# frozen_string_literals: true
#
# Copyright, 2019, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'protocol/websocket/digest'

require_relative '../connection'

module Async
	module WebSocket
		module Server
			class Rack
				def self.websocket?(env)
					env['HTTP_UPGRADE'] == "websocket"
				end
				
				def self.open(env, **options, &block)
					# Is hijack supported:
					return nil unless env['rack.hijack?']
					
					return nil unless websocket?(env)
					
					server = self.new(env, **options)
					
					if server.supported?
						return server.response(&block)
					else
						return nil
					end
				end
				
				def initialize(env, supported_protocols: [], connect: Connection)
					# scheme = env['rack.url_scheme'] == 'https' ? 'wss' : 'ws'
					# @url = "#{scheme}://#{env['HTTP_HOST']}#{env['REQUEST_URI']}"
					@key = env['HTTP_SEC_WEBSOCKET_KEY']
					@version = Integer(env['HTTP_SEC_WEBSOCKET_VERSION'])
					
					@protocol = negotiate_protocol(env, supported_protocols)
					
					@connect = connect
				end
				
				def negotiate_protocol(env, supported_protocols)
					if supported_protocols and client_protocols = env['HTTP_SEC_WEBSOCKET_PROTOCOL']
						return (supported_protocols & client_protocols.split(/\s*,\s/)).first
					end
				end
				
				attr :protocol
				
				def supported?
					@key and @version == 13
				end
				
				def make_connection(stream)
					framer = Protocol::WebSocket::Framer.new(stream)
					
					return @connect.call(framer, @protocol)
				end
				
				def response_headers
					headers = [
						['connection', 'upgrade'],
						['upgrade', 'websocket'],
						['sec-websocket-accept', ::Protocol::WebSocket.accept_digest(@key)],
					]
					
					if @protocol
						headers << ['sec-websocket-protocol', @protocol]
					end
					
					return headers
				end
				
				def response(&block)
					headers = [
						['rack.hijack', ->(stream){block.call(make_connection(stream))}]
					]
					
					# https://stackoverflow.com/questions/13545453/http-response-code-when-requested-websocket-subprotocol-isnt-supported-recogniz
					return [101, response_headers + headers, nil]
				end
			end
		end
	end
end