================================================================================
MWAMBA LOAN CALCULATION ISSUE - VISUAL EXPLANATION
================================================================================

LOAN-000131: PETER IRUNGU MAINA
Product: Mwamba (90 days, 10% monthly interest, 5% processing fee)

┌─────────────────────────────────────────────────────────────────────────────┐
│                         WHAT THE DATABASE SHOWS                             │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  Principal Amount:        KES 20,000.00  ✓ CORRECT                         │
│  Interest Amount:         KES  6,000.00  ✓ CORRECT (30% for 90 days)      │
│  Processing Fee:          KES  1,000.00  ✓ CORRECT (5%)                    │
│  ─────────────────────────────────────────────────────────                 │
│  Total Amount (stored):   KES 22,400.00  ✗ WRONG! (Missing 4,600)         │
│                                                                             │
│  Amount Paid:             KES  3,200.00  ✓ CORRECT                         │
│  ─────────────────────────────────────────────────────────                 │
│  Outstanding (displayed): KES 19,200.00  ✗ WRONG! (22,400 - 3,200)        │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

                                    ⬇️  FIX NEEDED  ⬇️

┌─────────────────────────────────────────────────────────────────────────────┐
│                         WHAT IT SHOULD SHOW                                 │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  Principal Amount:        KES 20,000.00  ✓                                 │
│  Interest Amount:         KES  6,000.00  ✓                                 │
│  Processing Fee:          KES  1,000.00  ✓                                 │
│  ─────────────────────────────────────────────────────────                 │
│  Total Amount (correct):  KES 27,000.00  ✓ (20,000 + 6,000 + 1,000)       │
│                                                                             │
│  Amount Paid:             KES  3,200.00  ✓                                 │
│  ─────────────────────────────────────────────────────────                 │
│  Outstanding (correct):   KES 23,800.00  ✓ (27,000 - 3,200)               │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

================================================================================
                              THE CALCULATION
================================================================================

MWAMBA PRODUCT RULES:
  • Interest Rate: 10% per month
  • Duration: 90 days = 3 months
  • Processing Fee: 5% (one-time)

CORRECT CALCULATION:
  Principal:       20,000.00
  Interest:        20,000 × 10% × 3 months = 6,000.00
  Processing Fee:  20,000 × 5% = 1,000.00
  ────────────────────────────────────────────
  TOTAL:           20,000 + 6,000 + 1,000 = 27,000.00

WHAT'S IN DATABASE:
  Principal:       20,000.00
  Interest:        6,000.00
  Processing Fee:  1,000.00
  ────────────────────────────────────────────
  TOTAL (stored):  22,400.00  ← WRONG!

DIFFERENCE:        27,000 - 22,400 = 4,600.00 MISSING

================================================================================
                              WHY THIS HAPPENED
================================================================================

The code logic is CORRECT:
  ✓ LoanApplication.save() calculates: principal + interest + processing_fee
  ✓ LoanApplication.approve() uses calculated_total
  ✓ LoanCalculationService uses the stored total_amount

The problem is BAD DATA in the database:
  ✗ Someone/something wrote 22,400 instead of 27,000 to the database
  ✗ This could be from:
      - Manual database edit
      - Old bug (now fixed)
      - Data migration issue
      - Direct SQL insert

================================================================================
                              THE FIX
================================================================================

UPDATE loans 
SET total_amount = principal_amount + interest_amount + processing_fee
WHERE loan_number = 'LOAN-000131';

This will change:
  total_amount: 22,400.00 → 27,000.00

Which will fix:
  Outstanding: 19,200.00 → 23,800.00

================================================================================
                              IMPACT
================================================================================

BEFORE FIX:
  Borrower sees: "You owe KES 19,200"
  Reality: They owe KES 23,800
  Difference: KES 4,600 underreported ❌

AFTER FIX:
  Borrower sees: "You owe KES 23,800"
  Reality: They owe KES 23,800
  Difference: KES 0 ✅

================================================================================
                              FILES PROVIDED
================================================================================

1. FIX_MWAMBA_CALCULATION_ISSUE.md     - Detailed analysis
2. fix_mwamba_loan_totals.sql          - SQL fix script
3. diagnose_and_fix_mwamba_loan_131.py - Python diagnostic tool
4. MWAMBA_CALCULATION_FIX_SUMMARY.md   - Complete summary
5. QUICK_FIX_MWAMBA.txt                - Quick reference
6. MWAMBA_ISSUE_DIAGRAM.txt            - This file

================================================================================