add durable statestore example

example/eventsource/main.go

@@ -0,0 +1,165 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022-2024 Tochemey
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+ package main
+
+ import (
+	 "context"
+	 "errors"
+	 "log"
+	 "os"
+	 "os/signal"
+	 "syscall"
+	 "time"
+
+	 "github.com/google/uuid"
+	 "google.golang.org/protobuf/proto"
+
+	 "github.com/tochemey/ego/v3"
+	 samplepb "github.com/tochemey/ego/v3/example/pbs/sample/pb/v1"
+	 "github.com/tochemey/ego/v3/plugins/eventstore/memory"
+ )
+
+ func main() {
+	 // create the go context
+	 ctx := context.Background()
+	 // create the event store
+	 eventStore := memory.NewEventsStore()
+	 // connect the event store
+	 _ = eventStore.Connect(ctx)
+	 // create the ego engine
+	 engine := ego.NewEngine("Sample", eventStore)
+	 // start ego engine
+	 _ = engine.Start(ctx)
+	 // create a persistence id
+	 entityID := uuid.NewString()
+	 // create an entity behavior with a given id
+	 behavior := NewAccountBehavior(entityID)
+	 // create an entity
+	 _ = engine.Entity(ctx, behavior)
+
+	 // send some commands to the pid
+	 var command proto.Message
+	 // create an account
+	 command = &samplepb.CreateAccount{
+		 AccountId:      entityID,
+		 AccountBalance: 500.00,
+	 }
+	 // send the command to the actor. Please don't ignore the error in production grid code
+	 reply, _, _ := engine.SendCommand(ctx, entityID, command, time.Minute)
+	 account := reply.(*samplepb.Account)
+	 log.Printf("current balance on opening: %v", account.GetAccountBalance())
+
+	 // send another command to credit the balance
+	 command = &samplepb.CreditAccount{
+		 AccountId: entityID,
+		 Balance:   250,
+	 }
+
+	 reply, _, _ = engine.SendCommand(ctx, entityID, command, time.Minute)
+	 account = reply.(*samplepb.Account)
+	 log.Printf("current balance after a credit of 250: %v", account.GetAccountBalance())
+
+	 // capture ctrl+c
+	 interruptSignal := make(chan os.Signal, 1)
+	 signal.Notify(interruptSignal, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
+	 <-interruptSignal
+
+	 // disconnect the event store
+	 _ = eventStore.Disconnect(ctx)
+	 // stop the actor system
+	 _ = engine.Stop(ctx)
+	 os.Exit(0)
+ }
+
+ // AccountBehavior implements EventSourcedBehavior
+ type AccountBehavior struct {
+	 id string
+ }
+
+ // make sure that AccountBehavior is a true persistence behavior
+ var _ ego.EventSourcedBehavior = &AccountBehavior{}
+
+ // NewAccountBehavior creates an instance of AccountBehavior
+ func NewAccountBehavior(id string) *AccountBehavior {
+	 return &AccountBehavior{id: id}
+ }
+
+ // ID returns the id
+ func (a *AccountBehavior) ID() string {
+	 return a.id
+ }
+
+ // InitialState returns the initial state
+ func (a *AccountBehavior) InitialState() ego.State {
+	 return ego.State(new(samplepb.Account))
+ }
+
+ // HandleCommand handles every command that is sent to the persistent behavior
+ func (a *AccountBehavior) HandleCommand(_ context.Context, command ego.Command, _ ego.State) (events []ego.Event, err error) {
+	 switch cmd := command.(type) {
+	 case *samplepb.CreateAccount:
+		 // TODO in production grid app validate the command using the prior state
+		 return []ego.Event{
+			 &samplepb.AccountCreated{
+				 AccountId:      cmd.GetAccountId(),
+				 AccountBalance: cmd.GetAccountBalance(),
+			 },
+		 }, nil
+
+	 case *samplepb.CreditAccount:
+		 // TODO in production grid app validate the command using the prior state
+		 return []ego.Event{
+			 &samplepb.AccountCredited{
+				 AccountId:      cmd.GetAccountId(),
+				 AccountBalance: cmd.GetBalance(),
+			 },
+		 }, nil
+
+	 default:
+		 return nil, errors.New("unhandled command")
+	 }
+ }
+
+ // HandleEvent handles every event emitted
+ func (a *AccountBehavior) HandleEvent(_ context.Context, event ego.Event, priorState ego.State) (state ego.State, err error) {
+	 switch evt := event.(type) {
+	 case *samplepb.AccountCreated:
+		 return &samplepb.Account{
+			 AccountId:      evt.GetAccountId(),
+			 AccountBalance: evt.GetAccountBalance(),
+		 }, nil
+
+	 case *samplepb.AccountCredited:
+		 account := priorState.(*samplepb.Account)
+		 bal := account.GetAccountBalance() + evt.GetAccountBalance()
+		 return &samplepb.Account{
+			 AccountId:      evt.GetAccountId(),
+			 AccountBalance: bal,
+		 }, nil
+
+	 default:
+		 return nil, errors.New("unhandled event")
+	 }
+ }