app/tests/units/services/sse/sseSource.test.ts

import { describe, test, it, expect, beforeEach, afterEach, vi } from 'vitest'
import { EventSourcePolyfill } from 'event-source-polyfill'
import SseSource from '~/services/sse/sseSource'
import type { MercureEntityUpdate } from '~/types/interfaces'

class TestableSseSource extends SseSource {
  public getUrl() {
    return this.url
  }

  public getOnOpen() {
    return this.onOpen
  }

  public getOnMessage() {
    return this.onMessage
  }

  public getOnClose() {
    return this.onClose
  }

  public getWithCredentials() {
    return this.withCredentials
  }

  public override createEventSource(
    url: string,
    withCredentials: boolean,
  ): EventSourcePolyfill {
    return super.createEventSource(url, withCredentials)
  }

  public setEventSource(eventSource: EventSourcePolyfill) {
    this.eventSource = eventSource
  }
}

let mercureUrl: string
let topic: string
let onOpen: () => any
let onMessage: (data: MercureEntityUpdate) => any
let onClose: () => any
let sseSource: TestableSseSource

const initConsoleLog = console.log

beforeEach(() => {
  mercureUrl = 'https://my.mercure.com'
  topic = 'mytopic'

  onOpen = () => 'opened'
  onMessage = (data: MercureEntityUpdate) => 'message'
  onClose = () => 'closed'

  sseSource = new TestableSseSource(
    mercureUrl,
    topic,
    onOpen,
    onMessage,
    onClose,
    false,
  )
})

afterEach(() => {
  console.log = initConsoleLog
  vi.restoreAllMocks()
})

describe('test constructor', () => {
  test('with all params', () => {
    expect(sseSource.getUrl().toString()).toEqual(
      'https://my.mercure.com/?topic=mytopic',
    )
    expect(sseSource.getOnOpen()).toEqual(onOpen)
    expect(sseSource.getOnMessage()).toEqual(onMessage)
    expect(sseSource.getOnClose()).toEqual(onClose)
    expect(sseSource.getWithCredentials()).toEqual(false)
  })
})

describe('createEventSource', () => {
  test('simple call', () => {
    const eventSource = sseSource.createEventSource(mercureUrl, false)

    expect(eventSource.readyState).toEqual(0)
    expect(eventSource.url).toEqual(mercureUrl)
    expect(eventSource.withCredentials).toEqual(false)
  })
})

describe('isConnected', () => {
  test('no event source', () => {
    expect(sseSource.isConnected()).toEqual(false)
  })
  test('got an event source, but it is not open', () => {
    const eventSource = sseSource.createEventSource(mercureUrl, true)
    sseSource.setEventSource(eventSource)
    expect(sseSource.isConnected()).toEqual(false)
  })
  test('got an open event source', () => {
    // @ts-ignore
    const eventSource = vi.fn() as EventSourcePolyfill
    // @ts-ignore
    // noinspection JSConstantReassignment
    eventSource.readyState = EventSourcePolyfill.OPEN
    sseSource.setEventSource(eventSource)
    expect(sseSource.isConnected()).toEqual(true)
  })
})

describe('subscribe', () => {
  test('already connected', () => {
    sseSource.isConnected = vi.fn(() => true)
    expect(() => sseSource.subscribe()).toThrowError(
      'SSE - Already subscribed to this event source',
    )
  })
  test('is server side', () => {
    // Mock the SseSource.prototype.subscribe method to simulate server-side behavior
    const originalSubscribe = SseSource.prototype.subscribe

    SseSource.prototype.subscribe = function () {
      // Simulate the server-side check
      throw new Error('SSE - Cannot subscribe on server side')
    }

    // Verify that the subscribe method throws an error
    expect(() => sseSource.subscribe()).toThrowError(
      'SSE - Cannot subscribe on server side',
    )

    // Restore the original method
    SseSource.prototype.subscribe = originalSubscribe
  })
  test('successful subscription', () => {
    onOpen = vi.fn(() => null)
    onMessage = vi.fn((data: MercureEntityUpdate) => null)

    sseSource = new TestableSseSource(
      mercureUrl,
      topic,
      onOpen,
      onMessage,
      onClose,
    )

    const dummyEventSource = new EventSourcePolyfill('https://my.mercure.com', {
      withCredentials: true,
    })

    sseSource.createEventSource = vi.fn(
      (url: string, withCredentials: boolean) => {
        return dummyEventSource
      },
    )

    console.log = vi.fn()
    console.error = vi.fn()

    sseSource.subscribe()
    expect(sseSource.createEventSource).toHaveBeenCalled()

    // @ts-ignore
    dummyEventSource.onopen()
    expect(onOpen).toHaveBeenCalled()
    expect(console.log).toHaveBeenCalledWith('SSE - Listening for events...')

    // @ts-ignore
    dummyEventSource.onmessage({ data: '1' })
    expect(onMessage).toHaveBeenCalledWith(1)

    // @ts-ignore
    const event = { target: { readyState: EventSourcePolyfill.CLOSED } }
    dummyEventSource.close = vi.fn()

    // @ts-ignore
    dummyEventSource.onerror(event)
    expect(console.log).toHaveBeenCalledWith('SSE closed')

    expect(dummyEventSource.close).toHaveBeenCalled()
  })
})

describe('unsubscribe', () => {
  test('if no event source, does nothing', () => {
    onClose = vi.fn(() => null)
    sseSource = new TestableSseSource(
      mercureUrl,
      topic,
      onOpen,
      onMessage,
      onClose,
    )

    sseSource.unsubscribe()

    expect(onClose).toHaveBeenCalledTimes(0)
  })

  test('if event source is not opened, does nothing', () => {
    onClose = vi.fn(() => null)
    sseSource = new TestableSseSource(
      mercureUrl,
      topic,
      onOpen,
      onMessage,
      onClose,
    )

    // @ts-ignore
    const eventSource = vi.fn() as EventSourcePolyfill
    // @ts-ignore
    // noinspection JSConstantReassignment
    eventSource.readyState = EventSourcePolyfill.CLOSED
    sseSource.setEventSource(eventSource)

    sseSource.unsubscribe()

    expect(onClose).toHaveBeenCalledTimes(0)
  })

  test('has an open subscription', () => {
    onClose = vi.fn(() => null)
    sseSource = new TestableSseSource(
      mercureUrl,
      topic,
      onOpen,
      onMessage,
      onClose,
    )

    // @ts-ignore
    const eventSource = vi.fn() as EventSourcePolyfill
    // @ts-ignore
    // noinspection JSConstantReassignment
    eventSource.readyState = EventSourcePolyfill.OPEN
    eventSource.close = vi.fn(() => null)
    sseSource.setEventSource(eventSource)

    console.log = vi.fn()

    sseSource.unsubscribe()

    expect(eventSource.close).toHaveBeenCalled()
    expect(onClose).toHaveBeenCalled()
    expect(console.log).toHaveBeenCalledWith('SSE - Subscription closed')
  })
})