# Technical Implementation Notes: Backend Architecture Pivot

**Feature**: 005-backend-arch-pivot  
**Created**: 2025-12-09  
**Purpose**: Detailed implementation guidance for developers (not part of business specification)

---

## BullMQ Setup

### Installation

```bash
npm install bullmq ioredis
```

### Redis Connection

**File**: `lib/queue/redis.ts`

```typescript
import IORedis from 'ioredis';
import { env } from '@/lib/env.mjs';

export const redisConnection = new IORedis(env.REDIS_URL, {
  maxRetriesPerRequest: null, // BullMQ requirement
});
```

### Queue Definition

**File**: `lib/queue/syncQueue.ts`

```typescript
import { Queue } from 'bullmq';
import { redisConnection } from './redis';

export const syncQueue = new Queue('intune-sync-queue', {
  connection: redisConnection,
});
```

---

## Worker Implementation

### Worker Entry Point

**File**: `worker/index.ts`

```typescript
import { Worker } from 'bullmq';
import { redisConnection } from '@/lib/queue/redis';
import { syncPolicies } from './jobs/syncPolicies';

const worker = new Worker(
  'intune-sync-queue',
  async (job) => {
    console.log(`Processing job ${job.id} for tenant ${job.data.tenantId}`);
    await syncPolicies(job.data.tenantId);
  },
  {
    connection: redisConnection,
    concurrency: 1, // Sequential processing
  }
);

worker.on('completed', (job) => {
  console.log(`Job ${job.id} completed`);
});

worker.on('failed', (job, err) => {
  console.error(`Job ${job?.id} failed:`, err);
});

console.log('Worker started, listening on intune-sync-queue...');
```

### Package.json Script

```json
{
  "scripts": {
    "worker:start": "tsx watch worker/index.ts"
  }
}
```

---

## Sync Logic Architecture

### Main Function

**File**: `worker/jobs/syncPolicies.ts`

```typescript
export async function syncPolicies(tenantId: string) {
  // 1. Get Access Token
  const token = await getGraphAccessToken();
  
  // 2. Fetch all policy types
  const policies = await fetchAllPolicies(token);
  
  // 3. Parse & Flatten
  const flattenedSettings = policies.flatMap(policy => 
    parsePolicySettings(policy)
  );
  
  // 4. Upsert to Database
  await upsertPolicySettings(tenantId, flattenedSettings);
}
```

### Authentication (Client Credentials)

```typescript
import { ClientSecretCredential } from '@azure/identity';

async function getGraphAccessToken(): Promise<string> {
  const credential = new ClientSecretCredential(
    'common', // or specific tenant ID
    env.AZURE_AD_CLIENT_ID,
    env.AZURE_AD_CLIENT_SECRET
  );
  
  const token = await credential.getToken('https://graph.microsoft.com/.default');
  return token.token;
}
```

### Pagination Handling

```typescript
async function fetchWithPagination<T>(url: string, token: string): Promise<T[]> {
  let results: T[] = [];
  let nextLink: string | undefined = url;
  
  while (nextLink) {
    const response = await fetch(nextLink, {
      headers: { Authorization: `Bearer ${token}` }
    });
    const data = await response.json();
    
    results = results.concat(data.value);
    nextLink = data['@odata.nextLink'];
  }
  
  return results;
}
```

### Graph API Endpoints

```typescript
const GRAPH_ENDPOINTS = {
  deviceConfigurations: 'https://graph.microsoft.com/v1.0/deviceManagement/deviceConfigurations',
  compliancePolicies: 'https://graph.microsoft.com/v1.0/deviceManagement/deviceCompliancePolicies',
  configurationPolicies: 'https://graph.microsoft.com/v1.0/deviceManagement/configurationPolicies',
  intents: 'https://graph.microsoft.com/v1.0/deviceManagement/intents',
};

async function fetchAllPolicies(token: string) {
  const [configs, compliance, configPolicies, intents] = await Promise.all([
    fetchWithPagination(GRAPH_ENDPOINTS.deviceConfigurations, token),
    fetchWithPagination(GRAPH_ENDPOINTS.compliancePolicies, token),
    fetchWithPagination(GRAPH_ENDPOINTS.configurationPolicies, token),
    fetchWithPagination(GRAPH_ENDPOINTS.intents, token),
  ]);
  
  return [...configs, ...compliance, ...configPolicies, ...intents];
}
```

