296 lines
9.4 KiB
JavaScript
296 lines
9.4 KiB
JavaScript
/**
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* @module awareness-protocol
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*/
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import * as encoding from 'lib0/encoding'
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import * as decoding from 'lib0/decoding'
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import * as time from 'lib0/time'
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import * as math from 'lib0/math'
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import { Observable } from 'lib0/observable'
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import * as f from 'lib0/function'
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import * as Y from 'yjs' // eslint-disable-line
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export const outdatedTimeout = 30000
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/**
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* @typedef {Object} MetaClientState
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* @property {number} MetaClientState.clock
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* @property {number} MetaClientState.lastUpdated unix timestamp
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*/
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/**
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* The Awareness class implements a simple shared state protocol that can be used for non-persistent data like awareness information
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* (cursor, username, status, ..). Each client can update its own local state and listen to state changes of
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* remote clients. Every client may set a state of a remote peer to `null` to mark the client as offline.
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*
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* Each client is identified by a unique client id (something we borrow from `doc.clientID`). A client can override
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* its own state by propagating a message with an increasing timestamp (`clock`). If such a message is received, it is
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* applied if the known state of that client is older than the new state (`clock < newClock`). If a client thinks that
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* a remote client is offline, it may propagate a message with
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* `{ clock: currentClientClock, state: null, client: remoteClient }`. If such a
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* message is received, and the known clock of that client equals the received clock, it will override the state with `null`.
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*
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* Before a client disconnects, it should propagate a `null` state with an updated clock.
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*
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* Awareness states must be updated every 30 seconds. Otherwise the Awareness instance will delete the client state.
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*
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* @extends {Observable<string>}
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*/
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export class Awareness extends Observable {
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/**
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* @param {Y.Doc} doc
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*/
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constructor (doc) {
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super()
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this.doc = doc
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/**
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* @type {number}
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*/
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this.clientID = doc.clientID
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/**
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* Maps from client id to client state
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* @type {Map<number, Object<string, any>>}
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*/
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this.states = new Map()
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/**
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* @type {Map<number, MetaClientState>}
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*/
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this.meta = new Map()
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this._checkInterval = /** @type {any} */ (setInterval(() => {
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const now = time.getUnixTime()
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if (this.getLocalState() !== null && (outdatedTimeout / 2 <= now - /** @type {{lastUpdated:number}} */ (this.meta.get(this.clientID)).lastUpdated)) {
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// renew local clock
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this.setLocalState(this.getLocalState())
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}
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/**
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* @type {Array<number>}
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*/
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const remove = []
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this.meta.forEach((meta, clientid) => {
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if (clientid !== this.clientID && outdatedTimeout <= now - meta.lastUpdated && this.states.has(clientid)) {
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remove.push(clientid)
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}
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})
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if (remove.length > 0) {
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removeAwarenessStates(this, remove, 'timeout')
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}
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}, math.floor(outdatedTimeout / 10)))
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doc.on('destroy', () => {
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this.destroy()
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})
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this.setLocalState({})
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}
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destroy () {
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this.emit('destroy', [this])
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this.setLocalState(null)
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super.destroy()
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clearInterval(this._checkInterval)
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}
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/**
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* @return {Object<string,any>|null}
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*/
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getLocalState () {
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return this.states.get(this.clientID) || null
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}
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/**
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* @param {Object<string,any>|null} state
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*/
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setLocalState (state) {
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const clientID = this.clientID
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const currLocalMeta = this.meta.get(clientID)
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const clock = currLocalMeta === undefined ? 0 : currLocalMeta.clock + 1
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const prevState = this.states.get(clientID)
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if (state === null) {
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this.states.delete(clientID)
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} else {
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this.states.set(clientID, state)
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}
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this.meta.set(clientID, {
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clock,
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lastUpdated: time.getUnixTime()
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})
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const added = []
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const updated = []
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const filteredUpdated = []
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const removed = []
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if (state === null) {
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removed.push(clientID)
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} else if (prevState == null) {
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if (state != null) {
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added.push(clientID)
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}
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} else {
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updated.push(clientID)
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if (!f.equalityDeep(prevState, state)) {
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filteredUpdated.push(clientID)
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}
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}
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if (added.length > 0 || filteredUpdated.length > 0 || removed.length > 0) {
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this.emit('change', [{ added, updated: filteredUpdated, removed }, 'local'])
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}
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this.emit('update', [{ added, updated, removed }, 'local'])
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}
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/**
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* @param {string} field
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* @param {any} value
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*/
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setLocalStateField (field, value) {
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const state = this.getLocalState()
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if (state !== null) {
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this.setLocalState({
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...state,
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[field]: value
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})
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}
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}
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/**
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* @return {Map<number,Object<string,any>>}
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*/
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getStates () {
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return this.states
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}
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}
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/**
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* Mark (remote) clients as inactive and remove them from the list of active peers.
