#
#--
# Copyright (c) 2006-2007, 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.
#++
#
# $Id: definitions.rb 2725 2006-06-02 13:26:32Z jmettraux $
#

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

require 'openwfe/utils'
require 'openwfe/rudefinitions'
require 'openwfe/expressions/flowexpression'


#
# base expressions like 'sequence' and 'concurrence'
#

module OpenWFE

    class ConcurrenceExpression < SequenceExpression

        attr_accessor \
            :sync_expression

        def apply (workitem)

            sync = lookup_attribute(:sync, workitem, :generic)

            @sync_expression = \
                get_expression_map().get_sync_class(sync).new(self, workitem)

            @children.each do |child|
                @sync_expression.add_child(child)
            end

            store_itself()

            concurrence = self

            @children.each do |child|
                Thread.new do
                    begin
                        concurrence.synchronize do
                            get_expression_pool().apply(child, workitem.dup)
                        end
                    rescue Exception => e
                        lwarn do 
                            "apply() " +
                            "caught exception in concurrent child  " + 
                            child.to_debug_s + "\n" + 
                            OpenWFE::exception_to_s(e)
                        end
                    end
                end
            end

            #@sync_expression.ready(self)
                #
                # this is insufficient, have to do that :

            synchronize do
                #
                # Making sure the freshest version of the concurrence
                # expression is used.
                # This is especially important when using pure persistence.
                #
                reloaded_self, _fei = get_expression_pool.fetch(@fei)
                reloaded_self.sync_expression.ready(reloaded_self)
            end
        end

        def reply (workitem)
            @sync_expression.reply(self, workitem)
        end
    end

    #
    # A base for sync expressions, currently empty.
    # That may change.
    #
    class SyncExpression

        def initialize()
            super()
        end
    end

    #
    # The classical OpenWFE sync expression.
    # Used by 'concurrence' and 'concurrent-iterator'
    #
    class GenericSyncExpression < SyncExpression

        attr_accessor \
            :remaining_children,
            :count,
            :reply_count,
            :cancel_remaining,
            :unready_queue

        def initialize (synchable, workitem)

            super()

            @remaining_children = []
            @reply_count = 0

            @count = determine_count(synchable, workitem)
            @cancel_remaining = cancel_remaining?(synchable, workitem)

            @unready_queue = []
        end

        #
        # when all the children got applied concurrently, the concurrence
        # calls this method to notify the sync expression that replies
        # can be processed
        #
        def ready (synchable)
            synchable.synchronize do

                synchable.ldebug do 
                    "ready() called by  #{synchable.fei.to_debug_s}  " +
                    "#{@unready_queue.length} wi waiting"
                end

                queue = @unready_queue
                @unready_queue = nil
                synchable.store_itself()

                queue.each do |workitem|
                    do_reply(synchable, workitem)
                end
            end
        end

        def add_child (child)
            @remaining_children << child
        end

        def reply (synchable, workitem)
            synchable.synchronize do

                if @unready_queue

                    @unready_queue << workitem

                    synchable.store_itself()

                    synchable.ldebug do 
                        "#{self.class}.reply() "+
                        "#{@unready_queue.length} wi waiting..."
                    end

                else
                    do_reply(synchable, workitem)
                end
            end
        end

        protected

            def do_reply (synchable, workitem)

                synchable.ldebug do 
                    "#{self.class}.do_reply()  "+
                    "#{workitem.last_expression_id.to_debug_s}"
                end

                @reply_count = @reply_count + 1

                @remaining_children.delete(workitem.last_expression_id)

                if @remaining_children.length <= 0
                    synchable.reply_to_parent(workitem)
                    return
                end

                if @count > 0 and @reply_count >= @count
                    treat_remaining_children(synchable)
                    synchable.reply_to_parent(workitem)
                    return
                end

                synchable.store_itself()

                #synchable.ldebug do
                #    "#{self.class}.do_reply() not replying to parent "+
                #    "#{workitem.last_expression_id.to_debug_s}"
                #end
            end

            def treat_remaining_children (synchable)

                expool = synchable.get_expression_pool

                @remaining_children.each do |child|

                    synchable.ldebug do 
                        "#{self.class}.treat_remainining_children() " +
                        "#{child.to_debug_s} " +
                        "(cancel ? #{@cancel_remaining})"
                    end

                    if @cancel_remaining
                        expool.cancel(child)
                    else
                        #expool.remove(child)
                        expool.forget(child)
                    end
                end
            end

            def cancel_remaining? (synchable_expression, workitem)

                s = synchable_expression.lookup_attribute(
                    :remaining, workitem, :cancel)

                return s == :cancel.to_s
            end

            def determine_count (synchable_expression, workitem)

                s = synchable_expression.lookup_attribute(:count, workitem)
                return -1 if not s
                i = s.to_i
                return -1 if i < 1
                return i
            end
    end

    #
    # Merges a workitem (source) into another (target).
    # If inPlace is left to false, a brand new workitem is returned,
    # else the merge occurs directly into the target workitem.
    #
    def merge (wiTarget, wiSource, inPlace=false)

        wiTarget = wiTarget.dup if not inPlace

        wiSource.attributes.each do | k, v |
            wiTarget.attributes[k.dup] = v.dup
        end
    end

end