#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2020 The Matrix.org Foundation C.I.C.
# Copyright 2014-2016 OpenMarket Ltd
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#

import abc
import collections.abc
from typing import (
    TYPE_CHECKING,
    Any,
    Dict,
    Generic,
    Iterable,
    List,
    Literal,
    Optional,
    Tuple,
    Type,
    TypeVar,
    Union,
    overload,
)

import attr
from unpaddedbase64 import encode_base64

from synapse.api.constants import EventTypes, RelationTypes
from synapse.api.room_versions import EventFormatVersions, RoomVersion, RoomVersions
from synapse.synapse_rust.events import EventInternalMetadata
from synapse.types import JsonDict, StrCollection
from synapse.util.caches import intern_dict
from synapse.util.frozenutils import freeze

if TYPE_CHECKING:
    from synapse.events.builder import EventBuilder


USE_FROZEN_DICTS = False
"""
Whether we should use frozen_dict in FrozenEvent. Using frozen_dicts prevents
bugs where we accidentally share e.g. signature dicts. However, converting a
dict to frozen_dicts is expensive.

NOTE: This is overridden by the configuration by the Synapse worker apps, but
for the sake of tests, it is set here because it cannot be configured on the
homeserver object itself.
"""

T = TypeVar("T")


# DictProperty (and DefaultDictProperty) require the classes they're used with to
# have a _dict property to pull properties from.
#
# TODO _DictPropertyInstance should not include EventBuilder but due to
# https://github.com/python/mypy/issues/5570 it thinks the DictProperty and
# DefaultDictProperty get applied to EventBuilder when it is in a Union with
# EventBase. This is the least invasive hack to get mypy to comply.
#
# Note that DictProperty/DefaultDictProperty cannot actually be used with
# EventBuilder as it lacks a _dict property.
_DictPropertyInstance = Union["EventBase", "EventBuilder"]


class DictProperty(Generic[T]):
    """An object property which delegates to the `_dict` within its parent object."""

    __slots__ = ["key"]

    def __init__(self, key: str):
        self.key = key

    @overload
    def __get__(
        self,
        instance: Literal[None],
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> "DictProperty": ...

    @overload
    def __get__(
        self,
        instance: _DictPropertyInstance,
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> T: ...

    def __get__(
        self,
        instance: Optional[_DictPropertyInstance],
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> Union[T, "DictProperty"]:
        # if the property is accessed as a class property rather than an instance
        # property, return the property itself rather than the value
        if instance is None:
            return self
        try:
            assert isinstance(instance, EventBase)
            return instance._dict[self.key]
        except KeyError as e1:
            # We want this to look like a regular attribute error (mostly so that
            # hasattr() works correctly), so we convert the KeyError into an
            # AttributeError.
            #
            # To exclude the KeyError from the traceback, we explicitly
            # 'raise from e1.__context__' (which is better than 'raise from None',
            # because that would omit any *earlier* exceptions).
            #
            raise AttributeError(
                "'%s' has no '%s' property" % (type(instance), self.key)
            ) from e1.__context__

    def __set__(self, instance: _DictPropertyInstance, v: T) -> None:
        assert isinstance(instance, EventBase)
        instance._dict[self.key] = v

    def __delete__(self, instance: _DictPropertyInstance) -> None:
        assert isinstance(instance, EventBase)
        try:
            del instance._dict[self.key]
        except KeyError as e1:
            raise AttributeError(
                "'%s' has no '%s' property" % (type(instance), self.key)
            ) from e1.__context__


class DefaultDictProperty(DictProperty, Generic[T]):
    """An extension of DictProperty which provides a default if the property is
    not present in the parent's _dict.

    Note that this means that hasattr() on the property always returns True.
    """

    __slots__ = ["default"]

    def __init__(self, key: str, default: T):
        super().__init__(key)
        self.default = default

    @overload
    def __get__(
        self,
        instance: Literal[None],
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> "DefaultDictProperty": ...

