class Async::Task

def self.current
	Thread.current[:async_task] or raise RuntimeError, "No async task available!"
end

def self.current?
	Thread.current[:async_task]
end

def self.yield
	if block_given?
		result = yield
	else
		result = Fiber.yield
	end
	
	if result.is_a? Exception
		raise result
	else
		return result
	end
end

def async(*args, &block)
	task = Task.new(@reactor, self, &block)
	
	task.run(*args)
	
	return task
end

def finish!
	# Attempt to remove this node from the task tree.
	consume
	
	# If this task was being used as a future, signal completion here:
	if @condition
		@condition.signal(@result)
	end
end

def finished?
	super && @status != :running
end

def initialize(reactor, parent = Task.current?)
	super(parent || reactor)
	
	@reactor = reactor
	
	@status = :initialized
	@result = nil
	
	@condition = nil
	
	@fiber = Fiber.new do |*args|
		set!
		
		begin
			@result = yield(self, *args)
			@status = :complete
			# Async.logger.debug("Task #{self} completed normally.")
		rescue Stop
			@status = :stop
			# Async.logger.debug("Task #{self} stopped: #{$!}")
		rescue Exception => error
			@result = error
			@status = :failed
			# Async.logger.debug("Task #{self} failed: #{$!}")
			raise
		ensure
			# Async.logger.debug("Task #{self} closing: #{$!}")
			finish!
		end
	end
end

def result
	raise RuntimeError.new("Cannot wait on own fiber") if Fiber.current.equal?(@fiber)
	
	if running?
		@condition ||= Condition.new
		@condition.wait
	else
		Task.yield {@result}
	end
end

def run(*args)
	if @status == :initialized
		@status = :running
		@fiber.resume(*args)
	else
		raise RuntimeError, "Task already running!"
	end
end

def running?
	@status == :running
end

def set!
	# This is actually fiber-local:
	Thread.current[:async_task] = self
end

def stop
	@children.each(&:stop)
	
	if @fiber.alive?
		@fiber.resume(Stop.new)
	end
end

def to_s
	"<#{self.description} status=#{@status}>"
end

def yield
	self.sleep(0)
end