#
#--
# Copyright (c) 2007, Tomaso Tosolini, 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 Italy"
#
# Tomaso Tosolini
# John Mettraux
# 

require 'rubygems'

#require_gem 'activerecord'
gem 'activerecord'
require 'active_record'

require 'monitor'


require 'openwfe/service'
require 'openwfe/rudefinitions'
require 'openwfe/expool/expstorage'
require 'openwfe/expool/threadedexpstorage'


module OpenWFE::Extras

    #
    # A migration for creating/dropping the "expressions" table.
    # 'expressions' are atomic pieces of running process instances.
    #
    class ExpressionTables < ActiveRecord::Migration

        def self.up

            create_table :expressions do |t|

                t.column :fei, :string, :null => false
                t.column :wfid, :string, :null => false
                #t.column :wfname, :string, :null => false
                t.column :exp_class, :string, :null => false
                t.column :svalue, :text, :null => false
                    # 'value' could be reserved, using 'svalue' instead
            end
            add_index :expressions, :fei
            add_index :expressions, :wfid
            #add_index :expressions, :wfname
            add_index :expressions, :exp_class
        end

        def self.down

            drop_table :expressions
        end
    end

    #
    # The ActiveRecord wrapper for an OpenWFEru FlowExpression instance.
    #
    class Expression < ActiveRecord::Base

        serialize :svalue
    end

    #
    # Storing OpenWFE flow expressions in a database.
    #
    class DbExpressionStorage
        include MonitorMixin
        include OpenWFE::ServiceMixin
        include OpenWFE::OwfeServiceLocator
        include OpenWFE::ExpressionStorageBase

        #
        # Constructor.
        #
        def initialize (service_name, application_context)

            require 'openwfe/storage/yamlcustom'
                # making sure this file has been required at this point
                # this yamlcustom thing prevents the whole OpenWFE ecosystem
                # to get serialized :)

            super() # absolutely necessary as we include MonitorMixin
            service_init service_name, application_context

            observe_expool
        end

        #
        # Stores an expression.
        #
        def []= (fei, flow_expression)

            ldebug { "[]= storing #{fei.to_s}" }

            synchronize do

                e = Expression.find_by_fei fei.to_s

                unless e
                    e = Expression.new
                    e.fei = fei.to_s
                    e.wfid = fei.wfid
                    #e.wfname = fei.wfname
                end

                e.exp_class = flow_expression.class.name
                e.svalue = flow_expression

                e.save!
            end
        end

        #
        # Retrieves a flow expression.
        #
        def [] (fei)

            e = Expression.find_by_fei fei.to_s
            return nil unless e

            as_owfe_expression e
        end

        #
        # Returns true if there is a FlowExpression stored with the given id.
        #
        def has_key? (fei)

            (Expression.find_by_fei(fei.to_s) != nil)
        end

        #
        # Deletes a flow expression.
        #
        def delete (fei)

            synchronize do
                Expression.delete_all ["fei = ?", fei.to_s]
            end
        end

        #
        # Returns the count of expressions currently stored.
        #
        def size

            Expression.count
        end

        alias :length :size

        #
        # Danger ! Will remove all the expressions in the database.
        #
        def purge 

            Expression.delete_all
        end

        #
        # Given an expression class (Schedulable or ParticipantExpression for
        # example), calls the passed block for each expression of that class.
        #
        def each_of_kind (kind, &block)

            classes = get_expression_map.get_expression_classes(kind)
            classes = classes.collect { |c| c.name }

            exps = Expression.find_all_by_exp_class(classes)

            exp_each exps, &block
        end

        #
        # Calls the block for each expression stored. If a wfid prefix is
        # passed, only the expressions whose workflow instance id begins
        # with it will be iterated over.
        #
        def each (wfid_prefix=nil, &block)

            params = {}

            params[:conditions] = [ "wfid LIKE ?", "#{wfid_prefix}%" ] \
                if wfid_prefix

            exps = Expression.find(:all, params)

            exp_each exps, &block
        end

        alias :real_each :each

        protected

            #
            # Used by each() and each_of_kind().
            #
            def exp_each (expressions, &block)

                expressions.each do |exp|
                    fexp = as_owfe_expression(exp)
                    block.call fexp.fei, fexp
                end
            end

            #
            # Extracts the OpenWFE FlowExpression instance from the
            # active record and makes sure its application_context is set.
            #
            def as_owfe_expression (record)

                fe = record.svalue
                fe.application_context = @application_context
                fe
            end
    end

    #
    # A DbExpressionStorage that does less work, for more performance,
    # thanks to the ThreadedStorageMixin.
    #
    class ThreadedDbExpressionStorage < DbExpressionStorage
        include OpenWFE::ThreadedStorageMixin

        def initialize (service_name, application_context)

            super

            start_processing_thread()
                #
                # which sets @thread_id
        end
    end
end