require File.expand_path('../../../spec_helper', __FILE__)
require 'thread'

describe "ConditionVariable#signal" do
  it "returns self if nothing to signal" do
    cv = ConditionVariable.new
    cv.signal.should == cv
  end

  it "returns self if something is waiting for a signal" do
    m = Mutex.new
    cv = ConditionVariable.new
    th = Thread.new do
      m.synchronize do
        cv.wait(m)
      end
    end

    # ensures that th grabs m before current thread
    Thread.pass while th.status and th.status != "sleep"

    m.synchronize { cv.signal }.should == cv

    th.join
  end

  ruby_bug "#", "1.8.7" do
    it "releases the first thread waiting in line for this resource" do
      m = Mutex.new
      cv = ConditionVariable.new
      threads = []
      r1 = []
      r2 = []

      # large number to attempt to cause race conditions
      100.times do |i|
        threads << Thread.new(i) do |tid|
          m.synchronize do
            r1 << tid
            cv.wait(m)
            r2 << tid
          end
        end
      end

      # wait for all threads to acquire the mutex the first time
      Thread.pass until m.synchronize { r1.size == threads.size }
      # wait until all threads are sleeping (ie waiting)
      Thread.pass until threads.all? {|th| th.status == "sleep" }

      r2.should be_empty
      100.times do |i|
        m.synchronize do
          cv.signal
        end
        Thread.pass until r2.size == i+1
      end

      threads.each {|t| t.join }

      # ensure that all the threads that went into the cv.wait are
      # released in the same order
      r2.should == r1
    end
  end
end