    @overload
    def __get__(
        self,
        instance: _DictPropertyInstance,
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> T: ...

    def __get__(
        self,
        instance: Optional[_DictPropertyInstance],
        owner: Optional[Type[_DictPropertyInstance]] = None,
    ) -> Union[T, "DefaultDictProperty"]:
        if instance is None:
            return self
        assert isinstance(instance, EventBase)
        return instance._dict.get(self.key, self.default)


class EventBase(metaclass=abc.ABCMeta):
    @property
    @abc.abstractmethod
    def format_version(self) -> int:
        """The EventFormatVersion implemented by this event"""
        ...

    def __init__(
        self,
        event_dict: JsonDict,
        room_version: RoomVersion,
        signatures: Dict[str, Dict[str, str]],
        unsigned: JsonDict,
        internal_metadata_dict: JsonDict,
        rejected_reason: Optional[str],
    ):
        assert room_version.event_format == self.format_version

        self.room_version = room_version
        self.signatures = signatures
        self.unsigned = unsigned
        self.rejected_reason = rejected_reason

        self._dict = event_dict

        self.internal_metadata = EventInternalMetadata(internal_metadata_dict)

    depth: DictProperty[int] = DictProperty("depth")
    content: DictProperty[JsonDict] = DictProperty("content")
    hashes: DictProperty[Dict[str, str]] = DictProperty("hashes")
    origin: DictProperty[str] = DictProperty("origin")
    origin_server_ts: DictProperty[int] = DictProperty("origin_server_ts")
    room_id: DictProperty[str] = DictProperty("room_id")
    sender: DictProperty[str] = DictProperty("sender")
    # TODO state_key should be Optional[str]. This is generally asserted in Synapse
    # by calling is_state() first (which ensures it is not None), but it is hard (not possible?)
    # to properly annotate that calling is_state() asserts that state_key exists
    # and is non-None. It would be better to replace such direct references with
    # get_state_key() (and a check for None).
    state_key: DictProperty[str] = DictProperty("state_key")
    type: DictProperty[str] = DictProperty("type")
    user_id: DictProperty[str] = DictProperty("sender")

    @property
    def event_id(self) -> str:
        raise NotImplementedError()

    @property
    def membership(self) -> str:
        return self.content["membership"]

    @property
    def redacts(self) -> Optional[str]:
        """MSC2176 moved the redacts field into the content."""
        if self.room_version.updated_redaction_rules:
            return self.content.get("redacts")
        return self.get("redacts")

    def is_state(self) -> bool:
        return self.get_state_key() is not None

    def get_state_key(self) -> Optional[str]:
        """Get the state key of this event, or None if it's not a state event"""
        return self._dict.get("state_key")

    def get_dict(self) -> JsonDict:
        d = dict(self._dict)
        d.update({"signatures": self.signatures, "unsigned": dict(self.unsigned)})

        return d

    def get(self, key: str, default: Optional[Any] = None) -> Any:
        return self._dict.get(key, default)

    def get_internal_metadata_dict(self) -> JsonDict:
        return self.internal_metadata.get_dict()

    def get_pdu_json(self, time_now: Optional[int] = None) -> JsonDict:
        pdu_json = self.get_dict()

        if time_now is not None and "age_ts" in pdu_json["unsigned"]:
            age = time_now - pdu_json["unsigned"]["age_ts"]
            pdu_json.setdefault("unsigned", {})["age"] = int(age)
            del pdu_json["unsigned"]["age_ts"]

        # This may be a frozen event
        pdu_json["unsigned"].pop("redacted_because", None)

        return pdu_json

    def get_templated_pdu_json(self) -> JsonDict:
        """
        Return a JSON object suitable for a templated event, as used in the
        make_{join,leave,knock} workflow.
        """
        # By using _dict directly we don't pull in signatures/unsigned.
        template_json = dict(self._dict)
        # The hashes (similar to the signature) need to be recalculated by the
        # joining/leaving/knocking server after (potentially) modifying the
        # event.
        template_json.pop("hashes")

        return template_json

    def __getitem__(self, field: str) -> Optional[Any]:
        return self._dict[field]

    def __contains__(self, field: str) -> bool:
        return field in self._dict

    def items(self) -> List[Tuple[str, Optional[Any]]]:
        return list(self._dict.items())

    def keys(self) -> Iterable[str]:
        return self._dict.keys()

    def prev_event_ids(self) -> List[str]:
        """Returns the list of prev event IDs. The order matches the order
        specified in the event, though there is no meaning to it.

