fix: clearer unequal-split language and prevent silent save failure

public/locales/en/common.json

@@ -189,6 +189,12 @@
         "warning": "Warning: Don't use send invite if it's invalid email. use add to Split Pro instead. Your account will be blocked if this feature is misused"
       },
       "split_type_section": {
+        "direction": {
+          "no_money_flow": "No one else owes anything",
+          "owes_payer": "{{debtor}} owes {{payer}}",
+          "owes_you": "{{debtor}} owes you",
+          "you_owe": "You owe {{payer}}"
+        },
         "split_equally": "split equally",
         "split_unequally": "split unequally",
         "types": {
@@ -213,6 +219,9 @@
             "title": "Share",
             "total_shares": "Total shares"
           }
+        },
+        "validation": {
+          "invalid_split": "Adjust who owes this expense before saving."
         }
       },
       "sponsor_us": "Sponsor us",

src/components/AddExpense/AddExpensePage.tsx

@@ -65,7 +65,6 @@ export const AddOrEditExpensePage: React.FC<{
     setAmount,
     setAmountStr,
     resetState,
-    setSplitScreenOpen,
     setExpenseDate,
     setMultipleTransactions,
     setIsTransactionLoading,
@@ -110,11 +109,6 @@ export const AddOrEditExpensePage: React.FC<{
       return;
     }
 
-    if (!isExpenseSettled) {
-      setSplitScreenOpen(true);
-      return;
-    }
-
     setMultipleTransactions([]);
     setIsTransactionLoading(false);
 
@@ -196,7 +190,6 @@ export const AddOrEditExpensePage: React.FC<{
       }
     }
   }, [
-    setSplitScreenOpen,
     description,
     currency,
     isNegative,
@@ -212,7 +205,6 @@ export const AddOrEditExpensePage: React.FC<{
     paidBy,
     splitType,
     fileKey,
-    isExpenseSettled,
     setMultipleTransactions,
     transactionId,
     setIsTransactionLoading,
@@ -351,6 +343,7 @@ export const AddOrEditExpensePage: React.FC<{
                         splitShares,
                         paidBy,
                         currentUser,
+                        isNegative,
                       )}
                     </Button>
                   </SplitExpenseForm>

src/components/AddExpense/SplitTypeSection.tsx

@@ -304,6 +304,11 @@ const SplitSection: React.FC<SplitSectionProps> = (props) => {
       >
         {fmtSummartyText(amount, totalShares, toUIString)}
       </p>
+      {!canSplitScreenClosed ? (
+        <p className="text-center text-xs text-red-500">
+          {t('expense_details.add_expense_details.split_type_section.validation.invalid_split')}
+        </p>
+      ) : null}
       {isBoolean && (
         <Button
           variant="outline"

src/store/addStore.ts

@@ -296,9 +296,7 @@ export function calculateParticipantSplit(
         ...p,
         amount: 0n === getSplitShare(p) ? 0n : amount / BigInt(totalParticipants),
       }));
-      canSplitScreenClosed = Boolean(
-        Object.values(splitShares).find((p) => 0n !== p[SplitType.EQUAL]),
-      );
+      canSplitScreenClosed = 0 < totalParticipants;
       break;
     case SplitType.PERCENTAGE:
       updatedParticipants = participants.map((p) => ({
@@ -371,6 +369,14 @@ export function calculateParticipantSplit(
         }
       }
     }
+
+    if (
+      canSplitScreenClosed &&
+      1 < participants.length &&
+      updatedParticipants.every((p) => 0n === (p.amount ?? 0n))
+    ) {
+      canSplitScreenClosed = false;
+    }
   }
 
   return { ...state, participants: updatedParticipants, canSplitScreenClosed };

src/tests/addStore.test.ts

@@ -132,6 +132,64 @@ describe('calculateParticipantSplit', () => {
       expect(result.participants[2]?.amount).toBe(0n); // Excluded from split
     });
 
