js-libp2p/doc/API.md

# API

* [Static Functions](#static-functions)
  * [`create`](#create)
* [Instance Methods](#instance-methods)
  * [`start`](#start)
  * [`stop`](#stop)
  * [`dial`](#dial)
  * [`dialProtocol`](#dialProtocol)
  * [`hangUp`](#hangUp)
  * [`handle`](#handle)
  * [`unhandle`](#unhandle)
  * [`peerRouting.findPeer`](#peerRouting.findPeer)
  * [`contentRouting.findProviders`](#contentRouting.findProviders)
  * [`contentRouting.provide`](#contentRouting.provide)
  * [`contentRouting.put`](#contentRouting.put)
  * [`contentRouting.get`](#contentRouting.get)
  * [`contentRouting.getMany`](#contentRouting.getMany)
  * [`pubsub.getSubscribers`](#pubsub.getSubscribers)
  * [`pubsub.getTopics`](#pubsub.getTopics)
  * [`pubsub.publish`](#pubsub.publish)
  * [`pubsub.subscribe`](#pubsub.subscribe)

## Static Functions

### create

Creates an instance of Libp2p.

`create(options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| options | `Object` | libp2p options |
| options.modules | `Array<Object>` | libp2p modules to use |
| [options.config] | `Object` | libp2p modules configuration and core configuration |
| [options.datastore] | `Object` | must implement [ipfs/interface-datastore](https://github.com/ipfs/interface-datastore) (in memory datastore will be used if not provided) |
| [options.peerInfo] | [PeerInfo](https://github.com/libp2p/js-peer-info) | peerInfo instance (it will be created if not provided) |

For Libp2p configurations and modules details read the [Configuration Document](./CONFIGURATION.md).

#### Returns

| Type | Description |
|------|-------------|
| `Promise<Libp2p>` | Promise resolves with the Libp2p instance |

#### Example

```js
const Libp2p = require('libp2p')

// specify options
const options = {}

// create libp2p
const libp2p = await Libp2p.create(options)
```

Note: The `PeerInfo` option is not required and will be generated if it is not provided.

<details><summary>Alternative</summary>
As an alternative, it is possible to create a Libp2p instance with the constructor:

#### Example

```js
const Libp2p = require('libp2p')

// specify options
const options = {}

// create libp2p
const libp2p = new Libp2p(options)
```

Required keys in the `options` object:

- `peerInfo`: instance of [PeerInfo][] that contains the [PeerId][], Keys and [multiaddrs][multiaddr] of the libp2p Node (optional when using `.create`).
- `modules.transport`: An array that must include at least 1 compliant transport. See [modules that implement the transport interface](https://github.com/libp2p/js-interfaces/tree/master/src/transport#modules-that-implement-the-interface).

</details>

Once you have a libp2p instance, you are able to listen to several events it emmits, so that you can be noticed of relevant network events.

<details><summary>Events</summary>

#### An error has occurred

`libp2p.on('error', (err) => {})`

- `err`: instance of `Error`

#### A peer has been discovered

`libp2p.on('peer:discovery', (peer) => {})`

If `autoDial` option is `true`, applications should **not** attempt to connect to the peer
unless they are performing a specific action. See [peer discovery and auto dial](./PEER_DISCOVERY.md) for more information.

- `peer`: instance of [PeerInfo][https://github.com/libp2p/js-peer-info]

#### We have a new connection to a peer

`libp2p.on('peer:connect', (peer) => {})`

- `peer`: instance of [PeerInfo][https://github.com/libp2p/js-peer-info]

#### We have closed a connection to a peer

`libp2p.on('peer:disconnect', (peer) => {})`

- `peer`: instance of [PeerInfo][https://github.com/libp2p/js-peer-info]

</details>

## Libp2p Instance Methods 

### start

Starts the libp2p node.

`libp2p.start()`

#### Returns

| Type | Description |
|------|-------------|
| `Promise` | Promise resolves when the node is ready |

#### Example

```js
const Libp2p = require('libp2p')

// ...

const libp2p = await Libp2p.create(options)

// start libp2p
await libp2p.start()
```

### stop

Stops the libp2p node.

`libp2p.stop()`

#### Returns

| Type | Description |
|------|-------------|
| `Promise` | Promise resolves when the node is fully stopped |

#### Example

```js
const Libp2p = require('libp2p')

// ...
const libp2p = await Libp2p.create(options)
// ...

// stop libp2p
await libp2p.stop()
```

### dial

Dials to another peer in the network and establishes the connection.

