import base64
import datetime
import requests
import sys


client_id = 'REPLACE ME'
client_secret = 'REPLACE ME'
expires = datetime.datetime.now().timestamp()
access_token = None


def has_expired():
    return (not access_token) or \
        expires < (datetime.datetime.now().timestamp())


def get_access_token():
    if has_expired():
        client_credentials = \
            bytes(client_id + ':' + client_secret, encoding='utf-8')
        base = base64.b64encode(client_credentials)
        payload = {'grant_type': 'client_credentials'}
        headers = {'Authorization': 'Basic {}'.format(base.decode('utf-8'))}
        r = requests.post(
            'https://accounts.spotify.com/api/token',
            data=payload, headers=headers)
        json_response = r.json()
        current = datetime.datetime.now().timestamp()
        setattr(
            sys.modules[__name__], 'expires',
            json_response.get('expires_in', 0) + current - 5)
        setattr(
            sys.modules[__name__], 'access_token',
            json_response['access_token'])

    return access_token