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gen_fsm.go
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gen_fsm.go
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package go_gen_fsm
import (
"errors"
"fmt"
"reflect"
"time"
)
type GenFSM struct {
fsm FSM
handlerResolver HandlerResolver
currentState State
handlers map[State][]EventHandler
eventsChannel chan EventMessage
errorChannel chan error
sync sync
timer *time.Timer
shutdown bool
}
type FSM interface {
Init(args ...interface{}) State
}
type State string
type Event string
type EventHandler struct {
event Event
handlerFunc reflect.Method
}
type EventMessage struct {
Kind Event
Data []interface{}
}
type sync struct {
req chan interface{}
resp chan interface{}
handlers map[interface{}]func() interface{}
}
const (
NOOP = "NOOP"
TIMEOUT = "Timeout"
STOP = "Stop"
genericState = State("Handle")
genericEvent = Event("Info")
)
func Start(fsm FSM, args ...interface{}) *GenFSM {
g := newGenFsm()
g.fsm = fsm
g.currentState = fsm.Init(args...)
g.registerHandlers()
go g.doStart()
return g
}
func newGenFsm() *GenFSM {
g := new(GenFSM)
g.handlers = make(map[State][]EventHandler)
g.eventsChannel = make(chan EventMessage)
g.errorChannel = make(chan error, 10)
g.sync = sync{make(chan interface{}, 1), make(chan interface{}, 1), make(map[interface{}]func() interface{})}
g.handlerResolver = NewHandlerResolver()
return g
}
func (g *GenFSM) registerHandlers() {
fsmType := reflect.TypeOf(g.fsm)
nMethods := fsmType.NumMethod()
for i := 0; i < nMethods; i++ {
m := fsmType.Method(i)
match, state, event := g.handlerResolver.Resolve(m)
if match {
eventHandler := EventHandler{event: event, handlerFunc: m}
var stateEventHandlers []EventHandler
if h, ok := g.handlers[state]; ok {
stateEventHandlers = append(h, eventHandler)
} else {
stateEventHandlers = append(stateEventHandlers, eventHandler)
}
g.handlers[state] = stateEventHandlers
}
}
//Sync handler. For now, just support noop and shutdown
g.sync.handlers[NOOP] = noopHandler(g, NOOP)
g.sync.handlers[STOP] = noopHandler(g, STOP)
}
func (g *GenFSM) doStart() {
for !g.shutdown{
select {
case e, _ := <-g.eventsChannel:
g.handleEvent(e)
case r, _ := <-g.sync.req:
g.handleSync(r)
}
}
}
func (g *GenFSM) handleEvent(e EventMessage) {
defer func() {
if r := recover(); r != nil {
g.errorChannel <- errors.New(r.(string))
}
}()
eventHandler, err := g.getHandler(e.Kind)
if err != nil {
fmt.Printf("%s\n", err.Error())
g.errorChannel <- err
fmt.Printf("Checking if there is a generic `handle_info` handler\n")
eventHandler, err = g.getGenericHandler()
if err != nil {
fmt.Printf("Cannot find a generic handler `handle_info`\n")
g.errorChannel <- err
return
}
}
g.cancelTimer()
values := []reflect.Value{reflect.ValueOf(g.fsm)}
for _, d := range e.Data {
values = append(values, reflect.ValueOf(d))
}
returnValues := eventHandler.handlerFunc.Func.Call(values)
g.currentState = State(returnValues[0].String())
if len(returnValues) == 2 {
timeout := returnValues[1].Interface().(time.Duration)
g.scheduleTimeout(timeout)
}
g.errorChannel <- nil
}
func getHandler(handlers map[State][]EventHandler, state State, event Event) (EventHandler, error) {
stateHandlers, ok := handlers[state]
if !ok {
return EventHandler{}, errors.New(fmt.Sprintf("No handlers found for state %s", state))
}
for _, h := range stateHandlers {
if h.event == event {
return h, nil
}
}
return EventHandler{}, errors.New(fmt.Sprintf("No handlers found for state `%s` and event `%s` ", state, event))
}
func (g *GenFSM) getHandler(event Event) (EventHandler, error) {
return getHandler(g.handlers, g.currentState, event)
}
func (g *GenFSM) getGenericHandler() (EventHandler, error) {
return getHandler(g.handlers, genericState, genericEvent)
}
func (g *GenFSM) handleSync(req interface{}) {
if h, ok := g.sync.handlers[req]; ok {
resp := h()
g.sync.resp <- resp
}else {
fmt.Println(req)
g.sync.resp <- 404
}
if req != nil && STOP == req.(string) {
g.shutdown = true
g.closeAllChannels()
}
}
func noopHandler(g *GenFSM, req string) func() interface{} {
return func() interface{} {
return req
}
}
func (g *GenFSM) closeAllChannels() {
close(g.eventsChannel)
close(g.errorChannel)
close(g.sync.req)
close(g.sync.resp)
}
func (g *GenFSM) scheduleTimeout(timeout time.Duration) {
if timeout == -1 {
return
}
g.timer = time.NewTimer(timeout)
go func() {
<-g.timer.C
g.SendEvent(TIMEOUT)
}()
}
func (g *GenFSM) cancelTimer() {
if g.timer != nil {
g.timer.Stop()
}
}
func (g *GenFSM) SendEvent(kind Event, data ...interface{}) {
g.eventsChannel <- EventMessage{kind, data}
}
func (g *GenFSM) SendSyncReq(req interface{}) (resp interface{}) {
g.sync.req <- req
resp = <-g.sync.resp
return resp
}
func (g *GenFSM) Wait() {
g.SendSyncReq(NOOP)
}
func (g *GenFSM) Stop() {
g.cancelTimer()
g.SendSyncReq(STOP)
}
func (g *GenFSM) GetCurrentState() State {
return g.currentState
}