`dial(peer, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| peer | [PeerInfo](https://github.com/libp2p/js-peer-info), [PeerId](https://github.com/libp2p/js-peer-id), [multiaddr](https://github.com/multiformats/js-multiaddr), `string` | peer to dial |
| [options] | `Object` | dial options |
| [options.signal] | [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) | An `AbortSignal` instance obtained from an [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) that can be used to abort the connection before it completes |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<Connection>` | Promise resolves with the [Connection](https://github.com/libp2p/js-interfaces/tree/master/src/connection) instance |

#### Example

```js
// ...
const conn = await libp2p.dial(remotePeerInfo)

// create a new stream within the connection
const { stream, protocol } = await conn.newStream(['/echo/1.1.0', '/echo/1.0.0'])

// protocol negotiated: 'echo/1.0.0' means that the other party only supports the older version

// ...
await conn.close()
```

### dialProtocol

Dials to another peer in the network and selects a protocol to communicate with that peer. The stream between both parties is returned, together with the negotiated protocol.

`dialProtocol(peer, protocols, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| peer | [PeerInfo](https://github.com/libp2p/js-peer-info), [PeerId](https://github.com/libp2p/js-peer-id), [multiaddr](https://github.com/multiformats/js-multiaddr), `string` | peer to dial |
| protocols | `String|Array<String>` |  A list of protocols (or single protocol) to negotiate with. Protocols are attempted in order until a match is made. (e.g '/ipfs/bitswap/1.1.0') |
| [options] | `Object` | dial options |
| [options.signal] | [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) | An `AbortSignal` instance obtained from an [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) that can be used to abort the connection before it completes |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<{ stream:*, protocol:string }>` | Promise resolves with a [duplex stream](https://gist.github.com/alanshaw/591dc7dd54e4f99338a347ef568d6ee9#duplex-it) and the protocol used |

#### Example

```js
// ...
const pipe = require('it-pipe')

const { stream, protocol } = await libp2p.dialProtocol(remotePeerInfo, protocols)

// Use this new stream like any other duplex stream
pipe([1, 2, 3], stream, consume)
```

### hangUp

Attempts to gracefully close an open connection to the given peer. If the connection is not closed in the grace period, it will be forcefully closed.

`hangUp(peer)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| peer | [PeerInfo](https://github.com/libp2p/js-peer-info), [PeerId](https://github.com/libp2p/js-peer-id), [multiaddr](https://github.com/multiformats/js-multiaddr), `string` | peer to hang up |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<void>` | Promise resolves once connection closes |

#### Example

```js
// ...
await libp2p.hangUp(remotePeerInfo)
```

### handle

Sets up [multistream-select routing](https://github.com/multiformats/multistream-select) of protocols to their application handlers. Whenever a stream is opened on one of the provided protocols, the handler will be called. `handle` must be called in order to register a handler and support for a given protocol. This also informs other peers of the protocols you support.

`libp2p.handle(protocols, handler)`

In the event of a new handler for the same protocol being added, the first one is discarded.

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| protocols | `Array<String>|String` | protocols to register |
| handler | `function({ connection:*, stream:*, protocol:string })` | handler to call |


#### Example

```js
// ...
const handler = ({ connection, stream, protocol }) => {
  // use stream or connection according to the needs
}

libp2p.handle('/echo/1.0.0', handler)
```

### unhandle

Unregisters all handlers with the given protocols

`libp2p.unhandle(protocols)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| protocols | `Array<String>|String` | protocols to unregister |

#### Example

```js
// ...
libp2p.unhandle(['/echo/1.0.0'])
```

### peerRouting.findPeer

Iterates over all peer routers in series to find the given peer. If the DHT is enabled, it will be tried first.

`libp2p.peerRouting.findPeer(peerId, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| peerId | [`PeerId`](https://github.com/libp2p/js-peer-id) | ID of the peer to find |
| options | `Object` | operation options |
| options.timeout | `number` | maximum time the query should run |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<PeerInfo>` | Peer info of a known peer |

#### Example

```js
// ...
const peerInfo = await libp2p.peerRouting.findPeer(peerId, options)
```

### contentRouting.findProviders

Iterates over all content routers in series to find providers of the given key.
Once a content router succeeds, the iteration will stop. If the DHT is enabled, it will be queried first.

