Enhance Cospend with debt breakdown and predefined users

- Add EnhancedBalance component with integrated single-user debt display
- Create DebtBreakdown component for multi-user debt overview
- Add predefined users configuration (alexander, anna)
- Implement personal + equal split payment method
- Add profile pictures throughout payment interfaces
- Integrate debt information with profile pictures in balance view
- Auto-hide debt breakdown when single user (shows in balance instead)
- Support both manual and predefined user management modes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/routes/api/cospend/debts/+server.ts

@@ -0,0 +1,110 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import { PaymentSplit } from '../../../../models/PaymentSplit';
+import { Payment } from '../../../../models/Payment';
+import { dbConnect, dbDisconnect } from '../../../../utils/db';
+import { error, json } from '@sveltejs/kit';
+
+interface DebtSummary {
+  username: string;
+  netAmount: number; // positive = you owe them, negative = they owe you
+  transactions: {
+    paymentId: string;
+    title: string;
+    amount: number;
+    date: Date;
+    category: string;
+  }[];
+}
+
+export const GET: RequestHandler = async ({ locals }) => {
+  const auth = await locals.auth();
+  if (!auth || !auth.user?.nickname) {
+    throw error(401, 'Not logged in');
+  }
+
+  const currentUser = auth.user.nickname;
+
+  await dbConnect();
+  
+  try {
+    // Get all splits for the current user
+    const userSplits = await PaymentSplit.find({ username: currentUser })
+      .populate('paymentId')
+      .lean();
+
+    // Get all other users who have splits with payments involving the current user
+    const paymentIds = userSplits.map(split => split.paymentId._id);
+    const allRelatedSplits = await PaymentSplit.find({
+      paymentId: { $in: paymentIds },
+      username: { $ne: currentUser }
+    })
+      .populate('paymentId')
+      .lean();
+
+    // Group debts by user
+    const debtsByUser = new Map<string, DebtSummary>();
+
+    // Process current user's splits to understand what they owe/are owed
+    for (const split of userSplits) {
+      const payment = split.paymentId as any;
+      if (!payment) continue;
+
+      // Find other participants in this payment
+      const otherSplits = allRelatedSplits.filter(s => 
+        s.paymentId._id.toString() === split.paymentId._id.toString()
+      );
+
+      for (const otherSplit of otherSplits) {
+        const otherUser = otherSplit.username;
+        
+        if (!debtsByUser.has(otherUser)) {
+          debtsByUser.set(otherUser, {
+            username: otherUser,
+            netAmount: 0,
+            transactions: []
+          });
+        }
+
+        const debt = debtsByUser.get(otherUser)!;
+        
+        // Current user's amount: positive = they owe, negative = they are owed
+        // We want to show net between the two users
+        debt.netAmount += split.amount;
+        
+        debt.transactions.push({
+          paymentId: payment._id.toString(),
+          title: payment.title,
+          amount: split.amount,
+          date: payment.date,
+          category: payment.category
+        });
+      }
+    }
+
+    // Convert map to array and sort by absolute amount (largest debts first)
+    const debtSummaries = Array.from(debtsByUser.values())
+      .filter(debt => Math.abs(debt.netAmount) > 0.01) // Filter out tiny amounts
+      .sort((a, b) => Math.abs(b.netAmount) - Math.abs(a.netAmount));
+
+    // Separate into who owes you vs who you owe
+    const whoOwesMe = debtSummaries.filter(debt => debt.netAmount < 0).map(debt => ({
+      ...debt,
+      netAmount: Math.abs(debt.netAmount) // Make positive for display
+    }));
+
+    const whoIOwe = debtSummaries.filter(debt => debt.netAmount > 0);
+
+    return json({
+      whoOwesMe,
+      whoIOwe,
+      totalOwedToMe: whoOwesMe.reduce((sum, debt) => sum + debt.netAmount, 0),
+      totalIOwe: whoIOwe.reduce((sum, debt) => sum + debt.netAmount, 0)
+    });
+
+  } catch (e) {
+    console.error('Error calculating debt breakdown:', e);
+    throw error(500, 'Failed to calculate debt breakdown');
+  } finally {
+    await dbDisconnect();
+  }
+};

src/routes/api/cospend/payments/+server.ts

@@ -48,7 +48,7 @@ export const POST: RequestHandler = async ({ request, locals }) => {
     throw error(400, 'Amount must be positive');
   }
 
-  if (!['equal', 'full', 'proportional'].includes(splitMethod)) {
+  if (!['equal', 'full', 'proportional', 'personal_equal'].includes(splitMethod)) {
     throw error(400, 'Invalid split method');
   }
 
@@ -56,6 +56,17 @@ export const POST: RequestHandler = async ({ request, locals }) => {
     throw error(400, 'Invalid category');
   }
 
+  // Validate personal + equal split method
+  if (splitMethod === 'personal_equal' && splits) {
+    const totalPersonal = splits.reduce((sum: number, split: any) => {
+      return sum + (parseFloat(split.personalAmount) || 0);
+    }, 0);
+    
+    if (totalPersonal > amount) {
+      throw error(400, 'Personal amounts cannot exceed total payment amount');
+    }
+  }
+
   await dbConnect();
   
   try {
@@ -77,7 +88,8 @@ export const POST: RequestHandler = async ({ request, locals }) => {
         paymentId: payment._id,
         username: split.username,
         amount: split.amount,
-        proportion: split.proportion
+        proportion: split.proportion,
+        personalAmount: split.personalAmount
       });
     });
 

src/routes/api/cospend/payments/[id]/+server.ts

@@ -75,7 +75,8 @@ export const PUT: RequestHandler = async ({ params, request, locals }) => {
           paymentId: id,
           username: split.username,
           amount: split.amount,
-          proportion: split.proportion
+          proportion: split.proportion,
+          personalAmount: split.personalAmount
         });
       });