import datetime
import json
import logging
import os

import requests
from django.conf import settings
from django.db import transaction
from django.db.models import F, Q
from django.db.models.deletion import Collector
from django.utils import timezone
from dynamic_preferences.registries import global_preferences_registry
from requests.exceptions import RequestException

from funkwhale_api.audio import models as audio_models
from funkwhale_api.common import models as common_models
from funkwhale_api.common import preferences, session
from funkwhale_api.common import utils as common_utils
from funkwhale_api.moderation import mrf
from funkwhale_api.music import models as music_models
from funkwhale_api.taskapp import celery

from . import (
    activity,
    actors,
    exceptions,
    jsonld,
    keys,
    models,
    routes,
    serializers,
    signing,
    utils,
    webfinger,
)

logger = logging.getLogger(__name__)


@celery.app.task(name="federation.clean_music_cache")
def clean_music_cache():
    preferences = global_preferences_registry.manager()
    delay = preferences["federation__music_cache_duration"]
    if delay < 1:
        return  # cache clearing disabled
    limit = timezone.now() - datetime.timedelta(minutes=delay)

    candidates = (
        music_models.Upload.objects.filter(
            Q(audio_file__isnull=False)
            & (Q(accessed_date__lt=limit) | Q(accessed_date=None)),
            # library__actor__user=None,
        )
        .local(False)
        .exclude(audio_file="")
        .filter(Q(source__startswith="http://") | Q(source__startswith="https://"))
        .only("audio_file", "id")
        .order_by("id")
    )
    for upload in candidates:
        upload.audio_file.delete()

    # we also delete orphaned files, if any
    storage = models.LibraryTrack._meta.get_field("audio_file").storage
    files = get_files(storage, "federation_cache/tracks")
    existing = music_models.Upload.objects.filter(audio_file__in=files)
    missing = set(files) - set(existing.values_list("audio_file", flat=True))
    for m in missing:
        storage.delete(m)


def get_files(storage, *parts):
    """
    This is a recursive function that return all files available
    in a given directory using django's storage.
    """
    if not parts:
        raise ValueError("Missing path")
    try:
        dirs, files = storage.listdir(os.path.join(*parts))
    except FileNotFoundError:
        return []
    for dir in dirs:
        files += get_files(storage, *(list(parts) + [dir]))
    return [os.path.join(parts[-1], path) for path in files]


@celery.app.task(name="federation.dispatch_inbox")
@celery.require_instance(models.Activity.objects.select_related(), "activity")
def dispatch_inbox(activity, call_handlers=True):
    """
    Given an activity instance, triggers our internal delivery logic (follow
    creation, etc.)
    """

    routes.inbox.dispatch(
        activity.payload,
        context={
            "activity": activity,
            "actor": activity.actor,
            "inbox_items": activity.inbox_items.filter(is_read=False).order_by("id"),
        },
        call_handlers=call_handlers,
    )


@celery.app.task(name="federation.dispatch_outbox")
@celery.require_instance(models.Activity.objects.select_related(), "activity")
def dispatch_outbox(activity):
    """
    Deliver a local activity to its recipients, both locally and remotely
    """
    inbox_items = activity.inbox_items.filter(is_read=False).select_related()

    if inbox_items.exists():
        call_handlers = activity.type in ["Follow"]
        dispatch_inbox.delay(activity_id=activity.pk, call_handlers=call_handlers)

    if not preferences.get("federation__enabled"):
        # federation is disabled, we only deliver to local recipients
        return

    deliveries = activity.deliveries.filter(is_delivered=False)

    for id in deliveries.values_list("pk", flat=True):
        deliver_to_remote.delay(delivery_id=id)


