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index.js
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index.js
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const each = require('async/each')
/**
* Default function to get connection ID, using the Request URL
*/
function defaultGetId(socket, {url})
{
return url
}
function filterItself(item)
{
return item !== this
}
function isError(error)
{
return error instanceof Error
}
/**
* Send `data` to the provided `socket` and call `callback` on responses
*/
function relay(socket, callback)
{
const {data, sender, timeout} = this
let sendId
// Don't send `id` for incoming notifications
if(data.id !== undefined)
{
sendId = socket._idCounter++
if(timeout)
response.timeout = setTimeout(
doResponse.bind(socket),
timeout,
sendId,
{code: -32300, message: 'Timeout waiting response from destination'}
)
// Store the callback, sender and timeout to call on the matching response
socket._responses[sendId] = {callback, sender, timeout}
}
// Overwrite message ID with the new one and reset destination
data.id = sendId
delete data.to
// Send the data to its destination
socket.send(JSON.stringify(data))
}
function removePendingResponses({_responses})
{
Object.entries(_responses).forEach(function([id, {sender}])
{
if(sender === this) delete _responses[id]
}, this)
}
function doResponse(id, error, data)
{
const {_responses} = this
const response = _responses[id]
if(!response) return console.warn(`Received unexpected response '${id}'`)
delete _responses[id]
clearTimeout(response.timeout)
response.callback(error, data)
}
function responseDestinationClossed(id)
{
const error = {code: -32300, message: 'Destination connection clossed'}
doResponse.call(this, id, error)
}
/**
* Conections factory
*/
module.exports = function({allowBroadcast, getId = defaultGetId, timeout} = {})
{
const sockets = {}
return function(socket, request, next)
{
const responses = {}
return Promise.resolve(getId(socket, request))
.then(function(id)
{
sockets[id] = socket
function onClose()
{
delete sockets[id]
// Response with an error to the connections waiting an answer from the
// one that have just clossed
Object.keys(responses).forEach(responseDestinationClossed, this)
// Remove pending responses from other connections to this one, since
// they will not be delivered
Object.values(sockets).forEach(removePendingResponses, this)
}
function onMessage({data})
{
const reply = (error, result) =>
{
this.send(JSON.stringify({error, id, jsonrpc: '2.0', result}))
}
function resultBroadcast(error, data)
{
if(error || !data.some(isError)) return reply(error, data)
reply({
code: -32400,
data,
message: 'There were errors delivering broadcast message'
})
}
try {
data = JSON.parse(data)
}
catch(e) {
return reply({code: -32700, message: 'Invalid JSON'})
}
// `to` field on requests is a custom extension to JsonRPC specification
const {error, id, jsonrpc, method, result, to} = data
if(jsonrpc !== '2.0')
return reply({code: -32600, message: `Invalid JsonRPC version '${jsonrpc}`})
// Request
if(method)
{
// Brodcast
if(allowBroadcast && to === null)
return each(Object.values(sockets).filter(filterItself, this),
relay.bind({data, sender: this, timeout}),
resultBroadcast)
// Destination is not defined, or brodcast is not allowed
if(to == null)
return reply({code: -32602, message: 'Destination is required'})
// Single destination
const dest = sockets[to.slice(to.indexOf('/'))]
if(dest) return relay.call({data, sender: this, timeout}, dest, reply)
// Unknown destination
return reply({code: -32300, message: `Unknown destination '${to}'`})
}
// Response
doResponse.call(this, id, error, result)
}
socket.addEventListener('close' , onClose)
socket.addEventListener('message', onMessage)
socket._idCounter = 0
socket._responses = responses
},
function(error)
{
if(next) return next(error)
throw error
})
}
}