#
#--
# Copyright (c) 2006-2007, Nicolas Modryzk, OpenWFE.org
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without 
# modification, are permitted provided that the following conditions are met:
# 
# . Redistributions of source code must retain the above copyright notice, this
#   list of conditions and the following disclaimer.  
# 
# . Redistributions in binary form must reproduce the above copyright notice, 
#   this list of conditions and the following disclaimer in the documentation 
#   and/or other materials provided with the distribution.
# 
# . Neither the name of the "OpenWFE" nor the names of its contributors may be
#   used to endorse or promote products derived from this software without
#   specific prior written permission.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
# POSSIBILITY OF SUCH DAMAGE.
#++
#
#  $Id: definitions.rb 2725 2006-06-02 13:26:32Z jmettraux $
#

#
# "made in Japan"
#
# Nicolas Modrzyk at openwfe.org
#

module OpenWFE

# Simple LRU cache based on 

	class LRUCache

		# initialize the LRU. 
		# cache contains the mapping key,value
		# queue contains the list of keys, according to the LRU
		# max is the maximum number of items to keep in the cache
		def initialize(max=20, maxttl=nil)
			@cache = {}
			@queue = []
			@ttl_cache = {}
			@max = max
			@maxttl = maxttl
			@finalizers = []
		end

		# Check to see if the cache contains the given key.
		def include?(key)
			@cache.include?(key)
		end

		# Return the element identified by the given key.
		def [](key)
			r = nil
			if @cache.has_key? key
				r = @cache[key]
				@queue.push @queue.delete(key)
				@ttl_cache[key] = Time.now.to_i
			end
			r
		end

		# Set the element of the cache identified by the given key.  
		def []=(key, val)
			if @queue.length == @max
				d = @queue.shift
				@cache.delete d
			end
			if @queue.first and @maxttl
				now = Time.now.to_i
				while ((@ttl_cache[@queue.first] + @maxttl) < now)
					d = @queue.shift
					do_finalization(d,@cache[d])
					@cache.delete d
				end
			end
			@cache[key] = val
			@ttl_cache[key] = Time.now.to_i
			@queue.push key
		end
		
		# delete the key. 
        # TODO: check this is working 
		def delete(key)
		    d = @queue.delete(key)
		    do_finalization(d,@cache[d])
		    @cache.delete key
		end

		# Allows one to set the maximum size of the cache queue.  If the queue
		# is currently larger than the size that it is being set to, elements
		# will be expired until the queue is at the maximum size.

		def size=(max)
			@max = max
			while @queue.length > @max
				d = @queue.shift
				do_finalization(d,@cache[d])
				@cache.delete d
			end
			@max
		end
		alias maxsize= size=

		# Return the maximum size of the cache.
		def maxsize
			@max
		end

		# Return the current size of the cache.
		def size
			@queue.length
		end

		# Return a copy of current set of keys to cache elements.
		def queue
			@queue.dup
		end
		
		def add_finalizer(*args,&block)
			@finalizers.push [block,args]
		end
		
		def do_finalization(key,obj)
			begin
			@finalizers.each do |f|
				f[0].call(key,obj,*f[1])
			end
			rescue Exception => e
				puts e, e.backtrace
				raise e
			end
		end
	end
end