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machine_impl.go
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machine_impl.go
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package statemachine
import (
"context"
"errors"
"fmt"
"reflect"
"sync"
"time"
"github.com/ayushmaanbhav/statemachine-go/internal/dynafunc"
)
type machineImpl struct {
def *MachineDef
previousState string
currentState string
supermachine *machineImpl
submachines map[string][]*machineImpl
mutex sync.RWMutex
hasExited bool
ctxTimedEvents context.Context
stopTimedEvents context.CancelFunc
}
// NewMachine returns a zero-valued instance of machine, which implements
// Machine.
func NewMachine() Machine {
ctxTimedEvents, stopTimedEvents := context.WithCancel(context.Background())
return &machineImpl{
def: NewMachineDef(),
submachines: map[string][]*machineImpl{},
ctxTimedEvents: ctxTimedEvents,
stopTimedEvents: stopTimedEvents,
}
}
// BuildNewMachine creates a zero-valued instance of machine, and builds it
// using the passed machineBuilderFn arg.
func BuildNewMachine(machineBuilderFn func(machineBuilder MachineBuilder)) Machine {
machine := NewMachine()
machine.Build(machineBuilderFn)
return machine
}
func (m *machineImpl) Build(machineBuilderFn func(machineBuilder MachineBuilder)) {
machineBuilder := NewMachineBuilder()
machineBuilderFn(machineBuilder)
machineBuilder.Build(m)
}
// SetMachineDef implements MachineBuildable.
func (m *machineImpl) SetMachineDef(def *MachineDef) {
m.mutex.Lock()
defer m.mutex.Unlock()
// b, _ := json.MarshalIndent(def, "", " ")
// // b, _ := hclencoder.Encode(def)
// fmt.Printf("machine def = %s\n", string(b))
m.def = def
if err := m.setCurrentState(m.def.InitialState); err != nil {
panic(err)
}
m.restartTimedEventsLoops()
}
func (m *machineImpl) GetID() string {
return m.def.ID
}
func (m *machineImpl) restartTimedEventsLoops() {
for event, eventDef := range m.def.Events {
if eventDef.TimedEvery > 0 {
go func(event string, timedEvery time.Duration) {
// fmt.Printf("event=%s timed_every=%d\n", event, timedEvery)
for {
select {
case <-time.After(timedEvery):
// fmt.Printf("firing timed event '%s'\n", event)
_ = m.Fire(event)
case <-m.ctxTimedEvents.Done():
// fmt.Printf("stopping timed event '%s'\n", event)
return
}
}
}(event, eventDef.TimedEvery)
}
}
}
// GetStateMap implements Machine.
func (m *machineImpl) GetStateMap() StateMap {
substate := StateMap{}
if submachines, ok := m.submachines[m.currentState]; ok {
for _, submachine := range submachines {
if _, ok := submachine.submachines[submachine.currentState]; ok {
substate[submachine.def.ID] = submachine.GetStateMap()
} else {
substate[submachine.def.ID] = submachine.currentState
}
}
}
return StateMap{
m.currentState: substate,
}
}
// GetState implements Machine.
func (m *machineImpl) GetState() string {
return m.currentState
}
// SetCurrentState implements Machine.
func (m *machineImpl) SetCurrentState(state interface{}) error {
m.mutex.Lock()
defer m.mutex.Unlock()
return m.setCurrentState(state)
}
// IsState implements Machine.
func (m *machineImpl) IsState(state string) bool {
return m.GetState() == state
}
// Send implements Machine.
func (m *machineImpl) Send(signal Message) error {
switch signal.(type) {
case TriggerEvent:
return m.Fire(signal.(TriggerEvent).Event)
case OverrideState:
return m.SetCurrentState(signal.(OverrideState).State)
}
return errors.New("no such signal")
}
// Fire implements Machine.
