#  imports {{{ # 

import math
import random
import requests
import os
import urllib
import secrets
import pprint
import string
from datetime import datetime

from django.shortcuts import render, redirect
from django.http import HttpResponseBadRequest

#  }}} imports # 

TIME_FORMAT = '%Y-%m-%d-%H-%M-%S'
TRACKS_TO_QUERY = 200

#  generate_random_string {{{ # 


def generate_random_string(length):
    """Generates a random string of a certain length

    Args:
        length: the desired length of the randomized string
    
    Returns:
        A random string
    """
    all_chars = string.ascii_letters + string.digits
    rand_str = "".join(random.choice(all_chars) for _ in range(length)) 
    
    return rand_str

#  }}} generate_random_string # 

#  token_expired {{{ # 

def token_expired(token_obtained_at, valid_for):
    """Returns True if token expired, False if otherwise

    Args:
        token_obtained_at: datetime object representing the date and time when the token was obtained
        valid_for: the time duration for which the token is valid, in seconds
    """
    time_elapsed = (datetime.today() - token_obtained_at).total_seconds()
    return time_elapsed >= valid_for

#  }}} token_expired # 

#  index {{{ # 

# Create your views here.
def index(request):
    return render(request, 'spotifyvis/index.html')

#  }}}  index # 

#  login {{{ # 

# uses Authorization Code flow
def spotify_login(request):
    # use a randomly generated state string to prevent cross-site request forgery attacks
    state_str = generate_random_string(16)
    request.session['state_string'] = state_str 

    payload = {
        'client_id': os.environ['SPOTIFY_CLIENT_ID'],
        'response_type': 'code',
        'redirect_uri': 'http://localhost:8000/callback',
        'state': state_str,
        'scope': 'user-library-read',
        'show_dialog': False
    }

    params = urllib.parse.urlencode(payload) # turn the payload dict into a query string
    authorize_url = "https://accounts.spotify.com/authorize/?{}".format(params)
    return redirect(authorize_url)

#  }}} login # 

#  callback {{{ # 

def callback(request):
    # Attempt to retrieve the authorization code from the query string
    try:
        code = request.GET['code']
    except KeyError:
        return HttpResponseBadRequest("<h1>Problem with login</h1>")

    payload = {
        'grant_type': 'authorization_code',
        'code': code,
        'redirect_uri': 'http://localhost:8000/callback',
        'client_id': os.environ['SPOTIFY_CLIENT_ID'],
        'client_secret': os.environ['SPOTIFY_CLIENT_SECRET'],
    }

    response = requests.post('https://accounts.spotify.com/api/token', data=payload).json()
    # despite its name, datetime.today() returns a datetime object, not a date object
    # use datetime.strptime() to get a datetime object from a string
    request.session['token_obtained_at'] = datetime.strftime(datetime.today(), TIME_FORMAT) 
    request.session['access_token'] = response['access_token']
    request.session['refresh_token'] = response['refresh_token']
    request.session['valid_for'] = response['expires_in']
    #  print(response)

    return redirect('user_data')

#  }}} callback # 

#  user_data {{{ # 

def user_data(request):

    #  get user token {{{ # 
    
    token_obtained_at = datetime.strptime(request.session['token_obtained_at'], TIME_FORMAT)
    valid_for = int(request.session['valid_for'])

    if token_expired(token_obtained_at, valid_for):
        req_body = {
            'grant_type': 'refresh_token',
            'refresh_token': request.session['refresh_token'],
            'client_id': os.environ['SPOTIFY_CLIENT_ID'],
            'client_secret': os.environ['SPOTIFY_CLIENT_SECRET']
        }
        
        refresh_token_response = requests.post('https://accounts.spotify.com/api/token', data=req_body).json()
        request.session['access_token'] = refresh_token_response['access_token']
        request.session['valid_for'] = refresh_token_response['expires_in']
    
    #  }}} get user token # 

    auth_token_str = "Bearer " + request.session['access_token']
    headers = {
        'Authorization': auth_token_str
    }

    user_data_response = requests.get('https://api.spotify.com/v1/me', headers = headers).json()
    # store the user_id so it may be used to create model
    request.session['user_id'] = user_data_response['id']  

    #  create user obj {{{ # 
    
    try:
        user = User.objects.get(user_id=user_data_response['id'])
    except User.DoesNotExist:
        # Python docs recommends 32 bytes of randomness against brute force attacks
        user = User(user_id=user_data_response['id'], user_secret=secrets.token_urlsafe(32))
        request.session['user_secret'] = user.user_secret
        user.save()
    
    #  }}} create user obj # 

    context = {
        'user_id': user.user_id,
        'user_secret': user.user_secret,
    }

    # TODO: redirect to API app to parse library or loading page
    #  parse_library(headers, TRACKS_TO_QUERY, user)
    return render(request, 'spotifyvis/logged_in.html', context)

#  }}} user_data  # 

def admin_graphs(request):
    """TODO
    """
    user_id = "polarbier"
    #  user_id = "chrisshyi13"
    user_obj = User.objects.get(user_id=user_id)
    context = {
        'user_id': user_id,
        'user_secret': user_obj.user_secret,
    }
    update_track_genres(user_obj)
    return render(request, 'spotifyvis/logged_in.html', context)