class Listen::File

def self.change(record, rel_path)
  path = Pathname.new(record.root) + rel_path
  lstat = path.lstat
  data = { mtime: lstat.mtime.to_f, mode: lstat.mode, size: lstat.size }
  record_data = record.file_data(rel_path)
  if record_data.empty?
    record.update_file(rel_path, data)
    return :added
  end
  if data[:mode] != record_data[:mode]
    record.update_file(rel_path, data)
    return :modified
  end
  if data[:mtime] != record_data[:mtime]
    record.update_file(rel_path, data)
    return :modified
  end
  if data[:size] != record_data[:size]
    record.update_file(rel_path, data)
    return :modified
  end
  return if /1|true/ =~ ENV['LISTEN_GEM_DISABLE_HASHING']
  return unless inaccurate_mac_time?(lstat)
  # Check if change happened within 1 second (maybe it's even
  # too much, e.g. 0.3-0.5 could be sufficient).
  #
  # With rb-fsevent, there's a (configurable) latency between
  # when file was changed and when the event was triggered.
  #
  # If a file is saved at ???14.998, by the time the event is
  # actually received by Listen, the time could already be e.g.
  # ???15.7.
  #
  # And since Darwin adapter uses directory scanning, the file
  # mtime may be the same (e.g. file was changed at ???14.001,
  # then at ???14.998, but the fstat time would be ???14.0 in
  # both cases).
  #
  # If change happened at ???14.999997, the mtime is 14.0, so for
  # an mtime=???14.0 we assume it could even be almost ???15.0
  #
  # So if Time.now.to_f is ???15.999998 and stat reports mtime
  # at ???14.0, then event was due to that file'd change when:
  #
  # ???15.999997 - ???14.999998 < 1.0s
  #
  # So the "2" is "1 + 1" (1s to cover rb-fsevent latency +
  # 1s maximum difference between real mtime and that recorded
  # in the file system)
  #
  return if data[:mtime].to_i + 2 <= Time.now.to_f
  sha = Digest::SHA256.file(path).digest
  record.update_file(rel_path, data.merge(sha: sha))
  if record_data[:sha] && sha != record_data[:sha]
    :modified
  end
rescue SystemCallError
  record.unset_path(rel_path)
  :removed
rescue
  Listen.logger.debug "lstat failed for: #{rel_path} (#{$ERROR_INFO})"
  raise
end

def self.inaccurate_mac_time?(stat)
  # 'mac' means Modified/Accessed/Created
  # Since precision depends on mounted FS (e.g. you can have a FAT partiion
  # mounted on Linux), check for fields with a remainder to detect this
  [stat.mtime, stat.ctime, stat.atime].map(&:usec).all?(&:zero?)
end