func (m *machineImpl) Fire(event string) (err error) {
m.mutex.Lock()
defer func() {
if err != nil {
args := make(map[reflect.Type]interface{})
args[reflect.TypeOf(new(Event))] = &eventImpl{name: event}
args[reflect.TypeOf(new(error))] = err
for _, callbackDef := range m.def.FailureCallbacks {
if callbackDef.MatchesEvent(event) {
for _, callback := range callbackDef.Do {
m.exec(callback.Func, args)
}
}
}
}
m.mutex.Unlock()
if m.hasExited {
// TODO: should we wait for `<-m.stoppedTimedEvents`?
m.stopTimedEvents()
*m = machineImpl{}
}
}()
if m.IsState("") {
err = errors.New("state machine not initialized")
return
}
// fmt.Printf("\n---\n🔁 %s\n", event)
// defer func() { fmt.Printf("=> %s\n---\n", m.GetState()) }()
fromState := m.GetState()
var transition Transition
transition, err = m.findTransition(event, fromState)
if err != nil {
return
}
err = m.applyTransition(event, transition)
return
}
func (m *machineImpl) findTransition(event string, fromState string) (transition Transition, err error) {
eventDef, ok := m.def.Events[event]
if !ok {
err = errors.New("no such event")
return
}
transition, err = m.matchTransition(eventDef.Transitions, fromState)
if err == nil || eventDef.Choice == nil {
return
}
transition, err = m.findChoiceTransition(event, eventDef, fromState)
return
}
func (m *machineImpl) findChoiceTransition(event string, eventDef *EventDef, fromState string) (transition Transition, err error) {
args := make(map[reflect.Type]interface{})
args[reflect.TypeOf(new(Machine))] = m
args[reflect.TypeOf(new(Event))] = &eventImpl{name: event}
if eventDef.Choice.UnlessGuard != nil {
if ok := execGuard(eventDef.Choice.UnlessGuard.Guard, args); ok {
err = ErrTransitionNotAllowed
return
}
}
if execChoice(eventDef.Choice.Condition.Condition, args) {
if eventDef.Choice.OnTrue.Choice != nil {
transition, err = m.findChoiceTransition(event, eventDef.Choice.OnTrue, fromState)
return
}
transition, err = m.matchTransition(eventDef.Choice.OnTrue.Transitions, fromState)
return
}
if eventDef.Choice.OnFalse.Choice != nil {
transition, err = m.findChoiceTransition(event, eventDef.Choice.OnFalse, fromState)
return
}
transition, err = m.matchTransition(eventDef.Choice.OnFalse.Transitions, fromState)
return
}
func (m *machineImpl) matchTransition(transitions []*TransitionDef, fromState string) (transition Transition, err error) {
for _, transitionDef := range transitions {
matches := transitionDef.Matches(fromState)
if !matches {
err = ErrNoMatchingTransition
continue
}
if !transitionDef.IsAllowed(fromState, m) {
err = ErrTransitionNotAllowed
continue
}
transition = newTransitionImpl(fromState, transitionDef.To)
err = nil
return
}
err = ErrNoMatchingTransition
return
}
func (m *machineImpl) Submachine(idPath ...string) (Machine, error) {
for _, submachine := range m.submachines[m.currentState] {
if submachine.def.ID == idPath[0] {
if len(idPath) > 1 {
return submachine.Submachine(idPath[1:]...)
