');
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/**
');
document.write('* GOAL: Write a quick-and-dirty DSL in Groovy that emulates Bruce Tate\'s
');
document.write('* example "acts_as_statemachine" Ruby code at
');
document.write('* http://www-128.ibm.com/developerworks/java/library/j-cb03137/index.html,
');
document.write('* within 20 minutes or less (i.e. steer clear of MOP-magic engineering ;).
');
document.write('*
');
document.write('* For more context, see the Apr\'07 "Symbols" thread on the groovy-user mailing
');
document.write('* list.
');
document.write('*/');
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');
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////////////////////////////////////////////////////////////');
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// Initialize');
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////////////////////////////////////////////////////////////');
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def fsm =
new StateMachine
()');
document.write('fsm.
current_state =
\'submitted\' // pretend to look up something with state from dBase');
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');
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////////////////////////////////////////////////////////////');
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// Define');
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////////////////////////////////////////////////////////////');
document.write('fsm.
state \'submitted\'');
document.write('fsm.
state \'processing\'');
document.write('fsm.
state \'nonprofit_reviewing\'');
document.write('fsm.
state \'accepted\'');
document.write('
');
document.write('fsm.
event(\'accept\',
[ ');
document.write('
[from:
\'processing\', to:
\'accepted\'],
');
document.write('
[from:
\'nonprofit_reviewing\', to:
\'accepted\']');
document.write('
])');
document.write('
');
document.write('fsm.
event(\'receive\',
[ ');
document.write('
[from:
\'submitted\', to:
\'processing\']');
document.write('
])');
document.write('fsm.
event(\'send_for_review\',
[');
document.write('
[from:
\'processing\', to:
\'nonprofit_reviewing\'],
');
document.write('
[from:
\'nonprofit_reviewing\', to:
\'processing\'],
');
document.write('
[from:
\'accepted\', to:
\'nonprofit_reviewing\']');
document.write('
])');
document.write('fsm.
event(\'revise\',
[');
document.write('
[from:
\'accepted\', to:
\'processing\']');
document.write('
])');
document.write('
println fsm
');
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println \'----------\'');
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println ()');
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');
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////////////////////////////////////////////////////////////');
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// Use:');
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//////////////////////////////////////////////////////////// ');
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println fsm.
current_state');
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assert fsm.
current_state ==
\'submitted\'');
document.write('fsm.
fire \'receive\'');
document.write('fsm.
fire \'accept\'');
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println fsm.
current_state');
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assert fsm.
current_state ==
\'accepted\'');
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');
document.write('
');
document.write('
');
document.write('
');
document.write('
/** A list/map-based implementation of a StateMachine DSL-ish thingy */');
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public class StateMachine
{ ');
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def current_state =
\'initial\' // literals are intern()ed automatically');
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def valid_states =
[\'initial\']');
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def transitions =
[:
] // a LUT from events to defined transitions');
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');
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/** add a new valid state to the machine */');
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def state =
{symbolic_name -> valid_states<<symbolic_name; valid_states.
unique()}');
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');
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/** define $transitions, which maps from (state,event) --> state */');
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def event
(event,tuples
) {');
document.write(' tuples.
each { transition ->
');
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assert valid_states.
contains(transition.
from)');
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assert valid_states.
contains(transition.
to)');
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');
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def trigger =
[event:event, from:transition.
from]');
document.write(' transitions
[trigger
] = transition.
to ');
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} ');
document.write('
}');
document.write('
');
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/** have the machine process an event */');
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def fire
(event
) { ');
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def context =
[event:event, from:current_state
]');
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');
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//BUG: Map::find() doesn\'t work with two-param Closures?');
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// def transition = transitions.find {trigger,_ -> trigger==context }');
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def transition = transitions.
findAll {trigger,_ -> trigger==context
} ');
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if (transition
) {');
document.write(' current_state = transition
[context
] // findAll() version');
document.write('
// current_state = transition.value // find() version');
document.write('
} ');
document.write('
}');
document.write('
');
document.write('
/** pretty-print the states and their defined transitions */');
document.write('
public String toString
() {');
document.write('
def result =
""');
document.write(' valid_states.
each { state ->
');
document.write(' result
<<=
"state ${state}:\n" // using <<= to coerce to StringBuffer');
document.write(' transitions.
each { transition ->
');
document.write('
def from = transition.
key.
from');
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def event = transition.
key.
event');
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def to = transition.
value');
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if (from==state
) {result<<
"\t |-- ${event} --> ${to}\n" }');
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}');
document.write('
}');
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return result
');
document.write('
}');
document.write('
');
document.write('
}');
document.write('