database_server.py

from wsgiref.simple_server import make_server
from urllib.parse import parse_qs

DATA_STORE = {}


def setter(qs, start_response, headers):
    # Some questions/observations:
    #  - What to do with empty values? (Here I'm just ignoring them)
    #  - I just assumed it was OK to store vectors instead of scalars because
    #   well...YAGNI, meaning this is valid:
    #      .../set?somekey1=someval1&somekey1=someval2
    #   The DATA_STORE will look like this afterwards:
    #       {'somekey1': ['someval1', 'someval2']}
    #  - I'm allowing the client to set values for different keys on the same
    #    requests, after:
    #       .../set?somekey1=someva1l&somekey2=someval2
    #   The DATA_STORE will look like this:
    #       {'somekey1': ['someval1'], 'somekey2': ['someval2']}
    r = {k: [v for v in qs[k] if v != '']
         for k in qs.keys()
         if k and all(v != '' for v in qs[k])}
    if r:
        DATA_STORE.update(r)
        start_response('200 OK', list(headers.items()))
        return 'OK'.encode('utf-8')
    else:
        start_response('400 Bad Request', list(headers.items()))
        err = 'Bad client! You provided an invalid key=value combination'
        return err.encode('utf-8')
    print(DATA_STORE)


def getter(qs, start_response, headers):
    # Some questions/observations:
    #  - I'm allowing the client to query multiple keys on the same request:
    #       key=somekey1&key=someval2
    #   Will return:
    #       DATA_STORE['somekey1'] + '\r\n'
    #       DATA_STORE['somekey2'] + '\r\n'
    if 'key' in qs:
        r = [DATA_STORE[val] for val in qs['key'] if val in DATA_STORE]
        if r:
            print(r)
            start_response('200 OK', list(headers.items()))
            return '\r\n'.join(repr(l) for l in r).encode('utf-8')
        else:
            start_response('400 Bad Request', list(headers.items()))
            err = 'Keywords are not on the data store!'
            return err.encode('utf-8')
    else:
        start_response('400 Bad Request', list(headers.items()))
        err = 'Bad client! Invalid request'
        return err.encode('utf-8')


def app(env, start_response):
    headers = {'Content-Type': 'text/plain; charset=utf-8'}

    handlers = {'/set': setter, '/get': getter}
    action = env['PATH_INFO']
    qs = parse_qs(env['QUERY_STRING'])

    if action not in handlers:
        start_response('404 Not Found', list(headers.items()))
        err = 'Sorry dude, I can only understand: {}'.format(
            list(handlers.keys()))
        yield err.encode('utf-8')
    else:
        yield handlers[action](qs, start_response, headers)


if __name__ == '__main__':
    httpd = make_server('', 4000, app)
    httpd.serve_forever()