packages/session-ui/src/components/markdown-worker-queue.test.ts

import { expect, test } from "bun:test"
import { createLatestWorkerQueue } from "./markdown-worker-queue"

test("keeps only the latest queued request for each key", async () => {
  const processed: number[] = []
  const superseded: number[] = []
  let release = () => {}
  const blocked = new Promise<void>((resolve) => {
    release = resolve
  })
  const queue = createLatestWorkerQueue<{ id: number; key: string }>({
    run: async (request) => {
      processed.push(request.id)
      if (request.id === 1) await blocked
    },
    supersede: (request) => superseded.push(request.id),
    dispose: () => {},
  })

  queue.highlight({ id: 1, key: "code" })
  await Promise.resolve()
  queue.highlight({ id: 2, key: "code" })
  queue.highlight({ id: 3, key: "code" })
  queue.highlight({ id: 4, key: "code" })

  expect(queue.pending()).toBe(1)
  expect(superseded).toEqual([2, 3])
  release()
  await queue.idle()
  expect(processed).toEqual([1, 4])
})

test("serializes disposal before a later request for the same key", async () => {
  const events: string[] = []
  const queue = createLatestWorkerQueue<{ id: number; key: string }>({
    run: async (request) => {
      events.push(`highlight:${request.id}`)
    },
    supersede: (request) => events.push(`supersede:${request.id}`),
    dispose: (key) => events.push(`dispose:${key}`),
  })

  queue.highlight({ id: 1, key: "code" })
  queue.dispose("code")
  queue.highlight({ id: 2, key: "code" })
  await queue.idle()

  expect(events).toEqual(["supersede:1", "dispose:code", "highlight:2"])
})