---

## Flattening Strategy

### Settings Catalog (Most Complex)

```typescript
function parseSettingsCatalog(policy: any): FlattenedSetting[] {
  if (!policy.settings) return [defaultEmptySetting(policy)];
  
  return policy.settings.flatMap(setting => {
    const settingId = setting.settingInstance.settingDefinitionId;
    const value = extractValue(setting.settingInstance);
    
    return {
      settingName: humanizeSettingId(settingId),
      settingValue: JSON.stringify(value),
      settingValueType: typeof value,
    };
  });
}

function extractValue(settingInstance: any): any {
  // Handle different value types
  if (settingInstance.simpleSettingValue) {
    return settingInstance.simpleSettingValue.value;
  }
  
  if (settingInstance.choiceSettingValue) {
    return settingInstance.choiceSettingValue.value;
  }
  
  if (settingInstance.groupSettingCollectionValue) {
    return settingInstance.groupSettingCollectionValue.children.map(
      (child: any) => extractValue(child)
    );
  }
  
  return null;
}
```

### OMA-URI

```typescript
function parseOmaUri(policy: any): FlattenedSetting[] {
  if (!policy.omaSettings) return [defaultEmptySetting(policy)];
  
  return policy.omaSettings.map(oma => ({
    settingName: oma.omaUri,
    settingValue: oma.value,
    settingValueType: oma.valueType || 'string',
  }));
}
```

### Humanizer

```typescript
function humanizeSettingId(id: string): string {
  return id
    .replace(/^device_vendor_msft_policy_config_/i, '')
    .replace(/_/g, ' ')
    .replace(/\b\w/g, c => c.toUpperCase());
}
```

### Default Empty Setting

```typescript
function defaultEmptySetting(policy: any): FlattenedSetting {
  return {
    policyId: policy.id,
    policyName: policy.displayName,
    policyType: detectPolicyType(policy['@odata.type']),
    settingName: '(No settings configured)',
    settingValue: '',
    settingValueType: 'empty',
    path: '',
  };
}
```

### Policy Type Detection

```typescript
function detectPolicyType(odataType: string): string {
  const typeMap: Record<string, string> = {
    '#microsoft.graph.deviceManagementConfigurationPolicy': 'configurationPolicy',
    '#microsoft.graph.windows10CustomConfiguration': 'deviceConfiguration',
    '#microsoft.graph.windows10EndpointProtectionConfiguration': 'endpointSecurity',
    '#microsoft.graph.deviceCompliancePolicy': 'compliancePolicy',
    '#microsoft.graph.windowsUpdateForBusinessConfiguration': 'windowsUpdateForBusiness',
    '#microsoft.graph.iosCustomConfiguration': 'deviceConfiguration',
    '#microsoft.graph.androidManagedAppProtection': 'appConfiguration',
  };
  
  return typeMap[odataType] || 'unknown';
}
```

