Refactor a bunch of things:

- move validation for duplicate beers out of storage and to the service
- change how we generate beer IDs, and from int to string
- add a test for adding beers (with known limitations)

domain-hex/pkg/adding/service.go

@@ -2,40 +2,57 @@ package adding
 
 import (
 	"errors"
+	"github.com/katzien/go-structure-examples/domain-hex-actor/pkg/adding"
+	"github.com/katzien/go-structure-examples/domain-hex/pkg/listing"
 )
 
 // ErrDuplicate is used when a beer already exists.
 var ErrDuplicate = errors.New("beer already exists")
 
 // Service provides beer adding operations.
 type Service interface {
-	AddBeer(...Beer)
+	AddBeer(...Beer) error
 	AddSampleBeers([]Beer)
 }
 
 // Repository provides access to beer repository.
 type Repository interface {
 	// AddBeer saves a given beer to the repository.
 	AddBeer(Beer) error
+	// GetAllBeers returns all beers saved in storage.
+	GetAllBeers() []listing.Beer
 }
 
 type service struct {
-	bR Repository
+	r Repository
 }
 
 // NewService creates an adding service with the necessary dependencies
 func NewService(r Repository) Service {
 	return &service{r}
 }
 
-// AddBeer adds the given beer(s) to the database
-func (s *service) AddBeer(b ...Beer) {
+// AddBeer persists the given beer(s) to storage
+func (s *service) AddBeer(b ...Beer) error {
+	// make sure we don't add any duplicates
+	existingBeers := s.r.GetAllBeers()
+	for _, bb := range b {
+		for _, e := range existingBeers {
+			if bb.Abv == e.Abv &&
+				bb.Brewery == e.Brewery &&
+				bb.Name == e.Name {
+				return adding.ErrDuplicate
+			}
+		}
+	}
 
-	// any validation can be done here
+	// any other validation can be done here
 
 	for _, beer := range b {
-		_ = s.bR.AddBeer(beer) // error handling omitted for simplicity
+		_ = s.r.AddBeer(beer) // error handling omitted for simplicity
 	}
+
+	return nil
 }
 
 // AddSampleBeers adds some sample beers to the database
@@ -44,6 +61,6 @@ func (s *service) AddSampleBeers(b []Beer) {
 	// any validation can be done here
 
 	for _, bb := range b {
-		_ = s.bR.AddBeer(bb) // error handling omitted for simplicity
+		_ = s.r.AddBeer(bb) // error handling omitted for simplicity
 	}
 }

domain-hex/pkg/adding/service_test.go

@@ -0,0 +1,60 @@
+package adding
+
+import (
+	"github.com/katzien/go-structure-examples/domain-hex/pkg/listing"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestAddBeers(t *testing.T) {
+	b1 := Beer{
+		Name:      "Test Beer 1",
+		Brewery:   "Brewery One",
+		Abv:       3.6,
+		ShortDesc: "Lorem Ipsum",
+	}
+
+	b2 := Beer{
+		Name:      "Test Beer 2",
+		Brewery:   "Brewery Two",
+		Abv:       4.8,
+		ShortDesc: "Bacon Ipsum",
+	}
+
+	mR := new(mockStorage)
+
+	s := NewService(mR)
+
+	err := s.AddBeer(b1, b2)
+	require.NoError(t, err)
+
+	beers := mR.GetAllBeers()
+	assert.Len(t, beers, 2)
+}
+
+type mockStorage struct {
+	beers []Beer
+}
+
+func (m *mockStorage) AddBeer(b Beer) error {
+	m.beers = append(m.beers, b)
+
+	return nil
+}
+
+func (m *mockStorage) GetAllBeers() []listing.Beer {
+	beers := []listing.Beer{}
+
+	for _, bb := range m.beers {
+		b := listing.Beer{
+			Name:      bb.Name,
+			Brewery:   bb.Brewery,
+			Abv:       bb.Abv,
+			ShortDesc: bb.ShortDesc,
+		}
+		beers = append(beers, b)
+	}
+
+	return beers
+}

domain-hex/pkg/http/rest/handler.go

@@ -37,7 +37,8 @@ func addBeer(s adding.Service) func(w http.ResponseWriter, r *http.Request, _ ht
 			return
 		}
 
-		s.AddBeer(newBeer)
+		_ := s.AddBeer(newBeer)
+		// error handling omitted for simplicity
 
 		w.Header().Set("Content-Type", "application/json")
 		json.NewEncoder(w).Encode("New beer added.")

