chore: initial commit

internal/svc/warehouse/api/gateway.go

@@ -0,0 +1,39 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package api
+
+import (
+	"context"
+
+	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
+	"github.com/rs/zerolog/log"
+
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+	"github.com/hexolan/stocklet/internal/pkg/serve"
+	"github.com/hexolan/stocklet/internal/svc/warehouse"
+)
+
+func PrepareGateway(cfg *warehouse.ServiceConfig) *runtime.ServeMux {
+	mux, clientOpts := serve.NewGatewayServeBase(&cfg.Shared)
+
+	ctx := context.Background()
+	err := pb.RegisterWarehouseServiceHandlerFromEndpoint(ctx, mux, serve.GetAddrToGrpc("localhost"), clientOpts)
+	if err != nil {
+		log.Panic().Err(err).Msg("failed to register endpoint for gateway")
+	}
+
+	return mux
+}

internal/svc/warehouse/api/grpc.go

@@ -0,0 +1,30 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package api
+
+import (
+	"google.golang.org/grpc"
+
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+	"github.com/hexolan/stocklet/internal/pkg/serve"
+	"github.com/hexolan/stocklet/internal/svc/warehouse"
+)
+
+func PrepareGrpc(cfg *warehouse.ServiceConfig, svc *warehouse.WarehouseService) *grpc.Server {
+	svr := serve.NewGrpcServeBase(&cfg.Shared)
+	pb.RegisterWarehouseServiceServer(svr, svc)
+	return svr
+}

internal/svc/warehouse/config.go

@@ -0,0 +1,42 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package warehouse
+
+import (
+	"github.com/hexolan/stocklet/internal/pkg/config"
+)
+
+// Order Service Configuration
+type ServiceConfig struct {
+	// Core Configuration
+	Shared config.SharedConfig
+
+	// Dynamically loaded configuration
+	Postgres config.PostgresConfig
+	Kafka    config.KafkaConfig
+}
+
+// load the base service configuration
+func NewServiceConfig() (*ServiceConfig, error) {
+	cfg := ServiceConfig{}
+
+	// Load the core configuration
+	if err := cfg.Shared.Load(); err != nil {
+		return nil, err
+	}
+
+	return &cfg, nil
+}

internal/svc/warehouse/controller/kafka.go

@@ -0,0 +1,161 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package controller
+
+import (
+	"context"
+
+	"github.com/rs/zerolog/log"
+	"github.com/twmb/franz-go/pkg/kgo"
+	"google.golang.org/protobuf/proto"
+
+	"github.com/hexolan/stocklet/internal/pkg/messaging"
+	eventpb "github.com/hexolan/stocklet/internal/pkg/protogen/events/v1"
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+	"github.com/hexolan/stocklet/internal/svc/warehouse"
+)
+
+type kafkaController struct {
+	cl *kgo.Client
+
+	svc pb.WarehouseServiceServer
+
+	ctx       context.Context
+	ctxCancel context.CancelFunc
+}
+
+func NewKafkaController(cl *kgo.Client) warehouse.ConsumerController {
+	// Create a cancellable context for the consumer
+	ctx, ctxCancel := context.WithCancel(context.Background())
+
+	// Ensure the required Kafka topics exist
+	err := messaging.EnsureKafkaTopics(
+		cl,
+
+		messaging.Warehouse_Stock_Created_Topic,
+		messaging.Warehouse_Stock_Added_Topic,
+		messaging.Warehouse_Stock_Removed_Topic,
+		messaging.Warehouse_Reservation_Failed_Topic,
+		messaging.Warehouse_Reservation_Reserved_Topic,
+		messaging.Warehouse_Reservation_Returned_Topic,
+		messaging.Warehouse_Reservation_Consumed_Topic,
+
+		messaging.Order_State_Pending_Topic,
+		messaging.Shipping_Shipment_Allocation_Topic,
+		messaging.Payment_Processing_Topic,
+	)
+	if err != nil {
+		log.Warn().Err(err).Msg("kafka: raised attempting to ensure svc topics")
+	}
+
+	// Add the consumption topics
+	cl.AddConsumeTopics(
+		messaging.Order_State_Pending_Topic,
+		messaging.Shipping_Shipment_Allocation_Topic,
+		messaging.Payment_Processing_Topic,
+	)
+
+	return &kafkaController{cl: cl, ctx: ctx, ctxCancel: ctxCancel}
+}
+
+func (c *kafkaController) Attach(svc pb.WarehouseServiceServer) {
+	c.svc = svc
+}
+
+func (c *kafkaController) Start() {
+	if c.svc == nil {
+		log.Panic().Msg("consumer: no service interface attached")
