venv/lib/python3.11/site-packages/werkzeug/middleware/dispatcher.py

   1 """
   2 Application Dispatcher
   3 ======================
   4
   5 This middleware creates a single WSGI application that dispatches to
   6 multiple other WSGI applications mounted at different URL paths.
   7
   8 A common example is writing a Single Page Application, where you have a
   9 backend API and a frontend written in JavaScript that does the routing
  10 in the browser rather than requesting different pages from the server.
  11 The frontend is a single HTML and JS file that should be served for any
  12 path besides "/api".
  13
  14 This example dispatches to an API app under "/api", an admin app
  15 under "/admin", and an app that serves frontend files for all other
  16 requests::
  17
  18     app = DispatcherMiddleware(serve_frontend, {
  19         '/api': api_app,
  20         '/admin': admin_app,
  21     })
  22
  23 In production, you might instead handle this at the HTTP server level,
  24 serving files or proxying to application servers based on location. The
  25 API and admin apps would each be deployed with a separate WSGI server,
  26 and the static files would be served directly by the HTTP server.
  27
  28 .. autoclass:: DispatcherMiddleware
  29
  30 :copyright: 2007 Pallets
  31 :license: BSD-3-Clause
  32 """
  33 from __future__ import annotations
  34
  35 import typing as t
  36
  37 if t.TYPE_CHECKING:
  38     from _typeshed.wsgi import StartResponse
  39     from _typeshed.wsgi import WSGIApplication
  40     from _typeshed.wsgi import WSGIEnvironment
  41
  42
  43 class DispatcherMiddleware:
  44     """Combine multiple applications as a single WSGI application.
  45     Requests are dispatched to an application based on the path it is
  46     mounted under.
  47
  48     :param app: The WSGI application to dispatch to if the request
  49         doesn't match a mounted path.
  50     :param mounts: Maps path prefixes to applications for dispatching.
  51     """
  52
  53     def __init__(
  54         self,
  55         app: WSGIApplication,
  56         mounts: dict[str, WSGIApplication] | None = None,
  57     ) -> None:
  58         self.app = app
  59         self.mounts = mounts or {}
  60
  61     def __call__(
  62         self, environ: WSGIEnvironment, start_response: StartResponse
  63     ) -> t.Iterable[bytes]:
  64         script = environ.get("PATH_INFO", "")
  65         path_info = ""
  66
  67         while "/" in script:
  68             if script in self.mounts:
  69                 app = self.mounts[script]
  70                 break
  71
  72             script, last_item = script.rsplit("/", 1)
  73             path_info = f"/{last_item}{path_info}"
  74         else:
  75             app = self.mounts.get(script, self.app)
  76
  77         original_script_name = environ.get("SCRIPT_NAME", "")
  78         environ["SCRIPT_NAME"] = original_script_name + script
  79         environ["PATH_INFO"] = path_info
  80         return app(environ, start_response)