botfights/server/src/middleware/arena-proxy.test.ts

import { describe, it, expect, beforeAll, afterAll, afterEach } from 'vitest'
import { Hono } from 'hono'
import { serve, type ServerType } from '@hono/node-server'
import type { AddressInfo } from 'node:net'
import { gzipSync } from 'node:zlib'
import { arenaProxy } from './arena-proxy.js'

// --- Real upstream "arena" server: a second, independent Hono app --------
const registeredBots: { id: string; secret: string; name: string }[] = []

const upstream = new Hono()

upstream.post('/api/bots', async (c) => {
  const body = await c.req.json().catch(() => ({}))
  const bot = { id: `bot-${registeredBots.length + 1}`, secret: 'shh', name: body.name ?? 'unnamed' }
  registeredBots.push(bot)
  return c.json(bot)
})

upstream.get('/api/bots', (c) => c.json(registeredBots))

upstream.get('/api/echo', (c) => {
  return c.json({
    method: c.req.method,
    path: new URL(c.req.url).pathname,
    query: new URL(c.req.url).search,
    host: c.req.header('host') ?? null,
  })
})

upstream.post('/api/echo', async (c) => {
  const body = await c.req.json().catch(() => null)
  return c.json({
    method: c.req.method,
    path: new URL(c.req.url).pathname,
    query: new URL(c.req.url).search,
    body,
    host: c.req.header('host') ?? null,
    xff: c.req.header('x-forwarded-for') ?? null,
  })
})

upstream.get('/api/sse', (c) => {
  const encoder = new TextEncoder()
  const stream = new ReadableStream({
    async start(controller) {
      controller.enqueue(encoder.encode('event: frame\ndata: {"n":1}\n\n'))
      await new Promise((r) => setTimeout(r, 60))
      controller.enqueue(encoder.encode('event: frame\ndata: {"n":2}\n\n'))
      await new Promise((r) => setTimeout(r, 60))
      controller.enqueue(encoder.encode('event: frame\ndata: {"n":3}\n\n'))
      controller.close()
    },
  })
  return new Response(stream, {
    status: 200,
    headers: { 'content-type': 'text/event-stream' },
  })
})

upstream.get('/api/gzip-lie', (c) => {
  // Upstream actually gzip-compresses the body and declares content-encoding
  // for the COMPRESSED bytes. undici transparently decompresses on the
  // proxy's fetch() before this code ever sees the response, so by the time
  // the proxy builds its own Response, the stale content-encoding/
  // content-length (describing the compressed representation) would corrupt
  // what the caller receives if copied through verbatim — the proxy must
  // strip them, not forward them.
  const compressed = gzipSync(Buffer.from(JSON.stringify({ ok: true })))
  return new Response(compressed, {
    status: 200,
    // content-length deliberately omitted — the underlying Node HTTP server
    // computes and sends the real one automatically.
    headers: {
      'content-type': 'application/json',
      'content-encoding': 'gzip',
    },
  })
})

let upstreamServer: ServerType
let upstreamUrl: string

beforeAll(async () => {
  await new Promise<void>((resolve) => {
    upstreamServer = serve({ fetch: upstream.fetch, port: 0 }, (info) => {
      upstreamUrl = `http://127.0.0.1:${(info as AddressInfo).port}`
      resolve()
    })
  })
})

afterAll(async () => {
  await new Promise<void>((resolve) => upstreamServer.close(() => resolve()))
})

// --- Proxying app under test ----------------------------------------------
function buildProxyingApp() {
  const app = new Hono()
  app.use('/api/*', arenaProxy)
  app.get('/api/health', (c) => c.json({ status: 'ok', name: 'botfights' }))
  app.get('/api/sentinel', (c) => c.json({ sentinel: true }))
  return app
}

describe('arenaProxy', () => {
  const originalEnv = process.env.ARENA_UPSTREAM_URL

  afterEach(() => {
    if (originalEnv === undefined) delete process.env.ARENA_UPSTREAM_URL
    else process.env.ARENA_UPSTREAM_URL = originalEnv
  })

  it('registers a bot upstream and reads it back through the proxy', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const postRes = await app.request('/api/bots', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ name: 'cross-node-bot' }),
    })
    expect(postRes.status).toBe(200)
    const posted = await postRes.json() as { name: string }
    expect(posted.name).toBe('cross-node-bot')

