#!/usr/bin/env ruby

if fetched_file_blank? or fetched_file_expired?
  fetch!
end

write_cached_screenfetch!

BEGIN {
  COMMAND = 'screenfetch'.freeze
  EXPIRATION_TIMEOUT = 5 * 60 # 5 minutes
  FETCHED_PATH = File.expand_path('~/.screenfetched').freeze
  WRITE_MODE = 'w'.freeze

  def fetch!
    File.open(FETCHED_PATH, WRITE_MODE) do |f|
      if f.flock(File::LOCK_EX|File::LOCK_NB)
        f.write(`#{COMMAND}`)
        f.flush
      else
        f.flock(File::LOCK_EX)
      end

      f.flock(File::LOCK_UN)
    end
  end

  def fetched_file_blank?
    !File.exist?(FETCHED_PATH)
  end

  def fetched_file_expired?
    Time.now - File.mtime(FETCHED_PATH) > EXPIRATION_TIMEOUT
  end

  def write_cached_screenfetch!
    File.open(FETCHED_PATH) do |f|
      f.flock(File::LOCK_SH)
      puts(f.read)
    end
  end
}