# Thread executing an HTTP request asynchronously
#
# The request is sent to `uri`.
# Either `uri`, or `uri_root` and `uri_tail`, must be set in subclasses.
#
# If `deserialize_json`, the default behavior, the response is deserialized from JSON
#
# If `delay > 0.0`, sending the request is delayed by the given `delay` in seconds.
# It can be used to delay resending a request on error.
#
# Four callback methods act on the main/UI thread,
# they should be implemented as needed in subclasses:
# * `before`
# * `on_load`
# * `on_fail`
# * `after`
#
# See full example at `examples/http_request_example.nit`.
abstract class AsyncHttpRequest
	super Thread

	# URI target of this request, by default it is composed of `uri_root / uri_tail`
	fun uri: Text do return uri_root / uri_tail

	# Root URI of the remote server, usually the scheme and remote host
	fun uri_root: String is abstract

	# Right part of the URI, after `uri_root`, often the resource path and the query
	fun uri_tail: String do return ""

	# Should the response content be deserialized from JSON?
	var deserialize_json = true is writable

	# Delay in seconds before sending this request
	var delay = 0.0 is writable

	redef fun start
	do
		before
		super
	end

	redef fun main
	do
		var delay = delay
		if delay > 0.0 then delay.sleep

		var uri = uri

		# Execute REST request
		var rep = uri.http_get
		if rep.is_error then
			app.run_on_ui_thread new RestRunnableOnFail(self, rep.error)
			return null
		end

		if deserialize_json then
			# Deserialize
			var deserializer = new JsonDeserializer(rep.value)
			var res = deserializer.deserialize
			if deserializer.errors.not_empty then
				app.run_on_ui_thread new RestRunnableOnFail(self, deserializer.errors.first)
			else
				app.run_on_ui_thread new RestRunnableOnLoad(self, res, rep.code)
			end
		else
			# Return text data
			app.run_on_ui_thread new RestRunnableOnLoad(self, rep.value, rep.code)
			return null
		end

		app.run_on_ui_thread new RestRunnableJoin(self)

		return null
	end

	# Prepare the UI or other parts of the program before executing the REST request
	fun before do end

	# Invoked when the HTTP request returned valid data
	#
	# If `deserialize_json`, the default behavior, this method is invoked only if deserialization was successful.
	# In this case, `result` may be any deserialized object.
	#
	# Otherwise, if `not deserialize_json`, `result` contains the content of the response as a `String`.
	fun on_load(result: nullable Object, http_status_code: Int) do end

	# Invoked when the HTTP request has failed and no data was received or deserialization failed
	fun on_fail(error: Error) do print_error "HTTP request '{uri}' failed with: {error}"

	# Complete this request whether it was a success or not
	fun after do end
end