@celery.app.task(
    name="federation.deliver_to_remote_inbox",
    autoretry_for=[RequestException],
    retry_backoff=30,
    max_retries=5,
)
@celery.require_instance(
    models.Delivery.objects.filter(is_delivered=False).select_related(
        "activity__actor"
    ),
    "delivery",
)
def deliver_to_remote(delivery):
    if not preferences.get("federation__enabled"):
        # federation is disabled, we only deliver to local recipients
        return

    actor = delivery.activity.actor
    logger.info("Preparing activity delivery to %s", delivery.inbox_url)
    auth = signing.get_auth(actor.private_key, actor.private_key_id)
    try:
        response = session.get_session().post(
            auth=auth,
            json=delivery.activity.payload,
            url=delivery.inbox_url,
            headers={"Content-Type": "application/activity+json"},
        )
        logger.debug("Remote answered with %s", response.status_code)
        response.raise_for_status()
    except Exception:
        delivery.last_attempt_date = timezone.now()
        delivery.attempts = F("attempts") + 1
        delivery.save(update_fields=["last_attempt_date", "attempts"])
        raise
    else:
        delivery.last_attempt_date = timezone.now()
        delivery.attempts = F("attempts") + 1
        delivery.is_delivered = True
        delivery.save(update_fields=["last_attempt_date", "attempts", "is_delivered"])


def fetch_nodeinfo(domain_name):
    s = session.get_session()
    wellknown_url = f"https://{domain_name}/.well-known/nodeinfo"
    response = s.get(url=wellknown_url)
    response.raise_for_status()
    serializer = serializers.NodeInfoSerializer(data=response.json())
    serializer.is_valid(raise_exception=True)
    nodeinfo_url = None
    for link in serializer.validated_data["links"]:
        if link["rel"] == "http://nodeinfo.diaspora.software/ns/schema/2.0":
            nodeinfo_url = link["href"]
            break

    response = s.get(url=nodeinfo_url)
    response.raise_for_status()
    return response.json()


@celery.app.task(name="federation.update_domain_nodeinfo")
@celery.require_instance(
    models.Domain.objects.external(), "domain", id_kwarg_name="domain_name"
)
def update_domain_nodeinfo(domain):
    now = timezone.now()
    try:
        nodeinfo = {"status": "ok", "payload": fetch_nodeinfo(domain.name)}
    except (
        requests.RequestException,
        serializers.serializers.ValidationError,
        ValueError,
    ) as e:
        nodeinfo = {"status": "error", "error": str(e)}

    service_actor_id = common_utils.recursive_getattr(
        nodeinfo, "payload.metadata.actorId", permissive=True
    )
    try:
        domain.service_actor = (
            utils.retrieve_ap_object(
                service_actor_id,
                actor=None,
                queryset=models.Actor,
                serializer_class=serializers.ActorSerializer,
            )
            if service_actor_id
            else None
        )
    except (
        serializers.serializers.ValidationError,
        RequestException,
        exceptions.BlockedActorOrDomain,
    ) as e:
        logger.warning(
            "Cannot fetch system actor for domain %s: %s", domain.name, str(e)
        )
    domain.nodeinfo_fetch_date = now
    domain.nodeinfo = nodeinfo
    domain.save(update_fields=["nodeinfo", "nodeinfo_fetch_date", "service_actor"])


@celery.app.task(name="federation.refresh_nodeinfo_known_nodes")
def refresh_nodeinfo_known_nodes():
    """
    Trigger a node info refresh on all nodes that weren't refreshed since
    settings.NODEINFO_REFRESH_DELAY
    """
    limit = timezone.now() - datetime.timedelta(seconds=settings.NODEINFO_REFRESH_DELAY)
    candidates = models.Domain.objects.external().exclude(
        nodeinfo_fetch_date__gte=limit
    )
    names = candidates.values_list("name", flat=True)
    logger.info("Launching periodic nodeinfo refresh on %s domains", len(names))
    for domain_name in names:
        update_domain_nodeinfo.delay(domain_name=domain_name)


def delete_qs(qs):
    label = qs.model._meta.label
    result = qs.delete()
    related = sum(result[1].values())

    logger.info(
        "Purged %s %s objects (and %s related entities)", result[0], label, related
    )


def handle_purge_actors(ids, only=[]):
    """
    Empty only means we purge everything
    Otherwise, we purge only the requested bits: media
    """
    # purge follows (received emitted)
    if not only:
        delete_qs(models.LibraryFollow.objects.filter(target__actor_id__in=ids))
        delete_qs(models.Follow.objects.filter(actor_id__in=ids))

