fix: normalize pending oauth email lookups

backend/internal/handler/auth_oauth_pending_flow.go

@@ -3,6 +3,7 @@ package handler
 import (
 	"context"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/url"
@@ -12,12 +13,14 @@ import (
 	"github.com/Wei-Shaw/sub2api/ent/authidentity"
 	"github.com/Wei-Shaw/sub2api/ent/authidentitychannel"
 	"github.com/Wei-Shaw/sub2api/ent/identityadoptiondecision"
+	"github.com/Wei-Shaw/sub2api/ent/predicate"
 	dbuser "github.com/Wei-Shaw/sub2api/ent/user"
 	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/oauth"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
+	entsql "entgo.io/ent/dialect/sql"
 	"github.com/gin-gonic/gin"
 )
 
@@ -531,11 +534,9 @@ func resolvePendingOAuthTargetUserID(ctx context.Context, client *dbent.Client,
 		return 0, infraerrors.BadRequest("PENDING_AUTH_TARGET_USER_MISSING", "pending auth target user is missing")
 	}
 
-	userEntity, err := client.User.Query().
+	userEntity, err := findUserByNormalizedEmail(ctx, client, email)
-		Where(dbuser.EmailEQ(email)).
-		Only(ctx)
 	if err != nil {
-		if dbent.IsNotFound(err) {
+		if errors.Is(err, service.ErrUserNotFound) {
 			return 0, infraerrors.InternalServer("PENDING_AUTH_TARGET_USER_NOT_FOUND", "pending auth target user was not found")
 		}
 		return 0, err
@@ -543,6 +544,40 @@ func resolvePendingOAuthTargetUserID(ctx context.Context, client *dbent.Client,
 	return userEntity.ID, nil
 }
 
+func userNormalizedEmailPredicate(email string) predicate.User {
+	normalized := strings.TrimSpace(email)
+	if normalized == "" {
+		return dbuser.EmailEQ(email)
+	}
+	return predicate.User(func(s *entsql.Selector) {
+		s.Where(entsql.ExprP(
+			fmt.Sprintf("LOWER(TRIM(%s)) = LOWER(TRIM(?))", s.C(dbuser.FieldEmail)),
+			normalized,
+		))
+	})
+}
+
+func findUserByNormalizedEmail(ctx context.Context, client *dbent.Client, email string) (*dbent.User, error) {
+	if client == nil {
+		return nil, infraerrors.ServiceUnavailable("PENDING_AUTH_NOT_READY", "pending auth service is not ready")
+	}
+
+	matches, err := client.User.Query().
+		Where(userNormalizedEmailPredicate(email)).
+		Order(dbent.Asc(dbuser.FieldID)).
+		All(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if len(matches) == 0 {
+		return nil, service.ErrUserNotFound
+	}
+	if len(matches) > 1 {
+		return nil, infraerrors.Conflict("USER_EMAIL_CONFLICT", "normalized email matched multiple users")
+	}
+	return matches[0], nil
+}
+
 func oauthIdentityIssuer(session *dbent.PendingAuthSession) *string {
 	if session == nil {
 		return nil
@@ -1102,8 +1137,8 @@ func (h *AuthHandler) createPendingOAuthAccount(c *gin.Context, provider string)
 	}
 
 	email := strings.TrimSpace(strings.ToLower(req.Email))
-	existingUser, err := client.User.Query().Where(dbuser.EmailEQ(email)).Only(c.Request.Context())
+	existingUser, err := findUserByNormalizedEmail(c.Request.Context(), client, email)
-	if err != nil && !dbent.IsNotFound(err) {
+	if err != nil && !errors.Is(err, service.ErrUserNotFound) {
 		response.ErrorFrom(c, infraerrors.ServiceUnavailable("SERVICE_UNAVAILABLE", "service temporarily unavailable"))
 		return
 	}

backend/internal/handler/auth_oauth_pending_flow_test.go

@@ -642,6 +642,60 @@ func TestCreateOIDCOAuthAccountExistingEmailReturnsAdoptExistingUserByEmailState
 	require.Zero(t, identityCount)
 }
 
