socketry/falcon

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lib/falcon/adapters/rack.rb

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# frozen_string_literal: true

# Copyright, 2017, 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 'rack'

require_relative 'input'
require_relative 'response'
require_relative 'early_hints'

require 'async/logger'

module Falcon
    module Adapters
        class Rack
            # CGI keys <https://tools.ietf.org/html/rfc3875#section-4.1>:
            
            HTTP_HOST = 'HTTP_HOST'
            PATH_INFO = 'PATH_INFO'
            REQUEST_METHOD = 'REQUEST_METHOD'
            REQUEST_PATH = 'REQUEST_PATH'
            REQUEST_URI = 'REQUEST_URI'
            SCRIPT_NAME = 'SCRIPT_NAME'
            QUERY_STRING = 'QUERY_STRING'
            SERVER_PROTOCOL = 'SERVER_PROTOCOL'
            SERVER_NAME = 'SERVER_NAME'
            SERVER_PORT = 'SERVER_PORT'
            REMOTE_ADDR = 'REMOTE_ADDR'
            CONTENT_TYPE = 'CONTENT_TYPE'
            CONTENT_LENGTH = 'CONTENT_LENGTH'
            
            # Rack environment variables:
            
            RACK_VERSION = 'rack.version'
            RACK_ERRORS = 'rack.errors'
            RACK_LOGGER = 'rack.logger'
            RACK_INPUT = 'rack.input'
            RACK_MULTITHREAD = 'rack.multithread'
            RACK_MULTIPROCESS = 'rack.multiprocess'
            RACK_RUNONCE = 'rack.run_once'
            RACK_URL_SCHEME = 'rack.url_scheme'
            RACK_HIJACK = 'rack.hijack'
            RACK_IS_HIJACK = 'rack.hijack?'
            RACK_HIJACK_IO = 'rack.hijack_io'
            RACK_EARLY_HINTS = "rack.early_hints"
            
            # Async::HTTP specific metadata:
            
            ASYNC_HTTP_REQUEST = "async.http.request"
            
            # Header constants:
            
            HTTP_X_FORWARDED_PROTO = 'HTTP_X_FORWARDED_PROTO'
            
            # Initialize the rack adaptor middleware.
            # @parameter app [Object] The rack middleware.
            # @parameter logger [Console::Logger] The logger to use.
            def initialize(app, logger = Async.logger)
                @app = app
                
                raise ArgumentError, "App must be callable!" unless @app.respond_to?(:call)
                
                @logger = logger
            end
            
            # Unwrap raw HTTP headers into the CGI-style expected by Rack middleware.
            #
            # Rack separates multiple headers with the same key, into a single field with multiple lines.
            #
            # @parameter headers [Protocol::HTTP::Headers] The raw HTTP request headers.
            # @parameter env [Hash] The rack request `env`.
            def unwrap_headers(headers, env)
                headers.each do |key, value|
                    http_key = "HTTP_#{key.upcase.tr('-', '_')}"
                    
                    if current_value = env[http_key]
                        env[http_key] = "#{current_value};#{value}"
                    else
                        env[http_key] = value
                    end
                end
            end
            
            # Process the incoming request into a valid rack `env`.
            #
            # - Set the `env['CONTENT_TYPE']` and `env['CONTENT_LENGTH']` based on the incoming request body. 
            # - Set the `env['HTTP_HOST']` header to the request authority.
            # - Set the `env['HTTP_X_FORWARDED_PROTO']` header to the request scheme.
            # - Set `env['REMOTE_ADDR']` to the request remote adress.
            #
            # @parameter request [Protocol::HTTP::Request] The incoming request.
            # @parameter env [Hash] The rack `env`.
            def unwrap_request(request, env)
                if content_type = request.headers.delete('content-type')
                    env[CONTENT_TYPE] = content_type
                end
                
