first commit

internal/auth/auth.go

@@ -0,0 +1,68 @@
+package auth
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"golang.org/x/crypto/bcrypt"
+
+	"a301_game_server/internal/db"
+)
+
+var (
+	ErrInvalidCredentials = errors.New("invalid credentials")
+	ErrUsernameTaken      = errors.New("username already taken")
+)
+
+// Service handles account registration and authentication.
+type Service struct {
+	pool *db.Pool
+}
+
+// NewService creates a new auth service.
+func NewService(pool *db.Pool) *Service {
+	return &Service{pool: pool}
+}
+
+// Register creates a new account. Returns the account ID.
+func (s *Service) Register(ctx context.Context, username, password string) (int64, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return 0, fmt.Errorf("hash password: %w", err)
+	}
+
+	var id int64
+	err = s.pool.QueryRow(ctx,
+		`INSERT INTO accounts (username, password) VALUES ($1, $2)
+		 ON CONFLICT (username) DO NOTHING
+		 RETURNING id`,
+		username, string(hash),
+	).Scan(&id)
+
+	if err != nil {
+		return 0, ErrUsernameTaken
+	}
+
+	return id, nil
+}
+
+// Login validates credentials and returns the account ID.
+func (s *Service) Login(ctx context.Context, username, password string) (int64, error) {
+	var id int64
+	var hash string
+
+	err := s.pool.QueryRow(ctx,
+		`SELECT id, password FROM accounts WHERE username = $1`, username,
+	).Scan(&id, &hash)
+
+	if err != nil {
+		return 0, ErrInvalidCredentials
+	}
+
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)); err != nil {
+		return 0, ErrInvalidCredentials
+	}
+
+	return id, nil
+}