}
return submachine, nil
}
}
return nil, errors.New("submachine not active")
}
func (m *machineImpl) setCurrentStateMap(state StateMap) error {
for rootState, subStates := range state {
switch subStates.(type) {
case nil:
// fmt.Printf("setting state to '%s'\n", rootState)
return m.setCurrentState(rootState)
case StateMap:
// fmt.Printf("setting state to '%s'\n", rootState)
if err := m.setCurrentState(rootState); err != nil {
return err
}
for id, state := range subStates.(StateMap) {
for _, submachine := range m.submachines[rootState] {
if submachine.def.ID == id {
switch state.(type) {
case StateMap:
// fmt.Printf("nesting into submachine '%s'\n", id)
if err := submachine.setCurrentStateMap(state.(StateMap)); err != nil {
return err
}
case string:
// fmt.Printf("setting submachine '%s' to '%s'\n", id, state)
if err := submachine.SetCurrentState(state); err != nil {
return err
}
default:
return ErrStateTypeNotSupported
}
}
}
}
default:
if err := m.setCurrentState(rootState); err != nil {
return err
}
return ErrStateTypeNotSupported
}
// there is only one kv in any given StateMap
break
}
return nil
}
func (m *machineImpl) setCurrentState(state interface{}) error {
if state, ok := state.(StateMap); ok {
if err := m.setCurrentStateMap(state); err != nil {
return err
}
return nil
}
if state, ok := state.(string); ok {
for _, s := range m.def.States {
if s == state {
m.previousState = m.currentState
m.currentState = state
return nil
}
}
for s, submachineDefs := range m.def.Submachines {
if s == state {
m.submachines[state] = []*machineImpl{}
for _, submachineDef := range submachineDefs {
submachine := &machineImpl{
supermachine: m,
submachines: map[string][]*machineImpl{},
}
submachine.SetMachineDef(submachineDef)
m.submachines[state] = append(m.submachines[state], submachine)
}
m.previousState = m.currentState
m.currentState = state
return nil
}
}
}
return ErrStateTypeNotSupported
}
func (m *machineImpl) applyTransition(event string, transition Transition) error {
fromState := m.GetState()
args := make(map[reflect.Type]interface{})
args[reflect.TypeOf(new(Transition))] = transition
args[reflect.TypeOf(new(string))] = event
for _, callbackDef := range m.def.BeforeCallbacks {
if callbackDef.Matches(fromState, transition.To()) {
for _, callback := range callbackDef.Do {
err := m.exec(callback.Func, args)
if err != nil {
return err
}
}
}
}
var matchingCallbacks []*TransitionCallbackFuncDef
for _, callbackDef := range m.def.AroundCallbacks {
if callbackDef.Matches(fromState, transition.To()) {
matchingCallbacks = append(matchingCallbacks, callbackDef.Do...)
}
}
applyTransition := func() {
m.setCurrentState(transition.To())
}
err := m.applyTransitionAroundCallbacks(matchingCallbacks, args, applyTransition)
if err != nil {
return err
}
for _, callbackDef := range m.def.AfterCallbacks {
if !callbackDef.Matches(fromState, transition.To()) {
continue
}
for _, callback := range callbackDef.Do {
m.exec(callback.Func, args)
}
if callbackDef.ExitToState != "" && m.supermachine != nil {
if err := m.supermachine.applyTransition(
event,
newTransitionImpl(m.supermachine.currentState, callbackDef.ExitToState),
); err != nil {
return fmt.Errorf("could not exit submachine: %s", err)
}
m.hasExited = true
return nil
}
}
return nil
}
// callback1(next: {
// callback2(next: {
// callback3(next: {
// applyTransition()
// })
// })
// })
func (m *machineImpl) applyTransitionAroundCallbacks(callbacks []*TransitionCallbackFuncDef, args map[reflect.Type]interface{}, applyTransition func()) error {
if len(callbacks) == 0 {
applyTransition()
return nil
}
calledBackNext := false
args[reflect.TypeOf(new(func()))] = func() {
calledBackNext = true
m.applyTransitionAroundCallbacks(callbacks[1:], args, applyTransition)
}
err := m.exec(callbacks[0].Func, args)
if !calledBackNext && err == nil {
panic("callbacks must call next() when err is nil")
}
return err
}
func (m *machineImpl) exec(callback TransitionCallbackFunc, args map[reflect.Type]interface{}) error {
args[reflect.TypeOf(new(Machine))] = m
fn := dynafunc.NewDynamicFunc(callback, args)
return fn.Call()
}