''' handles all of the activity coming in to the server '''
import json
from urllib.parse import urldefrag
import requests

import django.db.utils
from django.http import HttpResponse
from django.http import HttpResponseBadRequest, HttpResponseNotFound
from django.views.decorators.csrf import csrf_exempt

from fedireads import books_manager, models, outgoing
from fedireads import status as status_builder
from fedireads.remote_user import get_or_create_remote_user, refresh_remote_user
from fedireads.tasks import app
from fedireads.signatures import Signature


@csrf_exempt
def inbox(request, username):
    ''' incoming activitypub events '''
    # TODO: should do some kind of checking if the user accepts
    # this action from the sender probably? idk
    # but this will just throw a 404 if the user doesn't exist
    try:
        models.User.objects.get(localname=username)
    except models.User.DoesNotExist:
        return HttpResponseNotFound()

    return shared_inbox(request)


@csrf_exempt
def shared_inbox(request):
    ''' incoming activitypub events '''
    # TODO: should this be functionally different from the non-shared inbox??
    if request.method == 'GET':
        return HttpResponseNotFound()

    try:
        activity = json.loads(request.body)
    except json.decoder.JSONDecodeError:
        return HttpResponseBadRequest()

    if not activity.get('object'):
        return HttpResponseBadRequest()

    if not has_valid_signature(request, activity):
        return HttpResponse(status=401)

    handlers = {
        'Follow': handle_follow,
        'Accept': handle_follow_accept,
        'Reject': handle_follow_reject,
        'Create': handle_create,
        'Like': handle_favorite,
        'Announce': handle_boost,
        'Add': {
            'Tag': handle_tag,
        },
        'Undo': {
            'Follow': handle_unfollow,
            'Like': handle_unfavorite,
        },
        'Update': {
            'Person': None,# TODO: handle_update_user
            'Document': handle_update_book,
        },
    }
    activity_type = activity['type']

    handler = handlers.get(activity_type, None)
    if isinstance(handler, dict):
        handler = handler.get(activity['object']['type'], None)

    if not handler:
        return HttpResponseNotFound()

    handler.delay(activity)
    return HttpResponse()


def has_valid_signature(request, activity):
    try:
        signature = Signature.parse(request)

        key_actor = urldefrag(signature.key_id).url
        if key_actor != activity.get('actor'):
            raise ValueError("Wrong actor created signature.")

        remote_user = get_or_create_remote_user(key_actor)

        try:
            signature.verify(remote_user.public_key, request)
        except ValueError:
            old_key = remote_user.public_key
            refresh_remote_user(remote_user)
            if remote_user.public_key == old_key:
                raise # Key unchanged.
            signature.verify(remote_user.public_key, request)
    except (ValueError, requests.exceptions.HTTPError):
        return False
    return True


@app.task
def handle_follow(activity):
    ''' someone wants to follow a local user '''
    # figure out who they want to follow -- not using get_or_create because
    # we only allow you to follow local users
    try:
        to_follow = models.User.objects.get(remote_id=activity['object'])
    except models.User.DoesNotExist:
        return False
    # figure out who the actor is
    user = get_or_create_remote_user(activity['actor'])
    try:
        request = models.UserFollowRequest.objects.create(
            user_subject=user,
            user_object=to_follow,
            relationship_id=activity['id']
        )
    except django.db.utils.IntegrityError as err:
        if err.__cause__.diag.constraint_name != 'userfollowrequest_unique':
            raise
        # Duplicate follow request. Not sure what the correct behaviour is, but
        # just dropping it works for now. We should perhaps generate the
        # Accept, but then do we need to match the activity id?
        return

    if not to_follow.manually_approves_followers:
        status_builder.create_notification(
            to_follow,
            'FOLLOW',
            related_user=user
        )
        outgoing.handle_accept(user, to_follow, request)
    else:
        status_builder.create_notification(
            to_follow,
            'FOLLOW_REQUEST',
            related_user=user
        )


@app.task
def handle_unfollow(activity):
    ''' unfollow a local user '''
    obj = activity['object']
    try:
        requester = get_or_create_remote_user(obj['actor'])
        to_unfollow = models.User.objects.get(remote_id=obj['object'])
    except models.User.DoesNotExist:
        return False

    to_unfollow.followers.remove(requester)


