# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Support module for the `nitrestful` tool and the `restful` annotation
#
# The `restful` annotation is applied on a method to assign it to an HTTP resource.
# The `restful` method must be a property of a subclass of `RestfulAction` and
# return an `HTTPResponse`.
# Once an instance of the class is assigned to a route, the method
# can be invoked as a resource under that route.
# The returned `HTTPResponse` will be sent back to the client.
#
# The arguments of the method must be deserializable.
# So use simple data types like `String`, `Int`, `Float`, etc.
# or any other `Serializable` class.
# The method is invoked only if all the arguments are correctly passed
# in the JSON format by the HTTP client.
# There is one exception, `String` arguments are returned as is,
# they don't need the surrounding `""`.
# If an argument is missing or there a format error, the `answer` method responds to the request.
# Arguments that are `nullable` are optional,
# if they are missing `null` is passed to the `restful` method.
#
# The annotation accepts three kinds of arguments, in any order:
#
# * String literals rename or add an alias for the HTTP resource.
#   By default, the name of the HTTP resource is the name of the `restful` method.
#   The first string literal replaces the default name,
#   while additional string literals add aliases.
#
# * Ids such as `GET`, `POST`, `PUT` and `DELETE` restrict which HTTP methods
#   are accepted. By default, all HTTP methods are accepted.
#
# * The `async` keyword triggers executing calls to this service asynchronously
#   by the `thread_pool` attribute of the `RestfulAction`.
#   By default, each call are executed on the same thread in a FIFO order.
#
# See the example at `lib/nitcorn/examples/restful_annot.nit` or
# a real world use case at `contrib/benitlux/src/server/benitlux_controller.nit`.
#
# The `restful` annotation is implemented by then `nitrestful` tool.
# To compile a module (`my_module.nit`) that uses the `restful` annotation:
#
# * Run `nitrestful my_module.nit` to produce `my_module_rest.nit`
# * Link `my_module_rest.nit` at compilation: `nitc my_module.nit -m my_module_rest.nit`.
module restful is new_annotation(restful)

import nitcorn
private import json
import pthreads::threadpool

# Action with `restful` methods
class RestfulAction
	super Action

	redef fun answer(request, truncated_uri) do return new HttpResponse(400)

	# Deserialize `val` from JSON for a parameter typed by `static_type`
	#
	# Accepts `nullable String` for convenience, but returns `null` when `val == null`.
	#
	# This method is called by the code generated by `nitrestful`.
	# It can be specialized to customize its behavior.
	protected fun deserialize_arg(val: nullable String, static_type: String): nullable Object
	do
		if val == null then return null

		var deserializer = new JsonDeserializer(val)
		var obj = deserializer.deserialize(static_type)

		if deserializer.errors.not_empty then
			print_error deserializer.errors.join("\n")
			return null
		end

		return obj
	end

	# Thread pool used by methods annotated with `restful(async)`
	var thread_pool = new ThreadPool is writable
end

# Thread dedicated to a single `request`
abstract class RestfulTask
	super Task

	# Type of `action`
	type A: RestfulAction

	# Receiver action
	var action: A

	# Request that created this thread
	var request: HttpRequest

	# Server handling the `request`
	var http_server: HttpServer

	# Indirection to the real method in `action`
	protected fun indirect_restful_method: HttpResponse is abstract

	redef fun main
	do
		var response = indirect_restful_method
		http_server.respond response
		http_server.close
	end
end