''' views for pages you can go to in the application '''
import re

from django.contrib.auth.decorators import login_required, permission_required
from django.contrib.postgres.search import TrigramSimilarity
from django.core.paginator import Paginator
from django.db.models import Avg, Q, Max
from django.db.models.functions import Greatest
from django.http import HttpResponseNotFound, JsonResponse
from django.core.exceptions import PermissionDenied
from django.shortcuts import get_object_or_404, redirect
from django.template.response import TemplateResponse
from django.views.decorators.csrf import csrf_exempt
from django.views.decorators.http import require_GET

from bookwyrm import outgoing
from bookwyrm import forms, models
from bookwyrm.activitypub import ActivitypubResponse
from bookwyrm.connectors import connector_manager
from bookwyrm.settings import PAGE_LENGTH
from bookwyrm.tasks import app
from bookwyrm.utils import regex


def get_edition(book_id):
    ''' look up a book in the db and return an edition '''
    book = models.Book.objects.select_subclasses().get(id=book_id)
    if isinstance(book, models.Work):
        book = book.get_default_edition()
    return book

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


def is_api_request(request):
    ''' check whether a request is asking for html or data '''
    return 'json' in request.headers.get('Accept') or \
            request.path[-5:] == '.json'

def is_bookworm_request(request):
    ''' check if the request is coming from another bookworm instance '''
    user_agent = request.headers.get('User-Agent')
    if user_agent is None or \
            re.search(regex.bookwyrm_user_agent, user_agent) is None:
        return False

    return True

def server_error_page(request):
    ''' 500 errors '''
    return TemplateResponse(
        request, 'error.html', {'title': 'Oops!'}, status=500)


def not_found_page(request, _):
    ''' 404s '''
    return TemplateResponse(
        request, 'notfound.html', {'title': 'Not found'}, status=404)


@require_GET
def home(request):
    ''' this is the same as the feed on the home tab '''
    if request.user.is_authenticated:
        return home_tab(request, 'home')
    return discover_page(request)


@login_required
@require_GET
def home_tab(request, tab):
    ''' user's homepage with activity feed '''
    try:
        page = int(request.GET.get('page', 1))
    except ValueError:
        page = 1

    suggested_books = get_suggested_books(request.user)

    if tab == 'home':
        activities = get_activity_feed(
            request.user, ['public', 'unlisted', 'followers'],
            following_only=True)
    elif tab == 'local':
        activities = get_activity_feed(
            request.user, ['public', 'followers'], local_only=True)
    else:
        activities = get_activity_feed(
            request.user, ['public', 'followers'])
    paginated = Paginator(activities, PAGE_LENGTH)
    activity_page = paginated.page(page)

    prev_page = next_page = None
    if activity_page.has_next():
        next_page = '/%s/?page=%d#feed' % \
                (tab, activity_page.next_page_number())
    if activity_page.has_previous():
        prev_page = '/%s/?page=%d#feed' % \
                (tab, activity_page.previous_page_number())
    data = {
        'title': 'Updates Feed',
        'user': request.user,
        'suggested_books': suggested_books,
        'activities': activity_page.object_list,
        'tab': tab,
        'next': next_page,
        'prev': prev_page,
    }
    return TemplateResponse(request, 'feed.html', data)


def get_suggested_books(user, max_books=5):
    ''' helper to get a user's recent books '''
    book_count = 0
    preset_shelves = [
        ('reading', max_books), ('read', 2), ('to-read', max_books)
    ]
    suggested_books = []
    for (preset, shelf_max) in preset_shelves:
        limit = shelf_max if shelf_max < (max_books - book_count) \
                else max_books - book_count
        shelf = user.shelf_set.get(identifier=preset)

        shelf_books = shelf.shelfbook_set.order_by(
            '-updated_date'
        ).all()[:limit]
        if not shelf_books:
            continue
        shelf_preview = {
            'name': shelf.name,
            'books': [s.book for s in shelf_books]
        }
        suggested_books.append(shelf_preview)
        book_count += len(shelf_preview['books'])
    return suggested_books