+	}
+
+	for {
+		fetches := c.cl.PollFetches(c.ctx)
+		if errs := fetches.Errors(); len(errs) > 0 {
+			log.Panic().Any("kafka-errs", errs).Msg("consumer: unrecoverable kafka errors")
+		}
+
+		fetches.EachTopic(func(ft kgo.FetchTopic) {
+			switch ft.Topic {
+			case messaging.Order_State_Pending_Topic:
+				c.consumeOrderPendingEventTopic(ft)
+			case messaging.Shipping_Shipment_Allocation_Topic:
+				c.consumeShipmentAllocationEventTopic(ft)
+			case messaging.Payment_Processing_Topic:
+				c.consumePaymentProcessedEventTopic(ft)
+			default:
+				log.Warn().Str("topic", ft.Topic).Msg("consumer: recieved records from unexpected topic")
+			}
+		})
+	}
+}
+
+func (c *kafkaController) Stop() {
+	// Cancel the consumer context
+	c.ctxCancel()
+}
+
+func (c *kafkaController) consumeOrderPendingEventTopic(ft kgo.FetchTopic) {
+	log.Info().Str("topic", ft.Topic).Msg("consumer: recieved records from topic")
+
+	// Process each message from the topic
+	ft.EachRecord(func(record *kgo.Record) {
+		// Unmarshal the event
+		var event eventpb.OrderPendingEvent
+		err := proto.Unmarshal(record.Value, &event)
+		if err != nil {
+			log.Panic().Err(err).Msg("consumer: failed to unmarshal event")
+		}
+
+		// Process the event
+		ctx := context.Background()
+		c.svc.ProcessOrderPendingEvent(ctx, &event)
+	})
+}
+
+func (c *kafkaController) consumeShipmentAllocationEventTopic(ft kgo.FetchTopic) {
+	log.Info().Str("topic", ft.Topic).Msg("consumer: recieved records from topic")
+
+	// Process each message from the topic
+	ft.EachRecord(func(record *kgo.Record) {
+		// Unmarshal the event
+		var event eventpb.ShipmentAllocationEvent
+		err := proto.Unmarshal(record.Value, &event)
+		if err != nil {
+			log.Panic().Err(err).Msg("consumer: failed to unmarshal event")
+		}
+
+		// Process the event
+		ctx := context.Background()
+		c.svc.ProcessShipmentAllocationEvent(ctx, &event)
+	})
+}
+
+func (c *kafkaController) consumePaymentProcessedEventTopic(ft kgo.FetchTopic) {
+	log.Info().Str("topic", ft.Topic).Msg("consumer: recieved records from topic")
+
+	// Process each message from the topic
+	ft.EachRecord(func(record *kgo.Record) {
+		// Unmarshal the event
+		var event eventpb.PaymentProcessedEvent
+		err := proto.Unmarshal(record.Value, &event)
+		if err != nil {
+			log.Panic().Err(err).Msg("consumer: failed to unmarshal event")
+		}
+
+		// Process the event
+		ctx := context.Background()
+		c.svc.ProcessPaymentProcessedEvent(ctx, &event)
+	})
+}

internal/svc/warehouse/controller/postgres.go

@@ -0,0 +1,500 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package controller
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/hexolan/stocklet/internal/pkg/errors"
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+	"github.com/hexolan/stocklet/internal/svc/warehouse"
+)
+
+const (
+	pgProductStockBaseQuery     string = "SELECT product_id, quantity FROM product_stock"
+	pgReservationBaseQuery      string = "SELECT id, order_id, created_at FROM reservations"
+	pgReservationItemsBaseQuery string = "SELECT product_id, quantity FROM reservation_items"
+)
+
+type postgresController struct {
+	cl *pgxpool.Pool
+}
+
+func NewPostgresController(cl *pgxpool.Pool) warehouse.StorageController {
+	return postgresController{cl: cl}
+}
+
+func (c postgresController) GetProductStock(ctx context.Context, productId string) (*pb.ProductStock, error) {
+	return c.getProductStock(ctx, nil, productId)
+}
+
+func (c postgresController) getProductStock(ctx context.Context, tx *pgx.Tx, productId string) (*pb.ProductStock, error) {
+	// Determine if a db transaction is being used
+	var row pgx.Row
+	const query = pgProductStockBaseQuery + " WHERE product_id=$1"
+	if tx == nil {
+		row = c.cl.QueryRow(ctx, query, productId)
+	} else {
+		row = (*tx).QueryRow(ctx, query, productId)
+	}
+
+	// Scan row to protobuf obj
+	stock, err := scanRowToProductStock(row)
+	if err != nil {
+		return nil, err
+	}
