class Async::Actor::Variable

def self.fulfill(variable)
	variable.set(yield)
	variable = nil
rescue => error
	variable&.fail(error)
	variable = nil
ensure
	# throw, etc:
	variable&.fail(RuntimeError.new("Invalid flow control!"))
end

def fail(error)
	@guard.synchronize do
		raise "Variable already set!" unless @set.nil?
		
		@set = false
		@error = error
		@condition.broadcast
	end
end

def get
	@guard.synchronize do
		while @set.nil?
			@condition.wait(@guard)
		end
		
		if @set
			return @value
		else
			raise @error
		end
	end
end

def initialize
	@set = nil
	@value = nil
	
	@guard = Thread::Mutex.new
	@condition = Thread::ConditionVariable.new
end

def set(value)
	@guard.synchronize do
		raise "Variable already set!" unless @set.nil?
		
		@set = true
		@value = value
		@condition.broadcast
	end
end