smartwatch/readme.md

# @push.rocks/smartwatch

A lightweight, cross-runtime file watcher with glob pattern support for **Node.js**, **Deno**, and **Bun**. Zero heavyweight dependencies — just native file watching APIs for maximum performance. 🚀

## Issue Reporting and Security

For reporting bugs, issues, or security vulnerabilities, please visit [community.foss.global/](https://community.foss.global/). This is the central community hub for all issue reporting. Developers who sign and comply with our contribution agreement and go through identification can also get a [code.foss.global/](https://code.foss.global/) account to submit Pull Requests directly.

## Install

```sh
npm install @push.rocks/smartwatch
# or
pnpm add @push.rocks/smartwatch
```

## Features

🌐 **Cross-Runtime** — Works seamlessly on Node.js 20+, Deno, and Bun
🔍 **Glob Pattern Support** — Watch files using familiar patterns like `**/*.ts` and `src/**/*.{js,jsx}`
📡 **RxJS Observables** — Subscribe to file system events using reactive streams
🔄 **Dynamic Watching** — Add or remove watch patterns at runtime
⚡ **Native Performance** — Uses `fs.watch()` on Node.js/Bun and `Deno.watchFs()` on Deno
✨ **Write Stabilization** — Built-in debouncing prevents duplicate events during file writes
🎯 **TypeScript First** — Full TypeScript support with comprehensive type definitions
📦 **Minimal Footprint** — No chokidar, no FSEvents bindings — just ~500 lines of focused code

## Usage

### Basic Setup

```typescript
import { Smartwatch } from '@push.rocks/smartwatch';

// Create a watcher with glob patterns
const watcher = new Smartwatch([
  './src/**/*.ts',           // Watch all TypeScript files in src
  './public/assets/**/*'     // Watch all files in public/assets
]);

// Start watching
await watcher.start();
```

### Subscribing to File Events

Use RxJS observables to react to file system changes:

```typescript
// Get an observable for file changes
const changeObservable = await watcher.getObservableFor('change');

changeObservable.subscribe({
  next: ([path, stats]) => {
    console.log(`File changed: ${path}`);
    console.log(`New size: ${stats?.size} bytes`);
  },
  error: (err) => {
    console.error(`Error: ${err}`);
  }
});

// Watch for new files
const addObservable = await watcher.getObservableFor('add');
addObservable.subscribe(([path]) => {
  console.log(`File added: ${path}`);
});

// Watch for deleted files
const unlinkObservable = await watcher.getObservableFor('unlink');
unlinkObservable.subscribe(([path]) => {
  console.log(`File deleted: ${path}`);
});
```

### Supported Events

| Event       | Description                    |
|-------------|--------------------------------|
| `add`       | File has been added            |
| `addDir`    | Directory has been added       |
| `change`    | File has been modified         |
| `unlink`    | File has been removed          |
| `unlinkDir` | Directory has been removed     |
| `error`     | Error occurred                 |
| `ready`     | Initial scan complete          |

### Dynamic Watch Management

Add or remove patterns while the watcher is running:

```typescript
const watcher = new Smartwatch(['./src/**/*.ts']);
await watcher.start();

// Add more patterns to watch
watcher.add(['./tests/**/*.spec.ts', './config/*.json']);

// Remove a pattern
watcher.remove('./src/**/*.test.ts');
```

### Stopping the Watcher

```typescript
// Stop watching when done
await watcher.stop();
```

### Complete Example

```typescript
import { Smartwatch } from '@push.rocks/smartwatch';

async function watchProject() {
  // Initialize with patterns
  const watcher = new Smartwatch([
    './src/**/*.ts',
    './package.json'
  ]);

  // Start the watcher
  await watcher.start();
  console.log('👀 Watching for changes...');

  // Subscribe to changes
  const changes = await watcher.getObservableFor('change');
  changes.subscribe(([path, stats]) => {
    console.log(`📝 Modified: ${path}`);
    console.log(`   Size: ${stats?.size ?? 'unknown'} bytes`);
  });

  // Subscribe to new files
  const additions = await watcher.getObservableFor('add');
  additions.subscribe(([path]) => {
    console.log(`✨ New file: ${path}`);
  });

  // Subscribe to deletions
  const deletions = await watcher.getObservableFor('unlink');
  deletions.subscribe(([path]) => {
    console.log(`🗑️ Deleted: ${path}`);
  });

  // Handle graceful shutdown
  process.on('SIGINT', async () => {
    console.log('\n🛑 Stopping watcher...');
    await watcher.stop();
    process.exit(0);
  });
}

watchProject();
```