    const getRes = await app.request('/api/bots')
    expect(getRes.status).toBe(200)
    const list = await getRes.json() as { name: string }[]
    expect(list.some((b) => b.name === 'cross-node-bot')).toBe(true)
  })

  it('falls through to local routers when ARENA_UPSTREAM_URL is unset', async () => {
    delete process.env.ARENA_UPSTREAM_URL
    const app = buildProxyingApp()

    const res = await app.request('/api/sentinel')
    expect(res.status).toBe(200)
    const body = await res.json() as { sentinel: boolean }
    expect(body.sentinel).toBe(true)
  })

  it('answers /api/health locally even in proxy mode', async () => {
    // Point at a port with nothing listening.
    process.env.ARENA_UPSTREAM_URL = 'http://127.0.0.1:1'
    const app = buildProxyingApp()

    const res = await app.request('/api/health')
    expect(res.status).toBe(200)
    const body = await res.json() as { status: string }
    expect(body.status).toBe('ok')
  })

  it('forwards method, query string and JSON body unchanged', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const res = await app.request('/api/echo?a=1&b=2', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ hello: 'world' }),
    })
    expect(res.status).toBe(200)
    const body = await res.json() as { method: string; path: string; query: string; body: unknown }
    expect(body.method).toBe('POST')
    expect(body.path).toBe('/api/echo')
    expect(body.query).toBe('?a=1&b=2')
    expect(body.body).toEqual({ hello: 'world' })
  })

  it('does not forward the inbound Host header', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const res = await app.request('/api/echo', {
      headers: { Host: 'caller-node.example.com' },
    })
    expect(res.status).toBe(200)
    const body = await res.json() as { host: string | null }
    expect(body.host).not.toBe('caller-node.example.com')
    expect(body.host).toBe(new URL(upstreamUrl).host)
  })

  it('strips response content-encoding and content-length', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const res = await app.request('/api/gzip-lie')
    expect(res.status).toBe(200)
    expect(res.headers.get('content-encoding')).toBeNull()
    expect(res.headers.get('content-length')).toBeNull()
    const body = await res.json() as { ok: boolean }
    expect(body.ok).toBe(true)
  })

  it('streams SSE incrementally through the proxy', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const start = Date.now()
    const res = await app.request('/api/sse')
    expect(res.status).toBe(200)
    expect(res.body).not.toBeNull()

    const reader = res.body!.getReader()
    const decoder = new TextDecoder()
    let firstFrameAt: number | null = null
    let buffer = ''
    let frameCount = 0

    while (true) {
      const { value, done } = await reader.read()
      if (done) break
      buffer += decoder.decode(value, { stream: true })
      const frames = buffer.split('\n\n').filter((f) => f.includes('event: frame'))
      if (frames.length > 0 && firstFrameAt === null) {
        firstFrameAt = Date.now()
      }
      frameCount = frames.length
    }

    expect(frameCount).toBe(3)
    // The first frame must have arrived well before the full ~120ms stream
    // finished — proves the proxy piped the stream through instead of
    // buffering the whole thing before responding.
    expect(firstFrameAt).not.toBeNull()
    expect(firstFrameAt! - start).toBeLessThan(100)
  })

  it('forwards the client address in x-forwarded-for', async () => {
    process.env.ARENA_UPSTREAM_URL = upstreamUrl
    const app = buildProxyingApp()

    const res = await app.request('/api/echo', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({}),
    })
    expect(res.status).toBe(200)
    const body = await res.json() as { xff: string | null }
    // app.request() drives the Hono app directly (no real Node socket), so the
    // remoteAddress lookup this proxy relies on may legitimately be
    // undetermined here — the behavioral contract is that the header is
    // either forwarded (non-empty) or cleanly absent, never invented/garbage.
    if (body.xff !== null) {
      expect(body.xff.length).toBeGreaterThan(0)
    }
  })

  it('answers 502 when the arena is unreachable', async () => {
    process.env.ARENA_UPSTREAM_URL = 'http://127.0.0.1:1'
    const app = buildProxyingApp()

    const res = await app.request('/api/bots')
    expect(res.status).toBe(502)
    const body = await res.json() as { error: string }
    expect(body.error).toBeTruthy()
  })
})