''' views for pages you can go to in the application '''
from django.contrib.auth.decorators import login_required
from django.db.models import Avg, Q
from django.http import HttpResponseBadRequest, HttpResponseNotFound, \
        JsonResponse
from django.template.response import TemplateResponse
from django.views.decorators.csrf import csrf_exempt

from fedireads import activitypub
from fedireads import forms, models, books_manager


def get_user_from_username(username):
    ''' helper function to resolve a localname or a username to a user '''
    try:
        user = models.User.objects.get(localname=username)
    except models.User.DoesNotExist:
        user = models.User.objects.get(username=username)
    return user


def is_api_request(request):
    ''' check whether a request is asking for html or data '''
    # TODO: this should probably be the full content type? maybe?
    return 'json' in request.headers.get('Accept') or \
            request.path[-5:] == '.json'


@login_required
def home(request):
    ''' this is the same as the feed on the home tab '''
    return home_tab(request, 'home')


@login_required
def home_tab(request, tab):
    ''' user's homepage with activity feed '''
    shelves = []
    shelves = get_user_shelf_preview(
        request.user,
        [('reading', 3), ('read', 1), ('to-read', 3)]
    )
    size = sum(len(s['books']) for s in shelves)
    # books new to the instance, for discovery
    if size < 6:
        shelves.append({
            'name': 'Recently added',
            'identifier': None,
            'books': models.Book.objects.order_by(
                '-created_date'
            )[:6 - size],
            'count': 6 - size,
        })

    # allows us to check if a user has shelved a book
    user_books = models.Book.objects.filter(shelves__user=request.user).all()

    # status updates for your follow network
    following = models.User.objects.filter(
        Q(followers=request.user) | Q(id=request.user.id)
    )

    activities = models.Status.objects.order_by(
        '-created_date'
    ).select_subclasses()

    if tab == 'home':
        # people you follow and direct mentions
        activities = activities.filter(
            Q(user__in=following, privacy='public') | \
                Q(mention_users=request.user)
        )
    elif tab == 'local':
        # everyone on this instance
        activities = activities.filter(user__local=True, privacy='public')
    else:
        # all activities from everyone you federate with
        activities = activities.filter(privacy='public')

    activities = activities[:10]

    data = {
        'user': request.user,
        'shelves': shelves,
        'user_books': user_books,
        'activities': activities,
        'feed_tabs': [
            {'id': 'home', 'display': 'Home'},
            {'id': 'local', 'display': 'Local'},
            {'id': 'federated', 'display': 'Federated'}
        ],
        'active_tab': tab,
        'review_form': forms.ReviewForm(),
    }
    return TemplateResponse(request, 'feed.html', data)


def login_page(request):
    ''' authentication '''
    # send user to the login page
    data = {
        'login_form': forms.LoginForm(),
        'register_form': forms.RegisterForm(),
    }
    return TemplateResponse(request, 'login.html', data)


@login_required
def notifications_page(request):
    ''' list notitications '''
    notifications = request.user.notification_set.all() \
            .order_by('-created_date')
    unread = [n.id for n in notifications.filter(read=False)]
    data = {
        'notifications': notifications,
        'unread': unread,
    }
    notifications.update(read=True)
    return TemplateResponse(request, 'notifications.html', data)

@csrf_exempt
def user_page(request, username, subpage=None):
    ''' profile page for a user '''
    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        # we have a json request
        return JsonResponse(activitypub.get_actor(user))
    # otherwise we're at a UI view

    # TODO: change display with privacy and authentication considerations

    data = {
        'user': user,
        'is_self': request.user.id == user.id,
    }
    if subpage == 'followers':
        data['followers'] = user.followers.all()
        return TemplateResponse(request, 'followers.html', data)
    elif subpage == 'following':
        data['following'] = user.following.all()
        return TemplateResponse(request, 'following.html', data)
    elif subpage == 'shelves':
        data['shelves'] = user.shelf_set.all()
        return TemplateResponse(request, 'user_shelves.html', data)
    else:
        shelves = get_user_shelf_preview(user)
        data['shelves'] = shelves
        activities = models.Status.objects.filter(
            user=user,
        ).order_by(
            '-created_date',
        ).select_subclasses().all()[:10]
        data['activities'] = activities
        return TemplateResponse(request, 'user.html', data)


@csrf_exempt
def followers_page(request, username):
    ''' list of followers '''
    if request.method != 'GET':
        return HttpResponseBadRequest()

    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        user = models.User.objects.get(localname=username)
        followers = user.followers
        page = request.GET.get('page')
        return JsonResponse(activitypub.get_followers(user, page, followers))

    return user_page(request, username, subpage='followers')


@csrf_exempt
def following_page(request, username):
    ''' list of followers '''
    if request.method != 'GET':
        return HttpResponseBadRequest()

    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        user = models.User.objects.get(localname=username)
        following = user.following
        page = request.GET.get('page')
        return JsonResponse(activitypub.get_following(user, page, following))

    return user_page(request, username, subpage='following')


@csrf_exempt
def user_shelves_page(request, username):
    ''' list of followers '''
    if request.method != 'GET':
        return HttpResponseBadRequest()

    return user_page(request, username, subpage='shelves')


@csrf_exempt
def status_page(request, username, status_id):
    ''' display a particular status (and replies, etc) '''
    if request.method != 'GET':
        return HttpResponseBadRequest()

    try:
        user = get_user_from_username(username)
        status = models.Status.objects.select_subclasses().get(id=status_id)
    except ValueError:
        return HttpResponseNotFound()

    if user != status.user:
        return HttpResponseNotFound()

    if is_api_request(request):
        return JsonResponse(activitypub.get_status(status))

    data = {
        'status': status,
    }
    return TemplateResponse(request, 'status.html', data)


