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# qified
Task and Message Queues with Multiple Providers

## NOTE: This is a work in progress and not ready for production use. Please wait till v1.0.0 is released.

# Features

* Simple Message Queue for Processing Messages
* Simple Message Format `Message`
* Easily Send a Message `publish()`
* Easily Subscribe to a message Queue `subscribe()`
* Simple Task Format `Task` (Coming in v1.0.0)
* Easily Send a Task `enqueue()` (Coming in v1.0.0)
* Easily Subscribe to a Task Queue `dequeue()` (Coming in v1.0.0)
* Simple Acknowledge `Acknowledge()` in handler (Coming in v1.0.0)
* Async/Await Built In By Default
* Written in Typescript, Nodejs Last Two Versions, ESM and CJS
* Events and Hooks for all major actions via [Hookified](https://hookified.org)
* Customizable Serialize / Deserialize Handlers (Coming in v1.0.0)
* Customizable Compress / Decompress Handlers (Coming in v1.0.0)
* Provider Fail Over Support


# Installation

```bash
pnpm add qified
```

# Quick Start

```js
import { Qified, MemoryMessageProvider } from 'qified';

// Create a new Qified instance with a memory provider
const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});

// Subscribe to a topic
await qified.subscribe('notifications', {
  id: 'notificationHandler',
  handler: async (message) => {
    console.log('Received:', message.data);
  }
});

// Publish a message
await qified.publish('notifications', {
  id: 'msg-1',
  data: { text: 'Hello, World!' }
});

// Clean up
await qified.disconnect();
```

# Constructor

```js
new Qified(options?: QifiedOptions)
```

**Options:**
- `messageProviders?: MessageProvider | MessageProvider[]` - a provider or Array of message providers to use
- `taskProviders?: TaskProvider[]` - Array of task providers to use

**Example:**
```js
import { Qified, MemoryMessageProvider } from 'qified';

const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});
```

# Properties

### `messageProviders: MessageProvider[]`

Get or set the array of message providers. This property allows you to dynamically manage which message providers are active in your Qified instance.

**Type:** `MessageProvider[]`

**Access:** Read/Write

**Description:**
- **Getter**: Returns the current array of message providers being used
- **Setter**: Replaces all current message providers with a new array

**Use Cases:**
- Inspect which providers are currently configured
- Add or remove providers dynamically at runtime
- Replace all providers with a new set
- Migrate from one provider to another

**Example:**
```typescript
import { Qified, MemoryMessageProvider } from 'qified';
import { NatsMessageProvider } from '@qified/nats';
import { RedisMessageProvider } from '@qified/redis';

const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});

// Get current providers
const providers = qified.messageProviders;
console.log(`Currently using ${providers.length} provider(s)`);

// Add another provider
qified.messageProviders = [
  new MemoryMessageProvider(),
  new NatsMessageProvider()
];

// Replace all providers
qified.messageProviders = [
  new RedisMessageProvider({ uri: 'redis://localhost:6379' })
];

// Access provider properties
qified.messageProviders.forEach(provider => {
  console.log('Provider ID:', provider.id);
});
```

**Important Notes:**
- Setting this property does **not** automatically disconnect existing providers
- You should call `disconnect()` on old providers before replacing them to clean up resources
- All operations (`subscribe`, `publish`, `unsubscribe`) will execute across all providers in this array

# Methods

## subscribe

Subscribe to a topic to receive messages. If multiple message providers are configured, this will subscribe on all of them.

**Parameters:**
- `topic: string` - The topic to subscribe to
- `handler: TopicHandler` - Object containing an optional `id` and a `handler` function

**Example:**
```js
await qified.subscribe('user-events', {
  id: 'userEventHandler',
  handler: async (message) => {
    console.log('User event:', message.data);
  }
});
```

## publish

Publish a message to a topic. If multiple message providers are configured, this will publish to all of them.

**Parameters:**
- `topic: string` - The topic to publish to
- `message: Message` - The message object to publish

**Example:**
```js
await qified.publish('user-events', {
  id: 'evt-123',
  data: {
    userId: 'user-456',
    action: 'login',
    timestamp: Date.now()
  },
  headers: {
    'content-type': 'application/json'
  }
});
```

## unsubscribe

Unsubscribe from a topic. If an `id` is provided, only that handler is unsubscribed. Otherwise, all handlers for the topic are unsubscribed.

