# Handle to a thread
#
# Instances of this class are each used to launch and control a thread.
abstract class Thread
	super Finalizable

	# Type returned by `main`
	type E : nullable Object

	private var native: nullable NativePthread = null

	# Is this thread finished ? True when main returned
	var is_done = false

	# Main method of this thread
	#
	# The returned valued is passed to the caller of `join`.
	fun main: E do return null

	private fun main_intern: E
	do
		# Register thread local data
		sys.self_thread_key.set self
		var r = main
		self.is_done = true
		return r
	end

	# Start executing this thread
	#
	# Will launch `main` on a different thread.
	fun start
	do
		if native != null then return
		native = new NativePthread.create(self)
	end

	# Join this thread to the calling thread
	#
	# Blocks until the method `main` returns or the target thread calls
	# `Sys::thread_exit`. Returns the object returned from the other thread.
	#
	# Stats the thread if now already done by a call to `start`.
	fun join: E
	do
		if native == null then start
		var r = native.join
		native = null
		return r.as(E)
	end

	redef fun finalize
	do
		if native == null then return
		native.free
		native = null
	end
end