        Returns:
            The list of event IDs of this event's prev_events
        """
        return [e for e, _ in self._dict["prev_events"]]

    def auth_event_ids(self) -> StrCollection:
        """Returns the list of auth event IDs. The order matches the order
        specified in the event, though there is no meaning to it.

        Returns:
            The list of event IDs of this event's auth_events
        """
        return [e for e, _ in self._dict["auth_events"]]

    def freeze(self) -> None:
        """'Freeze' the event dict, so it cannot be modified by accident"""

        # this will be a no-op if the event dict is already frozen.
        self._dict = freeze(self._dict)

    def __str__(self) -> str:
        return self.__repr__()

    def __repr__(self) -> str:
        rejection = f"REJECTED={self.rejected_reason}, " if self.rejected_reason else ""

        conditional_membership_string = ""
        if self.get("type") == EventTypes.Member:
            conditional_membership_string = f"membership={self.membership}, "

        return (
            f"<{self.__class__.__name__} "
            f"{rejection}"
            f"event_id={self.event_id}, "
            f"type={self.get('type')}, "
            f"state_key={self.get('state_key')}, "
            f"{conditional_membership_string}"
            f"outlier={self.internal_metadata.is_outlier()}"
            ">"
        )


class FrozenEvent(EventBase):
    format_version = EventFormatVersions.ROOM_V1_V2  # All events of this type are V1

    def __init__(
        self,
        event_dict: JsonDict,
        room_version: RoomVersion,
        internal_metadata_dict: Optional[JsonDict] = None,
        rejected_reason: Optional[str] = None,
    ):
        internal_metadata_dict = internal_metadata_dict or {}

        event_dict = dict(event_dict)

        # Signatures is a dict of dicts, and this is faster than doing a
        # copy.deepcopy
        signatures = {
            name: dict(sigs.items())
            for name, sigs in event_dict.pop("signatures", {}).items()
        }

        unsigned = dict(event_dict.pop("unsigned", {}))

        # We intern these strings because they turn up a lot (especially when
        # caching).
        event_dict = intern_dict(event_dict)

        if USE_FROZEN_DICTS:
            frozen_dict = freeze(event_dict)
        else:
            frozen_dict = event_dict

        self._event_id = event_dict["event_id"]

        super().__init__(
            frozen_dict,
            room_version=room_version,
            signatures=signatures,
            unsigned=unsigned,
            internal_metadata_dict=internal_metadata_dict,
            rejected_reason=rejected_reason,
        )

    @property
    def event_id(self) -> str:
        return self._event_id


class FrozenEventV2(EventBase):
    format_version = EventFormatVersions.ROOM_V3  # All events of this type are V2

    def __init__(
        self,
        event_dict: JsonDict,
        room_version: RoomVersion,
        internal_metadata_dict: Optional[JsonDict] = None,
        rejected_reason: Optional[str] = None,
    ):
        internal_metadata_dict = internal_metadata_dict or {}

        event_dict = dict(event_dict)

        # Signatures is a dict of dicts, and this is faster than doing a
        # copy.deepcopy
        signatures = {
            name: dict(sigs.items())
            for name, sigs in event_dict.pop("signatures", {}).items()
        }

        assert "event_id" not in event_dict

        unsigned = dict(event_dict.pop("unsigned", {}))

        # We intern these strings because they turn up a lot (especially when
        # caching).
        event_dict = intern_dict(event_dict)

        if USE_FROZEN_DICTS:
            frozen_dict = freeze(event_dict)
        else:
            frozen_dict = event_dict

        self._event_id: Optional[str] = None

        super().__init__(
            frozen_dict,
            room_version=room_version,
            signatures=signatures,
            unsigned=unsigned,
            internal_metadata_dict=internal_metadata_dict,
            rejected_reason=rejected_reason,
        )

    @property
    def event_id(self) -> str:
        # We have to import this here as otherwise we get an import loop which
        # is hard to break.
        from synapse.crypto.event_signing import compute_event_reference_hash

        if self._event_id:
            return self._event_id
        self._event_id = "$" + encode_base64(compute_event_reference_hash(self)[1])
        return self._event_id

    def prev_event_ids(self) -> List[str]:
        """Returns the list of prev event IDs. The order matches the order
        specified in the event, though there is no meaning to it.

