nitter/src/tokens.nim

import asyncdispatch, httpclient, times, sequtils, strutils, json
import types, agents, consts

var
  tokenPool {.threadvar.}: seq[Token]
  lastFailed: Time
  minFail = initDuration(seconds=10)

proc fetchToken(): Future[Token] {.async.} =
  if getTime() - lastFailed < minFail:
    return Token()

  let
    headers = newHttpHeaders({
      "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
      "accept-language": "en-US,en;q=0.5",
      "connection": "keep-alive",
      "user-agent": getAgent(),
      "authorization": auth
    })
    client = newAsyncHttpClient(headers=headers)

  var
    resp: string
    tok: string

  try:
    resp = await client.postContent(activate)
    tok = parseJson(resp)["guest_token"].getStr

    let time = getTime()
    result = Token(tok: tok, remaining: 187, reset: time + 15.minutes,
                   init: time, lastUse: time)
  except Exception as e:
    lastFailed = getTime()
    echo "fetching token failed: ", e.msg
    result = Token()
  finally:
    client.close()

proc expired(token: Token): bool {.inline.} =
  const
    expirationTime = 2.hours
    maxLastUse = 1.hours
  let time = getTime()
  result = token.init < time - expirationTime or
           token.lastUse < time - maxLastUse

proc isLimited(token: Token): bool {.inline.} =
  token == nil or (token.remaining <= 1 and token.reset > getTime()) or
    token.expired

proc release*(token: Token) =
  if token != nil and not token.expired:
    token.lastUse = getTime()
    tokenPool.insert(token)

proc getToken*(): Future[Token] {.async.} =
  for i in 0 ..< tokenPool.len:
    if not result.isLimited: break
    result.release()
    result = tokenPool.pop()

  if result.isLimited:
    result.release()
    result = await fetchToken()

proc poolTokens*(amount: int) {.async.} =
  var futs: seq[Future[Token]]
  for i in 0 ..< amount:
    futs.add fetchToken()

  for token in futs:
    release(await token)

proc initTokenPool*(cfg: Config) {.async.} =
  while true:
    if tokenPool.countIt(not it.isLimited) < cfg.minTokens:
      await poolTokens(min(4, cfg.minTokens - tokenPool.len))
    await sleepAsync(2000)