+
+	return stock, nil
+}
+
+func (c postgresController) GetReservation(ctx context.Context, reservationId string) (*pb.Reservation, error) {
+	return c.getReservation(ctx, nil, reservationId)
+}
+
+func (c postgresController) getReservation(ctx context.Context, tx *pgx.Tx, reservationId string) (*pb.Reservation, error) {
+	// Determine if a db transaction is being used
+	var row pgx.Row
+	const query = pgReservationBaseQuery + " WHERE id=$1"
+	if tx == nil {
+		row = c.cl.QueryRow(ctx, query, reservationId)
+	} else {
+		row = (*tx).QueryRow(ctx, query, reservationId)
+	}
+
+	// Scan row to protobuf obj
+	reservation, err := scanRowToReservation(row)
+	if err != nil {
+		return nil, err
+	}
+
+	// Append items to reservation
+	reservation, err = c.appendItemsToReservation(ctx, tx, reservation)
+	if err != nil {
+		return nil, err
+	}
+
+	return reservation, nil
+}
+
+func (c postgresController) getReservationByOrderId(ctx context.Context, tx *pgx.Tx, orderId string) (*pb.Reservation, error) {
+	// Determine if a db transaction is being used
+	var row pgx.Row
+	const query = pgReservationBaseQuery + " WHERE order_id=$1"
+	if tx == nil {
+		row = c.cl.QueryRow(ctx, query, orderId)
+	} else {
+		row = (*tx).QueryRow(ctx, query, orderId)
+	}
+
+	// Scan row to protobuf obj
+	reservation, err := scanRowToReservation(row)
+	if err != nil {
+		return nil, err
+	}
+
+	// Append items to reservation
+	reservation, err = c.appendItemsToReservation(ctx, tx, reservation)
+	if err != nil {
+		return nil, err
+	}
+
+	return reservation, nil
+}
+
+func (c postgresController) CreateProductStock(ctx context.Context, productId string, startingQuantity int32) error {
+	// Begin a DB transaction
+	tx, err := c.cl.Begin(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+	}
+	defer tx.Rollback(ctx)
+
+	// Create stock
+	_, err = tx.Exec(ctx, "INSERT INTO product_stock (product_id, quantity) VALUES ($1, $2)", productId, startingQuantity)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to create product stock", err)
+	}
+
+	// Add the event to the outbox table with the transaction
+	evt, evtTopic, err := warehouse.PrepareStockCreatedEvent(&pb.ProductStock{ProductId: productId, Quantity: startingQuantity})
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+	}
+
+	_, err = tx.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", productId, evtTopic, evt)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+	}
+
+	// Commit the transaction
+	err = tx.Commit(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+	}
+
+	return nil
+}
+
+func (c postgresController) ReserveOrderStock(ctx context.Context, orderId string, orderMetadata warehouse.EventOrderMetadata, productQuantities map[string]int32) error {
+	// Begin a DB transaction
+	tx, err := c.cl.Begin(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+	}
+	defer tx.Rollback(ctx)
+
+	// Create reservation
+	var reservationId string
+	err = tx.QueryRow(ctx, "INSERT INTO reservations (order_id) VALUES ($1) RETURNING id", orderId).Scan(&reservationId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to create reservation", err)
+	}
+
+	// Reserve the items
+	insufficientStockProductIds := []string{}
+	for productId, quantity := range productQuantities {
+		err = c.reserveStock(ctx, &tx, reservationId, productId, quantity)
+		if err != nil {
+			insufficientStockProductIds = append(insufficientStockProductIds, productId)
+		}
+	}
+
+	// Ensure that all of the stock was reserved
+	if len(insufficientStockProductIds) > 0 {
+		// Add the event to the outbox table with the transaction
+		evt, evtTopic, err := warehouse.PrepareStockReservationEvent_Failed(orderId, orderMetadata, insufficientStockProductIds)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+		}
+
+		_, err = c.cl.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", orderId, evtTopic, evt)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+		}
+
+		return nil
+	}
+
