# Phase 2: Delivery Processing Core - Implementation Summary

## Files Created/Modified

### New Files Created

1. **`src/BuyerKiosk/SMS/Webhooks/DeliveryStatusProcessor.php`** (270 lines)
   - Central orchestrator for processing SMS delivery status updates
   - Implements 6-step processing flow
   - Handles idempotency and forward-only status transitions
   - Never throws on non-critical failures (Ably, store DB)

2. **`tests/Unit/SMS/Webhooks/DeliveryStatusProcessorTest.php`** (445 lines)
   - Comprehensive test suite with 10 test scenarios
   - Tests all major flows: success, failure, idempotency, edge cases
   - Mocks all dependencies for unit testing

### Files Modified

3. **`src/BuyerKiosk/Chat/Events/ChatAblyPublisher.php`**
   - Updated `publishDeliveryUpdate()` method signature
   - Added parameters: errorReason, customerName, typeNum
   - Enhanced payload with error context for failed deliveries

## Implementation Details

### DeliveryStatusProcessor Features

#### Constructor Dependencies (Injected)
- `SmsUsageTracker` - Updates billing records
- `SmsUsageRepository` - Queries billing records
- `ChatAblyPublisher` - Publishes real-time events
- `JobDispatcher` - Dispatches TaskEngine jobs (Phase 4)

#### Main Method: `processDeliveryUpdate()`

**Parameters:**
- `string $provider` - Provider name (twilio|vonage)
- `string $providerMessageId` - Provider's message ID
- `string $providerStatus` - Raw provider status
- `string|null $errorCode` - Provider error code (if failed)
- `float|null $providerCost` - Actual cost from provider (Vonage only)

**Returns:** `ProcessingResult` - Success status and operation flags

#### 6-Step Processing Flow

**Step 1: Map Status**
```php
$mappedStatus = ($provider === 'twilio')
    ? DeliveryStatusMapper::mapTwilioStatus($providerStatus)
    : DeliveryStatusMapper::mapVonageStatus($providerStatus);
```

**Step 2: Lookup Usage Record**
```php
$usageRecord = $this->repository->findByProviderMessageId($providerMessageId);
if ($usageRecord === null) {
    return ProcessingResult::failure($providerMessageId, 'Usage record not found');
}
```

**Step 3: Idempotency Check**
- Skip if exact same rawStatus already processed
- Skip if attempting backward transition (failed > delivered > sent)
- Always process first delivery update (deliveryStatus is null)

**Step 4: Update Central DB (billingSmsUsage)**
```php
$billingUpdated = $this->tracker->updateDeliveryStatus(
    $providerMessageId,
    $mappedStatus->getDisplayStatus(),
    $mappedStatus->getRawStatus(),
    $errorCode,
    $errorDescription
);
```

**Step 5: Update Store DB (chat_messages)** - NON-FATAL
```php
$chatMessageUpdated = $this->updateChatMessage(
    $typeNum,
    $providerMessageId,
    $mappedStatus->getDisplayStatus()
);
```

**Step 6: Publish Ably Event** - NON-FATAL
```php
$ablyPublished = $this->publishAblyEvent(
    $typeNum,
    $providerMessageId,
    $mappedStatus->getDisplayStatus(),
    $errorDescription
);
```

**Step 7: Dispatch Cost Lookup Job OR Update Cost Directly**
- **Twilio final status (delivered/failed):** Dispatch SmsCostLookupJob (Phase 4 TODO)
- **Vonage with cost:** Call `tracker->updateCost()` directly
- **Non-final status:** No cost job dispatch

**Step 8: Emit Tracking Events**
- `sms.delivery.status_updated` - Every successful status update
- `sms.delivery.failed` - When status is 'failed'
- `sms.webhook.processing_failed` - When processing fails

### Idempotency Strategy

```php
private function shouldProcess(array $usageRecord, MappedStatus $newStatus): bool
{
    $currentStatus = $usageRecord['deliveryStatus'];

    // First delivery update: always process
    if ($currentStatus === null) {
        return true;
    }

    // Skip if exact same rawStatus
    if ($usageRecord['providerRawStatus'] === $newStatus->getRawStatus()) {
        return false;
    }

    // Forward-only: Don't allow backward transitions
    $statusPriority = ['sent' => 0, 'delivered' => 1, 'failed' => 2];
    $currentPriority = $statusPriority[$currentStatus] ?? 0;
    $newPriority = $statusPriority[$newStatus->getDisplayStatus()] ?? 0;

    if ($newPriority <= $currentPriority) {
        return false;
    }

    return true;
}
```

### Error Handling

- **NEVER throws** on non-critical failures
- Store DB update failure → Continue processing, set `chatMessageUpdated = false`
- Ably publish failure → Continue processing, set `ablyPublished = false`
- All exceptions caught and logged via `error_log()`

## Test Coverage

### 10 Test Scenarios

1. **testTwilioDeliveredUpdatesAllSystems** - Full success path
2. **testVonageFailedWithErrorDescription** - Error handling with human-readable description
3. **testUnmatchedProviderMessageId** - Failure result for unknown message
4. **testIdempotencyDuplicateWebhook** - Duplicate webhook is no-op
5. **testForwardOnlyStatusTransitions** - "delivered" cannot be overwritten by "sent"
6. **testStoreDbFailureNonFatal** - Processing continues if store DB fails
7. **testAblyFailureNonFatal** - Processing continues if Ably fails
8. **testTwilioFinalStatusDispatchesCostJob** - Cost job for final status (Phase 4 TODO)
9. **testTwilioNonFinalDoesNotDispatchCostJob** - No cost job for "sent"
10. **testVonageWithCostUpdatesDirectly** - Vonage cost updated directly

### Test Results

```
OK (10 tests, 75 assertions)
```

### PHPStan Results

```
[OK] No errors
```

## Design Decisions

### 1. Store DB Connection Pattern

Used `dbConnectByName('kiosk_' . $typeNum)` to connect to store-specific databases. This follows the existing codebase pattern seen in `ChatBridgeService`.

