# NAME

State::Machine - Simple State Machine Implementation

# VERSION

version 0.04

# SYNOPSIS

    use State::Machine;
    use State::Machine::State;
    use State::Machine::Transition;

    # light-switch circular-state example

    my $is_on  = State::Machine::State->new(name => 'is_on');
    my $is_off = State::Machine::State->new(name => 'is_off');

    my $turn_on  = State::Machine::Transition->new(
        name   => 'turn_on',
        result => $is_on
    );
    my $turn_off = State::Machine::Transition->new(
        name   => 'turn_off',
        result => $is_off
    );

    $is_on->add_transition($turn_off); # on -> turn off
    $is_off->add_transition($turn_on); # off -> turn on

    my $lightswitch = State::Machine->new(
        topic => 'typical light switch',
        state => $is_off
    );

    $lightswitch->apply('turn_off');
    $lightswitch->status; # is_off

# DESCRIPTION

A finite-state machine (FSM) or finite-state automaton (plural: automata), or
simply a state machine, is an abstract machine that can be in one of a finite
number of states. The machine is in only one state at a time. It can change from
one state to another when initiated by a triggering event or condition; this is
called a transition. State::Machine is a system for creating state machines and
managing their transitions; It is also a great mechanism for enforcing and
tracking workflow, especially in distributed computing.

State machines are useful for modeling systems with perform a predetermined
sequence of event and result in deterministic state. State::Machine, as you
might expect, allows for the definition of events, states, state transitions
and user defined actions that can be executed before or after transitions. All
features of the state machine itself can be configured via a DSL,
[State::Machine::Simple](http://search.cpan.org/perldoc?State::Machine::Simple). __Note: This is an early release available for
testing and feedback and as such is subject to change.__

# ATTRIBUTES

## state

    my $state = $machine->state;
    $state = $machine->state(State::Machine::State->new(...));

The current state of the state machine. The value should be a
[State::Machine::State](http://search.cpan.org/perldoc?State::Machine::State) object.

## topic

    my $topic = $machine->topic;
    $topic = $machine->topic('Take over the world');

The topic or purpose of the state machine. The value can be any arbitrary
string describing intent.

# METHODS

## apply

    my $state = $machine->apply('transition_name');
    $state = $machine->apply; # apply known next transition

The apply method transitions the state machine from the current state into the
resulting state. If the apply method is called without a transition name, the
machine will transition into the next known state of the current state.

## next

    my $transition_name = $machine->next;

The next method returns the name of the next known transition of the current
state if exists, otherwise it will return undefined.

## status

    my $state_name = $machine->status;

The status method returns the name of the current state.

# AUTHOR

Al Newkirk <anewkirk@ana.io>

# COPYRIGHT AND LICENSE

This software is copyright (c) 2014 by Al Newkirk.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
