refactor: updated swagger;

feat: helper function in errors for checking postgres error types;
feat: sql query method for finding users by their email;
feat: registration begin/complete with checking existing username/email;
refactor: error handling in controller

backend/internal/services/auth.go

@@ -24,6 +24,7 @@ import (
 	"easywish/internal/utils"
 	"easywish/internal/utils/enums"
 
+	"github.com/jackc/pgerrcode"
 	"github.com/jackc/pgx/v5"
 	"go.uber.org/zap"
 )
@@ -55,11 +56,40 @@ func (a *authServiceImpl) RegistrationBegin(request models.RegistrationBeginRequ
 	var err error
 
 	if user, err = db.TXQueries.CreateUser(db.CTX, request.Username); err != nil {
+
+		if errs.IsPgErr(err, pgerrcode.UniqueViolation) {
+			a.log.Warn(
+				"Attempted registration for a taken username",
+				zap.String("username", request.Username),
+				zap.Error(err))
+			return false, errs.ErrUsernameTaken
+		}
+
 		a.log.Error("Failed to add user to database", zap.Error(err))
 		return false, errs.ErrServerError
 	}
 
-	a.log.Info("Registraion of a new user", zap.String("username", user.Username), zap.Int64("id", user.ID))
+	if _, err := db.TXQueries.GetUserByEmail(db.CTX, *request.Email); err == nil {
+		a.log.Warn(
+			"Attempted registration for a taken email",
+			zap.String("email", *request.Email))
+		return false, errs.ErrEmailTaken
+
+	} else if !errs.IsPgErr(err, pgerrcode.NoData) {
+		a.log.Error(
+			"Failed to check if email is not taken",
+			zap.String("email", *request.Email),
+			zap.Error(err))
+		return false, errs.ErrServerError
+
+	} else {
+		a.log.Debug("Verified that email is not taken", zap.String("email", *request.Email))
+	}
+
+	a.log.Info(
+		"Registraion of a new user",
+		zap.String("username", user.Username),
+		zap.Int64("id", user.ID))
 
 	if _, err = db.TXQueries.CreateLoginInformation(db.CTX, database.CreateLoginInformationParams{
 		UserID: user.ID,
@@ -109,11 +139,19 @@ func (a *authServiceImpl) RegistrationComplete(request models.RegistrationComple
 	user, err = db.TXQueries.GetUserByUsername(db.CTX, request.Username)
 
 	if err != nil {
+		if errs.IsPgErr(err, pgerrcode.NoData) {
+			a.log.Warn(
+				"Could not find user attempting to complete registration with given username", 
+				zap.String("username", request.Username), 
+				zap.Error(err))
+			return nil, errs.ErrUserNotFound
+		}
+
 		a.log.Error(
-			"Failed to find user attempting to complete registration", 
-			zap.String("username", request.Username), 
+			"Failed to get user",
+			zap.String("username", request.Username),
 			zap.Error(err))
-		return nil, errs.ErrUserNotFound
+		return nil, errs.ErrServerError
 	}
 
 	confirmationCode, err = db.TXQueries.GetConfirmationCodeByCode(db.CTX, database.GetConfirmationCodeByCodeParams{
@@ -123,11 +161,20 @@ func (a *authServiceImpl) RegistrationComplete(request models.RegistrationComple
 	})
 
 	if err != nil {
-		a.log.Warn(
-			"User supplied wrong confirmation code for completing registration", 
-			zap.String("username", user.Username), 
+		if errs.IsPgErr(err, pgerrcode.NoData) {
+			a.log.Warn(
+				"User supplied unexistent confirmation code for completing registration",
+				zap.String("username", user.Username),
+				zap.String("code", request.VerificationCode),
+				zap.Error(err))
+			return nil, errs.ErrForbidden
+		}
+
+		a.log.Error(
+			"Failed to acquire specified registration code",
+			zap.String("username", user.Username),
 			zap.Error(err))
-		return nil, errs.ErrForbidden
+		return nil, errs.ErrServerError
 	}
 
 	err = db.TXQueries.UpdateConfirmationCode(db.CTX, database.UpdateConfirmationCodeParams{
@@ -140,8 +187,7 @@ func (a *authServiceImpl) RegistrationComplete(request models.RegistrationComple
 			"Failed to update the user's registration code used state",
 			zap.String("username", user.Username),
 			zap.Int64("confirmation_code_id", confirmationCode.ID),
-			zap.Error(err),
-		)
+			zap.Error(err))
 		return nil, errs.ErrServerError
 	}
 
@@ -179,6 +225,7 @@ func (a *authServiceImpl) RegistrationComplete(request models.RegistrationComple
 		return nil, errs.ErrServerError
 	}
 
+	// TODO: session info
 	session, err = db.TXQueries.CreateSession(db.CTX, database.CreateSessionParams{
 		UserID: user.ID,
 		Name: utils.NewPointer("First device"),
@@ -206,6 +253,10 @@ func (a *authServiceImpl) RegistrationComplete(request models.RegistrationComple
 
 	helper.Commit()
 
+	a.log.Info(
+		"User verified registration",
+		zap.String("username", request.Username))
+
 	response := models.RegistrationCompleteResponse{Tokens: models.Tokens{
 		AccessToken: accessToken,
 		RefreshToken: refreshToken,