@require_GET
def discover_page(request):
    ''' tiled book activity page '''
    books = models.Edition.objects.filter(
        review__published_date__isnull=False,
        review__user__local=True,
        review__privacy__in=['public', 'unlisted'],
    ).exclude(
        cover__exact=''
    ).annotate(
        Max('review__published_date')
    ).order_by('-review__published_date__max')[:6]

    ratings = {}
    for book in books:
        reviews = models.Review.objects.filter(
            book__in=book.parent_work.editions.all()
        )
        reviews = get_activity_feed(
            request.user, ['public', 'unlisted'], queryset=reviews)
        ratings[book.id] = reviews.aggregate(Avg('rating'))['rating__avg']
    data = {
        'title': 'Discover',
        'register_form': forms.RegisterForm(),
        'books': list(set(books)),
        'ratings': ratings
    }
    return TemplateResponse(request, 'discover.html', data)


@login_required
@require_GET
def direct_messages_page(request, page=1):
    ''' like a feed but for dms only '''
    activities = get_activity_feed(request.user, 'direct')
    paginated = Paginator(activities, PAGE_LENGTH)
    activity_page = paginated.page(page)

    prev_page = next_page = None
    if activity_page.has_next():
        next_page = '/direct-message/?page=%d#feed' % \
                activity_page.next_page_number()
    if activity_page.has_previous():
        prev_page = '/direct-messages/?page=%d#feed' % \
                activity_page.previous_page_number()
    data = {
        'title': 'Direct Messages',
        'user': request.user,
        'activities': activity_page.object_list,
        'next': next_page,
        'prev': prev_page,
    }
    return TemplateResponse(request, 'direct_messages.html', data)


def get_activity_feed(
        user, privacy, local_only=False, following_only=False,
        queryset=models.Status.objects):
    ''' get a filtered queryset of statuses '''
    privacy = privacy if isinstance(privacy, list) else [privacy]
    # if we're looking at Status, we need this. We don't if it's Comment
    if hasattr(queryset, 'select_subclasses'):
        queryset = queryset.select_subclasses()

    # exclude deleted
    queryset = queryset.exclude(deleted=True).order_by('-published_date')

    # you can't see followers only or direct messages if you're not logged in
    if user.is_anonymous:
        privacy = [p for p in privacy if not p in ['followers', 'direct']]

    # filter to only privided privacy levels
    queryset = queryset.filter(privacy__in=privacy)

    # only include statuses the user follows
    if following_only:
        queryset = queryset.exclude(
            ~Q(# remove everythign except
                Q(user__in=user.following.all()) | # user follwoing
                Q(user=user) |# is self
                Q(mention_users=user)# mentions user
            ),
        )
    # exclude followers-only statuses the user doesn't follow
    elif 'followers' in privacy:
        queryset = queryset.exclude(
            ~Q(# user isn't following and it isn't their own status
                Q(user__in=user.following.all()) | Q(user=user)
            ),
            privacy='followers' # and the status is followers only
        )

    # exclude direct messages not intended for the user
    if 'direct' in privacy:
        queryset = queryset.exclude(
            ~Q(
                Q(user=user) | Q(mention_users=user)
            ), privacy='direct'
        )

    # filter for only local status
    if local_only:
        queryset = queryset.filter(user__local=True)

    # remove statuses that have boosts in the same queryset
    try:
        queryset = queryset.filter(~Q(boosters__in=queryset))
    except ValueError:
        pass

    return queryset


@require_GET
def search(request):
    ''' that search bar up top '''
    query = request.GET.get('q')
    min_confidence = request.GET.get('min_confidence', 0.1)

    if is_api_request(request):
        # only return local book results via json so we don't cause a cascade
        book_results = connector_manager.local_search(
            query, min_confidence=min_confidence)
        return JsonResponse([r.json() for r in book_results], safe=False)

    # use webfinger for mastodon style account@domain.com username
    if re.match(r'\B%s' % regex.full_username, query):
        outgoing.handle_remote_webfinger(query)

    # do a local user search
    user_results = models.User.objects.annotate(
        similarity=Greatest(
            TrigramSimilarity('username', query),
            TrigramSimilarity('localname', query),
        )
    ).filter(
        similarity__gt=0.5,
    ).order_by('-similarity')[:10]

    book_results = connector_manager.search(
        query, min_confidence=min_confidence)
    data = {
        'title': 'Search Results',
        'book_results': book_results,
        'user_results': user_results,
        'query': query,
    }
    return TemplateResponse(request, 'search_results.html', data)


@login_required
@require_GET
def import_page(request):
    ''' import history from goodreads '''
    return TemplateResponse(request, 'import.html', {
        'title': 'Import Books',
        'import_form': forms.ImportForm(),
        'jobs': models.ImportJob.
                objects.filter(user=request.user).order_by('-created_date'),
    })


