class Rake::CpuCounter

def self.count
  new.count_with_default
end

def count
  if defined?(Java::Java)
    count_via_java_runtime
  else
    case RbConfig::CONFIG['host_os']
    when /darwin9/
      count_via_hwprefs_cpu_count
    when /darwin/
      count_via_hwprefs_thread_count || count_via_sysctl
    when /linux/
      count_via_cpuinfo
    when /bsd/
      count_via_sysctl
    when /mswin|mingw/
      count_via_win32
    else
      # Try everything
      count_via_win32 ||
        count_via_sysctl ||
        count_via_hwprefs_thread_count ||
        count_via_hwprefs_cpu_count
    end
  end
end

def count_via_cpuinfo
  open('/proc/cpuinfo') { |f| f.readlines }.grep(/processor/).size
rescue StandardError
  nil
end

def count_via_hwprefs_cpu_count
  run 'hwprefs', 'cpu_count'
end

def count_via_hwprefs_thread_count
  run 'hwprefs', 'thread_count'
end

def count_via_java_runtime
  Java::Java.lang.Runtime.getRuntime.availableProcessors
rescue StandardError
  nil
end

def count_via_sysctl
  run 'sysctl', '-n', 'hw.ncpu'
end

def count_via_win32
  require 'win32ole'
  wmi = WIN32OLE.connect("winmgmts://")
  cpu = wmi.ExecQuery("select NumberOfCores from Win32_Processor") # TODO count hyper-threaded in this
  cpu.to_enum.first.NumberOfCores
rescue StandardError, LoadError
  nil
end

def count_with_default(default=4)
  count || default
rescue StandardError
  default
end

def in_path_command(command)
  Open3.popen3 'which', command do |_, out,|
    out.eof? ? nil : command
  end
end

def look_for_command(dir, command)
  path = File.join(dir, command)
  File.exist?(path) ? path : nil
end

def resolve_command(command)
  look_for_command("/usr/sbin", command) ||
    look_for_command("/sbin", command) ||
    in_path_command(command)
end

def run(command, *args)
  cmd = resolve_command(command)
  if cmd
    Open3.popen3 cmd, *args do |_, out|
      out.read.to_i
    end
  else
    nil
  end
end