# Data Handling Reference

## Overview
Handle sensitive data correctly when integrating with Supabase.

## Prerequisites
- Understanding of GDPR/CCPA requirements
- Supabase SDK with data export capabilities
- Database for audit logging
- Scheduled job infrastructure for cleanup

## Data Classification

| Category | Examples | Handling |
|----------|----------|----------|
| PII | Email, name, phone | Encrypt, minimize |
| Sensitive | API keys, tokens | Never log, rotate |
| Business | Usage metrics | Aggregate when possible |
| Public | Product names | Standard handling |

## PII Detection

```typescript
const PII_PATTERNS = [
  { type: 'email', regex: /[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/g },
  { type: 'phone', regex: /\d{3}[-.]?\d{3}[-.]?\d{4}/g },
  { type: 'ssn', regex: /\d{3}-\d{2}-\d{4}/g },
  { type: 'credit_card', regex: /\d{4}[- ]?\d{4}[- ]?\d{4}[- ]?\d{4}/g },
];

function detectPII(text: string): { type: string; match: string }[] {
  const findings: { type: string; match: string }[] = [];

  for (const pattern of PII_PATTERNS) {
    const matches = text.matchAll(pattern.regex);
    for (const match of matches) {
      findings.push({ type: pattern.type, match: match[0] });
    }
  }

  return findings;
}
```

## Data Redaction

```typescript
function redactPII(data: Record<string, any>): Record<string, any> {
  const sensitiveFields = ['email', 'phone', 'ssn', 'password', 'apiKey'];
  const redacted = { ...data };

  for (const field of sensitiveFields) {
    if (redacted[field]) {
      redacted[field] = '[REDACTED]';
    }
  }

  return redacted;
}

// Use in logging
console.log('Supabase request:', redactPII(requestData));
```

## Data Retention Policy

### Retention Periods
| Data Type | Retention | Reason |
|-----------|-----------|--------|
| API logs | 30 days | Debugging |
| Error logs | 90 days | Root cause analysis |
| Audit logs | 7 years | Compliance |
| PII | Until deletion request | GDPR/CCPA |

### Automatic Cleanup

```typescript
async function cleanupSupabaseData(retentionDays: number): Promise<void> {
  const cutoff = new Date();
  cutoff.setDate(cutoff.getDate() - retentionDays);

  await db.supabaseLogs.deleteMany({
    createdAt: { $lt: cutoff },
    type: { $nin: ['audit', 'compliance'] },
  });
}

// Schedule daily cleanup
cron.schedule('0 3 * * *', () => cleanupSupabaseData(30));
```

## GDPR/CCPA Compliance

### Data Subject Access Request (DSAR)

```typescript
async function exportUserData(userId: string): Promise<DataExport> {
  const supabaseData = await supabaseClient.getUserData(userId);

  return {
    source: 'Supabase',
    exportedAt: new Date().toISOString(),
    data: {
      profile: supabaseData.profile,
      activities: supabaseData.activities,
      // Include all user-related data
    },
  };
}
```

### Right to Deletion

```typescript
async function deleteUserData(userId: string): Promise<DeletionResult> {
  // 1. Delete from Supabase
  await supabaseClient.deleteUser(userId);

  // 2. Delete local copies
  await db.supabaseUserCache.deleteMany({ userId });

  // 3. Audit log (required to keep)
  await auditLog.record({
    action: 'GDPR_DELETION',
    userId,
    service: 'supabase',
    timestamp: new Date(),
  });

  return { success: true, deletedAt: new Date() };
}
```

## Data Minimization

```typescript
// Only request needed fields
const user = await supabaseClient.getUser(userId, {
  fields: ['id', 'name'], // Not email, phone, address
});

// Don't store unnecessary data
const cacheData = {
  id: user.id,
  name: user.name,
  // Omit sensitive fields
};
```

## Instructions

### Step 1: Classify Data
Categorize all Supabase data by sensitivity level.

### Step 2: Implement PII Detection
Add regex patterns to detect sensitive data in logs.

### Step 3: Configure Redaction
Apply redaction to sensitive fields before logging.

### Step 4: Set Up Retention
Configure automatic cleanup with appropriate retention periods.

## Output
- Data classification documented
- PII detection implemented
- Redaction in logging active
- Retention policy enforced

## Error Handling
| Issue | Cause | Solution |
|-------|-------|----------|
| PII in logs | Missing redaction | Wrap logging with redact |
| Deletion failed | Data locked | Check dependencies |
| Export incomplete | Timeout | Increase batch size |
| Audit gap | Missing entries | Review log pipeline |

## Examples

### Quick PII Scan
```typescript
const findings = detectPII(JSON.stringify(userData));
if (findings.length > 0) {
  console.warn(`PII detected: ${findings.map(f => f.type).join(', ')}`);
}
```

### Redact Before Logging
```typescript
const safeData = redactPII(apiResponse);
logger.info('Supabase response:', safeData);
```

### GDPR Data Export
```typescript
const userExport = await exportUserData('user-123');
await sendToUser(userExport);
```

## Resources
- [GDPR Developer Guide](https://gdpr.eu/developers/)
- [CCPA Compliance Guide](https://oag.ca.gov/privacy/ccpa)
- [Supabase Privacy Guide](https://supabase.com/docs/privacy)

## Next Steps
For enterprise access control, see `supabase-enterprise-rbac`.
