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source.js
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source.js
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import { derived, readable } from 'svelte/store'
import { stream } from './stream'
import { IS_BROWSER } from './constants'
/**
* @template T
* @typedef {{[K in keyof T]:T[K]} & {}} Pretty
*/
/**
* State of the stream.\
* It can be
* - `CONNECTING` = `0`
* - `OPEN` = `1`
* - `CLOSED` = `2`
* @typedef {0|1|2} StreamState
*/
/**
* Connection established.
* @typedef Connected
* @property {string} resource Path to the stream.
* @property {ReturnType<import('./stream').stream>} eventSource Stream has been established and this is information regarding the connection.
* @property {number} connectionsCounter How many other clients are connected to the stream.
* @property {()=>void} stopBeacon
*/
/**
* @typedef ConnectPayload
* @property {string} resource Path to the stream.
* @property {number} beacon How often to send a beacon to the server in `milliseconds`.\
* Defaults to `5000 milliseconds`.
*
* > **Note**\
* > You can set `beacon` to `0` or a negative value to disable this behavior.\
* > Remember that if you disable this behavior but the server sent event still declares
* > a `timeout`, the stream will close without notice after the `timeout` expires on the server.
* @property {Options} options Options for the underlying http request.
* @property {import('./types').EventListener} onError
* @property {import('./types').EventListener} onClose
*/
/**
* @param {ConnectPayload} payload
* @returns
*/
function connectable({ resource, beacon, options, onClose, onError }) {
let close = function noop() {}
const store = readable(
/** @type {false | { id: string, event: string, data: string }} */ (false),
function start(set) {
/**
* @type {undefined | NodeJS.Timeout}
*/
let interval = undefined
const eventSource = stream({
resource,
beacon,
options,
onIdFound(id) {
if (beacon <= 0) {
return
}
const path = resource.toString().split('?', 2)[0] ?? '/'
clearInterval(interval)
interval = setInterval(function run() {
navigator.sendBeacon(`${path}?x-sse-id=${id}`)
}, beacon)
},
onClose,
onError,
onMessage(e) {
set({ id: e.id, event: e.event, data: decodeURIComponent(e.data) })
},
})
function stopBeacon() {
eventSource.controller.abort()
clearInterval(interval)
}
close = stopBeacon
return stopBeacon
},
)
return { ...store, close }
}
/**
* Options for the underlying http request.
* @typedef {Pick<import('@microsoft/fetch-event-source').FetchEventSourceInit, "body"|"cache"|"credentials"|"fetch"|"headers"|"integrity"|"keepalive"|"method"|"mode"|"openWhenHidden"|"redirect"|"referrer"|"referrerPolicy"|"timeout"|"window">} Options
*/
/**
* Consume a server sent event as a readable store.
*
* > **Note**\
* > Calling this multiple times using the same `resource` string will not
* > create multiple streams, instead the same stream will be reused for all exposed
* > events on the given `resource`.
* @typedef SourceConfiguration
* @property {import('./types').EventListener} [close] Do something whenever the connection closes.
* @property {import('./types').EventListener} [error] Do something whenever there are errors.
* @property {Options} [options] Options for the underlying http request.
* @property {number} [beacon]
*/
/**
* Source a server sent event.
*
* Multiple sources may share the same underlying connection if they use the same path (`from`).
* > ## Example
* > ```js
* > const connection = source({
* > from: '/events',
* > beacon: 1000,
* > options: {
* > headers: {
* > 'Authorization': `Bearer ${token}`
* > }
* > }
* > })
* > ```
* @param {string} from Path to the stream.
* @param {SourceConfiguration} [configuration]
* @returns
*/
export function source(
from,
{ error, close, beacon = 5000, options = {} } = {},
) {
if (!IS_BROWSER) {
return {
close() {},
/**
* Select an event from the stream.
* @param {string} eventName Name of the event.
* @returns
*/
// eslint-disable-next-line @typescript-eslint/no-unused-vars
select(eventName) {
const storeLocal = readable('')
return {
...storeLocal,
/**
* @template [T = any]
* @param {(value:string) => T} transformer
* @returns
*/
transform(transformer) {
return derived(storeLocal, transformer)
},
/**
* @template [T = any]
* @param {import('./types').JsonPredicate} [or]
* @returns {import('svelte/store').Readable<null|T>}
*/
// eslint-disable-next-line @typescript-eslint/no-unused-vars
json(or) {
return readable(null)
},
}
},
}
}
const connected = connectable({
resource: from,
beacon,
options,
onClose(e) {
if (close) {
close(e)
}
},
onError(e) {
if (error) {
error(e)
}
},
})
return {
close() {
connected.close()
},
/**
* Select an event from the stream.
* @param {string} eventName Name of the event.
* @returns
*/
select(eventName) {
if (eventName.includes('\n')) {
throw new Error(
`The name of the event must not contain new line characters, received "${eventName}"`,
)
}
const typeOfValue = typeof eventName
if (typeOfValue !== 'string') {
throw new Error(
`Event name must be of type \`string\`, received \`${typeOfValue}\`.`,
)
}
const storeLocal = derived(connected, function pass(value, set) {
if (value && value.event === eventName) {
set(value.data)
}
})
return {
...storeLocal,
/**
* @template [T = any]
* @param {(value:string) => T} transformer
* @returns
*/
transform(transformer) {
return derived(storeLocal, transformer)
},
/**
* @template [T = any]
* @param {import('./types').JsonPredicate} [or]
* @returns {import('svelte/store').Readable<null|T>}
*/
json(or) {
/**
* @type {null|T}
*/
let previous = null
return derived(storeLocal, function convert(raw) {
try {
previous = JSON.parse(raw)
return previous
} catch (e) {
if (or) {
return or({
previous,
raw: raw,
// @ts-ignore
error: e,
})
}
}
})
},
}
},
}
}