''' 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.db.models import Q
from django.db.models.functions import Greatest
from django.http import HttpResponseNotFound, JsonResponse
from django.shortcuts import get_object_or_404
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.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 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 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
@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 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)