#!/usr/bin/env ruby

def to_s_bytes(value)
  values = {2**40 => 'TiB', 2**30 => 'GiB', 2**20 => 'MiB', 2**10 => 'KiB'}
  values.each_pair do |k, v|
    if value >= k
      return (value.to_f / k).round(2).to_s + ' ' + v
    end
  end
  value.to_s + ' B'
end

def wait_process(name)
  loop do
    list = `ps a | grep ruby`

    list.split("\n").each do |line|
      line.strip!

      if line =~ /#{name}/i and !line.include?(File.basename(__FILE__))
        return line.strip.split.first.to_i
      end
    end

    sleep 0.01
  end
end

def track_mem(pid, echo: true)
  values = []

  loop do
    value = `ps -o rss -p #{pid}`.strip.split.last.to_i * 1024
    break if value == 0

    values << value

    puts [pid, Time.now, to_s_bytes(value)].map { |s| s.to_s.ljust(30) }.join(" | ") if echo

    sleep 0.01
  end

  values
end

def dump_mem_values(values)
  name = "trackedmem.txt"

  File.open(name, 'wb') do |file|
    values.each { |num| file.write("#{num}\n") }
  end
end

pname = ARGV[0]

if pname.to_s.empty?
  puts "Usage: trackmem RUBY_SCRIPT_NAME"
  exit
end

loop do
  puts "Waiting for #{pname.inspect} to start..."
  pid = wait_process(pname)

  puts "Process stared with pid #{pid}"
  values = track_mem(pid)

  puts "Dumping mem values..."
  dump_mem_values(values)
end