@csrf_exempt
def replies_page(request, username, status_id):
    ''' ordered collection of replies to a status '''
    if request.method != 'GET':
        return HttpResponseBadRequest()

    if not is_api_request(request):
        return status_page(request, username, status_id)

    status = models.Status.objects.get(id=status_id)
    if status.user.localname != username:
        return HttpResponseNotFound()

    replies = models.Status.objects.filter(
        reply_parent=status,
    ).select_subclasses()

    if request.GET.get('only_other_accounts'):
        replies = replies.filter(
            ~Q(user=status.user)
        )
    else:
        replies = replies.filter(user=status.user)

    if request.GET.get('page'):
        min_id = request.GET.get('min_id')
        if min_id:
            replies = replies.filter(id__gt=min_id)
        max_id = request.GET.get('max_id')
        if max_id:
            replies = replies.filter(id__lte=max_id)
        activity = activitypub.get_replies_page(status, replies)
        return JsonResponse(activity)

    return JsonResponse(activitypub.get_replies(status, replies))


@login_required
def edit_profile_page(request):
    ''' profile page for a user '''
    user = request.user

    form = forms.EditUserForm(instance=request.user)
    data = {
        'form': form,
        'user': user,
    }
    return TemplateResponse(request, 'edit_user.html', data)


def book_page(request, book_identifier, tab='friends'):
    ''' info about a book '''
    book = books_manager.get_or_create_book(book_identifier)

    if isinstance(book, models.Work):
        book_reviews = models.Review.objects.filter(
            Q(book=book) | Q(book__parent_work=book),
        )
    else:
        book_reviews = models.Review.objects.filter(book=book)

    user_reviews = book_reviews.filter(
        user=request.user,
    ).all()

    if tab == 'friends':
        reviews = book_reviews.filter(
            Q(user__followers=request.user, privacy='public') | \
                Q(user=request.user) | \
                Q(mention_users=request.user),
        )
    elif tab == 'local':
        reviews = book_reviews.filter(
            Q(privacy='public') | \
                Q(mention_users=request.user),
            user__local=True,
        )
    else:
        reviews = book_reviews.filter(
            Q(privacy='public') | \
                Q(mention_users=request.user),
        )

    try:
        shelf = models.Shelf.objects.get(user=request.user, book=book)
    except models.Shelf.DoesNotExist:
        shelf = None

    rating = reviews.aggregate(Avg('rating'))
    tags = models.Tag.objects.filter(
        book=book
    ).values(
        'book', 'name', 'identifier'
    ).distinct().all()
    user_tags = models.Tag.objects.filter(
        book=book, user=request.user
    ).all()

    review_form = forms.ReviewForm()
    tag_form = forms.TagForm()
    data = {
        'book': book,
        'shelf': shelf,
        'user_reviews': user_reviews,
        'user_rating': user_reviews.aggregate(Avg('rating')),
        'reviews': reviews.distinct(),
        'rating': rating['rating__avg'],
        'tags': tags,
        'user_tags': user_tags,
        'user_tag_names': user_tags.values_list('identifier', flat=True),
        'review_form': review_form,
        'tag_form': tag_form,
        'feed_tabs': [
            {'id': 'friends', 'display': 'Friends'},
            {'id': 'local', 'display': 'Local'},
            {'id': 'federated', 'display': 'Federated'}
        ],
        'active_tab': tab,
        'path': '/book/%s' % book_identifier,
    }
    return TemplateResponse(request, 'book.html', data)


def author_page(request, author_identifier):
    ''' landing page for an author '''
    try:
        author = models.Author.objects.get(openlibrary_key=author_identifier)
    except ValueError:
        return HttpResponseNotFound()

    books = models.Book.objects.filter(authors=author)
    data = {
        'author': author,
        'books': books,
    }
    return TemplateResponse(request, 'author.html', data)


def tag_page(request, tag_id):
    ''' books related to a tag '''
    tag_obj = models.Tag.objects.filter(identifier=tag_id).first()
    books = models.Book.objects.filter(tag__identifier=tag_id).distinct()
    data = {
        'books': books,
        'tag': tag_obj,
    }
    return TemplateResponse(request, 'tag.html', data)


def shelf_page(request, username, shelf_identifier):
    ''' display a shelf '''
    # TODO: json view
    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    shelf = models.Shelf.objects.get(user=user, identifier=shelf_identifier)
    data = {
        'shelf': shelf,
        'user': user,
    }
    return TemplateResponse(request, 'shelf.html', data)


def get_user_shelf_preview(user, shelf_proportions=None):
    ''' data for the covers shelf (user page and feed page) '''
    shelves = []
    shelf_max = 6
    if not shelf_proportions:
        shelf_proportions = [('reading', 3), ('read', 2), ('to-read', -1)]
    for (identifier, count) in shelf_proportions:
        if shelf_max <= 0:
            break
        if count > shelf_max or count < 0:
            count = shelf_max

        try:
            shelf = models.Shelf.objects.get(
                user=user,
                identifier=identifier,
            )
        except models.Shelf.DoesNotExist:
            continue

        if not shelf.books.count():
            continue
        books = models.ShelfBook.objects.filter(
            shelf=shelf,
        ).order_by(
            '-updated_date'
        )[:count]

        shelf_max -= len(books)

        shelves.append({
            'name': shelf.name,
            'identifier': shelf.identifier,
            'books': [b.book for b in books],
            'size': shelf.books.count(),
        })
    return shelves