#  imports {{{ # 

from django.shortcuts import render, redirect
from django.http import HttpResponse, HttpResponseBadRequest
import math
import random
import requests
import os
import urllib
import json
import pprint
from datetime import datetime
from .utils import parse_library, process_library_stats
from .models import User, Track, AudioFeatures, Artist 

#  }}} imports # 

TIME_FORMAT = '%Y-%m-%d-%H-%M-%S'
TRACKS_TO_QUERY = 5

#  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
    """
    rand_str = ""
    possible_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

    for _ in range(length):
        rand_str += possible_chars[random.randint(0, len(possible_chars) - 1)]
    
    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 {{{ # 

def 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):
    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']

    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()
    request.session['user_id'] = user_data_response['id'] # store the user_id so it may be used to create model
    request.session['user_name'] = user_data_response['display_name']
    user = None # will be set to the current user object later
    #  try:
        #  user = User.objects.get(user_id=request.session['user_id'])
    #  except User.DoesNotExist:
        #  user = User.objects.create(user_id=request.session['user_id'], user_name=request.session['user_name'])
    context = {
       'user_name': user_data_response['display_name'],
       'id': user_data_response['id'],
    }

    library_stats = {
        "audio_features":{}, 
        "genres":{}, 
        "year_released":{}, 
        "artists":{}, 
        "num_songs": 0, 
        "popularity": {
            "average": 0,
            "std_dev": 0,
        },   
        "total_runtime": 0
    }
    parse_library(headers, TRACKS_TO_QUERY, library_stats, user)
    processed_library_stats = process_library_stats(library_stats)
    #  print("================================================")
    #  print("Processed data follows\n")
    #  pprint.pprint(processed_library_stats)
    return render(request, 'spotifyvis/user_data.html', context)

#  }}} user_data  #