@app.task
def handle_follow_accept(activity):
    ''' hurray, someone remote accepted a follow request '''
    # figure out who they want to follow
    requester = models.User.objects.get(remote_id=activity['object']['actor'])
    # figure out who they are
    accepter = get_or_create_remote_user(activity['actor'])

    try:
        request = models.UserFollowRequest.objects.get(
            user_subject=requester,
            user_object=accepter
        )
        request.delete()
    except models.UserFollowRequest.DoesNotExist:
        pass
    accepter.followers.add(requester)


@app.task
def handle_follow_reject(activity):
    ''' someone is rejecting a follow request '''
    requester = models.User.objects.get(remote_id=activity['object']['actor'])
    rejecter = get_or_create_remote_user(activity['actor'])

    try:
        request = models.UserFollowRequest.objects.get(
            user_subject=requester,
            user_object=rejecter
        )
        request.delete()
    except models.UserFollowRequest.DoesNotExist:
        return False


@app.task
def handle_create(activity):
    ''' someone did something, good on them '''
    user = get_or_create_remote_user(activity['actor'])

    if user.local:
        # we really oughtn't even be sending in this case
        return True

    if activity['object'].get('fedireadsType') and \
            'inReplyToBook' in activity['object']:
        if activity['object']['fedireadsType'] == 'Review':
            builder = status_builder.create_review_from_activity
        elif activity['object']['fedireadsType'] == 'Quotation':
            builder = status_builder.create_quotation_from_activity
        else:
            builder = status_builder.create_comment_from_activity

        # create the status, it'll throw a ValueError if anything is missing
        builder(user, activity['object'])
    elif activity['object'].get('inReplyTo'):
        # only create the status if it's in reply to a status we already know
        if not status_builder.get_status(activity['object']['inReplyTo']):
            return True

        status = status_builder.create_status_from_activity(
            user,
            activity['object']
        )
        if status and status.reply_parent:
            status_builder.create_notification(
                status.reply_parent.user,
                'REPLY',
                related_user=status.user,
                related_status=status,
            )
    return True


@app.task
def handle_favorite(activity):
    ''' approval of your good good post '''
    try:
        status_id = activity['object'].split('/')[-1]
        status = models.Status.objects.get(id=status_id)
        liker = get_or_create_remote_user(activity['actor'])
    except (models.Status.DoesNotExist, models.User.DoesNotExist):
        return False

    if not liker.local:
        status_builder.create_favorite_from_activity(liker, activity)

    status_builder.create_notification(
        status.user,
        'FAVORITE',
        related_user=liker,
        related_status=status,
    )


@app.task
def handle_unfavorite(activity):
    ''' approval of your good good post '''
    favorite_id = activity['object']['id']
    fav = models.Favorite.objects.filter(remote_id=favorite_id).first()
    if not fav:
        return False

    fav.delete()


@app.task
def handle_boost(activity):
    ''' someone gave us a boost! '''
    try:
        status_id = activity['object'].split('/')[-1]
        status = models.Status.objects.get(id=status_id)
        booster = get_or_create_remote_user(activity['actor'])
    except (models.Status.DoesNotExist, models.User.DoesNotExist):
        return False

    if not booster.local:
        status_builder.create_boost_from_activity(booster, activity)

    status_builder.create_notification(
        status.user,
        'BOOST',
        related_user=booster,
        related_status=status,
    )


@app.task
def handle_tag(activity):
    ''' someone is tagging a book '''
    user = get_or_create_remote_user(activity['actor'])
    if not user.local:
        book = activity['target']['id']
        status_builder.create_tag(user, book, activity['object']['name'])


@app.task
def handle_update_book(activity):
    ''' a remote instance changed a book (Document) '''
    document = activity['object']
    # check if we have their copy and care about their updates
    book = models.Book.objects.select_subclasses().filter(
        remote_id=document['url'],
        sync=True,
    ).first()
    if not book:
        return

    books_manager.update_book(book, data=document)