dal.rb

class Object
  def to_ast; self; end
end

module DAL
  class Call
    attr_accessor :message, :name, :args, :block
    def initialize context, name, *args, &block
      @context = context
      @name = name
      @args = args
      @block = Block.new &block if block
    end

    def method_missing meth, *args, &block
      @context.remove_statements *args
      @message = Call.new @context, meth, *args, &block
      self
    end

    def include? node
      self == node or
      (@message and @message.include? node) or
      (@args and @args.include? node) or
      (@block and @block.include? node)
    end

    def to_ast
      { :type => :call,
        :name => @name,
        :args => @args.map(&:to_ast),
        :block => @block.to_ast,
        :message => @message.to_ast }
    end
  end

  class Constant
    attr_accessor :name
    def initialize name
      @name = name
    end

    def to_ast
      { :type => :constant,
        :name => @name }
    end
  end

  class Block
    attr_accessor :statements
    def initialize &block
      @statements = []
      v = instance_eval &block
      @statements << v unless @statements.last.include? v
    end

    def include? node
      @statements.include? node
    end
    
    def remove_statements *a
      a.each{|x| @statements.delete x }
    end
    
    def method_missing meth, *args, &block
      e = Call.new self, meth, *args, &block
      remove_statements *args
      @statements << e
      e
    end

    def self.const_missing x
      c = Constant.new x
    end

    def to_ast
      { :type => :block,
        :statements => @statements.map(&:to_ast) }
    end
  end
  
  def self.block &block
    Block.new &block
  end
end