+func TestCreateOIDCOAuthAccountExistingEmailNormalizesLegacySpacingAndCase(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandlerWithEmailVerification(t, false, "owner@example.com", "135790")
+	ctx := context.Background()
+
+	existingUser, err := client.User.Create().
+		SetEmail(" Owner@Example.com ").
+		SetUsername("owner-user").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusActive).
+		Save(ctx)
+	require.NoError(t, err)
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("existing-email-normalized-session-token").
+		SetIntent("login").
+		SetProviderType("oidc").
+		SetProviderKey("https://issuer.example").
+		SetProviderSubject("oidc-existing-normalized-123").
+		SetBrowserSessionKey("existing-email-normalized-browser-session-key").
+		SetUpstreamIdentityClaims(map[string]any{
+			"username":               "oidc_user",
+			"suggested_display_name": "Existing OIDC User",
+			"suggested_avatar_url":   "https://cdn.example/existing.png",
+		}).
+		SetRedirectTo("/dashboard").
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	body := bytes.NewBufferString(`{"email":"owner@example.com","verify_code":"135790","password":"secret-123"}`)
+	recorder := httptest.NewRecorder()
+	ginCtx, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/oidc/create-account", body)
+	req.Header.Set("Content-Type", "application/json")
+	req.AddCookie(&http.Cookie{Name: oauthPendingSessionCookieName, Value: encodeCookieValue(session.SessionToken)})
+	req.AddCookie(&http.Cookie{Name: oauthPendingBrowserCookieName, Value: encodeCookieValue("existing-email-normalized-browser-session-key")})
+	ginCtx.Request = req
+
+	handler.CreateOIDCOAuthAccount(ginCtx)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(recorder.Body.Bytes(), &payload))
+	require.Equal(t, "adopt_existing_user_by_email", payload["intent"])
+
+	storedSession, err := client.PendingAuthSession.Get(ctx, session.ID)
+	require.NoError(t, err)
+	require.NotNil(t, storedSession.TargetUserID)
+	require.Equal(t, existingUser.ID, *storedSession.TargetUserID)
+	require.Equal(t, "owner@example.com", storedSession.ResolvedEmail)
+}
+
 func TestBindOIDCOAuthLoginBindsExistingUserAndConsumesSession(t *testing.T) {
 	handler, client := newOAuthPendingFlowTestHandler(t, false)
 	ctx := context.Background()
@@ -884,6 +938,37 @@ func TestBindOIDCOAuthLoginAppliesFirstBindGrantOnce(t *testing.T) {
 	require.Equal(t, 1, countProviderGrantRecords(t, client, existingUser.ID, "oidc", "first_bind"))
 }
 
+func TestResolvePendingOAuthTargetUserIDNormalizesLegacySpacingAndCase(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandler(t, false)
+	_ = handler
+	ctx := context.Background()
+
+	existingUser, err := client.User.Create().
+		SetEmail(" Owner@Example.com ").
+		SetUsername("owner-user").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusActive).
+		Save(ctx)
+	require.NoError(t, err)
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("resolve-target-session-token").
+		SetIntent("login").
+		SetProviderType("oidc").
+		SetProviderKey("https://issuer.example").
+		SetProviderSubject("oidc-target-123").
+		SetResolvedEmail("owner@example.com").
+		SetBrowserSessionKey("resolve-target-browser-session-key").
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	resolvedUserID, err := resolvePendingOAuthTargetUserID(ctx, client, session)
+	require.NoError(t, err)
+	require.Equal(t, existingUser.ID, resolvedUserID)
+}
+
 func TestBindOIDCOAuthLoginReturns2FAChallengeWhenUserHasTotp(t *testing.T) {
 	totpCache := &oauthPendingFlowTotpCacheStub{}
 	handler, client := newOAuthPendingFlowTestHandlerWithDependencies(t, oauthPendingFlowTestHandlerOptions{