@login_required
@require_GET
def import_status(request, job_id):
    ''' status of an import job '''
    job = models.ImportJob.objects.get(id=job_id)
    if job.user != request.user:
        raise PermissionDenied
    task = app.AsyncResult(job.task_id)
    items = job.items.order_by('index').all()
    failed_items = [i for i in items if i.fail_reason]
    items = [i for i in items if not i.fail_reason]
    return TemplateResponse(request, 'import_status.html', {
        'title': 'Import Status',
        'job': job,
        'items': items,
        'failed_items': failed_items,
        'task': task
    })


@require_GET
def login_page(request):
    ''' authentication '''
    if request.user.is_authenticated:
        return redirect('/')
    # send user to the login page
    data = {
        'title': 'Login',
        'login_form': forms.LoginForm(),
        'register_form': forms.RegisterForm(),
    }
    return TemplateResponse(request, 'login.html', data)


@require_GET
def about_page(request):
    ''' more information about the instance '''
    data = {
        'title': 'About',
    }
    return TemplateResponse(request, 'about.html', data)


@require_GET
def password_reset_request(request):
    ''' invite management page '''
    return TemplateResponse(
        request,
        'password_reset_request.html',
        {'title': 'Reset Password'}
    )


@require_GET
def password_reset(request, code):
    ''' endpoint for sending invites '''
    if request.user.is_authenticated:
        return redirect('/')
    try:
        reset_code = models.PasswordReset.objects.get(code=code)
        if not reset_code.valid():
            raise PermissionDenied
    except models.PasswordReset.DoesNotExist:
        raise PermissionDenied

    return TemplateResponse(
        request,
        'password_reset.html',
        {'title': 'Reset Password', 'code': reset_code.code}
    )


@require_GET
def invite_page(request, code):
    ''' endpoint for sending invites '''
    if request.user.is_authenticated:
        return redirect('/')
    invite = get_object_or_404(models.SiteInvite, code=code)

    data = {
        'title': 'Join',
        'register_form': forms.RegisterForm(),
        'invite': invite,
        'valid': invite.valid() if invite else True,
    }
    return TemplateResponse(request, 'invite.html', data)


@login_required
@permission_required('bookwyrm.create_invites', raise_exception=True)
@require_GET
def manage_invites(request):
    ''' invite management page '''
    data = {
        'title': 'Invitations',
        'invites': models.SiteInvite.objects.filter(
            user=request.user).order_by('-created_date'),
        'form': forms.CreateInviteForm(),
    }
    return TemplateResponse(request, 'manage_invites.html', data)


@login_required
@require_GET
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 = {
        'title': 'Notifications',
        'notifications': notifications,
        'unread': unread,
    }
    notifications.update(read=True)
    return TemplateResponse(request, 'notifications.html', data)


@csrf_exempt
@require_GET
def user_page(request, username):
    ''' 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 ActivitypubResponse(user.to_activity())
    # otherwise we're at a UI view

    try:
        page = int(request.GET.get('page', 1))
    except ValueError:
        page = 1

    shelf_preview = []

    # only show other shelves that should be visible
    shelves = user.shelf_set
    is_self = request.user.id == user.id
    if not is_self:
        follower = user.followers.filter(id=request.user.id).exists()
        if follower:
            shelves = shelves.filter(privacy__in=['public', 'followers'])
        else:
            shelves = shelves.filter(privacy='public')

    for user_shelf in shelves.all():
        if not user_shelf.books.count():
            continue
        shelf_preview.append({
            'name': user_shelf.name,
            'local_path': user_shelf.local_path,
            'books': user_shelf.books.all()[:3],
            'size': user_shelf.books.count(),
        })
        if len(shelf_preview) > 2:
            break

    # user's posts
    activities = get_activity_feed(
        request.user,
        ['public', 'unlisted', 'followers'],
        queryset=models.Status.objects.filter(user=user)
    )
    paginated = Paginator(activities, PAGE_LENGTH)
    activity_page = paginated.page(page)

    prev_page = next_page = None
    if activity_page.has_next():
        next_page = '/user/%s/?page=%d' % \
                (username, activity_page.next_page_number())
    if activity_page.has_previous():
        prev_page = '/user/%s/?page=%d' % \
                (username, activity_page.previous_page_number())
    data = {
        'title': user.name,
        'user': user,
        'is_self': is_self,
        'shelves': shelf_preview,
        'shelf_count': shelves.count(),
        'activities': activity_page.object_list,
        'next': next_page,
        'prev': prev_page,
    }

    return TemplateResponse(request, 'user.html', data)


