# Phase 4: SMS Integration Hooks — Implementation Summary

## Overview

Phase 4 integrates the SMS usage billing tracker into `TextMessageService` and adds dual-write capability to `ChatApiController`. After this phase, **every SMS send in the system is automatically tracked for billing**.

**Status:** ✅ COMPLETE

## What Was Implemented

### 1. TextMessageService Integration

**File:** `userfrosting/src/BuyerKiosk/SMS/TextMessageService/TextMessageService.php`

#### Changes:
- ✅ Added `SmsUsageTrackerInterface` as 4th constructor parameter
- ✅ Added `logBillingUsage()` private method (never blocks SMS sends)
- ✅ Added `logBillingFallback()` for filesystem logging when DB fails
- ✅ Added `calculateSegmentCount()` for GSM-7 and UCS-2 encoding
- ✅ Billing hooks added to all send methods:
  - `sendBuyText()` → logs `SmsCategory::BUY_COMPLETION`
  - `sendServiceText()` → logs `SmsCategory::SERVICE_COMPLETION`
  - `sendSurveyText()` → logs `SmsCategory::SURVEY`
  - `sendCustomText()` → logs `SmsCategory::CUSTOM`

#### Safety Features:
- Uses `try/catch (\Throwable $e)` to ensure billing failures never block SMS
- Falls back to filesystem logging (`logs/billing-sms-fallback.log`) if DB fails
- All logging happens AFTER the SMS send completes

### 2. Store Integration

**File:** `userfrosting/src/BuyerKiosk/Core/Store.php`

#### Changes:
- ✅ Modified `__construct()` to create usage tracker before TextMessageService
- ✅ Modified `setTextMessageService()` to pass usage tracker to TextMessageService
- ✅ Added `createSmsUsageTracker()` private method:
  - Returns `SmsUsageTracker` if billing is active
  - Returns `NullSmsUsageTracker` if billing initialization fails
  - Never throws — always returns a valid tracker

### 3. Chat API Dual-Write

**File:** `userfrosting/src/BuyerKiosk/Chat/Controllers/ChatApiController.php`

#### Changes:
- ✅ Added dual-write to `billingSmsUsage` table after existing `chatSmsUsage` write
- ✅ Maps chat categories to billing categories:
  - `interactive` → `SmsCategory::CHAT_INTERACTIVE`
  - `transactional` → `SmsCategory::CHAT_TRANSACTIONAL`
- ✅ Catches all exceptions to prevent request failures

#### ADR-5 Compliance:
Per ADR-5, `billingSmsUsage` is the **sole source of truth** for billing. The `chatSmsUsage` table will be migrated away in future phases. This dual-write ensures both tables stay in sync during transition.

## Testing

### Unit Tests

**File:** `userfrosting/tests/Unit/Billing/Integration/TextMessageServiceBillingTest.php`

✅ **13 tests, 38 assertions** — ALL PASSING

Tests cover:
1. ✅ Constructor requires 4th parameter (SmsUsageTrackerInterface)
2. ✅ Billing logging with successful SMS
3. ✅ Billing logging with failed SMS (billable=false)
4. ✅ Non-billable category handling
5. ✅ Tracker exceptions don't block SMS sends
6. ✅ NullSmsUsageTracker compatibility
7. ✅ GSM-7 segment calculation (single, multi-segment)
8. ✅ UCS-2 segment calculation (emoji support)
9. ✅ Empty message handling
10. ✅ Mixed content encoding detection

### Full Test Suite

```bash
./vendor/bin/phpunit tests/Unit/Billing/
```

**Result:** ✅ 150 tests, 793 assertions — ALL PASSING

No regressions introduced to existing billing functionality.

