module CSL
  
  class Node
    
    extend Forwardable
    
    include Enumerable
    include Comparable
    
    include Treelike
    include PrettyPrinter
    
    
    class << self

      def inherited(subclass)
        types << subclass
        subclass.nesting.each do |klass|
          klass.types << subclass if klass < Node
        end
      end
      
      def types
        @types ||= Set.new
      end
      
      def default_attributes
        @default_attributes ||= {}
      end
      
      def constantize(name)
        pattern = /#{name.to_s.tr('-', '')}$/i
        klass = types.detect { |t| t.matches?(pattern) }
        
        case
        when !klass.nil?
          klass
        when nesting[-2].respond_to?(:constantize)
          nesting[-2].constantize(name)
        else
          nil
        end
      end

      # @return [Boolean] whether or not the node's name matches the
      #   passed-in name pattern
      def match?(name_pattern)
        name_pattern === name
      end
      alias matches? match?
      
      # Returns a new node with the passed in name and attributes.
      def create(name, attributes = {}, &block)
        klass = constantize(name)

        node = (klass || Node).new(attributes, &block)        
        node.nodename = name
        node
      end
      
      def create_attributes(attributes)
        if const?(:Attributes)
          const_get(:Attributes).new(default_attributes.merge(attributes))
        else
          default_attributes.merge(attributes)
        end
      end

      private

      def attr_defaults(attributes)
        @default_attributes = attributes
      end

      # Creates a new Struct for the passed-in attributes. Node instances
      # will create an instance of this struct to manage their respective
      # attributes.
      #
      # The new Struct will be available as Attributes in the current node's
      # class scope.
      def attr_struct(*attributes)
        const_set(:Attributes, Struct.new(*attributes) {

          # 1.8 Compatibility
          @keys = attributes.map(&:to_sym).freeze

          class << self
            attr_reader :keys
          end

          def initialize(attrs = {})
            super(*attrs.symbolize_keys.values_at(*keys))
          end

          # @return [<Symbol>] a list of symbols representing the names/keys
          #   of the attribute variables.
          def keys
            __class__.keys
          end

          def values
            super.compact
          end
          
          # def to_a
          #   keys.zip(values_at(*keys)).reject { |k,v| v.nil? }
          # end
          
          # @return [Boolean] true if all the attribute values are nil;
          #   false otherwise.
          def empty?
            values.compact.empty?
          end
          
          def fetch(key, default = nil)
            value = keys.include?(key.to_sym) && send(:'[]', key)
            
            if block_given? 
              value || yield(key)
            else
              value || default
            end
          end
          
          # Merges the current with the passed-in attributes.
          #
          # @param other [#each_pair] the other attributes
          # @return [self]
          def merge(other)
            raise ArgumentError, "failed to merge #{other.class} into Attributes" unless
              other.respond_to?(:each_pair)

            other.each_pair do |part, value|
              part = part.to_sym
              send(:'[]=', part, value) if !value.nil? && keys.include?(part)
            end

            self
          end

          # @overload values_at(selector, ... )
          #   Returns an array containing the attributes in self according
          #   to the given selector(s). The selectors may be either integer
          #   indices, ranges (functionality inherited from Struct) or
          #   symbols idenifying valid keys (similar to Hash#values_at).
          #
          # @example
          #   attributes.values_at(:family, :nick) #=> ['Matsumoto', 'Matz']
          #
          # @see Struct#values_at
          # @return [Array] the list of values
          def values_at(*arguments)
            super(*arguments.flatten.map { |k| k.is_a?(Symbol) ? keys.index(k) : k })
          end

        })
      end

    end


    attr_reader :attributes

    def_delegators :attributes, :[], :[]=, :values, :values_at, :length, :size
    
    def initialize(attributes = {})
      @attributes = self.class.create_attributes(attributes)
      @children = self.class.create_children
      
      yield self if block_given?
    end
    
    # Iterates through the Node's attributes
    def each
      if block_given?
        attributes.each_pair(&Proc.new)
        self
      else
        to_enum
      end
    end
    alias each_pair each

    # Returns true if the node contains an attribute with the passed-in name;
    # false otherwise.
    def attribute?(name)
      attributes.fetch(name, false)
    end
    
    # Returns true if the node contains any attributes (ignores nil values);
    # false otherwise.
    def has_attributes?
      !attributes.empty?
    end

    def textnode?
      false
    end
    alias has_text? textnode?

