Replaced the mediasrv.py SimpleHttp server by flask and waitress,

fixing HTML5 media support.
https://stackoverflow.com/questions/37044064/html-audio-cant-set-currenttime
https://stackoverflow.com/questions/21956683/enable-access-control-on-simple-http-server
https://stackoverflow.com/questions/5052635/what-is-relation-between-content-length-and-byte-ranges-in-http-1-1
https://stackoverflow.com/questions/16725907/google-app-engine-serving-mp3-for-audio-element-needs-content-range-header

I was trying to use HTML5 audio tag to display audios like:
```html
<audio id="elem_audio" src="myfile.mp3" controls></audio>
```
![image](https://user-images.githubusercontent.com/5332158/79063321-565b5500-7c77-11ea-9f8d-6e1df6f07892.png)

But the progress bar seek was not working. After researching, I found the problem was the HTML server not properly responding to the HTML5 header requests. The HTML server should respond to quite complicated things as 206 partial, properly handle keep-alive, provide media ranges and other HTTP headers: https://stackoverflow.com/questions/37044064/html-audio-cant-set-currenttime

To implement all these on the Simple HTTP server would be quite complicated. Then, instead, I imported the `flask` web server, which is quite simple and straight forward to use. Now, the back-end is using a secure complaint HTTP back-end:
1. https://palletsprojects.com/p/flask/
    > Flask is a lightweight WSGI web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. It began as a simple wrapper around Werkzeug and Jinja and has become one of the most popular Python web application frameworks.
    >
    > Flask offers suggestions, but doesn't enforce any dependencies or project layout. It is up to the developer to choose the tools and libraries they want to use. There are many extensions provided by the community that make adding new functionality easy.

1. https://docs.pylonsproject.org/projects/waitress/en/latest/
    > Waitress is meant to be a production-quality pure-Python WSGI server with very acceptable performance. It has no dependencies except ones which live in the Python standard library. It runs on CPython on Unix and Windows under Python 2.7+ and Python 3.5+. It is also known to run on PyPy 1.6.0 on UNIX. It supports HTTP/1.0 and HTTP/1.1.

Right now, anki does not support fields passing file names directly to HTML audio tags, but this can be easily done with (https://github.com/ankitects/anki/pull 540 - Added arguments to the sound tag) plus the commit 826a97df61, the HTML5 audio tag can be used like this:
```html
// Audio = [sound:myfile.mp3|onlyfilename]
<audio id="elem_audio" src="{{Audio}}" controls controlsList="nodownload"></audio>
```
![image](https://user-images.githubusercontent.com/5332158/79063736-c539ad80-7c79-11ea-8420-40b72185f4e7.png)

# Conflicts:
#	qt/aqt/mediasrv.py

qt/aqt/mediasrv.py

@@ -1,20 +1,18 @@
 # Copyright: Ankitects Pty Ltd and contributors
 # -*- coding: utf-8 -*-
 # License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
-
+import logging
-from __future__ import annotations
+import os
-
-import http.server
 import re
-import socket
+import sys
-import socketserver
 import threading
+import traceback
 from http import HTTPStatus
-from typing import Optional
 
-import aqt
+import flask
-from anki.collection import Collection
+import flask_cors  # type: ignore
-from anki.rsbackend import from_json_bytes
+from waitress.server import create_server  # type: ignore
+
 from anki.utils import devMode
 from aqt.qt import *
 from aqt.utils import aqt_data_folder
@@ -33,181 +31,127 @@ def _getExportFolder():
 
 
 _exportFolder = _getExportFolder()
-
+app = flask.Flask(__name__)
-# webengine on windows sometimes opens a connection and fails to send a request,
+flask_cors.CORS(app)
-# which will hang the server if unthreaded
-class ThreadedHTTPServer(socketserver.ThreadingMixIn, http.server.HTTPServer):
-    # allow for a flood of requests before we've started up properly
-    request_queue_size = 100
-
-    # work around python not being able to handle non-latin hostnames
-    def server_bind(self):
-        """Override server_bind to store the server name."""
-        socketserver.TCPServer.server_bind(self)
-        host, port = self.server_address[:2]
-        try:
-            self.server_name = socket.getfqdn(host)
-        except:
-            self.server_name = "server"
-        self.server_port = port
 
 
 class MediaServer(threading.Thread):
 
