import tables, random, os, times, json, asyncfile, asyncdispatch, parseutils
import nimhafas
import cache_types, types

randomize()


proc toAlphaId (n: int): string =
  let chars = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"

  var tmp = n
  var digitValue: int = 1
  var digit: int = 0
  while tmp > 0:
    digitValue *= chars.len
    digit = tmp mod digitValue
    let char = int(digit * chars.len / digitValue)
    result = $(chars[char]) & result
    tmp -= digit

proc fromAlphaId (s: string): int =
  let chars = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"

  for char in s:
    result *= chars.len
    result += chars.skipUntil(char)

proc getFreeAlphaId (): string =
  result = toAlphaId(int32(rand(high(int32))))

  while fileExists(getEnv("CACHE_PATH") & "/" & $result & ".json"):
    result = toAlphaId(int32(rand(high(int32))))

proc cacheExists* (id: string ): bool =
  return fileExists(getEnv("CACHE_PATH") & "/" & $id & ".json")

proc getCacheObject* (reqId: string): CacheObject = 
  if not cacheExists(reqId): raise newException(notFoundException, "REQUEST_NOT_FOUND")
  return parseFile(getEnv("CACHE_PATH") & "/" & $reqId & ".json").to(CacheObject)

proc saveJourneys* (params: JourneysParams, journeysResponse: JourneysResponse): Future[CacheObject] {.async.} =
  let reqId       = getFreeAlphaId()
  let lastUpdated = getTime().toUnix()
  var journeys    = initTable[string, Journey]()
  var maxId       = -1

  for journey in journeysResponse.journeys:
    inc(maxId)
    journeys[$maxId] = journey

  var cacheObj = CacheObject(
      version:     1,
      reqId:       reqId,
      minId:       0,
      maxId:       maxId,
      earlierRef:  journeysResponse.earlierRef,
      laterRef:    journeysResponse.laterRef,
      lastUpdated: lastUpdated,
      params:      params,
      journeys:    journeys
    )

  var file = openAsync(getEnv("CACHE_PATH") & "/" & $reqId & ".json", fmReadWrite)
  await file.write($(%* cacheObj))

  return cacheObj

proc updateJourneys* (reqId: string, mode: moreJourneysMode, journeysResponse: JourneysResponse): Future[CacheObject] {.async.} =
  var cacheObj    = getCacheObject(reqId)

  if mode == earlier:
    cacheObj.minId -= journeysResponse.journeys.len
    var cnt = cacheObj.minId
    for journey in journeysResponse.journeys:
      cacheObj.journeys[$cnt] = journey
      inc(cnt)

  else:
    for journey in journeysResponse.journeys:
      inc(cacheObj.maxId)
      cacheObj.journeys[$cacheObj.maxId] = journey

  cacheObj.lastUpdated = getTime().toUnix()
  if mode != later:
    cacheObj.earlierRef  = journeysResponse.earlierRef
  else:
    cacheObj.laterRef    = journeysResponse.laterRef

  var file = openAsync(getEnv("CACHE_PATH") & "/" & $reqId & ".json", fmReadWrite)
  await file.write($(%* cacheObj))

  return cacheObj

proc updateJourney* (reqId: string, journeyId: string, journey: Journey): Future[CacheObject] {.async.} =
  var cacheObj    = getCacheObject(reqId)

  cacheObj.lastUpdated = getTime().toUnix()
  cacheObj.journeys[journeyId] = journey

  var file = openAsync(getEnv("CACHE_PATH") & "/" & $reqId & ".json", fmReadWrite)
  await file.write($(%* cacheObj))

  return cacheObj