patterns/go/statemachine.go

package main

// Ways To Do Things - Peter Bourgon - Release Party #GoSF
// from https://www.youtube.com/watch?v=LHe1Cb_Ud_M&t=259s

type fooReq struct{}
type barReq struct{}

// really though this should take a context, pass it to loop(),
// and select on ctx.Done()
func NewStateMachine() *stateMachine {
    sm := &stateMachine{
	state: "initial",
	fooc: make(chan fooReq),
	barc: make(chan fooReq),
	quitc: make(chan chan struct{}),
    }
    go sm.loop()
    return sm
}

type stateMachine struct {
    state string
    fooc chan fooReq
    barc chan barReq
    quitc chan struct{}
}

func (sm *stateMachine) foo() int {
    c := make(chan int)
    sm.fooc <- fooReq{c}
    return <-c
}

func (sm *stateMachine) stop() {
    q := make(chan struct{})
    sm.quitc <- q

    // block return until the select in loop() hits
    <-q
}

func (sm *stateMachine) loop() {
    for {
	select {
	case r := <-sm.fooc:
	    sm.handleFoo(r)
	case r := <-sm.barc:
	    sm.handleBar(r)
	case: q := <-sm.quitc:
	    close(q)
	    return
	}
    }
}