#
#--
# 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/workitem'
require 'openwfe/flowexpressionid'
require 'openwfe/expressions/flowexpression'


#
# expressions like 'set' and 'unset' and their utility methods
#

module OpenWFE

    #
    # A Mixin shared by CompareExpression and DefinedExpression.
    #
    module LookupMixin

        protected

            def lookup_var_value (workitem, suffix=nil)

                v = lookup_var workitem, suffix

                return lookup_variable(v) if v
                
                nil
            end

            def lookup_field_value (workitem, suffix=nil)

                f = lookup_field workitem, suffix

                return workitem.attributes[f] if f

                nil
            end

            def lookup_var (workitem, suffix=nil)

                do_lookup workitem, suffix, [ :variable, :var, :v ]
            end

            def lookup_field (workitem, suffix=nil)

                do_lookup workitem, suffix, [ :field, :f ]
            end

            def do_lookup (workitem, suffix, atts)

                atts.each do |a|
                    a = a.to_s + '-' + suffix if suffix
                    v = lookup_string_attribute a, workitem
                    return v if v
                end

                nil
            end
    end

    #
    # A parent class for the 'equals' expression.
    #
    # (there should be a 'greater-than' and a 'lesser-than' expression,
    # but there are not that needed for now).
    #
    class ComparisonExpression < FlowExpression
        include LookupMixin

        def apply (workitem)

            #
            # preparing for children handling... later...
            #

            reply workitem
        end

        def reply (workitem)

            value_a, value_b = lookup_values workitem

            result = compare value_a, value_b

            ldebug { "apply() result is '#{result}'  #{@fei.to_debug_s}" }

            workitem.set_result result

            reply_to_parent workitem
        end

        protected

            #
            # The bulk job of looking up the values to compare
            #
            def lookup_values (workitem)

                value_a = lookup_value workitem
                value_b = lookup_value workitem, :prefix => 'other'

                value_c = lookup_variable_or_field_value workitem

                if not value_a and value_b
                    value_a = value_c
                elsif value_a and not value_b
                    value_b = value_c
                end

                [ value_a, value_b ]
            end

            #
            # Returns the value pointed at by the variable attribute or by
            # the field attribute, in that order.
            #
            def lookup_variable_or_field_value (workitem)

                lookup_var_value(workitem) || lookup_field_value(workitem)
            end
    end

    #
    # The 'equals' expression compares two values. If those values are equal,
    # the field (attribute) of the workitem named '__result__' will be
    # set to true (else false).
    #
    # Usually, this expression is used within the 'if' expression.
    #
    #     <if>
    #         <equals field-value="customer_name" other-value="Dupont" />
    #         <!-- then -->
    #         <participant ref="special_salesman" />
    #         <!-- else -->
    #         <participant ref="ordinary_salesman" />
    #     </if>
    #
    # (The 'if' expression reads the '__result__' field to route the flow
    # either towards the then branch, either towards the else one).
    #
    #
    # With a Ruby process definition, a variation on the same 'equals' :
    #
    #     equals :field_value => "phone", :other_value => "090078367"
    #     equals :field_val => "phone", :other_value => "090078367"
    #     equals :f_value => "phone", :other_value => "090078367"
    #     equals :f_val => "phone", :other_value => "090078367"
    #     equals :f_val => "phone", :other_val => "090078367"
    #
    # Thus, note that 'variable' in an expression attribute can be 
    # shortened to 'var' or 'v'. 'value' can be shortened to 'val' and
    # 'field' to 'f'.
    #
    # Usually, the "test" attribute of the "if" expression is preferred
    # over this 'equals' expression, like in :
    #
    #     <if test="${f:customer_name} == Dupont">
    #         <!-- then -->
    #         <participant ref="special_salesman" />
    #         <!-- else -->
    #         <participant ref="ordinary_salesman" />
    #     </if>
    #
    # Another shortcut : the 'participant' and the 'subprocess' expressions
    # accept an optional 'if' (or 'unless') attribute, so that ifs can be
    # contracted to :
    #
    #     participant :ref => "toto", :if => "${f:customer_name} == Alfred"
    #     subprocess :ref => "special_delivery", :if => "'${f:special}' != ''"
    #
    # This also works with the implicit form of the participant and the 
    # subprocess :
    #
    #     toto :if => "${f:customer_name} == Alfred"
    #     special_delivery :if => "'${f:special}' != ''"
    #
    class EqualsExpression < ComparisonExpression

        names :equals

        protected

            def compare (a, b)

                (a == b)
            end
    end

    #
    # This expression class actually implements 'defined' and 'undefined'.
    #
    # They are some kind of 'equals' for validating the presence or not
    # of a variable or a workitem field (attribute).
    #
    #     <if>
    #         <defined field="customer">
    #         <!-- then -->
    #         <subprocess ref="call_customer" />
    #     </if>
    #
    # Since OpenWFEru 0.9.17, 'defined' and 'undefined' can be easily replaced
    # by the "is [not ]set" suffix in the dollar notation :
    #
    #     <if test="${f:customer_name} is set">
    #         <!-- then -->
    #         <subprocess ref="call_customer" />
    #     </if>
    #
    class DefinedExpression < FlowExpression
        include LookupMixin

        names :defined, :undefined

        def apply (workitem)

            fname = lookup_field(workitem, 'value') || lookup_field(workitem)

            fmatch = lookup_string_attribute(:field_match, workitem)

            vname = lookup_var(workitem, 'value') || lookup_var(workitem)

            result = if fname
                workitem.has_attribute?(fname)
            elsif vname
                lookup_variable(vname) != nil
            elsif fmatch
                field_match?(workitem, fmatch)
            else
                false # when in doubt, say 'no' (even when 'undefined' ?)
            end

            result = ( ! result) \
                if result != nil and fei.expression_name == 'undefined'

            workitem.set_result result

            reply_to_parent workitem
        end

        protected

            def field_match? (workitem, regex)

                workitem.attributes.each do |k, v|

                    return true if k.match(regex)
                end

                false
            end
    end

end