require_relative '../../spec_helper'
require_relative 'fixtures/clocks'

describe "Process.clock_getres" do
  platform_is_not :freebsd do # clock_getres() seems incorrect on FreeBSD
    ProcessSpecs.clock_constants_for_resolution_checks.each do |name, value|
      it "matches the clock in practice for Process::#{name}" do
        times = []
        10_000.times do
          times << Process.clock_gettime(value, :nanosecond)
        end
        reported = Process.clock_getres(value, :nanosecond)

        # CentOS seems to report a negative resolution:
        # https://rubyci.org/logs/rubyci.s3.amazonaws.com/centos6/ruby-trunk/log/20190428T093004Z.fail.html.gz
        unless name == :CLOCK_MONOTONIC_RAW and reported < 0
          # The clock should not be more accurate than reported (times should be
          # a multiple of reported precision.)
          times.select { |t| t % reported > 0 }.should be_empty

          # We're assuming precision is a multiple of ten - it may or may not
          # be an incompatibility if it isn't but we'd like to notice this,
          # and the spec following these wouldn't work if it isn't.
          reported.should > 0
          (reported == 1 || reported % 10 == 0).should be_true

          # The clock should not be less accurate than reported (times should
          # not all be a multiple of the next precision up, assuming precisions
          # are multiples of ten.)
          times.select { |t| t % (reported * 10) == 0  }.size.should_not == times.size
        end
      end
    end
  end

  # These are documented

  it "with :GETTIMEOFDAY_BASED_CLOCK_REALTIME reports 1 microsecond" do
    Process.clock_getres(:GETTIMEOFDAY_BASED_CLOCK_REALTIME, :nanosecond).should == 1_000
  end

  it "with :TIME_BASED_CLOCK_REALTIME reports 1 second" do
    Process.clock_getres(:TIME_BASED_CLOCK_REALTIME, :nanosecond).should == 1_000_000_000
  end

  platform_is_not :windows do
    it "with :GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID reports 1 microsecond" do
      Process.clock_getres(:GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID, :nanosecond).should == 1_000
    end
  end

  # These are observed

  platform_is_not :solaris do
    it "with Process::CLOCK_REALTIME reports at least 1 microsecond" do
      Process.clock_getres(Process::CLOCK_REALTIME, :nanosecond).should <= 1_000
    end
  end

  it "with Process::CLOCK_MONOTONIC reports at least 1 microsecond" do
    Process.clock_getres(Process::CLOCK_MONOTONIC, :nanosecond).should <= 1_000
  end
end