Spike JSON Stream Parser

require 'json/stream'


class MonsterParser
  FILE_BUFFER_SIZE = 1024

  def initialize(file_path,xpath)
    @file_obj = File.open(file_path,'r')

    @element_stack = []
    @xpath_stack = xpath.split("/").reverse
    @in_customer_array = false
    @finished_customer_array = false

    _configure_parser
  end

  def _stack_push(item)
    if @xpath_stack.size > 0
      @xpath_stack.pop() if item == _get_top(@xpath_stack)
    elsif ! @in_customer_array
      raise Exception.new("XPath destination must target a JSON array") if ! item.is_a?(Array)
      @in_customer_array = true
    elsif ! @finished_customer_array
      @element_stack.push(item)
    end
  end

  def _get_top(stack)
    return stack[-1] unless stack.size == 0
    nil
  end

  def _extract_object(obj)
        puts "Dumping a full object: #{obj}"
  end

  def _stack_merge_up
    return if @finished_customer_array
    value = @element_stack.pop()
    parent_element = _get_top(@element_stack)
    if parent_element.is_a?(String)
      key = @element_stack.pop()
      _get_top(@element_stack)[key] = value
    elsif parent_element.nil?
      if value.nil?
        @finished_customer_array = true
      else
        _extract_object(value)
      end
    elsif
      @element_stack[-1] << value
    end
  end

  def _configure_parser
    mParser = self
    @parser = JSON::Stream::Parser.new do
      start_object   { mParser._stack_push({}) }
      start_array    { mParser._stack_push([]) }
      end_object     { mParser._stack_merge_up }
      end_array      { mParser._stack_merge_up }
      key            {|k| mParser._stack_push(k) }
      value          {|v| mParser._stack_push(v)
                      mParser._stack_merge_up }
    end
  end

  def load_data
    begin
      while data = @file_obj.read(MonsterParser::FILE_BUFFER_SIZE) do
        @parser << data
      end
    #rescue JSON::Stream::ParserError => e
    end
  end
end



if __FILE__==$0
  parser = MonsterParser.new("customer100000.txt","customers")
  parser.load_data
end