                # In some situations we don't know the content length, e.g. when using chunked encoding, or when decompressing the body.
                if body = request.body and length = body.length
                    env[CONTENT_LENGTH] = length.to_s
                end
                
                self.unwrap_headers(request.headers, env)
                
                # HTTP/2 prefers `:authority` over `host`, so we do this for backwards compatibility.
                env[HTTP_HOST] ||= request.authority
                
                # This is the HTTP/1 header for the scheme of the request and is used by Rack.
                # Technically it should use the Forwarded header but this is not common yet.
                # https://tools.ietf.org/html/rfc7239#section-5.4
                # https://github.com/rack/rack/issues/1310
                env[HTTP_X_FORWARDED_PROTO] ||= request.scheme
                
                if remote_address = request.remote_address
                    env[REMOTE_ADDR] = remote_address.ip_address if remote_address.ip?
                end
            end
            
            # Build a rack `env` from the incoming request and apply it to the rack middleware.
            #
            # @parameter request [Protocol::HTTP::Request] The incoming request.
            def call(request)
                request_path, query_string = request.path.split('?', 2)
                server_name, server_port = (request.authority || '').split(':', 2)
                
                env = {
                    RACK_VERSION => [2, 0, 0],
                    
                    ASYNC_HTTP_REQUEST => request,
                    
                    RACK_INPUT => Input.new(request.body),
                    RACK_ERRORS => $stderr,
                    RACK_LOGGER => Async.logger,
                    
                    RACK_MULTITHREAD => true,
                    RACK_MULTIPROCESS => true,
                    RACK_RUNONCE => false,
                    
                    # The HTTP request method, such as “GET” or “POST”. This cannot ever be an empty string, and so is always required.
                    REQUEST_METHOD => request.method,
                    
                    # The initial portion of the request URL's “path” that corresponds to the application object, so that the application knows its virtual “location”. This may be an empty string, if the application corresponds to the “root” of the server.
                    SCRIPT_NAME => '',
                    
                    # The remainder of the request URL's “path”, designating the virtual “location” of the request's target within the application. This may be an empty string, if the request URL targets the application root and does not have a trailing slash. This value may be percent-encoded when originating from a URL.
                    PATH_INFO => request_path,
                    REQUEST_PATH => request_path,
                    REQUEST_URI => request.path,

                    # The portion of the request URL that follows the ?, if any. May be empty, but is always required!
                    QUERY_STRING => query_string || '',
                    
                    # The server protocol (e.g. HTTP/1.1):
                    SERVER_PROTOCOL => request.version,
                    
                    # The request scheme:
                    RACK_URL_SCHEME => request.scheme,
                    
                    # I'm not sure what sane defaults should be here:
                    SERVER_NAME => server_name,
                    SERVER_PORT => server_port,
                    
                    # We support both request and response hijack.
                    RACK_IS_HIJACK => true,
                }
                
                self.unwrap_request(request, env)
                
                if request.push?
                    env[RACK_EARLY_HINTS] = EarlyHints.new(request)
                end
                
                full_hijack = false
                
                if request.hijack?
                    env[RACK_HIJACK] = lambda do
                        wrapper = request.hijack!
                        full_hijack = true
                        
                        # We dup this as it might be taken out of the normal control flow, and the io will be closed shortly after returning from this method.
                        io = wrapper.io.dup
                        wrapper.close
                        
                        # This is implicitly returned:
                        env[RACK_HIJACK_IO] = io
                    end
                end
                
                status, headers, body = @app.call(env)
                
                # If there was a full hijack:
                if full_hijack
                    return nil
                else
                    return Response.wrap(status, headers, body, request)
                end
            rescue => exception
                @logger.error(self) {exception}
                
                return failure_response(exception)
            end
            
            # Generate a suitable response for the given exception.
            # @parameter exception [Exception]
            # @returns [Protocol::HTTP::Response]
            def failure_response(exception)
                Protocol::HTTP::Response.for_exception(exception)
            end
        end
    end
end