---

## Database Upsert

**File**: `worker/jobs/upsertPolicySettings.ts`

```typescript
import { db } from '@/lib/db';
import { policySettings } from '@/lib/db/schema/policySettings';
import { sql } from 'drizzle-orm';

async function upsertPolicySettings(
  tenantId: string, 
  settings: FlattenedSetting[]
) {
  const records = settings.map(s => ({
    tenantId,
    graphPolicyId: s.policyId,
    policyName: s.policyName,
    policyType: s.policyType,
    settingName: s.settingName,
    settingValue: s.settingValue,
    settingValueType: s.settingValueType,
    lastSyncedAt: new Date(),
  }));
  
  // Batch insert with conflict resolution
  await db.insert(policySettings)
    .values(records)
    .onConflictDoUpdate({
      target: [
        policySettings.tenantId, 
        policySettings.graphPolicyId, 
        policySettings.settingName
      ],
      set: {
        policyName: sql`EXCLUDED.policy_name`,
        policyType: sql`EXCLUDED.policy_type`,
        settingValue: sql`EXCLUDED.setting_value`,
        settingValueType: sql`EXCLUDED.setting_value_type`,
        lastSyncedAt: sql`EXCLUDED.last_synced_at`,
      },
    });
}
```

---

## Frontend Integration

### Server Action Update

**File**: `lib/actions/policySettings.ts`

**Before** (n8n Webhook):
```typescript
const response = await fetch(env.N8N_SYNC_WEBHOOK_URL, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ tenantId }),
});
```

**After** (BullMQ Job):
```typescript
import { syncQueue } from '@/lib/queue/syncQueue';

export async function triggerPolicySync(tenantId: string) {
  const job = await syncQueue.add('sync-tenant', { 
    tenantId,
    triggeredAt: new Date(),
  });
  
  return { 
    success: true,
    jobId: job.id,
    message: 'Sync job created successfully' 
  };
}
```

---

## Environment Variables

### .env Changes

**Add**:
```bash
REDIS_URL=redis://localhost:6379
```

**Remove**:
```bash
# POLICY_API_SECRET=... (DELETE)
# N8N_SYNC_WEBHOOK_URL=... (DELETE)
```

### lib/env.mjs Updates

```typescript
import { createEnv } from "@t3-oss/env-nextjs";
import { z } from "zod";

export const env = createEnv({
  server: {
    DATABASE_URL: z.string().url(),
    NEXTAUTH_SECRET: z.string().min(1),
    NEXTAUTH_URL: z.string().url(),
    AZURE_AD_CLIENT_ID: z.string().min(1),
    AZURE_AD_CLIENT_SECRET: z.string().min(1),
    REDIS_URL: z.string().url(), // ADD THIS
    // REMOVE: POLICY_API_SECRET, N8N_SYNC_WEBHOOK_URL
  },
  client: {},
  runtimeEnv: {
    DATABASE_URL: process.env.DATABASE_URL,
    NEXTAUTH_SECRET: process.env.NEXTAUTH_SECRET,
    NEXTAUTH_URL: process.env.NEXTAUTH_URL,
    AZURE_AD_CLIENT_ID: process.env.AZURE_AD_CLIENT_ID,
    AZURE_AD_CLIENT_SECRET: process.env.AZURE_AD_CLIENT_SECRET,
    REDIS_URL: process.env.REDIS_URL, // ADD THIS
  },
});
```

---

## Retry & Error Handling

### Exponential Backoff

```typescript
async function fetchWithRetry<T>(
  url: string,
  token: string,
  maxRetries = 3
): Promise<T> {
  let lastError: Error | null = null;
  
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      const response = await fetch(url, {
        headers: { Authorization: `Bearer ${token}` }
      });
      
      if (response.status === 429) {
        // Rate limit - exponential backoff
        const delay = Math.pow(2, attempt) * 1000;
        await new Promise(resolve => setTimeout(resolve, delay));
        continue;
      }
      
      if (!response.ok) {
        throw new Error(`HTTP ${response.status}: ${response.statusText}`);
      }
      
      return await response.json();
    } catch (error) {
      lastError = error as Error;
      
      // Don't retry on auth errors
      if (error instanceof Error && error.message.includes('401')) {
        throw error;
      }
      
      // Exponential backoff for transient errors
      if (attempt < maxRetries - 1) {
        const delay = Math.pow(2, attempt) * 1000;
        await new Promise(resolve => setTimeout(resolve, delay));
      }
    }
  }
  
  throw lastError || new Error('Max retries exceeded');
}
```