    # purge audio content
    if not only or "media" in only:
        delete_qs(common_models.Attachment.objects.filter(actor__in=ids))
        delete_qs(models.LibraryFollow.objects.filter(actor_id__in=ids))
        delete_qs(models.Follow.objects.filter(target_id__in=ids))
        delete_qs(audio_models.Channel.objects.filter(attributed_to__in=ids))
        delete_qs(audio_models.Channel.objects.filter(actor__in=ids))
        delete_qs(music_models.Upload.objects.filter(library__actor_id__in=ids))
        delete_qs(music_models.Library.objects.filter(actor_id__in=ids))

    # purge remaining activities / deliveries
    if not only:
        delete_qs(models.InboxItem.objects.filter(actor_id__in=ids))
        delete_qs(models.Activity.objects.filter(actor_id__in=ids))


@celery.app.task(name="federation.purge_actors")
def purge_actors(ids=[], domains=[], only=[]):
    actors = models.Actor.objects.filter(
        Q(id__in=ids) | Q(domain_id__in=domains)
    ).order_by("id")
    found_ids = list(actors.values_list("id", flat=True))
    logger.info("Starting purging %s accounts", len(found_ids))
    handle_purge_actors(ids=found_ids, only=only)


@celery.app.task(name="federation.rotate_actor_key")
@celery.require_instance(models.Actor.objects.local(), "actor")
def rotate_actor_key(actor):
    pair = keys.get_key_pair()
    actor.private_key = pair[0].decode()
    actor.public_key = pair[1].decode()
    actor.save(update_fields=["private_key", "public_key"])


@celery.app.task(name="federation.fetch")
@transaction.atomic
@celery.require_instance(
    models.Fetch.objects.filter(status="pending").select_related("actor"),
    "fetch_obj",
    "fetch_id",
)
def fetch(fetch_obj):
    def error(code, **kwargs):
        fetch_obj.status = "errored"
        fetch_obj.fetch_date = timezone.now()
        fetch_obj.detail = {"error_code": code}
        fetch_obj.detail.update(kwargs)
        fetch_obj.save(update_fields=["fetch_date", "status", "detail"])

    url = fetch_obj.url
    mrf_check_url = url
    if not mrf_check_url.startswith("webfinger://"):
        payload, updated = mrf.inbox.apply({"id": mrf_check_url})
        if not payload:
            return error("blocked", message="Blocked by MRF")

    actor = fetch_obj.actor
    if settings.FEDERATION_AUTHENTIFY_FETCHES:
        auth = signing.get_auth(actor.private_key, actor.private_key_id)
    else:
        auth = None
    try:
        if url.startswith("webfinger://"):
            # we first grab the corresponding webfinger representation
            # to get the ActivityPub actor ID
            webfinger_data = webfinger.get_resource(
                "acct:" + url.replace("webfinger://", "")
            )
            url = webfinger.get_ap_url(webfinger_data["links"])
            if not url:
                return error("webfinger", message="Invalid or missing webfinger data")
            payload, updated = mrf.inbox.apply({"id": url})
            if not payload:
                return error("blocked", message="Blocked by MRF")
        response = session.get_session().get(
            auth=auth,
            url=url,
            headers={"Accept": "application/activity+json"},
        )
        logger.debug("Remote answered with %s: %s", response.status_code, response.text)
        response.raise_for_status()
    except requests.exceptions.HTTPError as e:
        return error(
            "http",
            status_code=e.response.status_code if e.response else None,
            message=e.response.text,
        )
    except requests.exceptions.Timeout:
        return error("timeout")
    except requests.exceptions.ConnectionError as e:
        return error("connection", message=str(e))
    except requests.RequestException as e:
        return error("request", message=str(e))
    except Exception as e:
        return error("unhandled", message=str(e))

    try:
        payload = response.json()
    except json.decoder.JSONDecodeError:
        # we attempt to extract a <link rel=alternate> that points
        # to an activity pub resource, if possible, and retry with this URL
        alternate_url = utils.find_alternate(response.text)
        if alternate_url:
            fetch_obj.url = alternate_url
            fetch_obj.save(update_fields=["url"])
            return fetch(fetch_id=fetch_obj.pk)
        return error("invalid_json")

    payload, updated = mrf.inbox.apply(payload)
    if not payload:
        return error("blocked", message="Blocked by MRF")