    def save_to(path, options = {})
      File.open(path, 'w:UTF-8') do |f|
        f << (options[:compact] ? to_xml : pretty_print)
      end
      
      self
    end

    # Tests whether or not the Name matches the passed-in node name and
    # attribute conditions; if a Hash is passed as a single argument,
    # it is taken as the conditions parameter (the name parameter is
    # automatically matches in this case).
    #
    # Whether or not the arguments match the node is determined as
    # follows:
    #
    # 1. The name must match {#nodename}
    # 2. All attribute name/value pairs passed as conditions must match
    #    the corresponding attributes of the node
    #
    # Note that only attributes present in the passed-in conditions
    # influence the match – if you want to match only nodes that contain
    # no other attributes than specified by the conditions, {#exact_match?}
    # should be used instead.
    #
    # @see #exact_match?
    #
    # @param name [String,Regexp] must match the nodename
    # @param conditions [Hash] the conditions
    #
    # @return [Boolean] whether or not the query matches the node
    def match?(name = nodename, conditions = {})
      name, conditions = match_conditions_for(name, conditions)
      
      return false unless name === nodename
      return true  if conditions.empty?

      conditions.values.zip(
        attributes.values_at(*conditions.keys)).all? do |condition, value|
          condition === value
        end
    end
    alias matches? match?

    # Tests whether or not the Name matches the passed-in node name and
    # attribute conditions exactly; if a Hash is passed as a single argument,
    # it is taken as the conditions parameter (the name parameter is
    # automatically matches in this case).
    #
    # Whether or not the arguments match the node is determined as
    # follows:
    #
    # 1. The name must match {#nodename}
    # 2. All attribute name/value pairs of the node must match the
    #    corresponding pairs in the passed-in Hash
    #
    # Note that all node attributes are used by this method – if you want
    # to match only a subset of attributes {#match?} should be used instead.
    #
    # @see #match?
    #
    # @param name [String,Regexp] must match the nodename
    # @param conditions [Hash] the conditions
    #
    # @return [Boolean] whether or not the query matches the node exactly
    def exact_match?(name = nodename, conditions = {})
      name, conditions = match_conditions_for(name, conditions)
      
      return false unless name === nodename
      return true  if conditions.empty?
      
      conditions.values_at(*attributes.keys).zip(
        attributes.values_at(*attributes.keys)).all? do |condition, value|
          condition === value
        end
    end
    alias matches_exactly? exact_match?

    def <=>(other)
      [nodename, attributes, children] <=> [other.nodename, other.attributes, other.children]
    rescue
      nil
    end
    
    # Returns the node' XML tags (including attribute assignments) as an
    # array of strings.
    def tags
      if has_children?
        tags = []
        tags << "<#{[nodename, *attribute_assignments].join(' ')}>"
        
        tags << children.map { |node|
          node.respond_to?(:tags) ? node.tags : [node.to_s]
        }.flatten(1)
        
        tags << "</#{nodename}>"
        tags
      else
        ["<#{[nodename, *attribute_assignments].join(' ')}/>"]
      end
    end
    
    def inspect
      "#<#{[self.class.name, *attribute_assignments].join(' ')} children=[#{children.count}]>"
    end
    
    alias to_s pretty_print

    
    private
        
    def attribute_assignments
      each_pair.map { |name, value|
        value.nil? ? nil: [name, value.to_s.inspect].join('=')
      }.compact
    end
    
    def match_conditions_for(name, conditions)
      case name
      when Hash
        conditions, name = name, nodename
      when Symbol
        name = name.to_s
      end

      [name, conditions.symbolize_keys]
    end

  end
  
  
  class TextNode < Node
    
    has_no_children

    class << self
      undef_method :attr_children
      
      # @override
      def create(name, attributes = {}, &block)
        klass = constantize(name)

        node = (klass || TextNode).new(attributes, &block)
        node.nodename = name
        node
      end
    end

    attr_accessor :text
    alias to_s text

    # TextNodes quack like a string.
    # def_delegators :to_s, *String.instance_methods(false).reject do |m|
    #   m.to_s =~ /^\W|!$|(?:^(?:hash|eql?|to_s|length|size|inspect)$)/
    # end
    # 
    # String.instance_methods(false).select { |m| m.to_s =~ /!$/ }.each do |m|
    #   define_method(m) do
    #     content.send(m) if content.respond_to?(m)
    #   end
    # end
    
    def initialize(argument = '')
      case
      when argument.is_a?(Hash)
        super
      when argument.respond_to?(:to_s)
        super({})
        @text = argument.to_s
        yield self if block_given?
      else
        raise ArgumentError, "failed to create text node from #{argument.inspect}"
      end
    end
    
    def textnode?
      true
    end
    
    def tags
      ["<#{attribute_assignments.unshift(nodename).join(' ')}>#{text}</#{nodename}>"]
    end
    
    def inspect
      "#<#{[self.class.name, text.inspect, *attribute_assignments].join(' ')}>"
    end
    
  end
  
end