Created
March 4, 2020 20:21
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Intercept observable using middleware pattern
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| function interceptObservable(observable, middleware) { | |
| return new Observable(observer => { | |
| const initializedMiddleware = middleware(observer); | |
| const subscription = observable.subscribe({ | |
| close() { | |
| observer.close(); | |
| }, | |
| error(err) { | |
| observer.error(err); | |
| }, | |
| next(value) { | |
| initializedMiddleware(value => observer.next(value))(value); | |
| } | |
| }); | |
| return () => subscription.unsubscribe(); | |
| }); | |
| } | |
| async function directLineWithMiddleware(directLine, activityMiddleware, connectionStatusMiddleware, postActivityMiddleware) { | |
| await loadScript('https://unpkg.com/core-js@2/client/core.min.js'); | |
| postActivityMiddleware = postActivityMiddleware && postActivityMiddleware(); | |
| return { | |
| ...directLine, | |
| activity$: activityMiddleware | |
| ? share(interceptObservable(directLine.activity$, activityMiddleware)) | |
| : directLine.activity$, | |
| connectionStatus$: connectionStatusMiddleware | |
| ? share(interceptObservable(directLine.connectionStatus$, connectionStatusMiddleware)) | |
| : directLine.connectionStatus$, | |
| postActivity: postActivityMiddleware | |
| ? activity => { | |
| postActivityMiddleware(activity => directLine.postActivity(activity))(activity); | |
| } | |
| : directLine.postActivity.bind(directLine) | |
| }; | |
| } | |
| function share(observable) { | |
| const observers = []; | |
| let subscription; | |
| return new Observable(observer => { | |
| observers.push(observer); | |
| if (!subscription) { | |
| subscription = observable.subscribe({ | |
| complete: () => observers.forEach(observer => observer.complete()), | |
| error: err => observers.forEach(observer => observer.error(err)), | |
| next: value => observers.forEach(observer => observer.next(value)) | |
| }); | |
| } | |
| return () => { | |
| const index = observers.indexOf(observer); | |
| ~index && observers.splice(index, 1); | |
| if (!observers.length) { | |
| subscription.unsubscribe(); | |
| subscription = null; | |
| } | |
| }; | |
| }); | |
| } | |
| async function loadScript(src) { | |
| return new Promise((resolve, reject) => { | |
| const script = document.createElement('script'); | |
| script.addEventListener('load', resolve); | |
| script.addEventListener('error', reject); | |
| script.setAttribute('src', src); | |
| document.head.appendChild(script); | |
| }); | |
| } | |
| window.WebChat.customizations = { | |
| ...window.WebChat.customizations, | |
| patchProps: async props => { | |
| const directLine = await directLineWithMiddleware(props.directLine, () => next => activity => { | |
| if (!~(activity.text || '').indexOf('send failed')) { | |
| return next(activity); | |
| } | |
| }); | |
| return { | |
| ...props, | |
| activityStatusMiddleware: () => next => args => { | |
| const { sendState } = args; | |
| if (sendState === 'sending') { | |
| return 'Sending\u2026'; | |
| } else if (sendState === 'send failed') { | |
| return 'Send failed.'; | |
| } | |
| return next(args); | |
| }, | |
| directLine | |
| }; | |
| } | |
| }; |
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