class FileQueue

# File lib/filequeue.rb, line 6
def initialize(file_name, delimiter="\n", lock_timeout: 10)
  @delimiter = delimiter
  @file_name = file_name
  @lock_timeout = lock_timeout
end

# File lib/filequeue.rb, line 50
def clear
  safe_open 'w' do |file| end
end

# File lib/filequeue.rb, line 46
def empty?
  return length == 0
end

# File lib/filequeue.rb, line 35
def length
  count = 0
  unless(File.exist?(@file_name))
    return 0
  end
  safe_open 'r' do |file|
    count = file.read.count @delimiter
  end
  count
end

# File lib/filequeue.rb, line 23
def pop
  value = nil
  safe_open 'r+' do |file|
    value = file.gets @delimiter
    rest = file.read
    file.rewind
    file.truncate(0)
    file.write(rest)
  end
  value ? value[0..-(@delimiter.length) - 1] : nil
end

# File lib/filequeue.rb, line 12
def push(obj)
  if obj.match Regexp.new @delimiter
    raise "Queue objects cannot contain the queue delimiter"
  end
  safe_open 'a' do |file|
    file.write(obj + @delimiter)
  end
end

# File lib/filequeue.rb, line 71
def lock(file)
  deadline = (Time.now + lock_timeout)

  until Time.now >= deadline || lock_acquired = file.flock(File::LOCK_NB|File::LOCK_EX)
    sleep(rand(DELAY_RANGE))
  end

  (raise FileLockError, "Queue file appears to be permanently locked") unless lock_acquired
end

# File lib/filequeue.rb, line 56
def safe_open(mode)
  File.open(@file_name, mode) do |file|
    lock file
    yield file
  end
end