module Howlong

# File lib/howlong.rb, line 22
def self.build_sentence(process, delayed)
  return if delayed.nil?

  printable = "Process #{process} has been active for "
  if (delayed[:days]).positive?
    printable += "#{delayed[:days]} days, #{(delayed[:seconds].to_int / 86_400) % 24} hours, #{delayed[:minutes] % 60} minutes "
  elsif (delayed[:hours]).positive?
    printable += "#{delayed[:hours]} hours, #{delayed[:minutes] % 60} minutes "
  else
    printable += "#{delayed[:minutes]} minutes "
  end
  printable + "and #{delayed[:seconds] % delayed[:minutes]} seconds"
end

# File lib/howlong.rb, line 7
def self.find_processes(search)
  processes = processes_from_system(search).split(/\n/)
  names = []
  processes.each do |p|
    process = p.match(/\S+#{search}/)
    # Make sure the first executable contains the search string, so we
    # won't catch processes such as grep `parameter` or this script:
    if process
      time = elapsed_time(p)
      names << [process[0], time]
    end
  end
  names
end

# File lib/howlong.rb, line 40
def self.run(process)
  puts sentences_string(process)
end

# File lib/howlong.rb, line 44
def self.sentences_array(process)
  processes = find_processes(process)
  result = []
  processes.each do |p|
    result << build_sentence(p[0], p[1])
  end
  result
end

# File lib/howlong.rb, line 36
def self.sentences_string(process)
  sentences_array(process).join("\n")
end

# File lib/howlong.rb, line 60
def elapsed_time(process)
  # We need the current offset so we can make time operations in the
  # same timezone, yey timezones!
  offset = Time.now.gmt_offset / 3600
  # Get the date from ps in the "Day Mon  %m hh:mm:ss yyyy" format,
  # substract offset and pass it to time
  start = (DateTime.parse(process.match(/[a-zA-Z\s0-9:]+[0-9]{4}/)[0]) - (offset / 24.0)).to_time
  length = Time.now - start

  seconds = length.to_int
  minutes = seconds / 60
  hours   = seconds / 3_600
  days    = seconds / 86_400

  {
    seconds: length.to_int,
    minutes: minutes,
    hours: hours,
    days: days
  }
end

# File lib/howlong.rb, line 56
def processes_from_system(search)
  `ps -eo lstart,args | grep -i #{search}`
end