image-and-stash.py

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# This is a simple implementation of a server-side stash that supports two

# operations:

#   - increment:

#       Increments a value in the stash keyed by a given uuid, and returns an

#       image file

#   - read:

#       Returns the value in the stash keyed by a given uuid or 0 otherwise.

#       This is a read-only operation, and does not remove the value from the

#       stash as-is the default WPT stash behavior:

#       https://web-platform-tests.org/tools/wptserve/docs/stash.html.

import os

from wptserve.utils import isomorphic_decode

def main(request, response):

  if b"increment" in request.GET:

    uuid = request.GET[b"increment"]

    # First, increment the stash value keyed by `uuid`, and write it back to the

    # stash. Writing it back to the stash is necessary since `take()` actually

    # removes the value whereas we want to increment it.

    stash_value = request.server.stash.take(uuid)

    if stash_value is None:

      stash_value = 0

    request.server.stash.put(uuid, stash_value + 1)

    # Return a basic image.

    response_headers = [(b"Content-Type", b"image/png")]

    image_path = os.path.join(os.path.dirname(isomorphic_decode(__file__)), u"image.png")

    return (200, response_headers, open(image_path, mode='rb').read())

  elif b"read" in request.GET:

    uuid = request.GET[b"read"]

    stash_value = request.server.stash.take(uuid)

    if stash_value is None:

      stash_value = 0

    # Write the stash value keyed by `uuid` back to the stash. This is necessary

    # because `take()` actually removes it, but we want a read-only read.

    request.server.stash.put(uuid, stash_value);

    return (200, [], str(stash_value))

  return (404 , [], "Not found")