class ParallelTests::Pids

def add(pid)
  pids << pid.to_i
  save
end

def all
  read
  pids
end

def clear
  @pids = []
  save
end

def count
  read
  pids.count
end

def delete(pid)
  pids.delete(pid.to_i)
  save
end

def initialize(file_path)
  @file_path = file_path
  @mutex = Mutex.new
end

def pids
  @pids ||= []
end

def read
  sync do
    contents = IO.read(file_path)
    return if contents.empty?
    @pids = JSON.parse(contents)
  end
end

def save
  sync { IO.write(file_path, pids.to_json) }
end

def sync(&block)
  mutex.synchronize(&block)
end