# --
# Copyright (C) 2001-2016 OTRS AG, http://otrs.com/
# --
# This software comes with ABSOLUTELY NO WARRANTY. For details, see
# the enclosed file COPYING for license information (AGPL). If you
# did not receive this file, see http://www.gnu.org/licenses/agpl.txt.
# --

package Kernel::System::EventHandler;
## nofilter(TidyAll::Plugin::OTRS::Perl::PODSpelling)

use strict;
use warnings;

=head1 NAME

Kernel::System::EventHandler - event handler interface

=head1 SYNOPSIS

Inherit from this class if you want to use events there.

    use base qw(Kernel::System::EventHandler);

In your class, have to call L</EventHandlerInit()> first.

Then, to register events as they occur, use the L</EventHandler()>
method. It will call the event handler modules which are registered
for the given event, or queue them for later execution (so-called
'Transaction' events).

In the destructor, you should add a call to L</EventHandlerTransaction()>
to make sure that also 'Transaction' events will be executed correctly.
This is only neccessary if you use 'Transaction' events in your class.

=head1 PUBLIC INTERFACE

=over 4

=cut

=item EventHandlerInit()

Call this to initialize the event handling mechanisms to work
correctly with your object.

    $Self->EventHandlerInit(

        # name of configured event modules
        Config     => 'Example::EventModule',

        # current object, $Self, used in events as "ExampleObject"
        BaseObject => 'ExampleObject',

        # served default objects in any event backend
        Objects    => {
            UserObject => $UserObject,
            XZY        => $XYZ,
        },
    );

Example 1:

    $Self->EventHandlerInit(
        Config     => 'Ticket::EventModule',
        BaseObject => 'TicketObject',
        Objects    => {
            UserObject  => $UserObject,
            GroupObject => $GroupObject,
        },
    );

Example 1 XML config:

    <ConfigItem Name="Example::EventModule###99-EscalationIndex" Required="0" Valid="1">
        <Description Translatable="1">Example event module updates the example escalation index.</Description>
        <Group>Example</Group>
        <SubGroup>Core::Example</SubGroup>
        <Setting>
            <Hash>
                <Item Key="Module">Kernel::System::Example::Event::ExampleEscalationIndex</Item>
                <Item Key="Event">(ExampleSLAUpdate|ExampleQueueUpdate|ExampleStateUpdate|ExampleCreate)</Item>
                <Item Key="SomeOption">Some Option accessable via $Param{Config}->{SomeOption} in Run() of event module.</Item>
                <Item Key="Transaction">(0|1)</Item>
            </Hash>
        </Setting>
    </ConfigItem>

Example 2:

    $Self->EventHandlerInit(
        Config     => 'ITSM::EventModule',
        BaseObject => 'ChangeObject',
        Objects    => {},
    );

Example 2 XML config:

    <ConfigItem Name="ITSM::EventModule###01-HistoryAdd" Required="0" Valid="1">
        <Description Translatable="1">ITSM event module updates the history for Change and WorkOrder objects..</Description>
        <Group>ITSM Change Management</Group>
        <SubGroup>Core::ITSMEvent</SubGroup>
        <Setting>
            <Hash>
                <Item Key="Module">Kernel::System::ITSMChange::Event::HistoryAdd</Item>
                <Item Key="Event">(ChangeUpdate|WorkOrderUpdate|ChangeAdd|WorkOrderAdd)</Item>
                <Item Key="SomeOption">Some Option accessable via $Param{Config}->{SomeOption} in Run() of event module.</Item>
                <Item Key="Transaction">(0|1)</Item>
            </Hash>
        </Setting>
    </ConfigItem>
    <ConfigItem Name="ITSM::EventModule###02-HistoryAdd" Required="0" Valid="1">
        <Description Translatable="1">ITSM event module updates the ConfigItem History.</Description>
        <Group>ITSM Configuration Management</Group>
        <SubGroup>Core::ITSMEvent</SubGroup>
        <Setting>
            <Hash>
                <Item Key="Module">Kernel::System::ITSMConfigurationManagement::Event::HistoryAdd</Item>
                <Item Key="Event">(ConfigItemUpdate|ConfigItemAdd)</Item>
                <Item Key="SomeOption">Some Option accessable via $Param{Config}->{SomeOption} in Run() of event module.</Item>
                <Item Key="Transaction">(0|1)</Item>
            </Hash>
        </Setting>
    </ConfigItem>

=cut

sub EventHandlerInit {
    my ( $Self, %Param ) = @_;

    $Self->{EventHandlerInit} = \%Param;

    return 1;
}

=item EventHandler()

call event handler, returns true if it was executed successfully.

Example 1:

    my $Success = $EventHandler->EventHandler(
        Event => 'TicketStateUpdate',   # event classification, passed to the configured event handlers
        Data  => {                      # data payload for the event, passed to the configured event handlers
            TicketID => 123,
        },
        UserID => 123,
        Transaction => 1,               # optional, 0 or 1
    );

In 'Transaction' mode, all events will be collected and executed together,
usually in the destructor of your object.

