refactor eventHandlers into EventManager

event.go

@@ -2,21 +2,33 @@ package vabastegi
 
 import "time"
 
-// Event is what Vabastegi event look like.
+// Event is what Vabastegi event looks like.
 type Event interface {
 	event() // it's private to prevent outside implementation.
 }
 
-// EventHandlers is list of EventHandler.
-type EventHandlers []EventHandler
+// eventManager responsible to manage the event system.
+type eventManager struct {
+	handlers []EventHandler
+}
+
+// newEventManager create a new instance of eventManager.
+func newEventManager(handlers []EventHandler) *eventManager {
+	return &eventManager{handlers: handlers}
+}
 
 // Publish passed event using event handlers.
-func (e EventHandlers) Publish(event Event) {
-	for _, handler := range e {
+func (e *eventManager) Publish(event Event) {
+	for _, handler := range e.handlers {
 		handler.OnEvent(event)
 	}
 }
 
+// Register event handler.
+func (e *eventManager) Register(handler EventHandler) {
+	e.handlers = append(e.handlers, handler)
+}
+
 // EventHandler used if you need to handle the events.
 type EventHandler interface {
 	OnEvent(event Event)
@@ -106,15 +118,12 @@ type OnApplicationShutdownExecuting struct {
 	// ShutdownAt is the time shutdown happened.
 	ShutdownAt time.Time
 
-	// Reason is the reason for shutdown the application.
-	Reason string
+	// Cause is the reason for shutdown the application.
+	Cause error
 }
 
 // OnApplicationShutdownExecuted is emitted after the application Shutdown has been executed.
 type OnApplicationShutdownExecuted struct {
-	// Reason is the reason for shutdown the application.
-	Reason string
-
 	// Runtime specifies how long it took to run this hook.
 	Runtime time.Duration
 

go.mod

@@ -2,4 +2,4 @@ module github.com/mrsoftware/vabastegi
 
 go 1.18.0
 
-require github.com/mrsoftware/errors v0.1.0
+require github.com/mrsoftware/errors v0.2.0-alpha.3

go.sum

@@ -1,8 +1,8 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/mrsoftware/errors v0.1.0 h1:5MSHsrsqlBMPbNzwobVt39IpgsVee7LuSe+n8aQWPsI=
-github.com/mrsoftware/errors v0.1.0/go.mod h1:iHqx83gamUM9jhiV/rWZuVZe54NVqtqkIDnvZHywSM8=
+github.com/mrsoftware/errors v0.2.0-alpha.3 h1:T6UTulgnvEwUF+naTksmd6bO2tHb3hrTKdMm0Wxc0SI=
+github.com/mrsoftware/errors v0.2.0-alpha.3/go.mod h1:iHqx83gamUM9jhiV/rWZuVZe54NVqtqkIDnvZHywSM8=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

