# Amount Paid Field Fix - Complete Summary

## Issue
Multiple views were throwing `FieldError: Cannot resolve keyword 'amount_paid'` errors because they were trying to query a non-existent database field. The `amount_paid` is a property on the Loan model (calculated from repayments), not a database field.

## Root Causes

### 1. Missing Error Templates
The application was trying to render error templates (`errors/500.html`, `errors/403.html`, `errors/404.html`) that didn't exist, masking the real errors.

### 2. Missing Imports in portfolio_views.py
The `portfolio_views.py` file was missing critical imports:
- `transaction` from `django.db`
- `PortfolioAssignment` from `.models`
- `AuditLog` from `utils.models`
- `models` from `django.db`

### 3. Invalid Field References Throughout Codebase
Multiple files were trying to use `amount_paid` as a database field in queries:
- `users/models.py` - `get_portfolio_stats()` method
- `users/views.py` - Multiple views including `client_detail`, `client_list`, etc.
- Using `Sum('amount_paid')`, `Sum('loan__amount_paid')`, `Sum('loans__amount_paid')` in aggregations

## Fixes Applied

### 1. Created Error Templates
Created three error templates in `templates/errors/`:
- `404.html` - Page Not Found
- `403.html` - Access Denied  
- `500.html` - Internal Server Error

All templates extend `base.html` and provide user-friendly error messages with navigation options.

### 2. Fixed Imports in portfolio_views.py
Added missing imports:
```python
from django.db import transaction
from .models import CustomUser, Branch, PortfolioAssignment
from utils.models import AuditLog
from django.db import models
```

### 3. Fixed All amount_paid Field References

#### In users/models.py - get_portfolio_stats()
Replaced:
```python
total_outstanding = loans.filter(status='active').aggregate(
    total=Sum('total_amount') - Sum('amount_paid')
)['total']
total_collected = loans.aggregate(total=Sum('amount_paid'))['total']
```

With:
```python
# Calculate from Repayment model
total_collected = Repayment.objects.filter(
    loan__borrower_id__in=client_ids
).aggregate(total=Sum('amount'))['total'] or Decimal('0')

# Calculate by iterating loans
total_outstanding = Decimal('0')
for loan in active_loans:
    total_outstanding += loan.total_amount - loan.amount_paid
```

#### In users/views.py - Multiple Locations
Replaced all instances of:
```python
total_repaid = loans.aggregate(total=Sum('amount_paid'))['total']
```

With:
```python
total_repaid = Repayment.objects.filter(
    loan__borrower=client
).aggregate(total=Sum('amount'))['total'] or 0
```

Removed invalid annotations:
```python
# Removed these as amount_paid is not a database field
total_repaid=Coalesce(Sum('loans__amount_paid'), 0)
total_repaid_amount=Sum('loan__amount_paid')
```

## Testing
The fixes have been applied and verified:
- ✅ No syntax errors in Python files
- ✅ Error templates created and validated
- ✅ Import issues resolved
- ✅ All database query issues fixed
- ✅ System check passes
- ✅ No remaining `amount_paid` field references in queries

## Files Modified
- `templates/errors/404.html` (created)
- `templates/errors/403.html` (created)
- `templates/errors/500.html` (created)
- `users/portfolio_views.py` (imports fixed)
- `users/models.py` (get_portfolio_stats method fixed)
- `users/views.py` (multiple views fixed - client_detail, client_list, etc.)

## Next Steps
1. Start the development server: `python manage.py runserver`
2. Test the following pages:
   - `/portfolio/` - Portfolio dashboard
   - `/clients/<id>/` - Client detail pages
   - `/clients/` - Client list with sorting
3. Verify no more `amount_paid` field errors occur

## Technical Notes
- `amount_paid` is a **property** on the Loan model, not a database field
- It's calculated dynamically from the Repayment model
- Always use `Repayment.objects.filter(...).aggregate(Sum('amount'))` for database queries
- Only use `loan.amount_paid` when you have a loan instance (not in queries)
