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|
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|
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const GQL = { |
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CONNECTION_INIT: 'connection_init', |
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CONNECTION_ACK: 'connection_ack', |
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CONNECTION_ERROR: 'connection_error', |
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CONNECTION_KEEP_ALIVE: 'ka', |
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START: 'start', |
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STOP: 'stop', |
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CONNECTION_TERMINATE: 'connection_terminate', |
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DATA: 'data', |
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ERROR: 'error', |
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COMPLETE: 'complete' |
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} |
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|
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class Subscriber { |
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constructor (url, options, callback, protocols = 'graphql-ws') { |
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this.callback = callback |
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|
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this.nextId = 1 |
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this.subscriptions = new Map() |
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this.webSocket = new WebSocket(url, protocols) |
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|
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this.webSocket.onopen = event => { |
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// Initiate the connection |
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this.webSocket.send(JSON.stringify({ |
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type: GQL.CONNECTION_INIT, |
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payload: options |
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})) |
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} |
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|
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this.webSocket.onclose = event => { |
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// The code 1000 (Normal Closure) is special, and results in no error or payload. |
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const error = event.code === 1000 ? null : new Error(event) |
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// Notify the subscriber. |
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this.callback(error) |
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// Notify the subscriptions. |
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const callbacks = Array.from(this.subscriptions.values()) |
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this.subscriptions.clear() |
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for (const callback of callbacks) { |
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callback(error, null) |
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} |
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} |
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|
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this.webSocket.onmessage = this.onMessage.bind(this) |
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} |
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|
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subscribe (query, variables, operationName, callback) { |
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const id = (this.nextId++).toString() |
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this.subscriptions.set(id, callback) |
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|
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this.webSocket.send(JSON.stringify({ |
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type: GQL.START, |
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id, |
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payload: { query, variables, operationName } |
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})) |
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|
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// Return the unsubscriber. |
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return () => { |
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this.subscriptions.delete(id) |
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|
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this.webSocket.send(JSON.stringify({ |
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type: GQL.STOP, |
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id |
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})) |
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} |
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} |
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|
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shutdown () { |
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this.webSocket.send(JSON.stringify({ |
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type: GQL.CONNECTION_TERMINATE |
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})) |
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this.webSocket.close() |
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} |
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|
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onMessage (event) { |
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const data = JSON.parse(event.data) |
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|
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switch (data.type) { |
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case GQL.CONNECTION_ACK: { |
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// This is the successful response to GQL.CONNECTION_INIT |
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if (this.callback) { |
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this.callback(null, this.subscribe.bind(this)) |
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} |
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break |
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} |
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case GQL.CONNECTION_ERROR: { |
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// This may occur: |
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// 1. In response to GQL.CONNECTION_INIT |
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// 2. In case of parsing errors in the client which will not disconnect. |
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if (this.callback) { |
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this.callback(new Error(data.payload), this) |
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} |
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break |
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} |
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case GQL.CONNECTION_KEEP_ALIVE: { |
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// This may occur: |
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// 1. After GQL.CONNECTION_ACK, |
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// 2. Periodically to keep the connection alive. |
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break |
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} |
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case GQL.DATA: { |
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// This message is sent after GQL.START to transfer the result of the GraphQL subscription. |
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const callback = this.subscriptions.get(data.id) |
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if (callback) { |
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const error = data.payload.errors ? new Error(data.payload.errors) : null |
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callback(error, data.payload.data) |
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} |
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break |
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} |
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case GQL.ERROR: { |
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// This method is sent when a subscription fails. This is usually dues to validation errors |
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// as resolver errors are returned in GQL.DATA messages. |
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const callback = this.subscriptions.get(data.id) |
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if (callback) { |
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callback(new Error(data.payload), null) |
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} |
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break |
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} |
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case GQL.COMPLETE: { |
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// This is sent when the operation is done and no more dta will be sent. |
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const callback = this.subscriptions.get(data.id) |
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if (callback) { |
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this.subscriptions.delete(data.id) |
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// Return a null error and payload to indicate the subscription is closed. |
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callback(null, null) |
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} |
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break |
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} |
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} |
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} |
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} |
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|
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function graphQLSubscriber (url, options, callback, protocols = 'graphql-ws') { |
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const subscriber = new Subscriber(url, options, callback, protocols) |
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return subscriber.shutdown.bind(subscriber) |
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} |
