listing: implement a service layer stub along with tests

3 files changed, 214 insertions, 0 deletions

diff --git a/internal/listing/mock_test.go b/internal/listing/mock_test.go
new file mode 100644
index 0000000..5aa6d68
--- /dev/null
+++ b/internal/listing/mock_test.go
@@ -0,0 +1,89 @@
+package listing
+
+import "time"
+
+type RepositoryMock struct {
+	listings []Listing
+	err      error
+}
+
+func (r *RepositoryMock) GetAll() ([]Listing, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+
+	return r.listings, nil
+}
+
+func (r *RepositoryMock) GetByCategory(c string) ([]Listing, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+
+	var res []Listing
+	for _, l := range r.listings {
+		for _, cat := range l.category {
+			if cat == c {
+				res = append(res, l)
+				break
+			}
+		}
+	}
+
+	return res, nil
+}
+
+func NewRepositoryMock() *RepositoryMock {
+	mockListings := []Listing{
+		{
+			id:          0,
+			title:       "Audi a5 2.0 2015 godiste",
+			slug:        "audi-a5-2-0-2015-godiste",
+			location:    Location{city: "Novi Sad", street: "Bulevar Cara Lazara", premise: "3"},
+			status:      PublishedStatus,
+			category:    []string{"automobile", "audi", "a5"},
+			price:       5000,
+			currency:    "EUR",
+			description: "Pali odma ide lepo",
+			images:      []string{},
+			views:       10,
+			createdAt:   time.Now(),
+			author:      nil,
+			isExternal:  false,
+		},
+		{
+			id:          1,
+			title:       "Led lampa za glavu TJ-1608",
+			slug:        "led-lampa-za-glavu-tj-1608",
+			location:    Location{city: "Belgrade"},
+			status:      PublishedStatus,
+			category:    []string{"hunting", "hunting-lamps"},
+			price:       1200,
+			currency:    "RSD",
+			description: "Odlična lampa, svetli super",
+			images:      []string{},
+			views:       21,
+			createdAt:   time.Now(),
+			author:      nil,
+			isExternal:  false,
+		},
+		{
+			id:          2,
+			title:       "Školski anatomski ranac Minnie Mouse metalik",
+			slug:        "skolski-anatomski-ranac-minnie-mouse-metalik",
+			location:    Location{city: "Mladenovac"},
+			status:      PublishedStatus,
+			category:    []string{"school", "backpacks"},
+			price:       3400,
+			currency:    "RSD",
+			description: "Minnie ranac mnogo lep za devojčice",
+			images:      []string{},
+			views:       131,
+			createdAt:   time.Now(),
+			author:      nil,
+			isExternal:  false,
+		},
+	}
+
+	return &RepositoryMock{listings: mockListings}
+}
diff --git a/internal/listing/service.go b/internal/listing/service.go
new file mode 100644
index 0000000..302628b
--- /dev/null
+++ b/internal/listing/service.go
@@ -0,0 +1,36 @@
+package listing
+
+import "log/slog"
+
+type Repository interface {
+	GetAll() ([]Listing, error)
+	GetByCategory(category string) ([]Listing, error)
+}
+
+type Service struct {
+	repository Repository
+}
+
+func New(r Repository) *Service {
+	return &Service{repository: r}
+}
+
+func (s *Service) GetAll() ([]Listing, error) {
+	listings, err := s.repository.GetAll()
+	if err != nil {
+		slog.Error("listing service", "error", err)
+		return nil, err
+	}
+
+	return listings, nil
+}
+
+func (s *Service) GetByCategory(c string) ([]Listing, error) {
+	listings, err := s.repository.GetByCategory(c)
+	if err != nil {
+		slog.Error("listing service", "error", err)
+		return nil, err
+	}
+
+	return listings, nil
+}
diff --git a/internal/listing/service_test.go b/internal/listing/service_test.go
new file mode 100644
index 0000000..1d555c9
--- /dev/null
+++ b/internal/listing/service_test.go
@@ -0,0 +1,89 @@
+package listing
+
+import (
+	"errors"
+	"log/slog"
+	"os"
+	"slices"
+	"testing"
+)
+
+func TestMain(m *testing.M) {
+	slog.SetDefault(slog.New(slog.DiscardHandler))
+	os.Exit(m.Run())
+}
+
+func TestGetAll(t *testing.T) {
+	mock := NewRepositoryMock()
+	s := New(mock)
+	listings, err := s.GetAll()
+	if err != nil {
+		t.Error(err.Error())
+	}
+
+	if len(listings) != 3 {
+		t.Errorf("Listings lengths don't match. Have %d, want 3",
+			len(listings))
+	}
+}
+
+func TestGetAllWithError(t *testing.T) {
+	mock := &RepositoryMock{err: errors.New("db exploded")}
+	s := New(mock)
+	listings, err := s.GetAll()
+
+	if err == nil {
+		t.Error("No error returned from faulty GetAll call")
+	}
+
+	if listings != nil {
+		t.Error("Listings not nil when returned from faulty GetAll call")
+	}
+}
+
+func TestGetByCategory(t *testing.T) {
+	mock := NewRepositoryMock()
+	s := New(mock)
+
+	listings, err := s.GetByCategory("audi")
+	if err != nil {
+		t.Error(err.Error())
+	}
+
+	if len(listings) != 1 {
+		t.Errorf("Listings by category have wrong length. Have %d, want %d",
+			len(listings), 1)
+	}
+	if !slices.Contains(listings[0].category, "audi") {
+		t.Errorf("Returned listing has wrong category. Have %s, want audi",
+			listings[0].category)
+	}
+}
+
+func TestGetByCategoryNoMatches(t *testing.T) {
+	mock := &RepositoryMock{}
+	s := New(mock)
+
+	listings, err := s.GetByCategory("nonexistantcategory")
+	if err != nil {
+		t.Error(err.Error())
+	}
+
+	if listings != nil {
+		t.Error("Listings should be nil if no category matches")
+	}
+}
+
+func TestGetByCategoryWithError(t *testing.T) {
+	mock := &RepositoryMock{err: errors.New("datacenter hit by asteroid")}
+	s := New(mock)
+
+	listings, err := s.GetByCategory("mercedes")
+	if err == nil {
+		t.Error("Error nil when GetByCategory failed")
+	}
+
+	if listings != nil {
+		t.Error("Listings not nil when GetByCategory failed")
+	}
+}