NAME
    POE::Session::Cascading - Stack-like POE Sessions

AUTHOR
    Matt Cashner (eek+cpan@eekeek.org)

DATE
    $Date: 2004-04-24 13:55:11 -0400 (Sat, 24 Apr 2004) $

SYNOPSIS
        POE::Session::Cascading->new(
            name => 'foo',
            events => [
                'state1' => \&state1,
                'state2 => \&state2,
            ],
        );

        sub state1 {
            my %args = @_;
            $args{KERNEL}->post('somewhere','somestate');
            # [ snip ]
        
        }
    
        sub state2 {
            my %args = @_;
            # [ snip ]
        
            $args{SESSION}->stop;
        }

DESCRIPTION
  INTRODUCTION
    POE::Session::Cascading provides a stack-like session for POE. Another
    way of saying it is that a Cascading session is like a big switch
    statement. In the above example, when "state1" is called in session
    "foo", &state1 gets executed. When it finishes, "state2" gets fired and
    &state2 gets executed. If "state2" is called in session "foo", only
    "state2" will get executed.

  CONTROLLING PROPOGATION
    Each state can decide whether chain propogation should continue or not.
    If the state wishes to stop chain propogation, it must call
    "$args{SESSION}->stop". Otherwise, chain propogation will continue. A
    state can call "$args{SESSION}->go" to forcibly allow chain propogation.
    This is largely superflous as this is the default option.

    It would be appropriate to return call "stop", for instance, if the
    state has determined that further action by this chain is unnecessary or
    undesirable. The state might launch a different chain and cal "stop" to
    shutdown the current chain's propogation.

  LAUNCHING A CHAIN
    To initiate a chain, post a call to the relevant state with the
    session's name. For instance, to activate the chain in the example
    above, one would write:

        $poe_kernel->post('foo','state1');

    Arguments passes to POE's post method will be passed directly to the
    state and those which follow it.

  WRITING A STATE
    Cascading states are a bit different from the usual POE states, mainly
    in the argument list. Cascading states are passed a hash, containing
    three entries. "SESSION" contains a reference to the current session's
    object. "KERNEL" contains a reference to the POE kernel. "ARGS" contains
    an array reference of the arguments passed to the state.

    Cascading states can do anything perl can. Cascading states are passed a
    hash, containing three entries. "SESSION" contains a reference to the
    current session's object. "KERNEL" contains a reference to the POE
    kernel. "ARGS" contains an array reference of the arguments passed to
    the state, including any data passed from the previous state..

METHODS
  new()
        POE::Session::Cascading->new(
            name => 'foo',
            events => [
                step1 => \&step1,
                step2 => \&step2,
                step3 => \&step3,
            ]
        );

  stop
        $args{SESSION}->stop;

    Instruct the current session to stop chain propogation.

  go
        $args{SESSION}->go;

    Instruct the current session to continue chain propgation.

  swap
        $args{SESSION}->swap($state1, $state2);
    
    Reorder the event stack. Swap two states in the stack.

BUGS AND KNOWN ISSUES
    * Cannot register or unregister a stack element at runtime
    * Stack requires outside influence to start (is this actually a
    problem?)

LICENSE AND COPYRIGHT
    Copyright (c) 2002, Matt Cashner

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.