# M-Pesa Callback Validation Update Summary

## Changes Made

### 1. **Database Migration** 
- **File**: `database/migrations/2026_05_05_add_originator_conversation_id_to_transactions_table.php`
- Added explicit `originator_conversation_id` column to transactions table
- Column is indexed for fast lookups during callback processing
- Status: Created (column already existed in schema)

### 2. **MpesaCallbackController - b2cResult() Method**
- **File**: `app/Http/Controllers/Api/MpesaCallbackController.php`
- **Key Changes**:
  - **Explicit ResultCode Validation**: Now explicitly checks `$resultCode === 0` as the success criterion
  - **OriginatorConversationID Match Enforcement**: Validates that received OriginatorConversationID matches stored mpesa_code
  - **Transaction ID Handling**: Sets mpesa_transaction_id to "N/A" string when TransactionID is missing (sandbox behavior)
  - **Result Metadata Capture**: Extracts and logs ResultCode and ResultDesc from M-Pesa response
  - **Success Determination**: Status set to 'completed' ONLY when `ResultCode === 0 AND OriginatorConversationID matches`
  - **Enhanced Logging**: Added comprehensive logging at each validation step:
    - Callback receipt with all identifiers
    - OriginatorConversationID matching
    - Result code and description
    - Validation success/failure
  - **Error Handling**: Returns specific error messages for:
    - Missing Result payload
    - Missing OriginatorConversationID
    - Transaction not found
    - OriginatorConversationID mismatch

### 3. **TransactionService - updateMpesaCallback() Method**
- **File**: `app/Services/TransactionService.php`
- **Key Changes**:
  - Now stores `originator_conversation_id` in database
  - Captures mpesa_result_code and mpesa_result_desc in callback_data JSON for audit trail
  - Failed transactions now include failure reason in callback_data
  - All result metadata preserved for debugging and reporting

### 4. **LoanService - processMpesaCallback() Method**
- **File**: `app/Services/LoanService.php`
- **Key Changes**:
  - Added comprehensive logging for callback processing
  - Logs loan status transitions when loan is activated
  - Logs result_code and result_desc for each callback
  - Logs when loan activation occurs (only on successful ResultCode: 0)
  - Logs warnings for failed callbacks with failure reasons
  - Clear indication that status='completed' only occurs when ResultCode is 0

## Callback Validation Flow

```
M-Pesa Result Callback Received
├─ Extract OriginatorConversationID from Result.OriginatorConversationID
├─ Extract ResultCode (must be 0 for success)
├─ Extract ResultDesc (for error diagnosis)
├─ Find transaction by mpesa_code (OriginatorConversationID)
├─ Validate OriginatorConversationID matches stored mpesa_code
├─ Determine status:
│  ├─ If ResultCode === 0 AND OriginatorConversationID matches → status = 'completed'
│  └─ Otherwise → status = 'failed'
├─ Extract TransactionID (or store "N/A" if missing)
├─ Store result_code and result_desc in callback_data
└─ Activate loan only if status = 'completed'
```

## Success Criteria

A transaction is marked as **successfully completed** only when:
1. **ResultCode = 0** (M-Pesa transaction successful)
2. **OriginatorConversationID matches** the stored mpesa_code (correct transaction matched)
3. **Loan transitions from pending/approved → active** (only on combined success)

## Failure Handling

If ResultCode ≠ 0:
1. Transaction marked as 'failed'
2. ResultDesc captured in callback_data for audit trail
3. Loan remains in current status (not activated)
4. Full failure details logged for debugging

## Transaction ID Handling

- **Sandbox Environment**: TransactionID may not be provided in Result callback
  - Stored as "N/A" string (not null) for clarity
  - Distinguishes from failed transactions
- **Production Environment**: TransactionID always provided by M-Pesa
  - Stored as actual transaction ID from Result payload

## Database Storage

Each transaction now stores:
- **mpesa_code**: Original OriginatorConversationID (app-generated UUID)
- **originator_conversation_id**: Explicit copy of OriginatorConversationID  
- **mpesa_transaction_id**: M-Pesa TransactionID (or "N/A" in sandbox)
- **callback_data**: Full Result payload + metadata:
  - mpesa_result_code: ResultCode from M-Pesa
  - mpesa_result_desc: ResultDesc from M-Pesa (failure reason)
  - Original Result array for audit

## Logging Visibility

### Backend Logs (storage/logs/laravel.log)
- Callback receipt with all identifiers
- OriginatorConversationID validation
- Result code and description
- Loan activation confirmation
- Failure details with reason

### Transaction Callback Data
- Full M-Pesa Result payload stored
- ResultCode and ResultDesc preserved
- Transaction ID (actual or "N/A")
- Timestamp of processing

## Testing Recommendations

1. **Success Scenario**:
   - Initiate disbursement (generates OriginatorConversationID)
   - Send callback with ResultCode: 0
   - Verify loan activated and transaction marked 'completed'
   - Check logs show "Activating loan after successful M-Pesa callback"

2. **Failure Scenario**:
   - Send callback with ResultCode: 1 (insufficient balance) or other non-zero code
   - Verify transaction marked 'failed'
   - Check logs show "M-Pesa callback indicated failed status" with ResultDesc
   - Verify loan NOT activated

3. **Sandbox Edge Case**:
   - Verify TransactionID stored as "N/A" in sandbox responses
   - Confirm loan still activated when TransactionID is "N/A" + ResultCode is 0

4. **Originator Mismatch**:
   - Send callback with mismatched OriginatorConversationID
   - Verify 422 error response
   - Check logs show "OriginatorConversationID mismatch"