@csrf_exempt
@require_GET
def followers_page(request, username):
    ''' list of followers '''
    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        return ActivitypubResponse(user.to_followers_activity(**request.GET))

    data = {
        'title': '%s: followers' % user.name,
        'user': user,
        'is_self': request.user.id == user.id,
        'followers': user.followers.all(),
    }
    return TemplateResponse(request, 'followers.html', data)


@csrf_exempt
@require_GET
def following_page(request, username):
    ''' list of followers '''
    try:
        user = get_user_from_username(username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        return ActivitypubResponse(user.to_following_activity(**request.GET))

    data = {
        'title': '%s: following' % user.name,
        'user': user,
        'is_self': request.user.id == user.id,
        'following': user.following.all(),
    }
    return TemplateResponse(request, 'following.html', data)


@csrf_exempt
@require_GET
def status_page(request, username, status_id):
    ''' display a particular status (and replies, etc) '''
    try:
        user = get_user_from_username(username)
        status = models.Status.objects.select_subclasses().get(id=status_id)
    except ValueError:
        return HttpResponseNotFound()

    # the url should have the poster's username in it
    if user != status.user:
        return HttpResponseNotFound()

    # make sure the user is authorized to see the status
    if not status_visible_to_user(request.user, status):
        return HttpResponseNotFound()

    if is_api_request(request):
        return ActivitypubResponse(
            status.to_activity(pure=not is_bookworm_request(request)))

    data = {
        'title': 'Status by %s' % user.username,
        'status': status,
    }
    return TemplateResponse(request, 'status.html', data)


def status_visible_to_user(viewer, status):
    ''' is a user authorized to view a status? '''
    if viewer == status.user or status.privacy in ['public', 'unlisted']:
        return True
    if status.privacy == 'followers' and \
            status.user.followers.filter(id=viewer.id).first():
        return True
    if status.privacy == 'direct' and \
            status.mention_users.filter(id=viewer.id).first():
        return True
    return False


@csrf_exempt
@require_GET
def replies_page(request, username, status_id):
    ''' ordered collection of replies to a status '''
    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()

    return ActivitypubResponse(status.to_replies(**request.GET))


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

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


@require_GET
def book_page(request, book_id):
    ''' info about a book '''
    try:
        page = int(request.GET.get('page', 1))
    except ValueError:
        page = 1

    try:
        book = models.Book.objects.select_subclasses().get(id=book_id)
    except models.Book.DoesNotExist:
        return HttpResponseNotFound()

    if is_api_request(request):
        return ActivitypubResponse(book.to_activity())

    if isinstance(book, models.Work):
        book = book.get_default_edition()
    if not book:
        return HttpResponseNotFound()

    work = book.parent_work
    if not work:
        return HttpResponseNotFound()

    reviews = models.Review.objects.filter(
        book__in=work.editions.all(),
    )
    # all reviews for the book
    reviews = get_activity_feed(
        request.user,
        ['public', 'unlisted', 'followers', 'direct'],
        queryset=reviews
    )

    # the reviews to show
    paginated = Paginator(reviews.exclude(
        Q(content__isnull=True) | Q(content='')
    ), PAGE_LENGTH)
    reviews_page = paginated.page(page)

    prev_page = next_page = None
    if reviews_page.has_next():
        next_page = '/book/%d/?page=%d' % \
                (book_id, reviews_page.next_page_number())
    if reviews_page.has_previous():
        prev_page = '/book/%s/?page=%d' % \
                (book_id, reviews_page.previous_page_number())

    user_tags = readthroughs = user_shelves = other_edition_shelves = []
    if request.user.is_authenticated:
        user_tags = models.UserTag.objects.filter(
            book=book, user=request.user
        ).values_list('tag__identifier', flat=True)

        readthroughs = models.ReadThrough.objects.filter(
            user=request.user,
            book=book,
        ).order_by('start_date')

        user_shelves = models.ShelfBook.objects.filter(
            added_by=request.user, book=book
        )

        other_edition_shelves = models.ShelfBook.objects.filter(
            ~Q(book=book),
            added_by=request.user,
            book__parent_work=book.parent_work,
        )