        Returns:
            The list of event IDs of this event's prev_events
        """
        return self._dict["prev_events"]

    def auth_event_ids(self) -> StrCollection:
        """Returns the list of auth event IDs. The order matches the order
        specified in the event, though there is no meaning to it.

        Returns:
            The list of event IDs of this event's auth_events
        """
        return self._dict["auth_events"]


class FrozenEventV3(FrozenEventV2):
    """FrozenEventV3, which differs from FrozenEventV2 only in the event_id format"""

    format_version = EventFormatVersions.ROOM_V4_PLUS  # All events of this type are V3

    @property
    def event_id(self) -> str:
        # We have to import this here as otherwise we get an import loop which
        # is hard to break.
        from synapse.crypto.event_signing import compute_event_reference_hash

        if self._event_id:
            return self._event_id
        self._event_id = "$" + encode_base64(
            compute_event_reference_hash(self)[1], urlsafe=True
        )
        return self._event_id


def _event_type_from_format_version(
    format_version: int,
) -> Type[Union[FrozenEvent, FrozenEventV2, FrozenEventV3]]:
    """Returns the python type to use to construct an Event object for the
    given event format version.

    Args:
        format_version: The event format version

    Returns:
        A type that can be initialized as per the initializer of `FrozenEvent`
    """

    if format_version == EventFormatVersions.ROOM_V1_V2:
        return FrozenEvent
    elif format_version == EventFormatVersions.ROOM_V3:
        return FrozenEventV2
    elif format_version == EventFormatVersions.ROOM_V4_PLUS:
        return FrozenEventV3
    else:
        raise Exception("No event format %r" % (format_version,))


def make_event_from_dict(
    event_dict: JsonDict,
    room_version: RoomVersion = RoomVersions.V1,
    internal_metadata_dict: Optional[JsonDict] = None,
    rejected_reason: Optional[str] = None,
) -> EventBase:
    """Construct an EventBase from the given event dict"""
    event_type = _event_type_from_format_version(room_version.event_format)
    return event_type(
        event_dict, room_version, internal_metadata_dict or {}, rejected_reason
    )


@attr.s(slots=True, frozen=True, auto_attribs=True)
class _EventRelation:
    # The target event of the relation.
    parent_id: str
    # The relation type.
    rel_type: str
    # The aggregation key. Will be None if the rel_type is not m.annotation or is
    # not a string.
    aggregation_key: Optional[str]


def relation_from_event(event: EventBase) -> Optional[_EventRelation]:
    """
    Attempt to parse relation information an event.

    Returns:
        The event relation information, if it is valid. None, otherwise.
    """
    relation = event.content.get("m.relates_to")
    if not relation or not isinstance(relation, collections.abc.Mapping):
        # No relation information.
        return None

    # Relations must have a type and parent event ID.
    rel_type = relation.get("rel_type")
    if not isinstance(rel_type, str):
        return None

    parent_id = relation.get("event_id")
    if not isinstance(parent_id, str):
        return None

    # Annotations have a key field.
    aggregation_key = None
    if rel_type == RelationTypes.ANNOTATION:
        aggregation_key = relation.get("key")
        if not isinstance(aggregation_key, str):
            aggregation_key = None

    return _EventRelation(parent_id, rel_type, aggregation_key)


@attr.s(slots=True, frozen=True, auto_attribs=True)
class StrippedStateEvent:
    """
    A stripped down state event. Usually used for remote invite/knocks so the user can
    make an informed decision on whether they want to join.

    Attributes:
        type: Event `type`
        state_key: Event `state_key`
        sender: Event `sender`
        content: Event `content`
    """

    type: str
    state_key: str
    sender: str
    content: Dict[str, Any]
