feat: add durable statestore example (#102)

example/durablestate/main.go

@@ -0,0 +1,145 @@
+/*
+ * 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/statestore/memory"
+)
+
+func main() {
+	// create the go context
+	ctx := context.Background()
+	// create the event store
+	durableStore := memory.NewStateStore()
+	// connect the event store
+	_ = durableStore.Connect(ctx)
+	// create the ego engine
+	engine := ego.NewEngine("Sample", nil, ego.WithStateStore(durableStore))
+	// 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.DurableStateEntity(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
+	_ = durableStore.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.DurableStateBehavior = &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, priorVersion uint64, priorState ego.State) (event ego.State, newVersion uint64, err error) {
+	switch cmd := command.(type) {
+	case *samplepb.CreateAccount:
+		// TODO in production grid app validate the command using the prior state
+		return &samplepb.Account{
+			AccountId:      a.id,
+			AccountBalance: cmd.GetAccountBalance(),
+		}, priorVersion + 1, nil
+
+	case *samplepb.CreditAccount:
+		if cmd.GetAccountId() == a.id {
+			// TODO in production grid app validate the command using the prior state
+			account := priorState.(*samplepb.Account)
+			bal := account.GetAccountBalance() + cmd.GetBalance()
+
+			return &samplepb.Account{
+				AccountId:      a.id,
+				AccountBalance: bal,
+			}, priorVersion + 1, nil
+		}
+		return nil, 0, errors.New("command sent to the wrong entity")
+
+	default:
+		return nil, 0, errors.New("unhandled command")
+	}
+}