#!/usr/bin/env ruby

Signal.trap('INT') { exit } # graceful exit

module Wait4Inet
  require 'shellwords'
  require 'yaml'

  JOB_DIR = "/tmp/#{File.basename __FILE__}.jobs"
  MAX_RETRIES = 3

  def self.run(args)
    action = args.shift

    # extract action arguments
    data = case action
      when 'check'  # read and execute now every job file
        process_files
        exit

      when 'check-loop'
        interval = args[0].to_i == 0 ? 60 : args[0].to_i
        loop { process_files; sleep interval }
        exit

      when 'cmd'
        { args: args }

      else
        puts "USAGE: #{File.basename __FILE__} <action> [params]"
        puts "  * cmd   <command> [command params]"
        puts "  * check           # runs queued actions"
        puts "  * check-loop [S]  # run \"check\" action every S seconds"
        exit
    end

    save_job action, data
  end # self.run ---------------------------------------------------------------

  def self.process_files
    return unless online? 

    Dir.chdir('/tmp') # safe working directory

    Dir["#{JOB_DIR}/*.w4i"].sort.each do |job_file|
      next if File.exist?("#{job_file}.lock")
      File.open("#{job_file}.lock", 'w').close # touch

      data = YAML::load_file job_file rescue {}

      next unless data[:action] && data[:ts] # sanity check

      puts "\n===== #{File.basename job_file}: #{data}"
      next unless data[:retries].to_i < MAX_RETRIES

      case data[:action]
        when 'cmd'
          system %Q| #{data[:args].map(&:shellescape).join ' '}|
          update_job job_file, data, $?
      end

      File.unlink "#{job_file}.lock"

      sleep 1
    end # each job_file
  end # self.process_files -----------------------------------------------------

  def self.save_job(action, data)
    Dir.mkdir(JOB_DIR) unless File.exist?(JOB_DIR)
    File.chmod(0777, JOB_DIR) if File.owned?(JOB_DIR)

    # write job file with timestamp
    ts    = Time.now
    data  = data.merge action: action, ts: ts
    fname = "#{JOB_DIR}/#{ts.strftime '%F_%T_%3N'}.w4i"
    File.open(fname, 'w'){|f| f.write data.to_yaml }
  end # self.save_job ----------------------------------------------------------

  def self.update_job(job_file, data, exit_code, exit_code_ok = 0)
    if exit_code.to_i == exit_code_ok.to_i
      File.unlink job_file
    else
      data[:retries  ] = data[:retries].to_i + 1
      data[:exit_code] = exit_code.to_i
      File.open(job_file, 'w'){|f| f.write data.to_yaml }
      File.rename(job_file, "#{job_file}.failed") if data[:retries].to_i == MAX_RETRIES
    end
  end # self.update_job --------------------------------------------------------

  def self.online?
    `wget -q --spider -T 3 http://google.com`
    $?.to_i == 0
  end # self.online? -----------------------------------------------------------
end # module Wait4Inet ---------------------------------------------------------

Wait4Inet.run ARGV