-    _port: Optional[int] = None
     _ready = threading.Event()
     daemon = True
 
     def __init__(self, mw, *args, **kwargs):
         super().__init__(*args, **kwargs)
-        self.mw = mw
+        self.is_shutdown = False
+        _redirectWebExports.mw = mw
 
     def run(self):
-        RequestHandler.mw = self.mw
+        try:
-        desired_port = int(os.getenv("ANKI_API_PORT", "0"))
+            if devMode:
-        self.server = ThreadedHTTPServer(("127.0.0.1", desired_port), RequestHandler)
+                # idempotent if logging has already been set up
+                logging.basicConfig()
+            else:
+                logging.getLogger("waitress").setLevel(logging.ERROR)
+
+            self.server = create_server(app, host="127.0.0.1", port=0)
+            if devMode:
+                print(
+                    "Serving on http://%s:%s"
+                    % (self.server.effective_host, self.server.effective_port)
+                )
+
             self._ready.set()
-        self.server.serve_forever()
+            self.server.run()
+
+        except Exception:
+            if not self.is_shutdown:
+                raise
+
+    def shutdown(self):
+        self.is_shutdown = True
+        sockets = list(self.server._map.values())
+        for socket in sockets:
+            socket.handle_close()
+        # https://github.com/Pylons/webtest/blob/4b8a3ebf984185ff4fefb31b4d0cf82682e1fcf7/webtest/http.py#L93-L104
+        self.server.task_dispatcher.shutdown()
 
     def getPort(self):
         self._ready.wait()
-        return self.server.server_port
+        return int(self.server.effective_port)
-
-    def shutdown(self):
-        self.server.shutdown()
 
 
-class RequestHandler(http.server.SimpleHTTPRequestHandler):
+@app.route("/", defaults={"path": ""})
-
+@app.route("/<path:path>")
-    timeout = 10
+def allroutes(path):
-    mw: Optional[aqt.main.AnkiQt] = None
+    directory, path = _redirectWebExports(path)
-
+    try:
-    def do_GET(self):
+        isdir = os.path.isdir(os.path.join(directory, path))
-        f = self.send_head()
+    except ValueError:
-        if f:
+        return flask.Response(
+            "Path for '%s - %s' is too long!" % (directory, path),
+            status=HTTPStatus.BAD_REQUEST,
+            mimetype="text/plain",
+        )
+
+    if isdir:
+        return flask.Response(
+            "Path for '%s - %s' is a directory (not supported)!" % (directory, path),
+            status=HTTPStatus.FORBIDDEN,
+            mimetype="text/plain",
+        )
+
     try:
-                self.copyfile(f, self.wfile)
-            except Exception as e:
         if devMode:
-                    print("http server caught exception:", e)
+            print("Sending file '%s - %s'" % (directory, path))
-                else:
+        return flask.send_from_directory(directory, path)
+
+    except Exception as error:
+        if devMode:
+            print(
+                "Caught HTTP server exception,\n%s"
+                % "".join(traceback.format_exception(*sys.exc_info())),
+            )
+
         # swallow it - user likely surfed away from
         # review screen before an image had finished
         # downloading
-                    pass
+        return flask.Response(
-            finally:
+            "For path '%s - %s' %s!" % (directory, path, error),
-                f.close()
+            status=HTTPStatus.INTERNAL_SERVER_ERROR,
-
+            mimetype="text/plain",
-    def send_head(self):
-        path = self.translate_path(self.path)
-        path = self._redirectWebExports(path)
-        try:
-            isdir = os.path.isdir(path)
-        except ValueError:
-            # path too long exception on Windows
-            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
-            return None
-
-        if isdir:
-            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
-            return None
-
-        ctype = self.guess_type(path)
-        try:
-            f = open(path, "rb")
-        except OSError:
-            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
-            return None
-        try:
-            self.send_response(HTTPStatus.OK)
-            self.send_header("Content-type", ctype)
-            fs = os.fstat(f.fileno())
-            self.send_header("Content-Length", str(fs[6]))
-            self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
-            self.send_header("Access-Control-Allow-Origin", "*")
-            self.end_headers()
-            return f
-        except:
-            f.close()
-            raise
-
-    def log_message(self, format, *args):
-        if not devMode:
-            return
-        print(
-            "%s - - [%s] %s"
-            % (self.address_string(), self.log_date_time_string(), format % args)
         )
 
