from django.http import HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse
from django.utils import timezone
from django.views import generic

from .models import Choice, Question

import boto3
import os


def _get_environment_variable(key, example_value):
    value = os.getenv(key)
    if value is None:
        raise RuntimeError("Environment variable " + key + " must be set, e.g. " + example_value)
    return value


class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'

    def get_queryset(self):
        """
        Return the last five published questions (not including those set to be
        published in the future).
        """
        return Question.objects.filter(pub_date__lte=timezone.now()).order_by('-pub_date')[:5]


class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/detail.html'

    s3_key_name = 'resources/example-image.png'
    s3_bucket_name = _get_environment_variable(key="DEMO_APP_BUCKET_NAME",
                                               example_value="test-images-for-my-demo-django-app")

    def get_queryset(self):
        """
        Excludes any questions that aren't published yet.
        Creates a boto3 client and uploads a file to intentionally mimic some network behaviour.
        """
        s3_client = boto3.client('s3')
        s3_client.upload_file(self.s3_key_name, self.s3_bucket_name, self.s3_key_name)
        return Question.objects.filter(pub_date__lte=timezone.now())


class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'


def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))