A little QGIS3 Server wsgi experiment

A little experiment for a QGIS 3 Server wsgi wrapper

#!/usr/bin/env python

# Simple QGIS 3 Server wsgi test

import signal
import sys
from cgi import escape, parse_qs
from urllib.parse import quote
# Python's bundled WSGI server
from wsgiref.simple_server import make_server

from qgis.core import QgsApplication
from qgis.server import *

# Init QGIS
qgs_app = QgsApplication([], False)
# Init server
qgs_server = QgsServer()


def reconstruct_url(environ):
    """Standard algorithm to retrieve the full URL from wsgi request
    From: https://www.python.org/dev/peps/pep-0333/#url-reconstruction
    """
    url = environ['wsgi.url_scheme']+'://'

    if environ.get('HTTP_HOST'):
        url += environ['HTTP_HOST']
    else:
        url += environ['SERVER_NAME']

        if environ['wsgi.url_scheme'] == 'https':
            if environ['SERVER_PORT'] != '443':
                url += ':' + environ['SERVER_PORT']
        else:
            if environ['SERVER_PORT'] != '80':
                url += ':' + environ['SERVER_PORT']

    url += quote(environ.get('SCRIPT_NAME', ''))
    url += quote(environ.get('PATH_INFO', ''))
    if environ.get('QUERY_STRING'):
        url += '?' + environ['QUERY_STRING']
    return url

def application (environ, start_response):

    headers = {} # Parse headers from environ here if needed

    # the environment variable CONTENT_LENGTH may be empty or missing
    # When the method is POST the variable will be sent
    # in the HTTP request body which is passed by the WSGI server
    # in the file like wsgi.input environment variable.
    try:
        request_body_size = int(environ.get('CONTENT_LENGTH', 0))
        request_body = environ['wsgi.input'].read(request_body_size)
    except (ValueError):
        request_body_size = 0
        request_body = None

    request = QgsBufferServerRequest(reconstruct_url(environ), (QgsServerRequest.PostMethod 
        if environ['REQUEST_METHOD'] == 'POST' else QgsServerRequest.GetMethod), {}, request_body)
    response = QgsBufferServerResponse()
    qgs_server.handleRequest(request, response)
    headers_dict = response.headers()
    try:
        status = headers_dict['Status']
    except KeyError:
        status = '200 OK'
    start_response(status, [(k, v) for k, v in headers_dict.items()])
    return [bytes(response.body())]

# Instantiate the server
httpd = make_server (
    'localhost', # The host name
    8051, # A port number where to wait for the request
    application # The application object name, in this case a function
)

print("Listening to http://localhost:8051 press CTRL+C to quit")

def signal_handler(signal, frame):
    """Exit QGIS cleanly"""
    global qgs_app
    print("\nExiting QGIS...")
    qgs_app.exitQgis()
    sys.exit(0)

signal.signal(signal.SIGINT, signal_handler)

httpd.serve_forever()