# Copyright, 2018, 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 'async/http/client'

module Falcon
	module BadRequest
		def self.call(request)
			return Async::HTTP::Response[400, {}, []]
		end
		
		def self.close
		end
	end
	
	class Proxy < Async::HTTP::Middleware
		X_FORWARDED_FOR = 'x-forwarded-for'.freeze
		VIA = 'via'.freeze
		CONNECTION = Async::HTTP::Protocol::HTTP11::CONNECTION
		
		HOP_HEADERS = [
			'connection',
			'keep-alive',
			'public',
			'proxy-authenticate',
			'transfer-encoding',
			'upgrade',
		]
		
		def initialize(app, hosts)
			super(app)
			
			@server_context = nil
			
			@hosts = hosts
			@clients = {}
			
			@count = 0
		end
		
		attr :count
		
		def close
			@clients.each_value(&:close)
			
			super
		end
		
		def connect(endpoint)
			@clients[endpoint] ||= Async::HTTP::Client.new(endpoint)
		end
		
		def lookup(request)
			# Trailing dot and port is ignored/normalized.
			if authority = request.authority.sub(/(\.)?(:\d+)?$/, '')
				return @hosts[authority]
			end
		end
		
		def prepare_headers(headers)
			if connection = headers[CONNECTION]
				headers.slice!(connection)
			end
			
			headers.slice!(HOP_HEADERS)
		end
		
		def call(request)
			if endpoint = lookup(request)
				@count += 1
				
				if address = request.remote_address
					request.headers.add(X_FORWARDED_FOR, address.ip_address)
				end
				
				request.headers.add(VIA, "#{request.version} #{self.class}")
				
				client = connect(endpoint)
				
				prepare_headers(request.headers)
				client.call(request)
			else
				super
			end
		rescue
			Async.logger.error(self) {$!}
			return Async::HTTP::Response[502, {'content-type' => 'text/plain'}, ["#{$!.inspect}: #{$!.backtrace.join("\n")}"]]
		end
	end
end