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# frozen_string_literal: true
module Rack
### This middleware provides hooks to certain places in the request /
# response lifecycle. This is so that middleware that don't need to filter
# the response data can safely leave it alone and not have to send messages
# down the traditional "rack stack".
#
# The events are:
#
# * on_start(request, response)
#
# This event is sent at the start of the request, before the next
# middleware in the chain is called. This method is called with a request
# object, and a response object. Right now, the response object is always
# nil, but in the future it may actually be a real response object.
#
# * on_commit(request, response)
#
# The response has been committed. The application has returned, but the
# response has not been sent to the webserver yet. This method is always
# called with a request object and the response object. The response
# object is constructed from the rack triple that the application returned.
# Changes may still be made to the response object at this point.
#
# * on_send(request, response)
#
# The webserver has started iterating over the response body and presumably
# has started sending data over the wire. This method is always called with
# a request object and the response object. The response object is
# constructed from the rack triple that the application returned. Changes
# SHOULD NOT be made to the response object as the webserver has already
# started sending data. Any mutations will likely result in an exception.
#
# * on_finish(request, response)
#
# The webserver has closed the response, and all data has been written to
# the response socket. The request and response object should both be
# read-only at this point. The body MAY NOT be available on the response
# object as it may have been flushed to the socket.
#
# * on_error(request, response, error)
#
# An exception has occurred in the application or an `on_commit` event.
# This method will get the request, the response (if available) and the
# exception that was raised.
#
# ## Order
#
# `on_start` is called on the handlers in the order that they were passed to
# the constructor. `on_commit`, on_send`, `on_finish`, and `on_error` are
# called in the reverse order. `on_finish` handlers are called inside an
# `ensure` block, so they are guaranteed to be called even if something
# raises an exception. If something raises an exception in a `on_finish`
# method, then nothing is guaranteed.
class Events
module Abstract
def on_start(req, res)
end
def on_commit(req, res)
end
def on_send(req, res)
end
def on_finish(req, res)
end
def on_error(req, res, e)
end
end
class EventedBodyProxy < Rack::BodyProxy # :nodoc:
attr_reader :request, :response
def initialize(body, request, response, handlers, &block)
super(body, &block)
@request = request
@response = response
@handlers = handlers
end
def each
@handlers.reverse_each { |handler| handler.on_send request, response }
super
end
end
class BufferedResponse < Rack::Response::Raw # :nodoc:
attr_reader :body
def initialize(status, headers, body)
super(status, headers)
@body = body
end
def to_a; [status, headers, body]; end
end
def initialize(app, handlers)
@app = app
@handlers = handlers
end
def call(env)
request = make_request env
on_start request, nil
begin
status, headers, body = @app.call request.env
response = make_response status, headers, body
on_commit request, response
rescue StandardError => e
on_error request, response, e
on_finish request, response
raise
end
body = EventedBodyProxy.new(body, request, response, @handlers) do
on_finish request, response
end
[response.status, response.headers, body]
end
private
def on_error(request, response, e)
@handlers.reverse_each { |handler| handler.on_error request, response, e }
end
def on_commit(request, response)
@handlers.reverse_each { |handler| handler.on_commit request, response }
end
def on_start(request, response)
@handlers.each { |handler| handler.on_start request, nil }
end
def on_finish(request, response)
@handlers.reverse_each { |handler| handler.on_finish request, response }
end
def make_request(env)
Rack::Request.new env
end
def make_response(status, headers, body)
BufferedResponse.new status, headers, body
end
end
end
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