logceptor/README.md

NestJS interceptor to log HTTP requests and responses with full control, correlation IDs, file rotation, sensitive data masking, and production-ready features.

# logceptor

NestJS interceptor to log HTTP requests and responses with full control, correlation IDs, file rotation, sensitive data masking, and production-ready features for traceability, compliance, and debugging.

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## ✨ Features

- ✅ Log levels (`log`, `warn`, `error`, `debug`)
- ✅ JSON or plain-text format
- ✅ Sensitive field masking (e.g. `password`, `token`, `ssn`)
- ✅ Correlation ID (auto-generated UUID or incoming `x-correlation-id` header)
- ✅ File size-based log rotation (default 10MB, configurable)
- ✅ Automatically deletes logs older than 30 days
- ✅ Configurable output folder and filename

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## 📦 Installation

```bash
npm install logceptor
```

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## 🚀 Usage (Global Interceptor)

Add the following to your NestJS `main.ts`:

```ts
// ✅ Public usage (npm installed)
import { LoggingInterceptor } from 'logceptor';

// 🔄 Optional: if you're testing a local version before publishing
// import { LoggingInterceptor } from '@mobilefirst/logger';

app.useGlobalInterceptors(new LoggingInterceptor({
  format: 'json',                      // Log format: 'json' or 'text'
  level: 'debug',                      // Log level: 'log' | 'debug' | 'warn' | 'error'
  folder: 'logs',                      // Output directory for logs
  filename: 'access.log',              // File name
  maskFields: ['password', 'token', 'ssn'], // Fields to mask
  maxFileSizeMB: 10                    // Max file size before rotation (default: 10)
}));
```

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## 🧪 Output Example (`logs/access.log`)

```json
{"type":"request","timestamp":"2025-06-24T12:00:00Z","correlationId":"a3009ffe-430f-4481-ba55-eec7e6be9b44","method":"POST","url":"/api/users/login","body":{"email":"a@b.com","password":"****"}}
{"type":"response","timestamp":"2025-06-24T12:00:00Z","correlationId":"a3009ffe-430f-4481-ba55-eec7e6be9b44","url":"/api/users/login","duration":"31ms","response":{"message":"Logged in"}}
```

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## 🧹 Automatic Log Cleanup

- Logs are saved in the defined folder (e.g. `logs/`)
- Files older than **30 days** are automatically deleted

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## 👤 Author

Created by **Mehul Jadav** — [MobileFirst](https://mobilefirst.in)

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## 📝 License

MIT © Mobilefirst Applications