#
#--
# 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/expressions/condition'
require 'openwfe/expressions/wtemplate'
require 'openwfe/expressions/flowexpression'
require 'openwfe/expressions/fe_command'


module OpenWFE

    #
    # The 'cursor' is much like a sequence, but you can go
    # back and forth within it, as it reads the field '\_\_cursor_command__' (or
    # the field specified in the 'command-field' attribute) at each
    # transition (each time it's supposed to move from one child expression to
    # the next).
    #
    #     cursor do
    #         participant "alpha"
    #         skip :step => "2"
    #         participant "bravo"
    #         participant "charly"
    #         set :field => "__cursor_command__", value => "2"
    #         participant "delta"
    #         participant "echo"
    #         skip 2
    #         participant "fox"
    #         #
    #         # in that cursor example, only the participants alpha, charly and
    #         # echo will be handed a workitem
    #         # (notice the last 'skip' with its light syntax)
    #         #
    #     end
    #
    # As you can see, you can directly set the value of the field 
    # '\_\_cursor_command__' or use a CursorCommandExpression like 'skip' or
    # 'jump'.
    #
    class CursorExpression < WithTemplateExpression
        include CommandMixin

        names :cursor

        attr_accessor \
            :loop_id,
            :current_child_id,
            :current_child_fei

        def apply (workitem)

            @loop_id = 0

            @current_child_id = -1

            clean_children_list()

            reply(workitem)
        end

        def reply (workitem)

            if @children.length < 1
                #
                # well, currently, no infinite empty loop allowed
                #
                reply_to_parent(workitem)
                return
            end

            command, step = determine_command_and_step workitem

            ldebug { "reply() command is '#{command} #{step}'" }

            if command == C_BREAK or command == C_CANCEL
                reply_to_parent workitem
                return
            end

            if command == C_REWIND or command == C_CONTINUE

                @current_child_id = 0

            elsif command and command.match "^#{C_JUMP}"

                @current_child_id = step
                @current_child_id = 0 if @current_child_id < 0

                @current_child_id = @children.length - 1 \
                    if @current_child_id >= @children.length

            else # C_SKIP or C_BACK

                @current_child_id = @current_child_id + step

                @current_child_id = 0 if @current_child_id < 0

                if @current_child_id >= @children.length
                    if not is_loop
                        reply_to_parent(workitem)
                        return
                    end
                    @loop_id += 1
                    @current_child_id = 0
                end
            end

            @current_child_fei = nil

            store_itself()

            @current_child_fei = @children[@current_child_id]

            #
            # launch the next child as a template

            get_expression_pool.launch_template(
                self, @loop_id, @current_child_fei, workitem, nil)
        end

        #
        # takes care of cancelling the current child if necessary
        #
        def cancel

            get_expression_pool.cancel(@current_child_fei) \
                if @current_child_fei

            super
        end

        #
        # Returns false, the child class LoopExpression does return true.
        #
        def is_loop
            false
        end

        protected

            #
            # Makes sure that only flow expression are left in the cursor
            # children list (text and comment nodes get discarded).
            #
            def clean_children_list

                c = @children
                @children = []
                c.each do |child|
                    @children << child \
                        if child.kind_of?(OpenWFE::FlowExpressionId)
                end
            end
    end

    #
    # The 'loop' expression is like 'cursor' but it doesn't exit until
    # it's broken (with 'break' or 'cancel').
    #
    class LoopExpression < CursorExpression

        names :loop

        def is_loop
            true
        end
    end

end