**Parameters:**
- `topic: string` - The topic to unsubscribe from
- `id?: string` - Optional handler ID. If not provided, all handlers are unsubscribed

**Example:**
```js
// Unsubscribe a specific handler
await qified.unsubscribe('user-events', 'userEventHandler');

// Unsubscribe all handlers for a topic
await qified.unsubscribe('user-events');
```

## disconnect`

Disconnect from all providers and clean up resources.

**Example:**
```js
await qified.disconnect();
```

# Events

Qified extends [Hookified](https://hookified.org) and emits events for all major operations. You can listen to these events to add custom logging, monitoring, or error handling.

# Available Events

The following events are available via the `QifiedEvents` enum:

- `QifiedEvents.publish` - Emitted after a message is successfully published
- `QifiedEvents.subscribe` - Emitted after successfully subscribing to a topic
- `QifiedEvents.unsubscribe` - Emitted after successfully unsubscribing from a topic
- `QifiedEvents.disconnect` - Emitted after successfully disconnecting from all providers
- `QifiedEvents.error` - Emitted when an error occurs during any operation
- `QifiedEvents.info` - Emitted for informational messages
- `QifiedEvents.warn` - Emitted for warning messages

# Listening to Events

Use the `on()` method to listen to events:

```js
import { Qified, MemoryMessageProvider, QifiedEvents } from 'qified';

const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});

// Listen for publish events
await qified.on(QifiedEvents.publish, async (data) => {
  console.log('Message published to topic:', data.topic);
  console.log('Message:', data.message);
});

// Listen for subscribe events
await qified.on(QifiedEvents.subscribe, async (data) => {
  console.log('Subscribed to topic:', data.topic);
  console.log('Handler ID:', data.handler.id);
});

// Listen for unsubscribe events
await qified.on(QifiedEvents.unsubscribe, async (data) => {
  console.log('Unsubscribed from topic:', data.topic);
  if (data.id) {
    console.log('Handler ID:', data.id);
  }
});

// Listen for disconnect events
await qified.on(QifiedEvents.disconnect, async () => {
  console.log('Disconnected from all providers');
});

// Listen for errors
await qified.on(QifiedEvents.error, async (error) => {
  console.error('Error occurred:', error);
});

// Now perform operations
await qified.subscribe('events', {
  id: 'handler1',
  handler: async (message) => {
    console.log('Received:', message.data);
  }
});

await qified.publish('events', {
  id: 'msg-1',
  data: { text: 'Hello!' }
});

await qified.unsubscribe('events', 'handler1');
await qified.disconnect();
```

### Error Handling with Events

Events provide a centralized way to handle errors across all operations:

```js
import { Qified, QifiedEvents } from 'qified';
import { NatsMessageProvider } from '@qified/nats';

const qified = new Qified({
  messageProviders: new NatsMessageProvider()
});

// Centralized error handler
await qified.on(QifiedEvents.error, async (error) => {
  console.error('Qified error:', error.message);
  // Send to error tracking service
  // Log to file
  // Send alert
});

// Errors from publish, subscribe, etc. will be caught and emitted
await qified.publish('topic', { id: '1', data: { test: true } });
```

# Hooks

Qified provides before and after hooks for all major operations, allowing you to intercept and modify data before an operation executes, or perform actions after it completes. Hooks are powered by [Hookified](https://hookified.org).

## Available Hooks

The following hooks are available via the `QifiedHooks` enum:

| Hook | Description | Context Properties |
|------|-------------|-------------------|
| `beforeSubscribe` | Called before subscribing to a topic | `{ topic, handler }` |
| `afterSubscribe` | Called after subscribing to a topic | `{ topic, handler }` |
| `beforePublish` | Called before publishing a message | `{ topic, message }` |
| `afterPublish` | Called after publishing a message | `{ topic, message }` |
| `beforeUnsubscribe` | Called before unsubscribing from a topic | `{ topic, id }` |
| `afterUnsubscribe` | Called after unsubscribing from a topic | `{ topic, id }` |
| `beforeDisconnect` | Called before disconnecting from providers | `{ providerCount }` |
| `afterDisconnect` | Called after disconnecting from providers | `{ providerCount }` |