`libp2p.contentRouting.findProviders(cid, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| cid | [`CID`](https://github.com/multiformats/js-cid) | cid to find |
| options | `Object` | operation options |
| options.timeout | `number` | maximum time the query should run |
| options.maxNumProviders | `number` | maximum number of providers to find |

#### Returns

| Type | Description |
|------|-------------|
| `AsyncIterator<PeerInfo>` |  Async iterator for [`PeerInfo`](https://github.com/libp2p/js-peer-info) |

#### Example

```js
// Iterate over the providers found for the given cid
for await (const provider of libp2p.contentRouting.findProviders(cid)) {
  console.log(provider)
}
```

### contentRouting.provide

Iterates over all content routers in parallel, in order to notify it is a provider of the given key.

`libp2p.contentRouting.provide(cid)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| cid | [`CID`](https://github.com/multiformats/js-cid) | cid to provide |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<void>` | Promise resolves once notifications are sent |

#### Example

```js
// ...
await libp2p.contentRouting.provide(cid)
```

### contentRouting.put

Writes a value to a key in the DHT.

`libp2p.contentRouting.put(key, value, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| key | `String` | key to add to the dht |
| value | `Buffer` | value to add to the dht |
| [options] | `Object` | put options |
| [options.minPeers] | `number` | minimum number of peers required to successfully put (default: closestPeers.length) |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<void>` | Promise resolves once value is stored |

#### Example

```js
// ...
const key = '/key'
const value = Buffer.from('oh hello there')

await libp2p.contentRouting.put(key, value)
```

### contentRouting.get

Queries the DHT for a value stored for a given key.

`libp2p.contentRouting.get(key, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| key | `String` | key to get from the dht |
| [options] | `Object` | get options |
| [options.timeout] | `number` | maximum time the query should run |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<Buffer>` | Value obtained from the DHT |

#### Example

```js
// ...

const key = '/key'
const value = await libp2p.contentRouting.get(key)
```

### contentRouting.getMany

Queries the DHT for the n values stored for the given key (without sorting).

`libp2p.contentRouting.getMany(key, nvals, options)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| key | `String` | key to get from the dht |
| nvals | `number` | number of values aimed |
| [options] | `Object` | get options |
| [options.timeout] | `number` | maximum time the query should run |

#### Returns

| Type | Description |
|------|-------------|
| `Promise<Array<{from: PeerId, val: Buffer}>>` | Array of records obtained from the DHT |

#### Example

```js
// ...

const key = '/key'
const { from, val } = await libp2p.contentRouting.get(key)
```

### pubsub.getSubscribers

Gets a list of the peer-ids that are subscribed to one topic.

`libp2p.pubsub.getSubscribers(topic)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| topic | `string` | topic to publish |

#### Returns

| Type | Description |
|------|-------------|
| `Array<String>` | peer-id subscribed to the topic |

#### Example

```js
const peerIds = libp2p.pubsub.getSubscribers(topic)
```

### pubsub.getTopics

Gets a list of topics the node is subscribed to.

`libp2p.pubsub.getTopics()`

#### Returns

| Type | Description |
|------|-------------|
| `Array<String>` | topics the node is subscribed to |

#### Example

```js
const topics = libp2p.pubsub.getTopics()
```

### pubsub.publish

Publishes messages to the given topics.

`libp2p.pubsub.publish(topic, data)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| topic | `string` | topic to publish |
| data | `Buffer` | data to publish  |

#### Returns

| Type | Description |
|------|-------------|
| `Promise` | publish success |

#### Example

```js
const topic = 'topic'
const data = Buffer.from('data')

await libp2p.pubsub.publish(topic, data)
```

### pubsub.subscribe

Subscribes the given handler to a pubsub topic.

`libp2p.pubsub.subscribe(topic, handler)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| topic | `string` | topic to subscribe |
| handler | `function({ from: String, data: Buffer, seqno: Buffer, topicIDs: Array<String>, signature: Buffer, key: Buffer })` | handler for new data on topic |

#### Returns

| Type | Description |
|------|-------------|
| `void` |  |

#### Example

```js
const topic = 'topic'
const handler = (msg) => {
  // msg.data - pubsub data received
}

libp2p.pubsub.subscribe(topic, handler)
```

### pubsub.unsubscribe

Unsubscribes the given handler from a pubsub topic. If no handler is provided, all handlers for the topic are removed.

`libp2p.pubsub.unsubscribe(topic, handler)`

#### Parameters

| Name | Type | Description |
|------|------|-------------|
| topic | `string` | topic to unsubscribe |
| handler | `function(<Object>)` | handler subscribed |

#### Returns

| Type | Description |
|------|-------------|
| `void` |  |

#### Example

```js
const topic = 'topic'
const handler = (msg) => {
  // msg.data - pubsub data received
}

libp2p.pubsub.unsubscribe(topic, handler)
```