, :as => :cdata
      #    xml_reader :title
      #  end
      #
      # To map:
      #  <book>
      #   <title>Programming Ruby: the pragmatic programmers' guide</title>
      #   <description><![CDATA[Probably the best Ruby book out there]]></description>
      #   <Author>David Thomas</author>
      #  </book>
      #
      # Likewise, a number of :text node values can be collected in an array like so:
      #
      # Example:
      #  class Library
      #    xml_reader :books, [:text], :in => 'books'
      #  end
      #
      # To map:
      #  <library>
      #    <books>
      #      <book>To kill a mockingbird</book>
      #      <book>House of Leaves</book>
      #      <book>Gödel, Escher, Bach</book>
      #    </books>
      #  </library>
      #
      # === :content
      # A special case of :text, this refers to the content of the current node,
      # rather than a sub-node
      #
      # Example:
      #  class Contributor
      #    xml_reader :name, :content
      #    xml_reader :role, :attr
      #  end
      #
      # To map:
      #  <contributor role="editor">James Wick</contributor>
      #
      # === Hash
      # Somewhere between the simplicity of a :text/:attr mapping, and the complexity of
      # a full Object/Type mapping, lies the Hash mapping.  It serves in the case where you have
      # a collection of key-value pairs represented in your xml.  You create a hash declaration by
      # passing a hash mapping as the type argument.  A few examples:
      #
      # ==== Hash of :attrs
      # For xml such as this:
      #
      #    <dictionary>
      #      <definitions>
      #        <definition dt="quaquaversally"
      #                    dd="adjective: (of a geological formation) sloping downward from the center in all directions." />
      #        <definition dt="tergiversate"
      #                    dd="To use evasions or ambiguities; equivocate." />
      #      </definitions>
      #    </dictionary>
      #
      # You can use the :attrs key in you has with a [:key, :value] name array:
      #
      #    xml_reader :definitions, {:attrs => ['dt', 'dd']}, :in => :definitions
      #
      # ==== Hash of :texts
      # For xml such as this:
      #
      #    <dictionary>
      #      <definition>
      #        <word/>
      #        <meaning/>
      #      </definition>
      #      <definition>
      #        <word/>
      #        <meaning/>
      #      </definition>
      #    </dictionary>
      #
      # You can individually declare your key and value names:
      #    xml_reader :definitions, {:key => 'word',
      #                              :value => 'meaning'}
      #
      # ==== Hash of :content &c.
      # For xml such as this:
      #
      #    <dictionary>
      #      <definition word="quaquaversally">adjective: (of a geological formation) sloping downward from the center in all directions.</definition>
      #      <definition word="tergiversate">To use evasions or ambiguities; equivocate.</definition>
      #    </dictionary>
      #
      # You can individually declare the key and value, but with the attr, you need to provide both the type
      # and name of that type (i.e. {:attr => :word}), because omitting the type will result in ROXML
      # defaulting to :text
      #    xml_reader :definitions, {:key => {:attr => 'word'},
      #                              :value => :content}
      #
      # ==== Hash of :name &c.
      # For xml such as this:
      #
      #    <dictionary>
      #      <quaquaversally>adjective: (of a geological formation) sloping downward from the center in all directions.</quaquaversally>
      #      <tergiversate>To use evasions or ambiguities; equivocate.</tergiversate>
      #    </dictionary>
      #
      # You can pick up the node names (e.g. quaquaversally) using the :name keyword:
      #    xml_reader :definitions, {:key => :name,
      #                              :value => :content}
      #
      # === Other ROXML Class
      # Declares an accessor that represents another ROXML class as child XML element
      # (one-to-one or composition) or array of child elements (one-to-many or
      # aggregation) of this type. Default is one-to-one. Use :array option for one-to-many, or
      # simply pass the class in an array.
      #
      # Composition example:
      #  <book>
      #   <publisher>
      #     <name>Pragmatic Bookshelf</name>
      #   </publisher>
      #  </book>
      #
      # Can be mapped using the following code:
      #   class Book
      #     xml_reader :publisher, Publisher
      #   end
      #
      # Aggregation example:
      #  <library>
      #   <books>
      #    <book/>
      #    <book/>
      #   </books>
      #  </library>
      #
      # Can be mapped using the following code:
      #  class Library
      #    xml_reader :books, [Book], :in => "books"
      #  end
      #
      # If you don't have the <books> tag to wrap around the list of <book> tags:
      #  <library>
      #   <name>Ruby books</name>
      #   <book/>
      #   <book/>
      #  </library>
      #
      # You can skip the wrapper argument:
      #    xml_reader :books, [Book]
      #
      # == Blocks
      # You may also pass a block which manipulates the associated parsed value.
      #
      #  class Muffins
      #    include ROXML
      #
      #    xml_reader(:count, :from => 'bakers_dozens') {|val| val.to_i * 13 }
      #  end
      #
      # For hash types, the block recieves the key and value as arguments, and they should
      # be returned as an array of [key, value]
      #
      # === Block Shorthands
      #
      # Alternatively, you may use block shorthands to specify common coercions, such that:
      #
      #  xml_reader :count, :as => Integer
      #
      # is equivalent to:
      #
      #  xml_reader(:count) {|val| Integer(val) }
      #
      # Block shorthands :float, Float, :integer and Integer are currently available,
      # but only for non-Hash declarations.
      #
      # == Other options
      # [:from] The name by which the xml value will be found, either an attribute or tag name in XML.  Default is sym, or the singular form of sym, in the case of arrays and hashes.
      # [:as] :cdata for character data; :integer, Integer, :float, Float to coerce to Integer or Float respectively
      # [:in] An optional name of a wrapping tag for this XML accessor
      # [:else] Default value for attribute, if missing
      # [:required] If true, throws RequiredElementMissing when the element isn't present
      #
      def xml(sym, writable = false, type_and_or_opts = :text, opts = nil, &block)
        opts = Opts.new(sym, *[type_and_or_opts, opts].compact, &block)