+	// Add the event to the outbox table with the transaction
+	evt, evtTopic, err := warehouse.PrepareStockReservationEvent_Reserved(orderId, orderMetadata, reservationId, productQuantities)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+	}
+
+	_, err = tx.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", reservationId, evtTopic, evt)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+	}
+
+	// Commit the transaction
+	err = tx.Commit(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+	}
+
+	return nil
+}
+
+func (c postgresController) reserveStock(ctx context.Context, tx *pgx.Tx, reservationId string, productId string, quantity int32) error {
+	// Determine if a transaction has already been provided
+	var (
+		funcTx pgx.Tx
+		err    error
+	)
+	if tx != nil {
+		funcTx = *tx
+	} else {
+		funcTx, err = c.cl.Begin(ctx)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+		}
+		defer funcTx.Rollback(ctx)
+	}
+
+	// Subtract from quantity
+	_, err = funcTx.Exec(ctx, "UPDATE product_stock SET quantity = quantity - $1 WHERE product_id=$2", quantity, productId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to update product stock", err)
+	}
+
+	// Get updated stock
+	stock, err := c.getProductStock(ctx, tx, productId)
+	if err != nil {
+		return err
+	}
+
+	// Ensure that the stock is not negative
+	if stock.Quantity < 0 {
+		return errors.NewServiceError(errors.ErrCodeInvalidArgument, "insufficient stock")
+	}
+
+	// Add as reservation item
+	_, err = funcTx.Exec(ctx, "INSERT INTO reservation_items (reservation_id, product_id, quantity) VALUES ($1, $2, $3)", reservationId, productId, quantity)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to add as reservation item", err)
+	}
+
+	// Commit the transaction (if created in this func)
+	if tx == nil {
+		err = funcTx.Commit(ctx)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+		}
+	}
+
+	return nil
+}
+
+func (c postgresController) ReturnReservedOrderStock(ctx context.Context, orderId string) error {
+	// Begin a DB transaction
+	tx, err := c.cl.Begin(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+	}
+	defer tx.Rollback(ctx)
+
+	// Get the reservation
+	reservation, err := c.getReservationByOrderId(ctx, &tx, orderId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to locate order reservation", err)
+	}
+
+	// Return all of the reserved stock
+	for _, reservedStock := range reservation.ReservedStock {
+		err = c.returnReservedStock(ctx, &tx, reservation.Id, reservedStock.ProductId, reservedStock.Quantity)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to return reserved stock", err)
+		}
+	}
+
+	// Delete the reservation
+	_, err = tx.Exec(ctx, "DELETE FROM reservations WHERE id=$1", reservation.Id)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to delete reservation", err)
+	}
+
+	// Prepare and add reservation consumed event to outbox
+	evt, evtTopic, err := warehouse.PrepareStockReservationEvent_Returned(reservation.OrderId, reservation.Id, reservation.ReservedStock)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+	}
+
+	_, err = tx.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", reservation.Id, evtTopic, evt)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+	}
+
+	// Commit the transaction
+	err = tx.Commit(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+	}
+
+	return nil
+}
+
+func (c postgresController) returnReservedStock(ctx context.Context, tx *pgx.Tx, reservationId string, productId string, quantity int32) error {
+	// Determine if a transaction has already been provided
+	var (
+		funcTx pgx.Tx
+		err    error
+	)
+	if tx != nil {
+		funcTx = *tx
+	} else {
+		funcTx, err = c.cl.Begin(ctx)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+		}
+		defer funcTx.Rollback(ctx)
+	}
+
+	// Add back to stock quantity
+	_, err = funcTx.Exec(ctx, "UPDATE product_stock SET quantity = quantity + $1 WHERE product_id=$2", quantity, productId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to update product stock", err)