---

## Docker Compose Setup (Optional)

**File**: `docker-compose.yml`

```yaml
version: '3.8'

services:
  redis:
    image: redis:alpine
    ports:
      - '6379:6379'
    volumes:
      - redis-data:/data
    restart: unless-stopped

volumes:
  redis-data:
```

Start Redis:
```bash
docker-compose up -d redis
```

---

## Production Deployment

### Worker as Systemd Service

**File**: `/etc/systemd/system/tenantpilot-worker.service`

```ini
[Unit]
Description=TenantPilot Policy Sync Worker
After=network.target redis.service

[Service]
Type=simple
User=www-data
WorkingDirectory=/var/www/tenantpilot
ExecStart=/usr/bin/node /var/www/tenantpilot/worker/index.js
Restart=on-failure
RestartSec=10
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target
```

Enable & Start:
```bash
sudo systemctl enable tenantpilot-worker
sudo systemctl start tenantpilot-worker
sudo systemctl status tenantpilot-worker
```

---

## Testing Strategy

### Unit Tests

```typescript
import { describe, it, expect, vi } from 'vitest';
import { humanizeSettingId } from './humanizer';

describe('humanizeSettingId', () => {
  it('removes device_vendor_msft_policy_config prefix', () => {
    const result = humanizeSettingId('device_vendor_msft_policy_config_wifi_allowwifihotspotreporting');
    expect(result).toBe('Wifi Allowwifihotspotreporting');
  });
});
```

### Integration Tests

```typescript
describe('syncPolicies', () => {
  it('fetches and stores policies for tenant', async () => {
    const testTenantId = 'test-tenant-123';
    
    await syncPolicies(testTenantId);
    
    const settings = await db.query.policySettings.findMany({
      where: eq(policySettings.tenantId, testTenantId),
    });
    
    expect(settings.length).toBeGreaterThan(0);
  });
});
```

---

## Monitoring & Logging

### Structured Logging

```typescript
import winston from 'winston';

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.json(),
  transports: [
    new winston.transports.File({ filename: 'worker-error.log', level: 'error' }),
    new winston.transports.File({ filename: 'worker-combined.log' }),
  ],
});

// In worker:
logger.info('Job started', { jobId: job.id, tenantId: job.data.tenantId });
logger.error('Job failed', { jobId: job.id, error: err.message });
```

### Health Check Endpoint

**File**: `app/api/worker-health/route.ts`

```typescript
import { syncQueue } from '@/lib/queue/syncQueue';

export async function GET() {
  try {
    const jobCounts = await syncQueue.getJobCounts();
    
    return Response.json({
      status: 'healthy',
      queue: jobCounts,
    });
  } catch (error) {
    return Response.json(
      { status: 'unhealthy', error: (error as Error).message },
      { status: 500 }
    );
  }
}
```

---

## Migration Checklist

- [ ] Install dependencies (`bullmq`, `ioredis`, `@azure/identity`)
- [ ] Add `REDIS_URL` to `.env`
- [ ] Create `lib/queue/redis.ts` and `lib/queue/syncQueue.ts`
- [ ] Create `worker/index.ts` with BullMQ Worker
- [ ] Implement `worker/jobs/syncPolicies.ts` with full logic
- [ ] Update `lib/actions/policySettings.ts` → replace n8n webhook with BullMQ
- [ ] Remove `app/api/policy-settings/route.ts`
- [ ] Remove `app/api/admin/tenants/route.ts`
- [ ] Remove `POLICY_API_SECRET` from `.env` and `lib/env.mjs`
- [ ] Remove `N8N_SYNC_WEBHOOK_URL` from `.env` and `lib/env.mjs`
- [ ] Add `worker:start` script to `package.json`
- [ ] Test locally: Start Redis, Start Worker, Trigger Sync from UI
- [ ] Deploy Worker as background service (PM2/Systemd/Docker)
- [ ] Verify end-to-end: Job creation → Worker processing → Database updates