import system
import os
import hashes
import strutils
import httpclient

type
  SynchronizedFileInfo = object of RootObj
    url: string
    localPath: string
    localHash: Hash
  Config = ref object of RootObj
    infos: seq[SynchronizedFileInfo]

proc loadConfig(): Config =
  let configFile = open("urlsync.cfg", mode=FileMode.fmReadWriteExisting)
  defer: close configFile
  var infos = newSeq[SynchronizedFileInfo]()
  var hashBytes: array[sizeof(Hash), uint8]
  while true:
    if configFile.readBytes(hashBytes, 0, sizeof(Hash)) < sizeof(Hash): break
    let hash = cast[ptr Hash](addr hashBytes)[]
    let sl = configFile.readLine().split("|", maxsplit=1)
    #if sl.len != 2: error
    var sfi = SynchronizedFileInfo(url:sl[0], localPath:sl[1], localHash:hash)
    infos.add(sfi)
  return Config(infos: infos)

proc computeHash(file: File): Hash = file.readAll().hash()

proc computeFileHash(filePath: string): Hash =
  let file = open(filePath, mode=FileMode.fmRead)
  defer: close file
  return computeHash(file)


var config = loadConfig()
echo repr(config)

while true:
  sleep 1000*10 # 10 s

  for sfi in config.infos:
    var client = newHttpClient()
    defer: close client
    let downloadPath = sfi.localPath & ".new"
    if not os.existsFile(sfi.localPath):
      client.downloadFile(sfi.url, sfi.localPath)
      continue
    client.downloadFile(sfi.url, downloadPath)
    if computeFileHash(downloadPath) != computeFileHash(sfi.localPath):
      try:
        echo "updating " & sfi.localPath
        os.removeFile(sfi.localPath)
        os.moveFile(downloadPath, sfi.localPath)
      except OSError:
        echo getCurrentExceptionMsg()
    else:
      os.removeFile(downloadPath)