require 'xmlscan'

module XML
  class ParserError < Exception; end

  class Parser < XMLScanner

    DEFAULT = 0
    START_ELEM = 1
    END_ELEM = 2
    CDATA = 3
    PI = 4
    UNPARSED_ENTITY_DECL = 5
    NOTATION_DECL = 6
    EXTERNAL_ENTITY_REF = 7
    COMMENT = 8
    START_CDATA = 9
    END_CDATA = 10
    START_NAMESPACE_DECL = 11
    END_NAMESPACE_DECL = 12
    UNKNOWN_ENCODING = 13

    def initialize(*args)
      @inDocument = false
      @exception = nil
      @block = nil
      @line = nil
      super()
    end

    def parse(str, *rest, &block)
      @block = block
      super(str)
    end

    def on_error(path, lineno, msg)
      @line = lineno
      raise ParserError.new(msg)
    end

    def on_comment(strs)
      if @block
        @block.call(COMMENT, nil, strs.join) if respond_to?(:comment)

      else
        comment(strs.join) if respond_to?(:comment)
      end
    end

    def on_pi(target, pi)
      if @block
        @block.call(PI, target, pi)
      else
        processingInstruction(target, pi) if
          respond_to?(:processingInstruction)
      end
    end

    def on_chardata(str)
      return unless @inDocument
      if @block
        @block.call(CDATA, nil,str)
      else
        character(str) if respond_to?(:character)
      end
    end

    def on_etag(name)
      @inDocument = false if @inDocument == name
      if @block
        @block.call(END_ELEM, name, nil)
      else
        endElement(name) if respond_to?(:endElement)
      end
    end

    def on_stag(name, attr)
      @inDocument = name unless @inDocument
      if @block
        @block.call(START_ELEM, name, attr)
      else
        startElement(name, attr) if respond_to?(:startElement)
      end
    end

    def on_emptyelem(name, attr)
      if @block
        @block.call(START_ELEM, name, attr)
        @block.call(END_ELEM, name, nil)
      else
        startElement(name, attr) if respond_to?(:startElement)
        endElement(name) if respond_to?(:endElement)
      end
    end

    def done; end

    def defaultCurrent; end

    def line
      return @line if @line
      0
    end

    def column
      0
    end

    def byteIndex
      0
    end

    def setBase(baseURL); end


  end

end