lifecycle.go

@@ -0,0 +1,140 @@
+package vabastegi
+
+import (
+	"context"
+	"os/signal"
+	"reflect"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/mrsoftware/errors"
+)
+
+// ShutdownListener is what you need to pass to OnShutdown method.
+type ShutdownListener = func(ctx context.Context) error
+
+// lifecycle manage application lifecycle like running task or shutdown.
+type lifecycle struct {
+	listeners []ShutdownListener
+	publisher *eventManager
+	ctx       context.Context
+	cancel    context.CancelCauseFunc
+	waitGroup *errors.WaitGroup
+}
+
+// newLifecycle create a new instance of lifecycle.
+func newLifecycle(ctx context.Context, publisher *eventManager) *lifecycle {
+	waitGroup := errors.NewWaitGroup(errors.WaitGroupWithContext(ctx), errors.WaitGroupWithStopOnError())
+
+	return &lifecycle{
+		listeners: make([]ShutdownListener, 0),
+		publisher: publisher,
+		ctx:       waitGroup.Context(),
+		cancel:    waitGroup.Stop,
+		waitGroup: waitGroup,
+	}
+}
+
+// Wait on shutdown or application finish.
+func (l *lifecycle) Wait() error {
+	var err error
+	select {
+	case <-l.ctx.Done():
+		err = l.ctx.Err()
+	case err = <-errors.WaitChanel(l.waitGroup):
+		l.Stop(err)
+	}
+
+	return l.callShutdownListeners(l.ctx, err)
+}
+
+// RegisterGracefulShutdown start listing on os signal and cancel the parent context on getting one.
+func (l *lifecycle) RegisterGracefulShutdown() {
+	ctx, cancel := signal.NotifyContext(l.ctx, syscall.SIGINT, syscall.SIGTERM)
+
+	l.ctx, l.cancel = ctx, cancelToCancelCause(cancel)
+}
+
+// Stop the application.
+func (l *lifecycle) Stop(cause error) {
+	l.cancel(cause)
+}
+
+// GetContext of lifecycle.
+func (l *lifecycle) GetContext() context.Context {
+	return l.ctx
+}
+
+// do Shut down the application.
+func (l *lifecycle) callShutdownListeners(ctx context.Context, cause error) error {
+	errList := errors.NewMultiError()
+
+	startAt := time.Now()
+
+	l.publisher.Publish(&OnApplicationShutdownExecuting{
+		Cause:      cause,
+		ShutdownAt: startAt,
+	})
+
+	defer func() {
+		l.publisher.Publish(&OnApplicationShutdownExecuted{
+			Runtime: time.Now().Sub(startAt),
+			Err:     errList.Err(),
+		})
+	}()
+
+	for _, fn := range l.listeners {
+		errList.Add(l.shutdown(ctx, fn))
+	}
+
+	return errList.Err()
+}
+
+func (l *lifecycle) shutdown(ctx context.Context, callback ShutdownListener) (err error) {
+	startAt := time.Now()
+
+	l.publisher.Publish(&OnShutdownExecuting{
+		ProviderName: getProviderName(callback, 1),
+		CallerPath:   getProviderName(callback, -1),
+		ShutdownAt:   startAt,
+	})
+
+	defer func() {
+		l.publisher.Publish(&OnShutdownExecuted{
+			ProviderName: getProviderName(callback, 1),
+			CallerPath:   getProviderName(callback, -1),
+			Runtime:      time.Now().Sub(startAt),
+			Err:          err,
+		})
+	}()
+
+	return callback(ctx)
+}
+
+// OnShutdown add callback to a list of listeners.
+func (l *lifecycle) OnShutdown(callback ShutdownListener) {
+	l.listeners = append(l.listeners, callback)
+}
+
+// RunTask in the background.
+func (l *lifecycle) RunTask(ctx context.Context, fn func(ctx context.Context) error) {
+	l.waitGroup.DoWithContext(ctx, fn)
+}
+
+func getProviderName(creator interface{}, index int) string {
+	reference := runtime.FuncForPC(reflect.ValueOf(creator).Pointer()).Name()
+	if index == -1 {
+		return reference
+	}
+
+	parts := strings.Split(reference, ".")
+
+	return parts[len(parts)-(1+index)]
+}
+
+// cancelToCancelCause is just a wrapper to turn context.CancelFunc into context.CancelCauseFunc.
+func cancelToCancelCause(cancelFunc context.CancelFunc) context.CancelCauseFunc {
+	return func(cause error) { cancelFunc() }
+}

logger.go

@@ -75,7 +75,7 @@ func (l *EventLogger) OnEvent(event Event) {
 	case *OnShutdownExecuting:
 		l.log(InfoLogLevel, "Shutting Down %s", e.ProviderName)
 	case *OnApplicationShutdownExecuting:
-		l.log(InfoLogLevel, "Shutting Down Application: %s", e.Reason)
+		l.log(InfoLogLevel, "Shutting Down Application: %s", e.Cause)
 	case *OnLog:
 		l.log(e.Level, e.Message, e.Args...)
 	}

options.go

@@ -1,10 +1,13 @@
 package vabastegi
 
+import "context"
+
 // Options of Vabastegi.
 type Options struct {
 	GracefulShutdown bool
 	AppName          string
-	EventHandlers    EventHandlers
+	EventHandlers    []EventHandler
+	Ctx              context.Context
 }
 
 // Option of Vabastegi.
@@ -30,3 +33,10 @@ func WithEventHandlers(handlers ...EventHandler) Option {
 		options.EventHandlers = append(options.EventHandlers, handlers...)
 	}
 }
+
+// WithContext used if you need to pass custom context.
+func WithContext(ctx context.Context) Option {
+	return func(options *Options) {
+		options.Ctx = ctx
+	}
+}