+	}
+
+	// Delete reservation item
+	_, err = funcTx.Exec(ctx, "DELETE FROM reservation_items WHERE reservation_id=$1 AND product_id=$2", reservationId, productId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to add as reservation item", err)
+	}
+
+	// Commit the transaction (if created in this func)
+	if tx == nil {
+		err = funcTx.Commit(ctx)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+		}
+	}
+
+	return nil
+}
+
+func (c postgresController) ConsumeReservedOrderStock(ctx context.Context, orderId string) error {
+	// Begin a DB transaction
+	tx, err := c.cl.Begin(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to begin transaction", err)
+	}
+	defer tx.Rollback(ctx)
+
+	// Get the reservation
+	reservation, err := c.getReservationByOrderId(ctx, &tx, orderId)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to locate order reservation", err)
+	}
+
+	// Delete the reservation
+	_, err = tx.Exec(ctx, "DELETE FROM reservations WHERE id=$1", reservation.Id)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to delete reservation", err)
+	}
+
+	// Dispatch stock removed events
+	for _, reservedStock := range reservation.ReservedStock {
+		evt, evtTopic, err := warehouse.PrepareStockRemovedEvent(reservedStock.ProductId, reservedStock.Quantity, &reservation.Id)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+		}
+
+		_, err = tx.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", reservedStock.ProductId, evtTopic, evt)
+		if err != nil {
+			return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+		}
+	}
+
+	// Prepare and add reservation consumed event to outbox
+	evt, evtTopic, err := warehouse.PrepareStockReservationEvent_Consumed(reservation.OrderId, reservation.Id, reservation.ReservedStock)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeService, "failed to create event", err)
+	}
+
+	_, err = tx.Exec(ctx, "INSERT INTO event_outbox (aggregateid, aggregatetype, payload) VALUES ($1, $2, $3)", reservation.Id, evtTopic, evt)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to insert event", err)
+	}
+
+	// Commit the transaction
+	err = tx.Commit(ctx)
+	if err != nil {
+		return errors.WrapServiceError(errors.ErrCodeExtService, "failed to commit transaction", err)
+	}
+
+	return nil
+}
+
+func (c postgresController) getReservationItems(ctx context.Context, tx *pgx.Tx, reservationId string) ([]*pb.ReservationStock, error) {
+	// Determine if transaction is being used.
+	var rows pgx.Rows
+	var err error
+	const query = pgReservationItemsBaseQuery + " WHERE reservation_id=$1"
+	if tx == nil {
+		rows, err = c.cl.Query(ctx, query, reservationId)
+	} else {
+		rows, err = (*tx).Query(ctx, query, reservationId)
+	}
+
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeService, "query error whilst fetching reserved items", err)
+	}
+
+	items := []*pb.ReservationStock{}
+	for rows.Next() {
+		var reservStock pb.ReservationStock
+
+		err := rows.Scan(
+			&reservStock.ProductId,
+			&reservStock.Quantity,
+		)
+		if err != nil {
+			return nil, errors.WrapServiceError(errors.ErrCodeService, "failed to scan a reservation item", err)
+		}
+
+		items = append(items, &reservStock)
+	}
+
+	if rows.Err() != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeService, "error scanning item rows", rows.Err())
+	}
+
+	return items, nil
+}
+
+// Append items to the reservation
+func (c postgresController) appendItemsToReservation(ctx context.Context, tx *pgx.Tx, reservation *pb.Reservation) (*pb.Reservation, error) {
+	reservedItems, err := c.getReservationItems(ctx, tx, reservation.Id)
+	if err != nil {
+		return nil, err
+	}
+
+	// Add the items to the reservation protobuf
+	reservation.ReservedStock = reservedItems
+
+	return reservation, nil
+}
+
+// Scan a postgres row to a protobuf object
+func scanRowToProductStock(row pgx.Row) (*pb.ProductStock, error) {
