require 'monitor'

class Module
  def cache! *methods
    DeclarativeCache.cache! self, *methods
  end 
  
  def cache_with_params! *methods
    DeclarativeCache.cache_with_params! self, *methods
  end
end

module DeclarativeCache		
	DISABLED = false

	warn "CASHE DISABLED" if DISABLED
  unless DISABLED    
  	class << self  	    	    	  
  	  def alias_counter
  	    @alias_counter ||= 0
  			@alias_counter += 1
  			return "cached_method_#{@alias_counter}"
  		end
	
  		def cache! klass, *methods
  			methods.each do |method|
  			  klass.class_eval do
    				als = (method.to_s =~ /^[_a-zA-Z0-9]+$/) ? "cached_#{method}" : DeclarativeCache.alias_counter.to_sym
    				iv_check = "@#{als}_check"
  			    iv = "@#{als}"
			    
    				alias_method als, method
    				
    				define_method method do |*args|
    				  args.should! :be_empty
    				  unless cached = instance_variable_get(iv)
    				    unless check = instance_variable_get(iv_check)
    				      cached = send als
    				      instance_variable_set iv, cached
    				      instance_variable_set iv_check, true
    				    end
    				  end
    				  cached
    				end
    			end
  			end
  		end
  		
  		def cache_with_params! klass, *methods  		  
  			methods.each do |method|	
  			  klass.class_eval do			
    				als = (method.to_s =~ /^[_a-zA-Z0-9]+$/) ? "cached_#{method}" : DeclarativeCache.alias_counter.to_sym 
  			    iv = "@#{als}"
			    
    				alias_method als, method
  				  				
    				define_method method do |*args| 
    				  unless results = instance_variable_get(iv)
    				    results = {}
    				    instance_variable_set iv, results
    				  end
  				    				  
    				  unless results.include? args
    				    results[args] = send als, *args
    				  end
  				  
    				  results[args]
    				end
    			end
  			end
  		end
  		
  	end
  end
end