statemachine.go

package statemachine

// An implementation of a finite state machine in Go,
// inspired by David Mertz's article "Charming Python: Using state machines" 
// (http://www.ibm.com/developerworks/library/l-python-state/index.html)

type Handler func(interface{}) (string, interface{})

type Machine struct {
    Handlers   map[string]Handler
    StartState string
    EndStates  map[string]bool
}

func (machine *Machine) AddState(handlerName string, handlerFn Handler) {
    machine.Handlers[handlerName] = handlerFn
}

func (machine *Machine) AddEndState(endState string) {
    machine.EndStates[endState] = true
}

func (machine *Machine) Execute(cargo interface{}) {
    if handler, present := machine.Handlers[machine.StartState]; present {
        for {
            nextState, nextCargo := handler(cargo)
            _, finished := machine.EndStates[nextState]
            if finished {
                break
            } else {
                handler, present = machine.Handlers[nextState]
                cargo = nextCargo
            }
        }
    }
}