## Using Hooks

Use the `onHook()` method to register a hook handler:

```js
import { Qified, MemoryMessageProvider, QifiedHooks } from 'qified';

const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});

// Register a before hook
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  console.log('About to publish to:', context.topic);
});

// Register an after hook
qified.onHook(QifiedHooks.afterPublish, async (context) => {
  console.log('Published message:', context.message.id);
});
```

## Modifying Data with Before Hooks

Before hooks receive a mutable context object. Any changes you make to the context will be applied to the operation:

```js
import { Qified, MemoryMessageProvider, QifiedHooks } from 'qified';

const qified = new Qified({
  messageProviders: new MemoryMessageProvider()
});

// Add timestamp and headers to all messages
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  // Add timestamp if not present
  context.message.timestamp = context.message.timestamp ?? Date.now();

  // Add custom headers
  context.message.headers = {
    ...context.message.headers,
    'x-processed-by': 'qified',
    'x-environment': process.env.NODE_ENV
  };
});

// Modify message data
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  // Add metadata to the message data
  context.message.data = {
    ...context.message.data,
    _meta: {
      version: '1.0',
      source: 'api'
    }
  };
});

// Subscribe to receive messages
await qified.subscribe('events', {
  id: 'handler1',
  handler: async (message) => {
    // Message will have timestamp, headers, and modified data
    console.log('Timestamp:', message.timestamp);
    console.log('Headers:', message.headers);
    console.log('Data:', message.data);
  }
});

// Publish a message - hooks will modify it before sending
await qified.publish('events', {
  id: 'msg-1',
  data: { text: 'Hello!' }
});
```

## Modifying Topics with Before Hooks

You can also modify the topic in before hooks:

```js
// Route all messages to a prefixed topic
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  context.topic = `production/${context.topic}`;
});

// Subscribe to the prefixed topic
await qified.subscribe('production/events', {
  id: 'handler1',
  handler: async (message) => {
    console.log('Received:', message.data);
  }
});

// This publishes to 'production/events' due to the hook
await qified.publish('events', {
  id: 'msg-1',
  data: { text: 'Hello!' }
});
```

## Multiple Hooks

Multiple hooks for the same event execute in the order they were registered:

```js
// First hook - runs first
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  context.message.timestamp = Date.now();
});

// Second hook - runs second, can see changes from first hook
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  context.message.headers = { 'x-timestamp': String(context.message.timestamp) };
});

// Third hook - runs third
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  console.log('Final message:', context.message);
});
```

## Hooks vs Events

Both hooks and events are available, but they serve different purposes:

| Feature | Hooks | Events |
|---------|-------|--------|
| Timing | Before and after operations | After operations only |
| Data modification | Yes (before hooks) | No |
| Use case | Intercepting/transforming data | Logging, monitoring, side effects |

```js
// Hook - can modify the message before it's published
qified.onHook(QifiedHooks.beforePublish, async (context) => {
  context.message.timestamp = Date.now();
});

// Event - notified after publish completes (cannot modify)
qified.on(QifiedEvents.publish, async (data) => {
  console.log('Published:', data.message.id);
});
```

# Providers

There are multiple providers available to use:

* Memory - this is built into the current `qified` library as `MemoryMessageProvider`.
* [@qified/redis](packages/redis/README.md) - Redis Provider
* [@qified/rabbitmq](packages/rabbitmq/README.md) - RabbitMQ Provider
* [@qified/nats](packages/nats/README.md) - NATS Provider
* [@qified/zeromq](packages/zeromq/README.md) - ZeroMQ Provider

# Development and Testing

Qified is written in TypeScript and tests are written in `vitest`. To run the tests, use the following command:

1. `pnpm install` - This will install all the dependencies
2. `pnpm test:services:start` - This will start the services needed for testing (Redis, RabbitMQ, etc)
3. `pnpm test` - This will run the tests

To contribute follow the [Contributing Guidelines](CONTRIBUTING.md) and [Code of Conduct](CODE_OF_CONDUCT.md).

# License

[MIT & © Jared Wray](LICENSE)