+	var stock pb.ProductStock
+
+	err := row.Scan(
+		&stock.ProductId,
+		&stock.Quantity,
+	)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return nil, errors.WrapServiceError(errors.ErrCodeNotFound, "stock not found", err)
+		} else {
+			return nil, errors.WrapServiceError(errors.ErrCodeExtService, "something went wrong scanning object", err)
+		}
+	}
+
+	return &stock, nil
+}
+
+// Scan a postgres row to a protobuf object
+func scanRowToReservation(row pgx.Row) (*pb.Reservation, error) {
+	var reservation pb.Reservation
+
+	// Temporary variables that require conversion
+	var tmpCreatedAt pgtype.Timestamp
+
+	err := row.Scan(
+		&reservation.Id,
+		&reservation.OrderId,
+		&tmpCreatedAt,
+	)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return nil, errors.WrapServiceError(errors.ErrCodeNotFound, "reservation not found", err)
+		} else {
+			return nil, errors.WrapServiceError(errors.ErrCodeExtService, "something went wrong scanning object", err)
+		}
+	}
+
+	// convert postgres timestamps to unix format
+	if tmpCreatedAt.Valid {
+		reservation.CreatedAt = tmpCreatedAt.Time.Unix()
+	}
+
+	return &reservation, nil
+}

internal/svc/warehouse/event.go

@@ -0,0 +1,141 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package warehouse
+
+import (
+	"github.com/hexolan/stocklet/internal/pkg/messaging"
+	eventspb "github.com/hexolan/stocklet/internal/pkg/protogen/events/v1"
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+)
+
+type EventOrderMetadata struct {
+	CustomerId string
+	ItemsPrice float32
+	TotalPrice float32
+}
+
+func PrepareStockCreatedEvent(productStock *pb.ProductStock) ([]byte, string, error) {
+	topic := messaging.Warehouse_Stock_Created_Topic
+	event := &eventspb.StockCreatedEvent{
+		Revision: 1,
+
+		ProductId: productStock.ProductId,
+		Quantity:  productStock.Quantity,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockAddedEvent(productId string, amount int32, reservationId *string) ([]byte, string, error) {
+	topic := messaging.Warehouse_Stock_Added_Topic
+	event := &eventspb.StockAddedEvent{
+		Revision: 1,
+
+		ProductId:     productId,
+		Amount:        amount,
+		ReservationId: reservationId,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockRemovedEvent(productId string, amount int32, reservationId *string) ([]byte, string, error) {
+	topic := messaging.Warehouse_Stock_Removed_Topic
+	event := &eventspb.StockRemovedEvent{
+		Revision: 1,
+
+		ProductId:     productId,
+		Amount:        amount,
+		ReservationId: reservationId,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockReservationEvent_Failed(orderId string, orderMetadata EventOrderMetadata, insufficientStockProductIds []string) ([]byte, string, error) {
+	topic := messaging.Warehouse_Reservation_Failed_Topic
+	event := &eventspb.StockReservationEvent{
+		Revision: 1,
+
+		Type:    eventspb.StockReservationEvent_TYPE_INSUFFICIENT_STOCK,
+		OrderId: orderId,
+		OrderMetadata: &eventspb.StockReservationEvent_OrderMetadata{
+			CustomerId: orderMetadata.CustomerId,
+			ItemsPrice: orderMetadata.ItemsPrice,
+			TotalPrice: orderMetadata.TotalPrice,
+		},
+		InsufficientStock: insufficientStockProductIds,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockReservationEvent_Reserved(orderId string, orderMetadata EventOrderMetadata, reservationId string, reservationStock map[string]int32) ([]byte, string, error) {
+	topic := messaging.Warehouse_Reservation_Reserved_Topic
+	event := &eventspb.StockReservationEvent{
+		Revision: 1,
+
+		Type:    eventspb.StockReservationEvent_TYPE_STOCK_RESERVED,
+		OrderId: orderId,
+		OrderMetadata: &eventspb.StockReservationEvent_OrderMetadata{
+			CustomerId: orderMetadata.CustomerId,
+			ItemsPrice: orderMetadata.ItemsPrice,
+			TotalPrice: orderMetadata.TotalPrice,
+		},
+		ReservationId:    reservationId,
+		ReservationStock: reservationStock,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockReservationEvent_Returned(orderId string, reservationId string, reservedStock []*pb.ReservationStock) ([]byte, string, error) {
