graph.test.ts

import { beforeEach, describe, expect, test } from "vitest"
import { DifferenceStreamWriter } from "../src/graph.js"
import { MultiSet } from "../src/multiset.js"
import type { DifferenceStreamReader } from "../src/graph.js"

describe(`DifferenceStreamReader and DifferenceStreamWriter`, () => {
  let writer: DifferenceStreamWriter<number>
  let reader: DifferenceStreamReader<number>

  beforeEach(() => {
    writer = new DifferenceStreamWriter<number>()
    reader = writer.newReader()
  })

  test(`isEmpty returns true for empty queue`, () => {
    expect(reader.isEmpty()).toBe(true)
  })

  test(`isEmpty returns false when queue has messages`, () => {
    writer.sendData(new MultiSet())
    expect(reader.isEmpty()).toBe(false)
  })

  test(`drain returns all messages`, () => {
    writer.sendData(new MultiSet([[1, 1]]))
    writer.sendData(new MultiSet([[2, 1]]))

    const messages = reader.drain()
    expect(messages).toHaveLength(2)
    expect(messages[0]).toBeInstanceOf(MultiSet)
    expect(messages[1]).toBeInstanceOf(MultiSet)
    expect(reader.isEmpty()).toBe(true)
  })

  test(`multiple readers receive the same data`, () => {
    const reader2 = writer.newReader()

    writer.sendData(new MultiSet([[1, 1]]))
    writer.sendData(new MultiSet([[2, 1]]))

    const messages1 = reader.drain()
    const messages2 = reader2.drain()

    expect(messages1).toHaveLength(2)
    expect(messages2).toHaveLength(2)
    expect(messages1[0].getInner()).toEqual([[1, 1]])
    expect(messages2[0].getInner()).toEqual([[1, 1]])
    expect(messages1[1].getInner()).toEqual([[2, 1]])
    expect(messages2[1].getInner()).toEqual([[2, 1]])
  })

  test(`drain empties the queue`, () => {
    writer.sendData(new MultiSet([[1, 1]]))
    writer.sendData(new MultiSet([[2, 1]]))

    expect(reader.isEmpty()).toBe(false)
    reader.drain()
    expect(reader.isEmpty()).toBe(true)
  })
})