+    it('should allow one non-payer to owe the full amount', () => {
+      const participants = createParticipants([user1, user2]);
+      const splitShares = createSplitShares(participants, SplitType.EQUAL, [0n, 1n]);
+
+      const state: Partial<AddExpenseState> = {
+        amount: 10000n,
+        participants,
+        splitType: SplitType.EQUAL,
+        splitShares,
+        paidBy: user1,
+        expenseDate: new Date('2024-01-01'),
+      };
+
+      const result = calculateParticipantSplit(state as AddExpenseState);
+
+      expect(result.participants[0]?.amount).toBe(10000n);
+      expect(result.participants[1]?.amount).toBe(-10000n);
+      expect(result.canSplitScreenClosed).toBe(true);
+    });
+
+    it('should mark a multi-person self-only split as incomplete', () => {
+      const participants = createParticipants([user1, user2]);
+      const splitShares = createSplitShares(participants, SplitType.EQUAL, [1n, 0n]);
+
+      const state: Partial<AddExpenseState> = {
+        amount: 10000n,
+        participants,
+        splitType: SplitType.EQUAL,
+        splitShares,
+        paidBy: user1,
+        expenseDate: new Date('2024-01-01'),
+      };
+
+      const result = calculateParticipantSplit(state as AddExpenseState);
+
+      expect(result.participants[0]?.amount).toBe(0n);
+      expect(result.participants[1]?.amount).toBe(0n);
+      expect(result.canSplitScreenClosed).toBe(false);
+    });
+
+    it('should mark equal split incomplete when every share is disabled', () => {
+      const participants = createParticipants([user1, user2]);
+      const splitShares = createSplitShares(participants, SplitType.EQUAL, [0n, 0n]);
+
+      const state: Partial<AddExpenseState> = {
+        amount: 10000n,
+        participants,
+        splitType: SplitType.EQUAL,
+        splitShares,
+        paidBy: user1,
+        expenseDate: new Date('2024-01-01'),
+      };
+
+      const result = calculateParticipantSplit(state as AddExpenseState);
+
+      expect(result.canSplitScreenClosed).toBe(false);
+    });
+
     it('should handle uneven division with penny adjustment', () => {
       const participants = createParticipants([user1, user2, user3]);
       const splitShares = createSplitShares(participants, SplitType.EQUAL, [1n, 1n, 1n]);

src/utils/strings.ts

@@ -52,42 +52,58 @@ export function generateSplitDescription(
   splitShares: AddExpenseState['splitShares'],
   paidBy?: Participant,
   currentUser?: Participant,
+  isNegative = false,
 ): string {
-  // Only enhance the description for EQUAL split type
-  if (splitType !== SplitType.EQUAL) {
+  if (SplitType.EQUAL !== splitType) {
     return t('expense_details.add_expense_details.split_type_section.split_unequally');
   }
 
+  const splitEquallyText = t(
+    'expense_details.add_expense_details.split_type_section.split_equally',
+  );
   if (!paidBy || !currentUser) {
-    return t('expense_details.add_expense_details.split_type_section.split_equally');
+    return splitEquallyText;
   }
 
-  // Get participants who are actually selected for the split (have non-zero shares)
-  // If split shares are not initialized yet (undefined), include all participants
   const selectedParticipants = participants.filter((p) => {
     const share = splitShares[p.id]?.[SplitType.EQUAL];
-    return share === undefined || share !== 0n;
+    return share === undefined || 0n !== share;
   });
 
-  // If no one is selected, fall back to default
-  if (selectedParticipants.length === 0) {
-    return t('expense_details.add_expense_details.split_type_section.split_equally');
+  const splitParticipant = selectedParticipants[0];
+  if (!splitParticipant) {
+    return splitEquallyText;
   }
 
-  // Case 1: Paying for exactly one person
-  if (selectedParticipants.length === 1) {
-    const beneficiary = selectedParticipants[0];
-    const beneficiaryName = displayName(t, beneficiary as User, currentUser.id) || 'someone';
-    return `${t('ui.expense.user.paid')} ${t('ui.expense.for')} ${beneficiaryName}`;
+  if (1 !== selectedParticipants.length) {
+    return `${splitEquallyText} (${selectedParticipants.length})`;
   }
 
-  // Case 2: Splitting with multiple people
-  if (selectedParticipants.length > 1) {
-    return `${t('expense_details.add_expense_details.split_type_section.split_equally')} (${selectedParticipants.length})`;
+  if (splitParticipant.id === paidBy.id) {
+    return t('expense_details.add_expense_details.split_type_section.direction.no_money_flow');
   }
 
-  // Fallback to default for all other cases
-  return t('expense_details.add_expense_details.split_type_section.split_equally');
+  const debtor = isNegative ? paidBy : splitParticipant;
+  const payer = isNegative ? splitParticipant : paidBy;
+  const debtorName = displayName(t, debtor, currentUser.id);
+  const payerName = displayName(t, payer, currentUser.id);
+
+  if (payer.id === currentUser.id) {
+    return t('expense_details.add_expense_details.split_type_section.direction.owes_you', {
+      debtor: debtorName,
+    });
+  }
+
+  if (debtor.id === currentUser.id) {
+    return t('expense_details.add_expense_details.split_type_section.direction.you_owe', {
+      payer: payerName,
+    });
+  }
+
+  return t('expense_details.add_expense_details.split_type_section.direction.owes_payer', {
+    debtor: debtorName,
+    payer: payerName,
+  });
 }
 
 export function getCurrencyName(t: TFunction, code: CurrencyCode, plural = false): string {