⚡️ Added users.UserExists function

cmd/api/users/errors.go

@@ -3,5 +3,6 @@ package users
 import "errors"
 
 var (
-	FailedToInsertUser = errors.New("failed to insert user")
+	FailedToInsertUser                  = errors.New("failed to insert user")
+	FailedToRetrieveIfUserAlreadyExists = errors.New("failed to retrieve if user already exists")
 )

cmd/api/users/select.go

@@ -0,0 +1,37 @@
+package users
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+
+	"ahbcc/internal/database"
+	"ahbcc/internal/log"
+)
+
+// UserExists validates if the given username was already registered in the database
+type UserExists func(ctx context.Context, username string) (bool, error)
+
+// MakeUserExists creates a new UserExists
+func MakeUserExists(db database.Connection) UserExists {
+	const query string = `
+		SELECT EXISTS (
+			SELECT 1 
+			FROM users 
+			WHERE username = $1
+		)
+	`
+
+	return func(ctx context.Context, username string) (bool, error) {
+		var applied bool
+
+		err := db.QueryRow(ctx, query, username).Scan(&applied)
+		if errors.Is(err, pgx.ErrNoRows) {
+			log.Error(ctx, err.Error())
+			return false, FailedToRetrieveIfUserAlreadyExists
+		}
+
+		return applied, nil
+	}
+}

cmd/api/users/select_test.go

@@ -0,0 +1,45 @@
+package users_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+
+	"ahbcc/cmd/api/users"
+	"ahbcc/internal/database"
+)
+
+func TestUserExists_success(t *testing.T) {
+	mockPostgresConnection := new(database.MockPostgresConnection)
+	mockPgxRow := new(database.MockPgxRow)
+	database.MockScan(mockPgxRow, []any{true}, t)
+	mockPostgresConnection.On("QueryRow", mock.Anything, mock.Anything, mock.Anything).Return(mockPgxRow)
+
+	userExists := users.MakeUserExists(mockPostgresConnection)
+
+	got, err := userExists(context.Background(), "user")
+
+	assert.Nil(t, err)
+	assert.True(t, got)
+	mockPostgresConnection.AssertExpectations(t)
+	mockPgxRow.AssertExpectations(t)
+}
+
+func TestUserExists_failsWhenSelectOperationFails(t *testing.T) {
+	mockPostgresConnection := new(database.MockPostgresConnection)
+	mockPgxRow := new(database.MockPgxRow)
+	mockPgxRow.On("Scan", mock.Anything).Return(pgx.ErrNoRows)
+	mockPostgresConnection.On("QueryRow", mock.Anything, mock.Anything, mock.Anything).Return(mockPgxRow)
+
+	userExists := users.MakeUserExists(mockPostgresConnection)
+
+	want := users.FailedToRetrieveIfUserAlreadyExists
+	_, got := userExists(context.Background(), "user")
+
+	assert.Equal(t, want, got)
+	mockPostgresConnection.AssertExpectations(t)
+	mockPgxRow.AssertExpectations(t)
+}