#
#--
# 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/logging'
require 'openwfe/contextual'
require 'openwfe/rudefinitions'


module OpenWFE

    #
    # The 'participant' concept is displayed as a module, so that 
    # other pieces of code may easily 'mix it in'.
    #
    # Participant extensions should at least provide a consume(workitem)
    # method.
    # As an option, it can provide a cancel(cancelitem) method.
    #
    # The engine will transmit instances of OpenWFE:WorkItem via the
    # consume method.
    #
    # If there is a cancel method available and an OpenWFE::CancelItem instance
    # is emitted (cancelling a process or part of it), it will be fed to
    # the participant only via the cancel method.
    #
    # If there is no cancel method, the participant will not get notified
    # of the cancellation.
    #
    module Participant

        #
        # A Participant will be receiving OpenWFE::WorkItem's via this method.
        #
        def consume (workitem)

            raise NotImplementedError.new(
                "implementation for method consume() "+
                "is missing in class '#{self.class}'")
        end

        #--
        # (optional)
        #
        #def cancel (cancelitem)
        #end
        #++
    end

    #
    # Local participants provide handy methods like reply_to_engine() to
    # further implementations of the Participant concept.
    #
    module LocalParticipant
        include Participant, Contextual, Logging, OwfeServiceLocator

        #
        # Returns the FlowExpression instance that triggered this
        # participant. 
        # A ParticipantExpression instance will most likely be returned.
        #
        def get_flow_expression (workitem)

            return nil if not @application_context

            get_expression_pool.fetch_expression(workitem.flow_expression_id)
        end

        #
        # A convenience method for calling block passed to participants
        # for templates (mail participants) or execution (BlockParticipant).
        #
        # Allows for such blocks :
        #
        #     { |workitem| ... }
        #     { |participant_expression, workitem| ... }
        #     { |participant_expression, participant, workitem| ... }
        #
        # For 0 or more than 3 arguments, the block will be called without
        # arguments.
        #
        def call_block (block, workitem)

            if block.arity == 1
                block.call workitem
            elsif block.arity == 2
                block.call get_flow_expression(workitem), workitem
            elsif block.arity == 3
                block.call get_flow_expression(workitem), self, workitem
            else
                block.call
            end
        end

        #
        # Participants use this method to reply to their engine when
        # their job is done.
        #
        def reply_to_engine (workitem)

            get_engine.reply(workitem)
        end
    end

end