    try:
        doc = jsonld.expand(payload)
    except ValueError:
        return error("invalid_jsonld")

    try:
        type = doc.get("@type", [])[0]
    except IndexError:
        return error("missing_jsonld_type")
    try:
        serializer_classes = fetch_obj.serializers[type]
        model = serializer_classes[0].Meta.model
    except (KeyError, AttributeError):
        fetch_obj.status = "skipped"
        fetch_obj.fetch_date = timezone.now()
        fetch_obj.detail = {"reason": "unhandled_type", "type": type}
        return fetch_obj.save(update_fields=["fetch_date", "status", "detail"])
    try:
        id = doc.get("@id")
    except IndexError:
        existing = None
    else:
        existing = model.objects.filter(fid=id).first()

    serializer = None
    for serializer_class in serializer_classes:
        serializer = serializer_class(
            existing, data=payload, context={"fetch_actor": actor}
        )
        if not serializer.is_valid():
            continue
        else:
            break
    if serializer.errors:
        return error("validation", validation_errors=serializer.errors)
    try:
        obj = serializer.save()
    except Exception as e:
        error("save", message=str(e))
        raise

    # special case for channels
    # when obj is an actor, we check if the actor has a channel associated with it
    # if it is the case, we consider the fetch obj to be a channel instead
    # and also trigger a fetch on the channel outbox
    if isinstance(obj, models.Actor) and obj.get_channel():
        obj = obj.get_channel()
        if obj.actor.outbox_url:
            try:
                # first page fetch is synchronous, so that at least some data is available
                # in the UI after subscription
                result = fetch_collection(
                    obj.actor.outbox_url,
                    channel_id=obj.pk,
                    max_pages=1,
                )
            except Exception:
                logger.exception(
                    "Error while fetching actor outbox: %s", obj.actor.outbox_url
                )
            else:
                if result.get("next_page"):
                    # additional pages are fetched in the background
                    result = fetch_collection.delay(
                        result["next_page"],
                        channel_id=obj.pk,
                        max_pages=settings.FEDERATION_COLLECTION_MAX_PAGES - 1,
                        is_page=True,
                    )

    fetch_obj.object = obj
    fetch_obj.status = "finished"
    fetch_obj.fetch_date = timezone.now()
    return fetch_obj.save(
        update_fields=["fetch_date", "status", "object_id", "object_content_type"]
    )


class PreserveSomeDataCollector(Collector):
    """
    We need to delete everything related to an actor. Well… Almost everything.
    But definitely not the Delete Activity we send to announce the actor is deleted.
    """

    def __init__(self, *args, **kwargs):
        self.creation_date = timezone.now()
        super().__init__(*args, **kwargs)

    def related_objects(self, related, *args, **kwargs):
        qs = super().related_objects(related, *args, **kwargs)
        # We can only exclude the actions if these fields are available, most likely its a
        # model.Activity than
        if hasattr(related, "type") and hasattr(related, "creation_date"):
            # exclude the delete activity can be broadcasted properly
            qs = qs.exclude(type="Delete", creation_date__gte=self.creation_date)

        return qs


@celery.app.task(name="federation.remove_actor")
@transaction.atomic
@celery.require_instance(
    models.Actor.objects.all(),
    "actor",
)
def remove_actor(actor):
    # Then we broadcast the info over federation. We do this *before* deleting objects
    # associated with the actor, otherwise follows are removed and we don't know where
    # to broadcast
    logger.info("Broadcasting deletion to federation…")
    collector = PreserveSomeDataCollector(using="default")
    routes.outbox.dispatch(
        {"type": "Delete", "object": {"type": actor.type}}, context={"actor": actor}
    )

    # then we delete any object associated with the actor object, but *not* the actor
    # itself. We keep it for auditability and sending the Delete ActivityPub message
    logger.info(
        "Prepare deletion of objects associated with account %s…",
        actor.preferred_username,
    )
    collector.collect([actor])
    for model, instances in collector.data.items():
        if issubclass(model, actor.__class__):
            # we skip deletion of the actor itself
            continue

        to_delete = model.objects.filter(pk__in=[instance.pk for instance in instances])
        logger.info(
            "Deleting %s objects associated with account %s…",
            len(instances),
            actor.preferred_username,
        )
        to_delete.delete()