domain-hex/pkg/listing/beer.go

@@ -6,7 +6,7 @@ import (
 
 // Beer defines the properties of a beer to be listed
 type Beer struct {
-	ID        int       `json:"id"`
+	ID        string    `json:"id"`
 	Name      string    `json:"name"`
 	Brewery   string    `json:"brewery"`
 	Abv       float32   `json:"abv"`

domain-hex/pkg/listing/review.go

@@ -7,7 +7,7 @@ import (
 // Review defines a beer review
 type Review struct {
 	ID        string    `json:"id"`
-	BeerID    int       `json:"beer_id"`
+	BeerID    string       `json:"beer_id"`
 	FirstName string    `json:"first_name"`
 	LastName  string    `json:"last_name"`
 	Score     int       `json:"score"`

domain-hex/pkg/listing/service.go

@@ -10,18 +10,18 @@ var ErrNotFound = errors.New("beer not found")
 // Repository provides access to the beer and review storage.
 type Repository interface {
 	// GetBeer returns the beer with given ID.
-	GetBeer(int) (Beer, error)
+	GetBeer(string) (Beer, error)
 	// GetAllBeers returns all beers saved in storage.
 	GetAllBeers() []Beer
 	// GetAllReviews returns a list of all reviews for a given beer ID.
-	GetAllReviews(int) []Review
+	GetAllReviews(string) []Review
 }
 
 // Service provides beer and review listing operations.
 type Service interface {
-	GetBeer(int) (Beer, error)
+	GetBeer(string) (Beer, error)
 	GetBeers() []Beer
-	GetBeerReviews(int) []Review
+	GetBeerReviews(string) []Review
 }
 
 type service struct {
@@ -39,11 +39,11 @@ func (s *service) GetBeers() []Beer {
 }
 
 // GetBeer returns a beer
-func (s *service) GetBeer(id int) (Beer, error) {
+func (s *service) GetBeer(id string) (Beer, error) {
 	return s.r.GetBeer(id)
 }
 
 // GetBeerReviews returns all requests for a beer
-func (s *service) GetBeerReviews(beerID int) []Review {
+func (s *service) GetBeerReviews(beerID string) []Review {
 	return s.r.GetAllReviews(beerID)
 }

domain-hex/pkg/reviewing/review.go

@@ -2,7 +2,7 @@ package reviewing
 
 // Review defines a beer review
 type Review struct {
-	BeerID    int    `json:"beer_id"`
+	BeerID    string    `json:"beer_id"`
 	FirstName string `json:"first_name"`
 	LastName  string `json:"last_name"`
 	Score     int    `json:"score"`

domain-hex/pkg/reviewing/service.go

@@ -20,7 +20,7 @@ type Service interface {
 }
 
 type service struct {
-	rR Repository
+	r Repository
 }
 
 // NewService creates an adding service with the necessary dependencies
@@ -30,12 +30,12 @@ func NewService(r Repository) Service {
 
 // AddBeerReview saves a new beer review in the database
 func (s *service) AddBeerReview(r Review) {
-	_ = s.rR.AddReview(r) // error handling omitted for simplicity
+	_ = s.r.AddReview(r) // error handling omitted for simplicity
 }
 
 // AddSampleReviews adds some sample reviews to the database
 func (s *service) AddSampleReviews(r []Review) {
 	for _, rr := range r {
-		_ = s.rR.AddReview(rr) // error handling omitted for simplicity
+		_ = s.r.AddReview(rr) // error handling omitted for simplicity
 	}
 }

domain-hex/pkg/storage/idgen.go

@@ -0,0 +1,20 @@
+package storage
+
+import (
+	"crypto/rand"
+	"fmt"
+)
+
+// GetID returns a random ID string of the format prefix_random16chars, e.g. beer_ts72nf6ak8dts73g.
+// This is a simple (naive) implementation using the rand package,
+// just to avoid importing external UUID packages in this demo app.
+// This implementation in no way guarantees uniqueness, so please don't use it for any production purposes!
+func GetID(prefix string) (string, error) {
+ 	b := make([]byte, 8)
+	_, err := rand.Read(b)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s_%x", prefix, b), nil
+}

domain-hex/pkg/storage/idgen_test.go

@@ -0,0 +1,26 @@
+package storage
+
+import (
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"strings"
+	"testing"
+)
+
+func TestGetID(t *testing.T) {
+	id, err := GetID("testing")
+
+	require.NoError(t, err)
+
+	assert.True(t, strings.HasPrefix(id, "testing_"))
+	assert.Len(t, id, 24)
+}
+
+func TestGetIDEmptyPrefix(t *testing.T) {
+	id, err := GetID("")
+
+	require.NoError(t, err)
+
+	assert.True(t, strings.HasPrefix(id, "_"))
+	assert.Len(t, id, 17)
+}

domain-hex/pkg/storage/json/beer.go

@@ -4,7 +4,7 @@ import "time"
 
