#
#--
# Copyright (c) 2006-2008, 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 'openwfe/utils'
require 'openwfe/rudefinitions'
require 'openwfe/expressions/filter'
require 'openwfe/expressions/timeout'


#
# The participant expression, in its own file
#

module OpenWFE

    #
    # Participants sit at the edge between the engine and the external
    # world. The participant expression transmit the workitem applied
    # to it to the Participant instance it looks up in the participant map
    # tied to the engine.
    #
    #  direct reference to participant alpha :
    #
    #     <participant ref="alpha" />
    #
    #  the name of the participant is the value found in 
    #  the field 'target' :
    #
    #     <participant field-ref="target" />
    #     <participant ref="${f:target}" />
    #
    #  the name of the participant is the value found in 
    #  the variable 'target' :
    #
    #     <participant variable-ref="target" />
    #     <participant ref="${target}" />
    #
    #  direct reference to participant 'alpha'
    #  if a subprocess named 'alpha' has been defined, the 
    #  subprocess will be called instead :
    #
    #     <alpha />
    #
    # The Participant expressions includes the FilterMixin and thus
    # understands and applies the "filter" attribute.
    #
    # Since OpenWFEru 0.9.9, the attributes of the participant expression are
    # set inside a hash field named 'params' just available to the participant.
    # Thus in
    #
    #     <participant ref="toto" task="play golf" location="Minami Center" />
    #
    # participant 'toto' will receive a workitem with a field named 'params'
    # containing the hash 
    # { "ref"=>"toto", "task"=>"play golf", "location"=>"Minami Center" }.
    # 
    # When the workitem gets back from the participant, the field 'params' is 
    # deleted.
    #
    # The participant expressions include the TimeoutMixin, it means that
    # a timeout can be stated :
    #
    #     <participant ref="toto" timeout="2w1d" />
    #
    # If after 2 weeks and 1 day (15 days), participant "toto" hasn't replied,
    # the workitem will get cancelled and the flow will resume (behind the 
    # scene, participant "toto", will receive a CancelItem instance bearing
    # the same FlowExpressionId as the initial workitem and the participant
    # implementation is responsible for the cancel application).
    #
    # The participant expression accepts an optional 'if' (or 'unless') 
    # attribute. It's used for conditional execution of the participant :
    #
    #     participant :ref => "toto", :if => "${weather} == raining"
    #         # the participant toto will receive a workitem only if
    #         # it's raining
    #
    #     boss :unless => "#{f:matter} == 'very trivial'"
    #         # the boss will not participate in the proces if the matter
    #         # is 'very trivial'
    #
    class ParticipantExpression < FlowExpression
        include FilterMixin
        include TimeoutMixin
        include ConditionMixin

        names :participant

        attr_accessor :participant_name
        attr_accessor :applied_workitem


        def apply (workitem)

            conditional = eval_condition :if, workitem, :unless

            return super_reply_to_parent(workitem) \
                if conditional == false
                    #
                    # skip expression 
                    # <participant ref="x" if="y" /> (where y evals to false)

            @participant_name = lookup_ref workitem

            @participant_name = fetch_text_content workitem \
                unless @participant_name

            participant =
                get_participant_map.lookup_participant @participant_name

            raise "No participant named '#{@participant_name}'" \
                unless participant

            remove_timedout_flag workitem

            @applied_workitem = workitem.dup

            schedule_timeout

            filter_in workitem

            store_itself

            workitem.params = lookup_attributes workitem

            #
            # threading AFTER the store_itself()
            #
            Thread.new do
                begin

                    # these two pmap calls were combined, but with the :reply
                    # notification in reply_to_parent() it feels more
                    # elegant like that

                    get_participant_map.dispatch(
                        participant, @participant_name, workitem)

                    get_participant_map.onotify(
                        @participant_name, :apply, workitem)

                rescue Exception => e

                    get_expression_pool.notify_error(
                        e, fei, :do_apply, workitem)
                end
            end
        end

        alias :super_reply_to_parent :reply_to_parent

        def reply_to_parent (workitem)

            get_participant_map.onotify @participant_name, :reply, workitem
                #
                # for 'listen' expressions waiting for replies

            unschedule_timeout()

            workitem.attributes.delete "params"

            filter_out workitem

            super workitem
        end

        #
        # The cancel() method of a ParticipantExpression is particular : it
        # will emit a CancelItem instance towards the participant itself
        # to notify it of the cancellation.
        #
        def cancel

            unschedule_timeout

            cancel_participant

            @applied_workitem
        end

        #
        # Upon timeout, the ParticipantExpression will cancel itself and
        # the flow will resume.
        #
        def trigger (scheduler)

            linfo { "trigger() timeout requested for #{@fei.to_debug_s}" }

            begin

                #@scheduler_job_id = nil
                    #
                    # so that cancel won't unschedule without need 

                cancel_participant

                set_timedout_flag @applied_workitem

                reply_to_parent @applied_workitem

            rescue

                lerror do
                    "trigger() problem while timing out\n"+
                    OpenWFE::exception_to_s($!)
                end
            end
        end

        protected

            #
            # Have to cancel the workitem on the participant side
            #
            def cancel_participant

                return unless @applied_workitem
                    #
                    # if there is an applied workitem, it means there
                    # is a participant to cancel...

                participant = \
                    get_participant_map.lookup_participant(@participant_name)

                cancelitem = CancelItem.new(@applied_workitem)

                get_participant_map.dispatch(
                    participant, @participant_name, cancelitem)
            end
    end

end