        tag_refs << case opts.type
        when :attr    then XMLAttributeRef
        when :content then XMLTextRef
        when :text    then XMLTextRef
        when :hash    then XMLHashRef
        when Symbol   then raise ArgumentError, "Invalid type argument #{opts.type}"
        else               XMLObjectRef
        end.new(sym, opts)

        add_accessor(sym, writable, opts.array?, opts.default)
      end

      # Declares a read-only xml reference. See xml for details.
      def xml_reader(sym, type_and_or_opts = :text, opts = nil, &block)
        xml sym, false, type_and_or_opts, opts, &block
      end

      # Declares a writable xml reference. See xml for details.
      def xml_accessor(sym, type_and_or_opts = :text, opts = nil, &block)
        xml sym, true, type_and_or_opts, opts, &block
      end

      # On parse, call the target object's initialize function with the listed arguments
      def xml_construct(*args)
        if missing_tag = args.detect {|arg| !tag_refs.map(&:name).include?(arg.to_s) }
          raise ArgumentError, "All construction tags must be declared first using xml, " +
                               "xml_reader, or xml_accessor. #{missing_tag} is missing. " +
                               tag_refs.map(&:name).join(', ') + ' are declared.'
        end
        @xml_construction_args = args
      end

    private
      def assert_accessor(name)
        @tag_accessors ||= []
        raise "Accessor #{name} is already defined as XML accessor in class #{self}" if @tag_accessors.include?(name)
        @tag_accessors << name
      end

      def add_accessor(name, writable, as_array, default = nil)
        assert_accessor(name)
        unless instance_methods.include?(name)
          default ||= Array.new if as_array

          define_method(name) do
            val = instance_variable_get("@#{name}")
            if val.nil?
              val = default.duplicable? ? default.dup : default
              instance_variable_set("@#{name}", val)
            end
            val
          end
        end
        if writable && !instance_methods.include?("#{name}=")
          define_method("#{name}=") do |v|
            instance_variable_set("@#{name}", v)
          end
        end
      end
    end

    module Accessors
      def xml_construction_args # :nodoc:
        @xml_construction_args ||= []
      end


      # Returns the tag name (also known as xml_name) of the class.
      # If no tag name is set with xml_name method, returns default class name
      # in lowercase.
      def tag_name
        @tag_name ||= name.split('::').last.downcase
      end

      # Returns array of internal reference objects, such as attributes
      # and composed XML objects
      def tag_refs
        @xml_refs ||= []
      end
    end

    module Operations
      #
      # Creates a new Ruby object from XML using mapping information
      # annotated in the class.
      #
      # The input data is either an XML::Node or a String representing
      # the XML document.
      #
      # Example
      #  book = Book.from_xml(File.read("book.xml"))
      # or
      #  book = Book.from_xml("<book><name>Beyond Java</name></book>")
      #
      # See also: xml_construct
      #
      def from_xml(data)
        xml = (data.kind_of?(XML::Node) ? data : XML::Parser.parse(data).root)

        unless xml_construction_args.empty?
          args = xml_construction_args.map do |arg|
             tag_refs.find {|ref| ref.name == arg.to_s }
          end.map {|ref| ref.value(xml) }
          new(*args)
        else
          returning allocate do |inst|
            tag_refs.each do |ref|
              ref.populate(xml, inst)
            end
          end
        end
      end

      # Deprecated in favor of #from_xml
      def parse(data)
        ActiveSupport::Deprecation.warn '#parse has been deprecated, please use #from_xml instead'
        from_xml(data)
      end
    end
  end
end