#
#--
# Copyright (c) 2007, John Mettraux, 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.
#++
#

#
# "made in Japan"
#
# John Mettraux at openwfe.org
#

require 'thread'
require 'openwfe/utils'


module OpenWFE

    module WorkqueueMixin

        WQF_LOW = 0.500

        #
        # Starts the workqueue with a given frequency (seconds)
        #
        def start_workqueue

            @workqueue_mutex = Mutex.new
            @workqueue = []
            @workqueue_frequency = 0

            OpenWFE::call_in_thread "workqueue", self do
                while true
                    break if @workqueue_frequency == nil
                    sleep @workqueue_frequency
                    do_process_workqueue
                end
            end
        end

        #
        # Returns true if there is or there just was activity for the ]
        # work queue.
        #
        def is_workqueue_busy?
            (@workqueue.size > 0 or @workqueue_frequency < WQF_LOW)
        end

        #
        # Stops the workqueue.
        #
        def stop_workqueue
            @workqueue_frequency = nil
            do_process_workqueue
                #
                # maybe could process the work queue until it's really empty
        end

        #
        # the method called by the mixer to actually queue the work.
        #
        def queue_work (*args)
            @workqueue_mutex.synchronize do

                if @workqueue
                    @workqueue.push args
                        #
                        # work will be done later (millisec order)
                        # by the work thread
                else
                    do_process_workelement args
                        #
                        # degraded mode : as if there were no workqueue
                end
            end
        end

        #
        # Returns the current workqueue size
        #
        def workqueue_size
            return 0 unless @workqueue
            @workqueue.size
        end

        #
        # Called by the workqueue thread, copies the workqueue and clears
        # it, and then processes the elt in the copied workqueue.
        # (meanwhile, the empty workqueue gets filled by queue_work() 
        # calls)
        #
        # This method calls the do_process_workelement() method of
        # its 'mixer' with each work element queued.
        #
        def do_process_workqueue

            q = nil

            @workqueue_mutex.synchronize do

                if @workqueue.size < 1
                    increment_workqueue_frequency
                    return
                end

                q = Array.new(@workqueue)
                @workqueue.clear

                @workqueue_frequency = 0
                    #
                    # back to maximum reponsiveness
            end

            #ldebug { "do_process_workqueue() #{q.size} items to process" }

            q.each do |elt|
            
                do_process_workelement elt
                    #
                    # exception management is now done in the 
                    # do_process_workelement method
            end

            # TODO : have a pool of workers handle that

            #q.size
        end

        protected

            #
            # No activity spotted, so decrease responsiveness
            #
            def increment_workqueue_frequency

                return if @workqueue_frequency == nil

                @workqueue_frequency *= 3

                if @workqueue_frequency == 0
                    @workqueue_frequency = 0.001
                elsif @workqueue_frequency > WQF_LOW
                    @workqueue_frequency = WQF_LOW
                end
            end
    end
end