import socket
from http.client import HTTPConnection

import selectors
from threading import Thread

sel = selectors.DefaultSelector()
PORT = 8081


def handle_GET(sock, req):
    sock.sendall(
        b'HTTP/1.1 200 OK\r\n'
        b'Connection: keep-alive\r\n\r\n')


def handle(sock, mask):
    req = buf = sock.recv(1024)
    while True:
        try:
            buf = sock.recv(1024)
            req += buf
        except BlockingIOError:
            break

    first_space = req.find(b' ')
    method = req[:first_space].decode('ascii')

    try:
        globals()['handle_{}'.format(method)](sock, req)
    except KeyError:
        # in this proof of concept, i had initially simply done a pass here,
        # keeping the socket open, effectively being a noop.
        # because of the logic in HTTPResponse (specifically readline()),
        # this will cause the client to
        # hang. the /only/ situation where the client can possibly get an empty
        # read is, in fact, when the socket has been closed and the client gets
        # the EOS read.
        sock.close()


def accept(server, mask):
    con, addr = server.accept()
    con.setblocking(False)
    sel.register(con, selectors.EVENT_READ, handle)


def start_server(server):
    server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    server.bind(('localhost', PORT))
    server.listen()
    server.setblocking(False)
    sel.register(server, selectors.EVENT_READ, accept)

    while True:
        try:
            events = sel.select()
            for key, mask in events:
                key.data(key.fileobj, mask)
        except ValueError:
            # selector has likely been closed
            break


def main():
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    Thread(target=start_server, args=(server,)).start()

    con = HTTPConnection('localhost', PORT)
    con.connect()

    con.request('GET', '/')
    r = con.getresponse()
    assert r.status == 200

    con.request('OPTIONS', '/')
    r = con.getresponse()
    assert r.status == 200

    con.request('GET', '/')
    r = con.getresponse()
    assert r.status == 200

    try:
        server.shutdown(socket.SHUT_RDWR)
    except OSError:
        # fine, no connection
        pass

    server.close()
    sel.close()


if __name__ == '__main__':
    main()