#
#--
# 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 'openwfe/workitem'
require 'openwfe/expressions/merge'


#
# save and restore
#

module OpenWFE

    #
    # Saves a copy of the current workitem to a variable or saves the
    # attributes of the current workitem into a field (of that current 
    # workitem).
    #
    #    save :to_variable => "/wix"
    #        #
    #        # saves a copy of the current workitem to the process
    #        # level variable "wix"
    #
    #    save :to_field => "old_version"
    #        #
    #        # saves a copy of the current workitem attributes in the
    #        # field 'old_version' of that current workitem.
    #
    # 'save' is often used in conjuntion with 'restore' 
    # (RestoreWorkItemExpression).
    #
    class SaveWorkItemExpression < FlowExpression

        names :save

        def apply (workitem)

            field = lookup_string_attribute :to_field, workitem
            variable = lookup_string_attribute :to_variable, workitem

            wi = workitem.dup

            if field

                workitem.set_attribute field, wi.attributes

            elsif variable

                set_variable variable, wi
            end

            # else, simply don't save

            reply_to_parent workitem
        end
    end

    #
    # "restore" is often used in conjunction with "save" 
    # (SaveWorkItemExpression).
    #
    # It can restore a workitem saved to a variable (it will actually
    # restore the payload of that workitem) or transfer the content of a field
    # as top attribute field.
    #
    #     restore :from_variable => "freezed_workitem"
    #         #
    #         # takes the freezed payload at 'freezed_workitem' and makes it
    #         # the payload of the current workitem
    #
    #     restore :from_field => "some_data"
    #         #
    #         # replaces the payload of the current workitem with the hash
    #         # found in the field "some_data"
    #
    #     restore :from_variable => "v", :to_field => "f"
    #         #
    #         # will copy the payload saved under variable "v" as the value
    #         # of the field "f"
    #
    #     restore :from_variable => "v", :merge_lead => :current
    #         #
    #         # will restore the payload of the workitem saved under v
    #         # but if fields of v are already present in the current workitem
    #         # the current values will be kept
    #
    #     restore :from_variable => "v", :merge_lead => :restored
    #         #
    #         # will restore the payload of the workitem saved under v
    #         # but the workitem v payload will have priority.
    #
    # Beware : you should not restore from a field that is not a hash. The
    # top level attributes (payload) of a workitem should always be a hash.
    #
    class RestoreWorkItemExpression < FlowExpression
        include MergeMixin

        names :restore

        def apply (workitem)

            from_field = lookup_string_attribute :from_field, workitem
            from_variable = lookup_string_attribute :from_variable, workitem
            merge_lead = lookup_sym_attribute :merge_lead, workitem

            source = if from_field

                att = workitem.lookup_attribute from_field

                lwarn do 
                    "apply() field '#{from_field}' is NOT a hash, " +
                    "restored anyway"
                end unless att.kind_of?(Hash)

                att

            elsif from_variable

                lookup_variable from_variable

            else

                nil
            end

            if source
                workitem = if merge_lead
                    do_merge merge_lead, workitem, source
                else
                    do_overwrite workitem, source
                end
            end
            # else, don't restore anything

            reply_to_parent workitem
        end

        protected

            #
            # The default case, restored values simply overwrite current
            # values.
            #
            def do_overwrite (workitem, source)

                return workitem unless source

                attributes = if source.kind_of?(WorkItem)
                    OpenWFE::fulldup source.attributes
                else
                    source
                end

                to_field = lookup_string_attribute :to_field, workitem

                if to_field
                    workitem.set_attribute to_field, attributes
                else
                    workitem.attributes = attributes
                end

                workitem
            end

            #
            # If the attribute 'merge-lead' (or 'merge_lead') is specified,
            # the workitems get merged.
            #
            def do_merge (merge_lead, workitem, source)

                if source.kind_of?(Hash)
                    wi = InFlowWorkItem.new
                    wi.attributes = source
                    source = wi
                end

                wiTarget, wiSource = if merge_lead == :current
                    [ source, workitem ]
                else
                    [ workitem, source ]
                end

                merge_workitems wiTarget, wiSource
            end
    end

end