require "nokogiri"

module SAXMachine
  class SAXHandler < Nokogiri::XML::SAX::Document
    attr_reader :object
    
    def initialize(object)
      @object = object
      @parsed_configs = {}
    end
    
    def characters(string)
      if parsing_collection?
        @collection_handler.characters(string)
      elsif @element_config
        @value << string
      end
    end
    
    def start_element(name, attrs = [])
      @name   = name
      @attrs  = attrs
      
      if parsing_collection?
        @collection_handler.start_element(@name, @attrs)
        
      elsif @collection_config = sax_config.collection_config(@name)
        @collection_handler = @collection_config.handler
        
      elsif @element_config = sax_config.element_config_for_attribute(@name, @attrs)
        parse_element_attribute
        
      else
        @value = ""
        @element_config = sax_config.element_config_for_tag(@name, @attrs)
      end
    end
    
    def end_element(name)
      if parsing_collection? && @collection_config.name == name
        @object.send(@collection_config.accessor) << @collection_handler.object
        reset_current_collection
        
      elsif parsing_collection?
        @collection_handler.end_element(name)
        
      elsif characaters_captured? && !parsed_config?
        mark_as_parsed
        @object.send(@element_config.setter, @value)
      end
      
      reset_current_tag
    end
    
    def characaters_captured?
      !@value.nil? && !@value.empty?
    end
    
    def parsing_collection?
      !@collection_handler.nil?
    end
    
    def parse_element_attribute
      unless parsed_config?
        mark_as_parsed
        @object.send(@element_config.setter, @element_config.value_from_attrs(@attrs))
      end
      
      @element_config = nil
    end
    
    def mark_as_parsed
      @parsed_configs[@element_config] = true
    end
    
    def parsed_config?
      @parsed_configs[@element_config]
    end
    
    def reset_current_collection
      @collection_handler = nil
      @collection_config  = nil
    end
    
    def reset_current_tag
      @name   = nil
      @attrs  = nil
      @value  = nil
      @element_config = nil
    end
    
    def sax_config
      @object.class.sax_config
    end
  end
end