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
	Fiber.scheduler.transfer
end

def alive?
	@fiber&.alive?
end

def async(*arguments, **options, &block)
	raise "Cannot create child task within a task that has finished execution!" if self.finished?
	
	task = Task.new(self, **options, &block)
	
	task.run(*arguments)
	
	return task
end

def backtrace(*arguments)
	@fiber&.backtrace(*arguments)
end

def complete?
	@status == :complete
end

def current?
	self.equal?(Thread.current[:async_task])
end

def fail!(exception = false, propagate = true)
	@status = :failed
	@result = exception
	
	if exception
		if propagate
			raise exception
		elsif @finished.nil?
			# If no one has called wait, we log this as a warning:
			Console.logger.warn(self, "Task may have ended with unhandled exception.", exception)
		else
			Console.logger.debug(self, exception)
		end
	end
end

def failed?
	@status == :failed
end

def finish!
	# Allow the fiber to be recycled.
	@fiber = nil
	
	# Attempt to remove this node from the task tree.
	consume
	
	# If this task was being used as a future, signal completion here:
	if @finished
		@finished.signal(self)
	end
end

def finished?
	super && @fiber.nil?
end

def initialize(parent = Task.current?, finished: nil, **options, &block)
	super(parent, **options)
	
	@status = :initialized
	@result = nil
	@finished = finished
	
	@block = block
	@fiber = nil
end

def reactor
	self.root
end

def run(*arguments)
	if @status == :initialized
		@status = :running
		
		schedule do
			@block.call(self, *arguments)
		end
	else
		raise RuntimeError, "Task already running!"
	end
end

def running?
	@status == :running
end

def schedule(&block)
	@fiber = Fiber.new do
		set!
		
		begin
			@result = yield
			@status = :complete
			# Console.logger.debug(self) {"Task was completed with #{@children.size} children!"}
		rescue Stop
			stop!
		rescue StandardError => error
			fail!(error, false)
		rescue Exception => exception
			fail!(exception, true)
		ensure
			# Console.logger.info(self) {"Task ensure $! = #{$!} with #{@children&.size.inspect} children!"}
			finish!
		end
	end
	
	self.root.resume(@fiber)
end

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

def sleep(duration = nil)
	super
end

def stop(later = false)
	if self.stopped?
		# If we already stopped this task... don't try to stop it again:
		return
	end
	
	if self.running?
		if self.current?
			if later
				Fiber.scheduler.push(Stop::Later.new(self))
			else
				raise Stop, "Stopping current task!"
			end
		elsif @fiber&.alive?
			begin
				Fiber.scheduler.raise(@fiber, Stop)
			rescue FiberError
				Fiber.scheduler.push(Stop::Later.new(self))
			end
		end
	else
		# We are not running, but children might be, so transition directly into stopped state:
		stop!
	end
end

def stop!
	# Console.logger.info(self, self.annotation) {"Task was stopped with #{@children&.size.inspect} children!"}
	@status = :stopped
	
	stop_children(true)
end

def stopped?
	@status == :stopped
end

def to_s
	"\#<#{self.description} (#{@status})>"
end

def wait
	raise "Cannot wait on own fiber!" if Fiber.current.equal?(@fiber)
	
	if running?
		@finished ||= Condition.new
		@finished.wait
	end
	
	if @result.is_a?(Exception)
		raise @result
	else
		return @result
	end
end

def with_timeout(duration, exception = TimeoutError, message = "execution expired", &block)
	Fiber.scheduler.with_timeout(duration, exception, message, &block)
end

def yield
	Fiber.scheduler.yield
end