This polyfill library implements the Braid-HTTP v04 protocol, modified slightly to follow the HTTP Multiresponse concept discussed at braid.org/meeting-89. It provides browsers with a braid_fetch() drop-in replacement for the fetch() API, and offers nodejs an http plugin, enabling simple Braid communication.
Developed in braid.org.
Browsers:
<script src="https://unpkg.com/braid-http/braid-http-client.js"></script>
<script>
// To live on the cutting edge, you can now replace the browser's fetch() if desired:
// window.fetch = braid_fetch
</script>Node.js:
npm install braid-http// Import with require()
require('braid-http').fetch // A polyfill for require('node-fetch')
require('braid-http').http_client // A polyfill for require('http') clients
require('braid-http').http_server // A polyfill for require('http') servers
// Or as es6 module
import {fetch, http_client, http_server} from 'braid-http'This library adds a {subscribe: true} option to fetch(), and lets you
access the result of a subscription with two new fields on the fetch response:
response.subscribe( update => ... )-
response.subscription: an iterator that can be used withfor await
Here is an example of subscribing to a Braid resource using promises:
fetch('https://braid.org/chat', {subscribe: true}).then(
res => res.subscribe(
(update) => {
console.log('We got a new update!', update)
// {
// version: ["me"],
// parents: ["mom", "dad"],
// patches: [{
//. unit: "json",
// range: ".foo",
// content: new Uint8Array([51]),
// content_text: "3" <-- getter
//. }],
// body: new Uint8Array([51]),
// body_text: "3" <-- getter
// }
//
// Note that `update` will contain either patches *or* body
}
)
)If you want automatic reconnections, this library add a {retry: true} option to fetch().
fetch('https://braid.org/chat', {subscribe: true, retry: true}).then(
res => res.subscribe(
(update) => {
console.log('We got a new update!', update)
// Do something with the update
}
)
)For use in conjunction with {retry: true}, it's possible to make the parents param equal to a function, which will be called to get the current parents each time the fetch establishes a new connection.
fetch('https://braid.org/chat', {subscribe: true, retry: true, parents: () => {
return current_parents
}}).then(
res => res.subscribe(
(update) => {
console.log('We got a new update!', update)
// Do something with the update
}
)
)(await fetch('/chat', {subscribe: true, retry: true})).subscribe(
(update) => {
// We got a new update!
})var subscription_iterator = (await fetch('/chat',
{subscribe: true, retry: true})).subscription
for await (var update of subscription_iterator) {
// Updates might come in the form of patches:
if (update.patches)
chat = apply_patches(update.patches, chat)
// Or complete snapshots:
else
// Beware the server doesn't send these yet.
chat = JSON.parse(update.body_text)
render_stuff()
}Braidify adds these fields and methods to requests and responses:
req.subscribereq.startSubscription({onClose: cb})await req.parseUpdate()res.sendUpdate()
Use it like this:
var braidify = require('braid-http').http_server
// or:
import {http_server as braidify} from 'braid-http'
require('http').createServer(
(req, res) => {
// Add braid stuff to req and res
braidify(req, res)
// Now use it
if (req.subscribe)
res.startSubscription({ onClose: _=> null })
// startSubscription automatically sets statusCode = 209
else
res.statusCode = 200
// Send the current version
res.sendUpdate({
version: ['greg'],
body: JSON.stringify({greg: 'greg'})
})
}
).listen(9935)With express, you can simply call app.use(braidify) to get braid features
added to every request and response.
var braidify = require('braid-http').http_server
// or:
import {http_server as braidify} from 'braid-http'
var app = require('express')()
app.use(braidify) // Add braid stuff to req and res
app.get('/', (req, res) => {
// Now use it
if (req.subscribe)
res.startSubscription({ onClose: _=> null })
// startSubscription automatically sets statusCode = 209
else
res.statusCode = 200
// Send the current version
res.sendUpdate({
version: ['greg'],
parents: ['gr','eg'],
body: JSON.stringify({greg: 'greg'})
})
// Or you can send patches like this:
// res.sendUpdate({
// version: ['greg'],
// parents: ['gr','eg'],
// patches: [{range: '.greg', unit: 'json', content: '"greg"'}]
// })
})
require('http').createServer(app).listen(8583)// Use this line if necessary for self-signed certs
// process.env["NODE_TLS_REJECT_UNAUTHORIZED"] = 0
var https = require('braid-http').http_client(require('https'))
// or:
// import braid_http from 'braid-http'
// https = braid_http.http_client(require('https'))
https.get(
'https://braid.org/chat',
{subscribe: true},
(res) => {
res.on('update', (update) => {
console.log('well we got one', update)
})
}
)To get auto-reconnections use:
function connect () {
https.get(
'https://braid.org/chat',
{subscribe: true},
(res) => {
res.on('update', (update) => {
// {
// version: ["me"],
// parents: ["mom", "dad"],
// patches: [{
//. unit: "json",
// range: ".foo",
// content: new Uint8Array([51]),
// content_text: "3" <-- getter
//. }],
// body: new Uint8Array([51]),
// body_text: "3" <-- getter
// }
// Update will contain either patches *or* body, but not both
console.log('We got a new update!', update)
})
res.on('end', e => setTimeout(connect, 1000))
res.on('error', e => setTimeout(connect, 1000))
})
}
connect()var fetch = require('braid-http').fetch
// or:
import {fetch} from 'braid-http'
// process.env["NODE_TLS_REJECT_UNAUTHORIZED"] = 0
fetch('https://localhost:3009/chat',
{subscribe: true}).andThen(
x => console.log('Got ', x)
)Note: the current version of node-fetch doesn't properly throw errors when a
response connection dies, and thus you cannot attach a .catch() handler to
automatically reconnect. (See
issue #980 and
#753.) We recommend
using the http library (below) for requests on nodejs instead.