import { afterEach, describe, expect, it, vi } from 'vitest'
import { limiter, pacer, request } from './client'

describe('limiter', () => {
  it('runs at most n calls at once, all of them, failures included', async () => {
    const limit = limiter(2)
    let running = 0, peak = 0
    const call = (n: number) => limit(async () => {
      peak = Math.max(peak, ++running)
      await new Promise(r => setTimeout(r, 5))
      running--
      if (n === 2) throw new Error('503')
      return n
    })
    const out = await Promise.allSettled([1, 2, 3, 4, 5].map(call))
    expect(peak).toBe(2)
    expect(out.map(r => (r.status === 'fulfilled' ? r.value : 'x'))).toEqual([1, 'x', 3, 4, 5])
  })
})

describe('pacer', () => {
  it('lets a burst through, then spaces the rest out in order', async () => {
    const pace = pacer(100, 2)
    const t0 = Date.now()
    const order: number[] = []
    await Promise.all([1, 2, 3, 4, 5, 6].map(n => pace.wait().then(() => order.push(n))))
    // Two at once, then four more at 10 ms each.
    expect(Date.now() - t0).toBeGreaterThanOrEqual(35)
    expect(order).toEqual([1, 2, 3, 4, 5, 6])
  })

  it('pauses everything after the proxy turns one away', async () => {
    const pace = pacer(100, 5)
    pace.pause(50)
    const t0 = Date.now()
    await pace.wait()
    expect(Date.now() - t0).toBeGreaterThanOrEqual(45)
  })
})

describe('request with revalidate', () => {
  afterEach(() => vi.unstubAllGlobals())

  it('sends the last ETag back and answers a 304 with the last body', async () => {
    const sent: (string | null)[] = []
    vi.stubGlobal('fetch', vi.fn(async (_url: string, init: RequestInit) => {
      const tag = new Headers(init.headers).get('If-None-Match')
      sent.push(tag)
      return tag
        ? new Response(null, { status: 304, headers: { ETag: 'W/"1"' } })
        : new Response(JSON.stringify({ agents: [1] }), { status: 200, headers: { ETag: 'W/"1"' } })
    }))
    expect(await request('/etag-test', { revalidate: true })).toEqual({ agents: [1] })
    expect(await request('/etag-test', { revalidate: true })).toEqual({ agents: [1] })
    expect(sent).toEqual([null, 'W/"1"'])
  })
})