    # Finally, we update the actor itself and mark it as removed
    logger.info("Marking actor as Tombsone…")
    actor.type = "Tombstone"
    actor.name = None
    actor.summary = None
    actor.save(update_fields=["type", "name", "summary"])


COLLECTION_ACTIVITY_SERIALIZERS = [
    (
        {"type": "Create", "object.type": "Audio"},
        serializers.ChannelCreateUploadSerializer,
    )
]


def match_serializer(payload, conf):
    return [
        serializer_class
        for route, serializer_class in conf
        if activity.match_route(route, payload)
    ]


@celery.app.task(name="federation.fetch_collection")
@celery.require_instance(
    audio_models.Channel.objects.all(),
    "channel",
    allow_null=True,
)
def fetch_collection(url, max_pages, channel, is_page=False):
    actor = actors.get_service_actor()
    results = {
        "items": [],
        "skipped": 0,
        "errored": 0,
        "seen": 0,
        "total": 0,
    }
    if is_page:
        # starting immediately from a page, no need to fetch the wrapping collection
        logger.debug("Fetch collection page immediately at %s", url)
        results["next_page"] = url
    else:
        logger.debug("Fetching collection object at %s", url)
        collection = utils.retrieve_ap_object(
            url,
            actor=actor,
            serializer_class=serializers.PaginatedCollectionSerializer,
        )
        results["next_page"] = collection["first"]
        results["total"] = collection.get("totalItems")

    seen_pages = 0
    context = {}
    if channel:
        context["channel"] = channel

    for i in range(max_pages):
        page_url = results["next_page"]
        logger.debug("Handling page %s on max %s, at %s", i + 1, max_pages, page_url)
        page = utils.retrieve_ap_object(
            page_url,
            actor=actor,
            serializer_class=None,
        )
        try:
            items = page["orderedItems"]
        except KeyError:
            try:
                items = page["items"]
            except KeyError:
                logger.error("Invalid collection page at %s", page_url)
                break

        for item in items:
            results["seen"] += 1

            matching_serializer = match_serializer(
                item, COLLECTION_ACTIVITY_SERIALIZERS
            )
            if not matching_serializer:
                results["skipped"] += 1
                logger.debug("Skipping unhandled activity %s", item.get("type"))
                continue

            s = matching_serializer[0](data=item, context=context)
            if not s.is_valid():
                logger.warn("Skipping invalid activity: %s", s.errors)
                results["errored"] += 1
                continue

            results["items"].append(s.save())

        seen_pages += 1
        results["next_page"] = page.get("next", None) or None
        if not results["next_page"]:
            logger.debug("No more pages to fetch")
            break

    logger.info(
        "Finished fetch of collection pages at %s. Results:\n"
        "  Total in collection: %s\n"
        "  Seen: %s\n"
        "  Handled: %s\n"
        "  Skipped: %s\n"
        "  Errored: %s",
        url,
        results.get("total"),
        results["seen"],
        len(results["items"]),
        results["skipped"],
        results["errored"],
    )
    return results


@celery.app.task(name="federation.check_all_remote_instance_availability")
def check_all_remote_instance_availability():
    domains = models.Domain.objects.all().prefetch_related()
    for domain in domains:
        if domain.name == settings.FUNKWHALE_HOSTNAME:
            # No need to check the instance itself: Its always reachable
            domain.reachable = True
            domain.last_successful_contact = timezone.now()
        else:
            check_single_remote_instance_availability(domain)


@celery.app.task(name="federation.check_single_remote_instance_availability")
def check_single_remote_instance_availability(domain):
    try:
        nodeinfo = fetch_nodeinfo(domain.name)
    except Exception as e:
        logger.info(
            f"Domain {domain.name} could not be reached because of the following error : {e}. \
            Setting domain as unreachable."
        )
        domain.reachable = False
        domain.save()
        return domain.reachable

    if "version" in nodeinfo.keys():
        domain.reachable = True
        domain.last_successful_contact = timezone.now()
        domain.save()
        return domain.reachable
    else:
        logger.info(
            f"Domain {domain.name} is not reachable at the moment. Setting domain as unreachable."
        )
        domain.reachable = False
        domain.save()
        return domain.reachable