Slashtags Feeds

A library for creating and managing feeds using the web-relay

Usage

const { Client, Relay } = require('@synonymdev/web-relay')
const path = require('path')

const { Feed, Reader } = require('@synonymdev/feeds')

const relay = new Relay(path.join(__dirname, '/storage/relay'));

(async () => {
  const relayAddress = await relay.listen()

  const client = new Client({ storage: path.join(__dirname, '/storage/writer'), relay: relayAddress })

  const icon = Buffer.from('icon-data')

  const config = {
    name: 'price-feed',
    description: 'a price feed',
    icons: {
      32: 'icon.png'
    },
    type: 'price-feed',
    version: '1.0.0',
    fields: [
      {
        name: 'latest',
        description: 'Bitcoin / US Dollar price history',
        main: '/feed/BTCUSD-last'
      }
    ]
  }

  const feed = new Feed(client, config, { icon })
  // Wait for config file to be saved
  await feed.ready()

  confsole.log(feed.config.fields.map(f => f.main)) //  ["/feed/BTCUSD-last"]

  // may need to wait more for a the relay to get the files from the client in production.
  // await new Promise(resolve => settimeout(resolve, 200))

  // Update a field, by its name in the config above.
  feed.put('latest', 1000000)

  {
    const client = new Client({ storage: path.join(__dirname, '/storage/reader') })
    const reader = new Reader(client, feed.url)

    console.log('Config:', await reader.getConfig())
    console.log('BTCUSD-last', await reader.getField('latest'))
  }

  relay.close()
})()

API

const feed = new Feed(client, config, [opts])

Create a Feed instance.

client is a web-relay client

config is a feed config file to be saved at ./slashfeed.json

opts includes:

• icon: an optional icon data as Uint8Array

const url = feed.url

The feed's url in the format slashfeed:<client.id>/<feed-name>/[?query]

await feed.ready()

Await to fetch and populate feed.config and feed.icon.

await feeds.put(key, value)

Updates a feed. key is a string, and value is Uint8Array, a utf-8 string or a JSON.

await feeds.get(key)

Returns a Uint8Array value from a the local feed.

await feeds.close()

Gracefully closing feeds and the underlying client.

const buffer = Feed.encode(value)

Encodes a value (string, number, null, boolean, array, or object) as JSON and return a Uint8Array

const value = Feed.dcode(buffer)

Decodes a Uint8Array as JSON if possible, or return the Uint8Array itself.

const reader = new Reader(client, url)

Create an instance of the helper Reader class.

client is a web-relay client

url is a feed url feed.url

const config = await reader.getConfig()

Returns the slashfeed.json configuration file, and sets the reader.config value. Internally this method gets called as soon as you initialize the Reader instance.

const iconData = await reader.getIcon([size])

Returns the data buffer of the feed icon if it exists. size is an optional input to choose icon size to fetch, by default it will return the first size in the config.icons.

const value = await reader.getField(fieldName, [decode])

Returns the value of a specific field.

decode is an opitonal funciton that expects a Uint8Array and returns the decoded value.

await reader.subscribe(fieldName, onupdate, [decode])

Returns the value of a specific field.

onupdate(value: T) => any is a callback function that gets the decoded value as an argument. decode(buf:Uint8Array) => T is an opitonal funciton that expects a Uint8Array and returns the decoded value.

How it works

As of this first version, Slashtags feeds is a directory with the current structure:

├── feed
│   ├── foo
│   ├── bar
└── slashfeed.json

Where slashfeed.json defines the name, image and other future metadata about the feed. And feed directory contains the feed files, where each file represents a key value pair.