## How It Works

smartwatch uses native file watching APIs for each runtime:

| Runtime         | API Used                         |
|-----------------|----------------------------------|
| **Node.js 20+** | `fs.watch({ recursive: true })`  |
| **Deno**        | `Deno.watchFs()`                 |
| **Bun**         | Node.js compatibility layer      |

### Under the Hood

Native file watching APIs don't support glob patterns directly, so smartwatch handles pattern matching internally:

1. **Base path extraction** — Extracts the static portion from each glob pattern (e.g., `./src/` from `./src/**/*.ts`)
2. **Efficient watching** — Native watchers monitor only the base directories
3. **Pattern filtering** — Events are filtered through [picomatch](https://github.com/micromatch/picomatch) matchers before emission
4. **Event deduplication** — Built-in throttling prevents duplicate events from rapid file operations

### Write Stabilization

smartwatch includes built-in write stabilization (similar to chokidar's `awaitWriteFinish`). When a file is being written, events are held until the file size stabilizes, preventing multiple events for a single write operation.

Default settings:
- **Stability threshold**: 300ms
- **Poll interval**: 100ms

## Requirements

| Runtime         | Version                                |
|-----------------|----------------------------------------|
| **Node.js**     | 20+ (required for native recursive watching) |
| **Deno**        | Any version with `Deno.watchFs()` support |
| **Bun**         | Uses Node.js compatibility             |

## API Reference

### `Smartwatch`

#### Constructor

```typescript
new Smartwatch(patterns: string[])
```

Creates a new Smartwatch instance with the given glob patterns.

**Parameters:**
- `patterns` — Array of glob patterns to watch (e.g., `['./src/**/*.ts', './config/*.json']`)

#### Methods

| Method                                 | Returns                                        | Description                                    |
|----------------------------------------|------------------------------------------------|------------------------------------------------|
| `start()`                              | `Promise<void>`                                | Starts watching for file changes               |
| `stop()`                               | `Promise<void>`                                | Stops the file watcher and cleans up resources |
| `add(patterns: string[])`              | `void`                                         | Adds additional patterns to watch              |
| `remove(pattern: string)`              | `void`                                         | Removes a pattern from the watch list          |
| `getObservableFor(event: TFsEvent)`    | `Promise<Observable<[string, Stats]>>`         | Returns an RxJS observable for the specified event |

#### Properties

| Property | Type                                      | Description              |
|----------|-------------------------------------------|--------------------------|
| `status` | `'idle' \| 'starting' \| 'watching'`      | Current watcher status   |

### Types

```typescript
type TFsEvent = 'add' | 'addDir' | 'change' | 'error' | 'unlink' | 'unlinkDir' | 'ready' | 'raw';
type TSmartwatchStatus = 'idle' | 'starting' | 'watching';
```

## Why smartwatch?

| Feature                 | smartwatch            | chokidar           |
|-------------------------|----------------------|--------------------|
| Native API              | ✅ Direct `fs.watch`  | ❌ FSEvents bindings |
| Cross-runtime           | ✅ Node, Deno, Bun    | ❌ Node only        |
| Dependencies            | 4 small packages     | ~20 packages       |
| Write stabilization     | ✅ Built-in           | ✅ Built-in         |
| Glob support            | ✅ picomatch          | ✅ anymatch         |
| Bundle size             | ~15KB                | ~200KB+            |

If you need a lightweight file watcher without native compilation headaches, smartwatch has you covered.

## License and Legal Information

This repository contains open-source code licensed under the MIT License. A copy of the license can be found in the [LICENSE](./LICENSE) file.

**Please note:** The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH or third parties, and are not included within the scope of the MIT license granted herein.

Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines or the guidelines of the respective third-party owners, and any usage must be approved in writing. Third-party trademarks used herein are the property of their respective owners and used only in a descriptive manner, e.g. for an implementation of an API or similar.

### Company Information

Task Venture Capital GmbH
Registered at District Court Bremen HRB 35230 HB, Germany

For any legal inquiries or further information, please contact us via email at hello@task.vc.

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.