    data = {
        'title': book.title,
        'book': book,
        'reviews': reviews_page,
        'review_count': reviews.count(),
        'ratings': reviews.filter(Q(content__isnull=True) | Q(content='')),
        'rating': reviews.aggregate(Avg('rating'))['rating__avg'],
        'tags':  models.UserTag.objects.filter(book=book),
        'user_tags': user_tags,
        'user_shelves': user_shelves,
        'other_edition_shelves': other_edition_shelves,
        'readthroughs': readthroughs,
        'path': '/book/%s' % book_id,
        'next': next_page,
        'prev': prev_page,
    }
    return TemplateResponse(request, 'book.html', data)


@login_required
@permission_required('bookwyrm.edit_book', raise_exception=True)
@require_GET
def edit_book_page(request, book_id):
    ''' info about a book '''
    book = get_edition(book_id)
    if not book.description:
        book.description = book.parent_work.description
    data = {
        'title': 'Edit Book',
        'book': book,
        'form': forms.EditionForm(instance=book)
    }
    return TemplateResponse(request, 'edit_book.html', data)


@login_required
@permission_required('bookwyrm.edit_book', raise_exception=True)
@require_GET
def edit_author_page(request, author_id):
    ''' info about a book '''
    author = get_object_or_404(models.Author, id=author_id)
    data = {
        'title': 'Edit Author',
        'author': author,
        'form': forms.AuthorForm(instance=author)
    }
    return TemplateResponse(request, 'edit_author.html', data)


@require_GET
def editions_page(request, book_id):
    ''' list of editions of a book '''
    work = get_object_or_404(models.Work, id=book_id)

    if is_api_request(request):
        return ActivitypubResponse(work.to_edition_list(**request.GET))

    data = {
        'title': 'Editions of %s' % work.title,
        'editions': work.editions.order_by('-edition_rank').all(),
        'work': work,
    }
    return TemplateResponse(request, 'editions.html', data)


@require_GET
def author_page(request, author_id):
    ''' landing page for an author '''
    author = get_object_or_404(models.Author, id=author_id)

    if is_api_request(request):
        return ActivitypubResponse(author.to_activity())

    books = models.Work.objects.filter(
        Q(authors=author) | Q(editions__authors=author)).distinct()
    data = {
        'title': author.name,
        'author': author,
        'books': [b.get_default_edition() for b in books],
    }
    return TemplateResponse(request, 'author.html', data)


@require_GET
def tag_page(request, tag_id):
    ''' books related to a tag '''
    tag_obj = models.Tag.objects.filter(identifier=tag_id).first()
    if not tag_obj:
        return HttpResponseNotFound()

    if is_api_request(request):
        return ActivitypubResponse(tag_obj.to_activity(**request.GET))

    books = models.Edition.objects.filter(
        usertag__tag__identifier=tag_id
    ).distinct()
    data = {
        'title': tag_obj.name,
        'books': books,
        'tag': tag_obj,
    }
    return TemplateResponse(request, 'tag.html', data)


@csrf_exempt
@require_GET
def user_shelves_page(request, username):
    ''' list of followers '''
    return shelf_page(request, username, None)


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

    if shelf_identifier:
        shelf = user.shelf_set.get(identifier=shelf_identifier)
    else:
        shelf = user.shelf_set.first()

    is_self = request.user == user

    shelves = user.shelf_set
    if not is_self:
        follower = user.followers.filter(id=request.user.id).exists()
        # make sure the user has permission to view the shelf
        if shelf.privacy == 'direct' or \
                (shelf.privacy == 'followers' and not follower):
            return HttpResponseNotFound()

        # only show other shelves that should be visible
        if follower:
            shelves = shelves.filter(privacy__in=['public', 'followers'])
        else:
            shelves = shelves.filter(privacy='public')


    if is_api_request(request):
        return ActivitypubResponse(shelf.to_activity(**request.GET))

    books = models.ShelfBook.objects.filter(
        added_by=user, shelf=shelf
    ).order_by('-updated_date').all()

    data = {
        'title': '%s\'s %s shelf' % (user.display_name, shelf.name),
        'user': user,
        'is_self': is_self,
        'shelves': shelves.all(),
        'shelf': shelf,
        'books': [b.book for b in books],
    }

    return TemplateResponse(request, 'shelf.html', data)