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* This change will be propagated to remote clients.
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*
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* @param {Awareness} awareness
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* @param {Array<number>} clients
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* @param {any} origin
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*/
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export const removeAwarenessStates = (awareness, clients, origin) => {
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const removed = []
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for (let i = 0; i < clients.length; i++) {
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const clientID = clients[i]
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if (awareness.states.has(clientID)) {
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awareness.states.delete(clientID)
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if (clientID === awareness.clientID) {
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const curMeta = /** @type {MetaClientState} */ (awareness.meta.get(clientID))
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awareness.meta.set(clientID, {
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clock: curMeta.clock + 1,
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lastUpdated: time.getUnixTime()
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})
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}
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removed.push(clientID)
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}
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}
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if (removed.length > 0) {
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awareness.emit('change', [{ added: [], updated: [], removed }, origin])
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awareness.emit('update', [{ added: [], updated: [], removed }, origin])
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}
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}
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/**
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* @param {Awareness} awareness
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* @param {Array<number>} clients
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* @return {Uint8Array}
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*/
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export const encodeAwarenessUpdate = (awareness, clients, states = awareness.states) => {
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const len = clients.length
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const encoder = encoding.createEncoder()
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encoding.writeVarUint(encoder, len)
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for (let i = 0; i < len; i++) {
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const clientID = clients[i]
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const state = states.get(clientID) || null
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const clock = /** @type {MetaClientState} */ (awareness.meta.get(clientID)).clock
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encoding.writeVarUint(encoder, clientID)
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encoding.writeVarUint(encoder, clock)
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encoding.writeVarString(encoder, JSON.stringify(state))
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}
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return encoding.toUint8Array(encoder)
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}
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/**
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* Modify the content of an awareness update before re-encoding it to an awareness update.
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*
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* This might be useful when you have a central server that wants to ensure that clients
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* cant hijack somebody elses identity.
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*
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* @param {Uint8Array} update
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* @param {function(any):any} modify
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* @return {Uint8Array}
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*/
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export const modifyAwarenessUpdate = (update, modify) => {
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const decoder = decoding.createDecoder(update)
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const encoder = encoding.createEncoder()
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const len = decoding.readVarUint(decoder)
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encoding.writeVarUint(encoder, len)
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for (let i = 0; i < len; i++) {
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const clientID = decoding.readVarUint(decoder)
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const clock = decoding.readVarUint(decoder)
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const state = JSON.parse(decoding.readVarString(decoder))
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const modifiedState = modify(state)
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encoding.writeVarUint(encoder, clientID)
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encoding.writeVarUint(encoder, clock)
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encoding.writeVarString(encoder, JSON.stringify(modifiedState))
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}
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return encoding.toUint8Array(encoder)
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}
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/**
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* @param {Awareness} awareness
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* @param {Uint8Array} update
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* @param {any} origin This will be added to the emitted change event
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*/
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export const applyAwarenessUpdate = (awareness, update, origin) => {
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const decoder = decoding.createDecoder(update)
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const timestamp = time.getUnixTime()
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const added = []
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const updated = []
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const filteredUpdated = []
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const removed = []
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const len = decoding.readVarUint(decoder)
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for (let i = 0; i < len; i++) {
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const clientID = decoding.readVarUint(decoder)
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let clock = decoding.readVarUint(decoder)
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const state = JSON.parse(decoding.readVarString(decoder))
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const clientMeta = awareness.meta.get(clientID)
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const prevState = awareness.states.get(clientID)
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const currClock = clientMeta === undefined ? 0 : clientMeta.clock
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if (currClock < clock || (currClock === clock && state === null && awareness.states.has(clientID))) {
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if (state === null) {
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// never let a remote client remove this local state
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if (clientID === awareness.clientID && awareness.getLocalState() != null) {
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// remote client removed the local state. Do not remote state. Broadcast a message indicating
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// that this client still exists by increasing the clock
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clock++
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} else {
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awareness.states.delete(clientID)
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}
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} else {
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awareness.states.set(clientID, state)
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}
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awareness.meta.set(clientID, {
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clock,
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lastUpdated: timestamp
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})
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if (clientMeta === undefined && state !== null) {
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added.push(clientID)
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} else if (clientMeta !== undefined && state === null) {
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removed.push(clientID)
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} else if (state !== null) {
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if (!f.equalityDeep(state, prevState)) {
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filteredUpdated.push(clientID)
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}
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updated.push(clientID)
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}
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}
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}
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if (added.length > 0 || filteredUpdated.length > 0 || removed.length > 0) {
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awareness.emit('change', [{
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added, updated: filteredUpdated, removed
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}, origin])
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}
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if (added.length > 0 || updated.length > 0 || removed.length > 0) {
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awareness.emit('update', [{
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added, updated, removed
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}, origin])
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}
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}
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