from typing import Iterable, List, Optional, Sequence, Union, cast

from django.utils.translation import gettext as _

from zerver.lib.exceptions import JsonableError
from zerver.lib.string_validation import check_stream_topic
from zerver.models import (
    Realm,
    Stream,
    UserProfile,
    get_user_by_id_in_realm_including_cross_realm,
    get_user_including_cross_realm,
)


def get_user_profiles(emails: Iterable[str], realm: Realm) -> List[UserProfile]:
    user_profiles: List[UserProfile] = []
    for email in emails:
        try:
            user_profile = get_user_including_cross_realm(email, realm)
        except UserProfile.DoesNotExist:
            raise JsonableError(_("Invalid email '{}'").format(email))
        user_profiles.append(user_profile)
    return user_profiles


def get_user_profiles_by_ids(user_ids: Iterable[int], realm: Realm) -> List[UserProfile]:
    user_profiles: List[UserProfile] = []
    for user_id in user_ids:
        try:
            user_profile = get_user_by_id_in_realm_including_cross_realm(user_id, realm)
        except UserProfile.DoesNotExist:
            raise JsonableError(_("Invalid user ID {}").format(user_id))
        user_profiles.append(user_profile)
    return user_profiles


class Addressee:
    # This is really just a holder for vars that tended to be passed
    # around in a non-type-safe way before this class was introduced.
    #
    # It also avoids some nonsense where you have to think about whether
    # topic should be None or '' for a PM, or you have to make an array
    # of one stream.
    #
    # Eventually we can use this to cache Stream and UserProfile objects
    # in memory.
    #
    # This should be treated as an immutable class.
    def __init__(
        self,
        msg_type: str,
        user_profiles: Optional[Sequence[UserProfile]] = None,
        stream: Optional[Stream] = None,
        stream_name: Optional[str] = None,
        stream_id: Optional[int] = None,
        topic: Optional[str] = None,
    ) -> None:
        assert msg_type in ["stream", "private"]
        if msg_type == "stream" and topic is None:
            raise JsonableError(_("Missing topic"))
        self._msg_type = msg_type
        self._user_profiles = user_profiles
        self._stream = stream
        self._stream_name = stream_name
        self._stream_id = stream_id
        self._topic = topic

    def is_stream(self) -> bool:
        return self._msg_type == "stream"

    def is_private(self) -> bool:
        return self._msg_type == "private"

    def user_profiles(self) -> Sequence[UserProfile]:
        assert self.is_private()
        assert self._user_profiles is not None
        return self._user_profiles

    def stream(self) -> Optional[Stream]:
        assert self.is_stream()
        return self._stream

    def stream_name(self) -> Optional[str]:
        assert self.is_stream()
        return self._stream_name

    def stream_id(self) -> Optional[int]:
        assert self.is_stream()
        return self._stream_id

    def topic(self) -> str:
        assert self.is_stream()
        assert self._topic is not None
        return self._topic

    @staticmethod
    def legacy_build(
        sender: UserProfile,
        message_type_name: str,
        message_to: Union[Sequence[int], Sequence[str]],
        topic_name: Optional[str],
        realm: Optional[Realm] = None,
    ) -> "Addressee":

        # For legacy reason message_to used to be either a list of
        # emails or a list of streams.  We haven't fixed all of our
        # callers yet.
        if realm is None:
            realm = sender.realm

        if message_type_name == "stream":
            if len(message_to) > 1:
                raise JsonableError(_("Cannot send to multiple streams"))

            if message_to:
                stream_name_or_id = message_to[0]
            else:
                # This is a hack to deal with the fact that we still support
                # default streams (and the None will be converted later in the
                # call path).
                if sender.default_sending_stream:
                    # Use the user's default stream
                    stream_name_or_id = sender.default_sending_stream.id
                else:
                    raise JsonableError(_("Missing stream"))

            if topic_name is None:
                raise JsonableError(_("Missing topic"))

            if isinstance(stream_name_or_id, int):
                return Addressee.for_stream_id(stream_name_or_id, topic_name)

            return Addressee.for_stream_name(stream_name_or_id, topic_name)
        elif message_type_name == "private":
            if not message_to:
                raise JsonableError(_("Message must have recipients"))

            if isinstance(message_to[0], str):
                emails = cast(Sequence[str], message_to)
                return Addressee.for_private(emails, realm)
            elif isinstance(message_to[0], int):
                user_ids = cast(Sequence[int], message_to)
                return Addressee.for_user_ids(user_ids=user_ids, realm=realm)
        else:
            raise JsonableError(_("Invalid message type"))

    @staticmethod
    def for_stream(stream: Stream, topic: str) -> "Addressee":
        topic = topic.strip()
        check_stream_topic(topic)
        return Addressee(
            msg_type="stream",
            stream=stream,
            topic=topic,
        )

    @staticmethod
    def for_stream_name(stream_name: str, topic: str) -> "Addressee":
        topic = topic.strip()
        check_stream_topic(topic)
        return Addressee(
            msg_type="stream",
            stream_name=stream_name,
            topic=topic,
        )

    @staticmethod
    def for_stream_id(stream_id: int, topic: str) -> "Addressee":
        topic = topic.strip()
        check_stream_topic(topic)
        return Addressee(
            msg_type="stream",
            stream_id=stream_id,
            topic=topic,
        )

    @staticmethod
    def for_private(emails: Sequence[str], realm: Realm) -> "Addressee":
        assert len(emails) > 0
        user_profiles = get_user_profiles(emails, realm)
        return Addressee(
            msg_type="private",
            user_profiles=user_profiles,
        )

    @staticmethod
    def for_user_ids(user_ids: Sequence[int], realm: Realm) -> "Addressee":
        assert len(user_ids) > 0
        user_profiles = get_user_profiles_by_ids(user_ids, realm)
        return Addressee(
            msg_type="private",
            user_profiles=user_profiles,
        )

    @staticmethod
    def for_user_profile(user_profile: UserProfile) -> "Addressee":
        user_profiles = [user_profile]
        return Addressee(
            msg_type="private",
            user_profiles=user_profiles,
        )