+	reservationStock := make(map[string]int32)
+	for _, item := range reservedStock {
+		reservationStock[item.ProductId] = item.Quantity
+	}
+
+	topic := messaging.Warehouse_Reservation_Returned_Topic
+	event := &eventspb.StockReservationEvent{
+		Revision: 1,
+
+		Type:             eventspb.StockReservationEvent_TYPE_STOCK_RESERVED,
+		OrderId:          orderId,
+		ReservationId:    reservationId,
+		ReservationStock: reservationStock,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}
+
+func PrepareStockReservationEvent_Consumed(orderId string, reservationId string, reservedStock []*pb.ReservationStock) ([]byte, string, error) {
+	reservationStock := make(map[string]int32)
+	for _, item := range reservedStock {
+		reservationStock[item.ProductId] = item.Quantity
+	}
+
+	topic := messaging.Warehouse_Reservation_Consumed_Topic
+	event := &eventspb.StockReservationEvent{
+		Revision: 1,
+
+		Type:             eventspb.StockReservationEvent_TYPE_STOCK_CONSUMED,
+		OrderId:          orderId,
+		ReservationId:    reservationId,
+		ReservationStock: reservationStock,
+	}
+
+	return messaging.MarshalEvent(event, topic)
+}

internal/svc/warehouse/warehouse.go

@@ -0,0 +1,168 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package warehouse
+
+import (
+	"context"
+
+	"github.com/bufbuild/protovalidate-go"
+	"github.com/rs/zerolog/log"
+	"google.golang.org/protobuf/types/known/emptypb"
+
+	"github.com/hexolan/stocklet/internal/pkg/errors"
+	"github.com/hexolan/stocklet/internal/pkg/messaging"
+	commonpb "github.com/hexolan/stocklet/internal/pkg/protogen/common/v1"
+	eventpb "github.com/hexolan/stocklet/internal/pkg/protogen/events/v1"
+	pb "github.com/hexolan/stocklet/internal/pkg/protogen/warehouse/v1"
+)
+
+// Interface for the service
+type WarehouseService struct {
+	pb.UnimplementedWarehouseServiceServer
+
+	store StorageController
+	pbVal *protovalidate.Validator
+}
+
+// Interface for database methods
+// Flexibility for implementing seperate controllers for different databases (e.g. Postgres, MongoDB, etc)
+type StorageController interface {
+	GetProductStock(ctx context.Context, productId string) (*pb.ProductStock, error)
+	GetReservation(ctx context.Context, reservationId string) (*pb.Reservation, error)
+
+	CreateProductStock(ctx context.Context, productId string, startingQuantity int32) error
+
+	ReserveOrderStock(ctx context.Context, orderId string, orderMetadata EventOrderMetadata, productQuantities map[string]int32) error
+	ReturnReservedOrderStock(ctx context.Context, orderId string) error
+	ConsumeReservedOrderStock(ctx context.Context, orderId string) error
+}
+
+// Interface for event consumption
+// Flexibility for seperate controllers for different messaging systems (e.g. Kafka, NATS, etc)
+type ConsumerController interface {
+	messaging.ConsumerController
+
+	Attach(svc pb.WarehouseServiceServer)
+}
+
+// Create the shipping service
+func NewWarehouseService(cfg *ServiceConfig, store StorageController) *WarehouseService {
+	// Initialise the protobuf validator
+	pbVal, err := protovalidate.New()
+	if err != nil {
+		log.Panic().Err(err).Msg("failed to initialise protobuf validator")
+	}
+
+	// Initialise the service
+	return &WarehouseService{
+		store: store,
+		pbVal: pbVal,
+	}
+}
+
+func (svc WarehouseService) ServiceInfo(ctx context.Context, req *commonpb.ServiceInfoRequest) (*commonpb.ServiceInfoResponse, error) {
+	return &commonpb.ServiceInfoResponse{
+		Name:          "warehouse",
+		Source:        "https://github.com/hexolan/stocklet",
+		SourceLicense: "AGPL-3.0",
+	}, nil
+}
+
+func (svc WarehouseService) ViewProductStock(ctx context.Context, req *pb.ViewProductStockRequest) (*pb.ViewProductStockResponse, error) {
+	// Validate the request args
+	if err := svc.pbVal.Validate(req); err != nil {
+		// Provide the validation error to the user.
