module FartSystem

# File lib/fart_system.rb, line 110
def default_readers
  {
    meminfo: -> { File.read("/proc/meminfo") },
    loadavg: -> { File.read("/proc/loadavg") },
    uptime: -> { File.read("/proc/uptime") },
    cpu_ping: -> { FartCpuPing.sample_ns }
  }
end

# File lib/fart_system.rb, line 71
def format_loadavg(load)
  return nil unless load

  "#{load[:load1]} #{load[:load5]} #{load[:load15]}"
end

# File lib/fart_system.rb, line 48
def format_swap(info)
  total = swap_total_kb(info)
  return nil unless total.positive?

  "#{human_ram(used_swap_kb(info))} #{swap_percent(info)}%"
end

# File lib/fart_system.rb, line 81
def format_uptime(seconds)
  total = seconds.to_f.round
  days = total / 86_400
  hours = (total % 86_400) / 3600
  minutes = (total % 3600) / 60

  parts = []
  parts << "#{days}d" if days.positive?
  parts << "#{hours}h" if days.positive? || hours.positive?
  parts << "#{minutes}m"
  parts.join(" ")
end

# File lib/fart_system.rb, line 22
def free_ram_kb(info)
  available = info["MemAvailable"] || info["MemFree"]
  available.to_i
end

# File lib/fart_system.rb, line 27
def free_swap_kb(info)
  info["SwapFree"].to_i
end

# File lib/fart_system.rb, line 55
def human_ram(kilobytes)
  bytes = kilobytes.to_i * 1024
  if bytes >= 1_073_741_824
    format("%.1fG", bytes / 1_073_741_824.0)
  else
    format("%.1fM", bytes / 1_048_576.0)
  end
end

# File lib/fart_system.rb, line 64
def parse_loadavg(text)
  fields = text.to_s.strip.split
  return nil if fields.length < 3

  { load1: fields[0], load5: fields[1], load15: fields[2] }
end

# File lib/fart_system.rb, line 14
def parse_meminfo(text)
  text.to_s.each_line.with_object({}) do |line, info|
    next unless line =~ /^(\w+):\s+(\d+)/

    info[Regexp.last_match(1)] = Regexp.last_match(2).to_i
  end
end

# File lib/fart_system.rb, line 77
def parse_uptime(text)
  text.to_s.split.first.to_f
end

# File lib/fart_system.rb, line 94
def snapshot(readers: default_readers)
  meminfo = parse_meminfo(readers.fetch(:meminfo).call)
  free_kb = free_ram_kb(meminfo)
  load = parse_loadavg(readers.fetch(:loadavg).call)
  uptime_sec = parse_uptime(readers.fetch(:uptime).call)
  {
    free_ram: human_ram(free_kb),
    loadavg: format_loadavg(load),
    uptime: format_uptime(uptime_sec),
    swap: format_swap(meminfo),
    cpu_ns: readers.fetch(:cpu_ping).call
  }
rescue StandardError
  { free_ram: nil, loadavg: nil, uptime: nil, swap: nil, cpu_ns: nil }
end

# File lib/fart_system.rb, line 41
def swap_percent(info)
  total = swap_total_kb(info)
  return 0 unless total.positive?

  (used_swap_kb(info) * 100.0 / total).round
end

# File lib/fart_system.rb, line 37
def swap_total_kb(info)
  info["SwapTotal"].to_i
end

# File lib/fart_system.rb, line 31
def used_swap_kb(info)
  total = swap_total_kb(info)
  free = free_swap_kb(info)
  [total - free, 0].max
end