# frozen_string_literal: true

# Released under the MIT License.
# Copyright, 2018-2024, by Samuel Williams.
# Copyright, 2020, by Igor Sidorov.
# Copyright, 2023, by Thomas Morgan.
# Copyright, 2024, by Anton Zhuravsky.

require_relative 'connection'
require 'console/event/failure'

module Async
	module HTTP
		module Protocol
			module HTTP1
				class Server < Connection
					def fail_request(status)
						@persistent = false
						write_response(@version, status, {})
						write_body(@version, nil)
					rescue => error
						# At this point, there is very little we can do to recover:
						Console::Event::Failure.for(error).emit(self, "Failed to write failure response.", severity: :debug)
					end
					
					def next_request
						# The default is true.
						return unless @persistent
						
						# Read an incoming request:
						return unless request = Request.read(self)
						
						unless persistent?(request.version, request.method, request.headers)
							@persistent = false
						end
						
						return request
					rescue ::Protocol::HTTP1::BadRequest
						fail_request(400)
						# Conceivably we could retry here, but we don't really know how bad the error is, so it's better to just fail:
						raise
					end
					
					# Server loop.
					def each(task: Task.current)
						task.annotate("Reading #{self.version} requests for #{self.class}.")
						
						while request = next_request
							response = yield(request, self)
							body = response&.body
							
							if hijacked?
								body&.close
								return
							end
							
							task.defer_stop do
								# If a response was generated, send it:
								if response
									trailer = response.headers.trailer!
									
									# Some operations in this method are long running, that is, it's expected that `body.call(stream)` could literally run indefinitely. In order to facilitate garbage collection, we want to nullify as many local variables before calling the streaming body. This ensures that the garbage collection can clean up as much state as possible during the long running operation, so we don't retain objects that are no longer needed.
									
									if body and protocol = response.protocol
										# We force a 101 response if the protocol is upgraded - HTTP/2 CONNECT will return 200 for success, but this won't be understood by HTTP/1 clients:
										write_response(@version, 101, response.headers)
										
										stream = write_upgrade_body(protocol)
										
										# At this point, the request body is hijacked, so we don't want to call #finish below.
										request = nil
										response = nil
										
										# We must return here as no further request processing can be done:
										return body.call(stream)
									elsif response.status == 101
										# This code path is to support legacy behavior where the response status is set to 101, but the protocol is not upgraded. This may not be a valid use case, but it is supported for compatibility. We expect the response headers to contain the `upgrade` header.
										write_response(@version, response.status, response.headers)
										
										stream = write_tunnel_body(request.version)
										
										# Same as above:
										request = nil
										response = nil
										
										# We must return here as no further request processing can be done:
										return body&.call(stream)
									else
										write_response(@version, response.status, response.headers)
										
										if request.connect? and response.success?
											stream = write_tunnel_body(request.version)
											
											# Same as above:
											request = nil
											response = nil
											
											# We must return here as no further request processing can be done:
											return body.call(stream)
										else
											head = request.head?
											version = request.version
											
											# Same as above:
											request = nil unless request.body
											response = nil
											
											write_body(version, body, head, trailer)
										end
									end
									
									# We are done with the body, you shouldn't need to call close on it:
									body = nil
								else
									# If the request failed to generate a response, it was an internal server error:
									write_response(@version, 500, {})
									write_body(request.version, nil)
								end
								
								# Gracefully finish reading the request body if it was not already done so.
								request&.each{}
								
								# This ensures we yield at least once every iteration of the loop and allow other fibers to execute.
								task.yield
							rescue => error
								raise
							ensure
								body&.close(error)
							end
						end
					end
				end
			end
		end
	end
end