-    def _redirectWebExports(self, path):
+
+def _redirectWebExports(path):
     # catch /_anki references and rewrite them to web export folder
-        targetPath = os.path.join(os.getcwd(), "_anki", "")
+    targetPath = "_anki/"
     if path.startswith(targetPath):
-            newPath = os.path.join(_exportFolder, path[len(targetPath) :])
+        return _exportFolder, path[len(targetPath) :]
-            return newPath
 
     # catch /_addons references and rewrite them to addons folder
-        targetPath = os.path.join(os.getcwd(), "_addons", "")
+    targetPath = "_addons/"
     if path.startswith(targetPath):
-            try:
-                addMgr = self.mw.addonManager
-            except AttributeError:
-                return path
-
         addonPath = path[len(targetPath) :]
 
+        try:
+            addMgr = _redirectWebExports.mw.addonManager
+        except AttributeError as error:
+            if devMode:
+                print("_redirectWebExports: %s" % error)
+            return _exportFolder, addonPath
+
         try:
             addon, subPath = addonPath.split(os.path.sep, 1)
         except ValueError:
-                return path
+            return addMgr.addonsFolder(), path
         if not addon:
-                return path
+            return addMgr.addonsFolder(), path
 
         pattern = addMgr.getWebExports(addon)
         if not pattern:
-                return path
+            return addMgr.addonsFolder(), path
 
-            subPath2 = subPath.replace(os.sep, "/")
+        if re.fullmatch(pattern, subPath):
-            if re.fullmatch(pattern, subPath) or re.fullmatch(pattern, subPath2):
+            return addMgr.addonsFolder(), addonPath
-                newPath = os.path.join(addMgr.addonsFolder(), addonPath)
-                return newPath
 
-        return path
+    return _redirectWebExports.mw.col.media.dir(), path
-
-    def do_POST(self):
-        if not self.path.startswith("/_anki/"):
-            self.send_error(HTTPStatus.NOT_FOUND, "Method not found")
-            return
-
-        cmd = self.path[len("/_anki/") :]
-
-        if cmd == "graphData":
-            content_length = int(self.headers["Content-Length"])
-            body = self.rfile.read(content_length)
-            data = graph_data(self.mw.col, **from_json_bytes(body))
-        elif cmd == "i18nResources":
-            data = self.mw.col.backend.i18n_resources()
-        else:
-            self.send_error(HTTPStatus.NOT_FOUND, "Method not found")
-            return
-
-        self.send_response(HTTPStatus.OK)
-        self.send_header("Content-Type", "application/binary")
-        self.send_header("Content-Length", str(len(data)))
-        self.send_header("Access-Control-Allow-Origin", "*")
-        self.end_headers()
-
-        self.wfile.write(data)
-
-
-def graph_data(col: Collection, search: str, days: int) -> bytes:
-    try:
-        return col.backend.graphs(search=search, days=days)
-    except Exception as e:
-        # likely searching error
-        print(e)
-        return b""
-
-
-# work around Windows machines with incorrect mime type
-RequestHandler.extensions_map[".css"] = "text/css"

qt/setup.py

@@ -28,6 +28,9 @@ install_requires = [
     "jsonschema",
     # "pyaudio", # https://anki.tenderapp.com/discussions/add-ons/44009-problems-with-code-completion
     # "pyqtwebengine", # https://github.com/ankitects/anki/pull/530 - Set to checks.yml install and import anki wheels
+    "flask",
+    "flask_cors",
+    "waitress",
     "pyqt5>=5.9",
     'psutil; sys.platform == "win32"',
     'pywin32; sys.platform == "win32"',