### 2. PDO Parameter Naming

Used unique parameter names (`:status1`, `:msgId1`, `:threadId1`) to avoid PDO's "HY093: Invalid parameter number" error when reusing named parameters.

### 3. Ably Publisher Signature Enhancement

Enhanced `ChatAblyPublisher::publishDeliveryUpdate()` to accept:
- `errorReason` - Human-readable error for failed deliveries
- `customerName` - Customer name for UI display
- `typeNum` - Store identifier for routing

This allows richer real-time UI updates in the Chat panel.

### 4. Cost Job Dispatch Placeholder

`dispatchCostLookupJob()` method logs a TODO and returns false. This will be implemented in Phase 4 (TaskEngine Jobs) when `SmsCostLookupJob` class is created.

### 5. Tracking Events

Used simple `error_log()` for tracking events. This matches the existing pattern in the codebase. Events can be enhanced later with a dedicated tracking service.

### 6. Non-Fatal Error Handling

Critical path: Update billingSmsUsage (central DB) - MUST succeed
Optional paths: Update chat_messages, publish Ably - MAY fail without breaking flow

This ensures webhook processing is resilient. If store DB is temporarily unavailable, billing tracking continues.

## Integration Points

### Phase 1 Dependencies (✅ Complete)
- `DeliveryStatusMapper` - Status mapping
- `MappedStatus` - Value object
- `ProcessingResult` - Value object
- `SmsUsageTracker` - Billing updates
- `SmsUsageRepository` - Billing queries

### Phase 3 Integration (Next)
- **Twilio Webhook Handler** - Will call `processDeliveryUpdate()` for Twilio DLRs
- **Vonage Webhook Handler** - Will call `processDeliveryUpdate()` for Vonage DLRs

### Phase 4 Integration (Future)
- **SmsCostLookupJob** - TaskEngine job for Twilio cost lookup
- **Job Registry** - Register SmsCostLookupJob
- **JobDispatcher** - Dispatch job with idempotency key

### Frontend Integration (Phase 5)
- **Chat UI** - Listens for `workbook:chat:delivered` Ably events
- **Completed Buys** - Shows delivery status updates
- **Toast Notifications** - Shows failed delivery alerts

## Known Limitations / TODOs

1. **Cost Job Dispatch Not Implemented** (Phase 4)
   - `dispatchCostLookupJob()` logs TODO and returns false
   - Tests marked with `// TODO Phase 4` comments
   - Will be completed when `SmsCostLookupJob` is created

2. **Store DB Mocking in Unit Tests**
   - Unit tests don't mock `dbConnectByName()` - tested in integration tests
   - `chatMessageUpdated` always false in unit tests
   - Full store DB integration tested in Phase 4.5b

3. **Ably Mocking in Unit Tests**
   - Ably calls happen inside `publishAblyEvent()` which catches exceptions
   - Difficult to test Ably throwing in unit tests
   - Full Ably integration tested in Phase 4.5b

## Validation Results

### Unit Tests
```bash
./vendor/bin/phpunit --filter "DeliveryStatusProcessor" tests/Unit/SMS/Webhooks/DeliveryStatusProcessorTest.php
OK (10 tests, 75 assertions)
```

### SMS Test Suite
```bash
./vendor/bin/phpunit tests/Unit/SMS/
OK (116 tests, 509 assertions)
```

### PHPStan Analysis
```bash
./vendor/bin/phpstan analyse src/BuyerKiosk/SMS/Webhooks/
[OK] No errors
```

## Next Steps (Phase 3)

1. **Twilio Webhook Handler** (`TwilioWebhookController.php`)
   - POST endpoint `/api/sms/webhooks/twilio/delivery`
   - Validates Twilio signature
   - Extracts delivery status from webhook payload
   - Calls `DeliveryStatusProcessor::processDeliveryUpdate()`

2. **Vonage Webhook Handler** (`VonageWebhookController.php`)
   - POST endpoint `/api/sms/webhooks/vonage/delivery`
   - Validates Vonage signature
   - Extracts delivery status and cost from webhook payload
   - Calls `DeliveryStatusProcessor::processDeliveryUpdate()`

3. **Sender Modifications**
   - Update `TwilioTextSender::send()` to log `providerMessageId`
   - Update `VonageTextSender::send()` to log `providerMessageId`
   - Ensure all SMS sends create `billingSmsUsage` records

## Summary

Phase 2 is **COMPLETE** with:
- ✅ `DeliveryStatusProcessor` class implemented (270 lines)
- ✅ 10 comprehensive unit tests (445 lines)
- ✅ All tests passing (10/10)
- ✅ PHPStan clean (0 errors)
- ✅ Idempotency and forward-only transitions working
- ✅ Non-fatal error handling implemented
- ✅ Tracking events emitted
- ✅ Ably publisher enhanced with error context
- ⏳ Cost job dispatch placeholder (Phase 4)

The DeliveryStatusProcessor is ready for integration in Phase 3 (Webhook Handlers).