+		return nil, errors.NewServiceError(errors.ErrCodeInvalidArgument, "invalid request: "+err.Error())
+	}
+
+	// Get stock from db
+	stock, err := svc.store.GetProductStock(ctx, req.ProductId)
+	if err != nil {
+		return nil, err
+	}
+
+	return &pb.ViewProductStockResponse{Stock: stock}, nil
+}
+
+func (svc WarehouseService) ViewReservation(ctx context.Context, req *pb.ViewReservationRequest) (*pb.ViewReservationResponse, error) {
+	// Validate the request args
+	if err := svc.pbVal.Validate(req); err != nil {
+		// Provide the validation error to the user.
+		return nil, errors.NewServiceError(errors.ErrCodeInvalidArgument, "invalid request: "+err.Error())
+	}
+
+	// Get reservation from db
+	reservation, err := svc.store.GetReservation(ctx, req.ReservationId)
+	if err != nil {
+		return nil, err
+	}
+
+	return &pb.ViewReservationResponse{Reservation: reservation}, nil
+}
+
+func (svc WarehouseService) ProcessProductCreatedEvent(ctx context.Context, req *eventpb.ProductCreatedEvent) (*emptypb.Empty, error) {
+	err := svc.store.CreateProductStock(ctx, req.ProductId, 0)
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeExtService, "error processing event", err)
+	}
+
+	return &emptypb.Empty{}, nil
+}
+
+func (svc WarehouseService) ProcessOrderPendingEvent(ctx context.Context, req *eventpb.OrderPendingEvent) (*emptypb.Empty, error) {
+	err := svc.store.ReserveOrderStock(
+		ctx,
+		req.OrderId,
+		EventOrderMetadata{
+			CustomerId: req.CustomerId,
+			ItemsPrice: req.ItemsPrice,
+			TotalPrice: req.TotalPrice,
+		},
+		req.ItemQuantities,
+	)
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeExtService, "error processing event", err)
+	}
+
+	return &emptypb.Empty{}, nil
+}
+
+func (svc WarehouseService) ProcessShipmentAllocationEvent(ctx context.Context, req *eventpb.ShipmentAllocationEvent) (*emptypb.Empty, error) {
+	if req.Type == eventpb.ShipmentAllocationEvent_TYPE_FAILED {
+		err := svc.store.ReturnReservedOrderStock(ctx, req.OrderId)
+		if err != nil {
+			return nil, errors.WrapServiceError(errors.ErrCodeExtService, "error processing event", err)
+		}
+	}
+
+	return &emptypb.Empty{}, nil
+}
+
+func (svc WarehouseService) ProcessPaymentProcessedEvent(ctx context.Context, req *eventpb.PaymentProcessedEvent) (*emptypb.Empty, error) {
+	if req.Type == eventpb.PaymentProcessedEvent_TYPE_FAILED {
+		err := svc.store.ReturnReservedOrderStock(ctx, req.OrderId)
+		if err != nil {
+			return nil, errors.WrapServiceError(errors.ErrCodeExtService, "error processing event", err)
+		}
+	} else if req.Type == eventpb.PaymentProcessedEvent_TYPE_SUCCESS {
+		err := svc.store.ConsumeReservedOrderStock(ctx, req.OrderId)
+		if err != nil {
+			return nil, errors.WrapServiceError(errors.ErrCodeExtService, "error processing event", err)
+		}
+	}
+
+	return &emptypb.Empty{}, nil
+}