Example 2:

    my $Success = $EventHandler->EventHandler(
        Event => 'ChangeUpdate',
        Data  => {
            ChangeID => 123,
        },
        UserID => 123,
    );

=cut

sub EventHandler {
    my ( $Self, %Param ) = @_;

    # check log object
    if ( !$Self->{LogObject} ) {
        print STDERR 'Need LogObject to activate event handler!';
        return;
    }

    # check needed objects
    for my $Object (qw(ConfigObject MainObject)) {
        if ( !$Self->{$Object} ) {
            $Self->{LogObject}->Log(
                Priority => 'error',
                Message  => "Need $Object to activate event handler!",
            );
            return;
        }
    }

    # check needed stuff
    for (qw(Data Event UserID)) {
        if ( !$Param{$_} ) {
            $Self->{LogObject}->Log(
                Priority => 'error',
                Message  => "Need $_!"
            );
            return;
        }
    }

    # get configured modules
    my $Modules = $Self->{ConfigObject}->Get( $Self->{EventHandlerInit}->{Config} );

    # return if there is no one
    return 1 if !$Modules;

    # remember events only on normal mode
    if ( !$Self->{EventHandlerTransaction} ) {
        push @{ $Self->{EventHandlerPipe} }, \%Param;
    }

    # load modules and execute
    MODULE:
    for my $Module ( sort keys %{$Modules} ) {

        # If the module has an event configuration, determine if it should be executed for this event,
        #   and store the result in a small cache to avoid repetition on jobs involving many tickets.
        if ( !defined $Self->{ExecuteModuleOnEvent}->{$Module}->{ $Param{Event} } ) {
            if ( !$Modules->{$Module}->{Event} ) {
                $Self->{ExecuteModuleOnEvent}->{$Module}->{ $Param{Event} } = 1;
            }
            else {
                $Self->{ExecuteModuleOnEvent}->{$Module}->{ $Param{Event} } =
                    $Param{Event} =~ /$Modules->{$Module}->{Event}/;
            }
        }

        if ( $Self->{ExecuteModuleOnEvent}->{$Module}->{ $Param{Event} } ) {

            if ( $Self->{EventHandlerTransaction} && !$Param{Transaction} ) {

                # This is a special case. A new event was fired during processing of
                #   the queued events in transaction mode. This event must be immediately
                #   processed.
            }
            else {

                # This is the regular case. A new event was fired in regular mode, or
                #   we are processing a queued event in transaction mode. Only execute
                #   this if the transaction settings of event and listener are the same.

                # next if we are not in transaction mode, but module is in transaction
                next MODULE if !$Param{Transaction} && $Modules->{$Module}->{Transaction};

                # next if we are in transaction mode, but module is not in transaction
                next MODULE if $Param{Transaction} && !$Modules->{$Module}->{Transaction};
            }

            # load event module
            next MODULE if !$Self->{MainObject}->Require( $Modules->{$Module}->{Module} );

            # execute event backend
            my $Generic = $Modules->{$Module}->{Module}->new(
                %{ $Self->{EventHandlerInit}->{Objects} || {} },
                $Self->{EventHandlerInit}->{BaseObject} => $Self,
            );

            $Generic->Run(
                %Param,
                Config => $Modules->{$Module},
            );
        }
    }

    return 1;
}

=item EventHandlerTransaction()

handle all queued 'Transaction' events which were collected up to this point.

    $EventHandler->EventHandlerTransaction();

Call this method in the destructor of your object which inherits from
Kernel::System::EventHandler, like this:

    sub DESTROY {
        my $Self = shift;

        # execute all transaction events
        $Self->EventHandlerTransaction();

        return 1;
    }

=cut

sub EventHandlerTransaction {
    my ( $Self, %Param ) = @_;

    # remember, we are in destroy mode, do not execute new events
    $Self->{EventHandlerTransaction} = 1;

    # execute events on end of transaction
    if ( $Self->{EventHandlerPipe} ) {

        for my $Params ( @{ $Self->{EventHandlerPipe} } ) {
            $Self->EventHandler(
                %Param,
                %{$Params},
                Transaction => 1,
            );
        }

        # delete event pipe
        $Self->{EventHandlerPipe} = undef;
    }

    # reset transaction mode
    $Self->{EventHandlerTransaction} = 0;

    return 1;
}

1;

=back

=head1 TERMS AND CONDITIONS

This software is part of the OTRS project (L<http://otrs.org/>).

This software comes with ABSOLUTELY NO WARRANTY. For details, see
the enclosed file COPYING for license information (AGPL). If you
did not receive this file, see L<http://www.gnu.org/licenses/agpl.txt>.

=cut