 // Beer defines the storage form of a beer
 type Beer struct {
-	ID        int       `json:"id"`
+	ID        string    `json:"id"`
 	Name      string    `json:"name"`
 	Brewery   string    `json:"brewery"`
 	Abv       float32   `json:"abv"`

domain-hex/pkg/storage/json/repository.go

@@ -3,9 +3,10 @@ package json
 import (
 	"encoding/json"
 	"fmt"
+	"github.com/katzien/go-structure-examples/domain-hex/pkg/storage"
+	"log"
 	"path"
 	"runtime"
-	"strconv"
 	"time"
 
 	"github.com/katzien/go-structure-examples/domain-hex/pkg/adding"
@@ -48,27 +49,21 @@ func NewStorage() (*Storage, error) {
 
 // AddBeer saves the given beer to the repository
 func (s *Storage) AddBeer(b adding.Beer) error {
-
-	existingBeers := s.GetAllBeers()
-	for _, e := range existingBeers {
-		if b.Abv == e.Abv &&
-			b.Brewery == e.Brewery &&
-			b.Name == e.Name {
-			return adding.ErrDuplicate
-		}
+	id, err := storage.GetID("beer")
+	if err != nil {
+		log.Fatal(err)
 	}
 
 	newB := Beer{
-		ID:        len(existingBeers) + 1,
+		ID:        id,
 		Created:   time.Now(),
 		Name:      b.Name,
 		Brewery:   b.Brewery,
 		Abv:       b.Abv,
 		ShortDesc: b.ShortDesc,
 	}
 
-	resource := strconv.Itoa(newB.ID)
-	if err := s.db.Write(CollectionBeer, resource, newB); err != nil {
+	if err := s.db.Write(CollectionBeer, newB.ID, newB); err != nil {
 		return err
 	}
 	return nil
@@ -78,7 +73,7 @@ func (s *Storage) AddBeer(b adding.Beer) error {
 func (s *Storage) AddReview(r reviewing.Review) error {
 
 	var beer Beer
-	if err := s.db.Read(CollectionBeer, strconv.Itoa(r.BeerID), &beer); err != nil {
+	if err := s.db.Read(CollectionBeer, r.BeerID, &beer); err != nil {
 		return listing.ErrNotFound
 	}
 
@@ -101,13 +96,11 @@ func (s *Storage) AddReview(r reviewing.Review) error {
 }
 
 // Get returns a beer with the specified ID
-func (s *Storage) GetBeer(id int) (listing.Beer, error) {
+func (s *Storage) GetBeer(id string) (listing.Beer, error) {
 	var b Beer
 	var beer listing.Beer
 
-	var resource = strconv.Itoa(id)
-
-	if err := s.db.Read(CollectionBeer, resource, &b); err != nil {
+	if err := s.db.Read(CollectionBeer, id, &b); err != nil {
 		// err handling omitted for simplicity
 		return beer, listing.ErrNotFound
 	}
@@ -155,7 +148,7 @@ func (s *Storage) GetAllBeers() []listing.Beer {
 }
 
 // GetAll returns all reviews for a given beer
-func (s *Storage) GetAllReviews(beerID int) []listing.Review {
+func (s *Storage) GetAllReviews(beerID string) []listing.Review {
 	list := []listing.Review{}
 
 	records, err := s.db.ReadAll(CollectionReview)

domain-hex/pkg/storage/json/review.go

@@ -5,7 +5,7 @@ import "time"
 // Review defines the storage form of a beer review
 type Review struct {
 	ID        string    `json:"id"`
-	BeerID    int       `json:"beer_id"`
+	BeerID    string       `json:"beer_id"`
 	FirstName string    `json:"first_name"`
 	LastName  string    `json:"last_name"`
 	Score     int       `json:"score"`

domain-hex/pkg/storage/memory/beer.go

@@ -4,9 +4,9 @@ import (
 	"time"
 )
 
-// Beer defines the properties of a beer to be listed
+// Beer defines the storage form of a beer
 type Beer struct {
-	ID        int
+	ID        string
 	Name      string
 	Brewery   string
 	Abv       float32