### Validation Script

**File:** `userfrosting/validate_billing_integration.php`

```bash
php userfrosting/validate_billing_integration.php
```

**Result:** ✅ All 5 validation tests passed

Validates:
- Constructor signature
- Store creates usage tracker
- NullTracker compatibility
- Segment calculation
- Billing methods exist

## Segment Count Logic

### GSM-7 Encoding (Standard ASCII)
- **1 segment:** ≤160 characters
- **2+ segments:** First 160 chars + 153 chars per additional segment

### UCS-2 Encoding (Unicode/Emoji)
- **1 segment:** ≤70 characters
- **2+ segments:** First 70 chars + 67 chars per additional segment

**Detection:** Uses regex `/^[\x20-\x7E\n\r]*$/` to determine if message is GSM-7 compatible.

## Database Schema

All SMS sends now write to `billingSmsUsage` table:

```sql
CREATE TABLE billingSmsUsage (
  id INT AUTO_INCREMENT PRIMARY KEY,
  typeNum VARCHAR(6) NOT NULL,
  category VARCHAR(30) NOT NULL,
  segmentCount TINYINT UNSIGNED NOT NULL,
  provider VARCHAR(20) NOT NULL,
  providerMessageId VARCHAR(100),
  sentAt DATETIME NOT NULL,
  success TINYINT(1) NOT NULL,
  billable TINYINT(1) NOT NULL,
  INDEX idx_typenum_sentat (typeNum, sentAt),
  INDEX idx_category (category),
  INDEX idx_billable (billable)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
```

## Usage Flow

```mermaid
graph TD
    A[SMS Send Request] --> B[TextMessageService.sendBuyText]
    B --> C[textSender.sendText]
    C --> D{Send Success?}
    D -->|Yes| E[logBillingUsage]
    D -->|No| E
    E --> F{isCategoryBillable?}
    F -->|Yes & Success| G[billable=true]
    F -->|No or Failed| H[billable=false]
    G --> I[usageTracker.logUsage]
    H --> I
    I --> J{Insert Success?}
    J -->|Yes| K[Return SMS Result]
    J -->|No| L[logBillingFallback]
    L --> K
```

**Key Point:** SMS send ALWAYS completes. Billing tracking failures are logged but never block sends.

## Files Modified

1. `userfrosting/src/BuyerKiosk/SMS/TextMessageService/TextMessageService.php`
2. `userfrosting/src/BuyerKiosk/Core/Store.php`
3. `userfrosting/src/BuyerKiosk/Chat/Controllers/ChatApiController.php`

## Files Created

1. `userfrosting/tests/Unit/Billing/Integration/TextMessageServiceBillingTest.php`
2. `userfrosting/validate_billing_integration.php`
3. `docs/billing/PHASE4_IMPLEMENTATION_SUMMARY.md` (this file)

## What Happens Now

✅ **Every SMS send across the entire system is tracked for billing:**

| Send Method | Category | Tracked? |
|-------------|----------|----------|
| `sendBuyText()` | `buy_completion` | ✅ |
| `sendServiceText()` | `service_completion` | ✅ |
| `sendSurveyText()` | `survey` | ✅ |
| `sendCustomText()` | `custom` | ✅ |
| Chat Interactive | `chat_interactive` | ✅ |
| Chat Transactional | `chat_transactional` | ✅ |

## Next Phase

**Phase 5:** Billing API Endpoints (if needed for admin UI)

Potential endpoints:
- `GET /api/billing/sms-usage?typeNum=ou00&period=2025-01` — Usage summary
- `GET /api/billing/sms-usage/trends?typeNum=ou00` — Monthly trends
- `POST /api/billing/invoices/generate` — Generate invoice for period

## Rollback Plan

If issues arise, Phase 4 can be rolled back without data loss:

1. Revert TextMessageService to 3-parameter constructor
2. Revert Store changes (remove createSmsUsageTracker)
3. Revert ChatApiController dual-write
4. Billing data remains intact — no destructive migrations

**Data Safety:** All changes are additive. No existing functionality is removed.

## Verification Checklist

- [x] TextMessageService requires SmsUsageTrackerInterface
- [x] Store creates usage tracker automatically
- [x] NullSmsUsageTracker works for testing
- [x] All send methods log billing usage
- [x] Failed sends mark billable=false
- [x] Tracker exceptions don't block SMS
- [x] Segment calculation handles GSM-7 and UCS-2
- [x] Chat API dual-writes to billingSmsUsage
- [x] Unit tests pass (150/150)
- [x] Validation script passes
- [x] PHPStan shows no new type errors

---

**Implementation Date:** 2026-02-10
**Status:** ✅ Complete and Tested
**Breaking Changes:** None
**Migration Required:** No