minimal WebDAV implementation for TiddlyWiki

webdav

#!/usr/bin/env python3

import os

from hashlib import md5


ROOT_DIR = os.path.dirname(__file__)
STATUSES = {
    200: "OK",
    204: "No Content",
    404: "Not Found",
    405: "Method Not Allowed",
    412: "Precondition Failed",
    415: "Unsupported Media Type"
}


def handler(environ, start_response):
    method = environ["REQUEST_METHOD"]

    respond = lambda *args, **kwargs: make_response(start_response, *args, **kwargs)

    if method == "OPTIONS":
        return respond(200, [("DAV", "1")]) # XXX: TiddlyWiki expects 200 rather than 204
    if method == "HEAD":
        filepath = _determine_filepath(environ)
        return respond(204, headers=[
            ("ETag", _determine_etag(filepath))
        ])
    elif method == "GET":
        uri = environ.get("PATH_INFO", "")
        if uri == "/favicon.ico": # TODO: read from disk
            return respond(404)
        else:
            return serve_file(environ, start_response)
    if method == "PUT":
        return store_file(environ, start_response)
    else:
        return respond(405, body="invalid request")


def serve_file(environ, start_response):
    filepath = _determine_filepath(environ)
    with open(filepath) as fh:
        return make_response(start_response, 200,
                headers=[("Content-Type", "text/html")], # NB: TiddlyWiki-specific
                body=fh.read()) # XXX: inefficient


def store_file(environ, start_response):
    respond = lambda *args, **kwargs: make_response(start_response, *args, **kwargs)

    if environ["CONTENT_TYPE"] != "text/html;charset=UTF-8": # NB: TiddlyWiki-specific heuristic
        return respond(415)

    filepath = _determine_filepath(environ)
    etag = environ.get("HTTP_IF_MATCH")
    if etag is not None:
        _hash = _determine_etag(filepath)
        if etag != _hash:
            return respond(412, body=("expected ETag %s, received %s" % (_hash, etag)))

    try:
        size = int(environ["CONTENT_LENGTH"])
        content = environ["wsgi.input"].read(size)
    except (KeyError, ValueError):
        return make_response(400, body="missing `Content-Length` request header")

    with open(filepath, "w") as fh:
        fh.write(content.decode("utf-8"))
    return respond(204)


def make_response(start_response, status, headers=[], body=[]):
    status_line = "%s %s" % (status, STATUSES[status])
    start_response(status_line, headers)
    if isinstance(body, str): # XXX: simplistic
        return [body.encode("utf-8")]
    return body


def _determine_etag(filepath):
    with open(filepath) as fh:
        content = fh.read()
    return md5(content.encode("utf-8")).hexdigest()


def _determine_filepath(environ):
    uri = environ.get("PATH_INFO", "")
    filename = uri[1:] if uri.startswith("/") else uri
    if len(filename) == 0:
        filename = "index.html" # NB: TiddlyWki-specific
    return os.path.abspath(os.path.join(ROOT_DIR, filename))


if __name__ == "__main__":
    from wsgiref.simple_server import make_server

    host = "localhost"
    port = 8080

    srv = make_server(host, port, handler)
    print("→ http://%s:%s" % (host, port))
    srv.serve_forever()

This script will not work if placed in /local/bin, it will search for index.html there rather than the cwd.

Hey @Dialga, I didn't expect anyone but myself to use this, but you could change line 8 to make that work:

-ROOT_DIR = os.path.dirname(__file__)
+ROOT_DIR = os.getcwd()

How did you come across this script in the first place?

Note that there might be security risks if others can access it via the web because modifying the URL might allow targeting arbitrary files on your disk (see line 94).

I searched for it on gist.
I was looking for a tiddlywiki server that behaves like the nodejs version, which saves individual tiddlers, rather than saving the whole file each time.
If this script is in the cwd then it would be accessible at localhost:8080/webdav.