from email.headerregistry import Address
from typing import Iterable, Optional, Sequence, Union, cast

from django.core import validators
from django.core.exceptions import ValidationError
from django.http import HttpRequest, HttpResponse
from django.utils.translation import gettext as _

from zerver.actions.message_send import (
    check_send_message,
    compute_irc_user_fullname,
    compute_jabber_user_fullname,
    create_mirror_user_if_needed,
    extract_private_recipients,
    extract_stream_indicator,
)
from zerver.lib.exceptions import JsonableError
from zerver.lib.message import render_markdown
from zerver.lib.request import REQ, RequestNotes, has_request_variables
from zerver.lib.response import json_success
from zerver.lib.topic import REQ_topic
from zerver.lib.validator import check_string_in, to_float
from zerver.lib.zcommand import process_zcommands
from zerver.lib.zephyr import compute_mit_user_fullname
from zerver.models import Client, Message, RealmDomain, UserProfile, get_user_including_cross_realm


class InvalidMirrorInputError(Exception):
    pass


def create_mirrored_message_users(
    client: Client,
    user_profile: UserProfile,
    recipients: Iterable[str],
    sender: str,
    recipient_type_name: str,
) -> UserProfile:
    sender_email = sender.strip().lower()
    referenced_users = {sender_email}
    if recipient_type_name == "private":
        for email in recipients:
            referenced_users.add(email.lower())

    if client.name == "zephyr_mirror":
        user_check = same_realm_zephyr_user
        fullname_function = compute_mit_user_fullname
    elif client.name == "irc_mirror":
        user_check = same_realm_irc_user
        fullname_function = compute_irc_user_fullname
    elif client.name in ("jabber_mirror", "JabberMirror"):
        user_check = same_realm_jabber_user
        fullname_function = compute_jabber_user_fullname
    else:
        raise InvalidMirrorInputError("Unrecognized mirroring client")

    for email in referenced_users:
        # Check that all referenced users are in our realm:
        if not user_check(user_profile, email):
            raise InvalidMirrorInputError("At least one user cannot be mirrored")

    # Create users for the referenced users, if needed.
    for email in referenced_users:
        create_mirror_user_if_needed(user_profile.realm, email, fullname_function)

    sender_user_profile = get_user_including_cross_realm(sender_email, user_profile.realm)
    return sender_user_profile


def same_realm_zephyr_user(user_profile: UserProfile, email: str) -> bool:
    #
    # Are the sender and recipient both addresses in the same Zephyr
    # mirroring realm?  We have to handle this specially, inferring
    # the domain from the e-mail address, because the recipient may
    # not existing in Zulip and we may need to make a stub Zephyr
    # mirroring user on the fly.
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    domain = Address(addr_spec=email).domain.lower()

    # Assumes allow_subdomains=False for all RealmDomain's corresponding to
    # these realms.
    return (
        user_profile.realm.is_zephyr_mirror_realm
        and RealmDomain.objects.filter(realm=user_profile.realm, domain=domain).exists()
    )


def same_realm_irc_user(user_profile: UserProfile, email: str) -> bool:
    # Check whether the target email address is an IRC user in the
    # same realm as user_profile, i.e. if the domain were example.com,
    # the IRC user would need to be username@irc.example.com
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    domain = Address(addr_spec=email).domain.lower()
    if domain.startswith("irc."):
        domain = domain[len("irc.") :]

    # Assumes allow_subdomains=False for all RealmDomain's corresponding to
    # these realms.
    return RealmDomain.objects.filter(realm=user_profile.realm, domain=domain).exists()


def same_realm_jabber_user(user_profile: UserProfile, email: str) -> bool:
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    # If your Jabber users have a different email domain than the
    # Zulip users, this is where you would do any translation.
    domain = Address(addr_spec=email).domain.lower()

    # Assumes allow_subdomains=False for all RealmDomain's corresponding to
    # these realms.
    return RealmDomain.objects.filter(realm=user_profile.realm, domain=domain).exists()


@has_request_variables
def send_message_backend(
    request: HttpRequest,
    user_profile: UserProfile,
    req_type: str = REQ("type", str_validator=check_string_in(Message.API_RECIPIENT_TYPES)),
    req_to: Optional[str] = REQ("to", default=None),
    req_sender: Optional[str] = REQ("sender", default=None, documentation_pending=True),
    forged_str: Optional[str] = REQ("forged", default=None, documentation_pending=True),
    topic_name: Optional[str] = REQ_topic(),
    message_content: str = REQ("content"),
    widget_content: Optional[str] = REQ(default=None, documentation_pending=True),
    local_id: Optional[str] = REQ(default=None),
    queue_id: Optional[str] = REQ(default=None),
    time: Optional[float] = REQ(default=None, converter=to_float, documentation_pending=True),
) -> HttpResponse:
    recipient_type_name = req_type
    if recipient_type_name == "direct":
        # For now, use "private" from Message.API_RECIPIENT_TYPES.
        # TODO: Use "direct" here, as well as in events and
        # message (created, schdeduled, drafts) objects/dicts.
        recipient_type_name = "private"

    # If req_to is None, then we default to an
    # empty list of recipients.
    message_to: Union[Sequence[int], Sequence[str]] = []

    if req_to is not None:
        if recipient_type_name == "stream":
            stream_indicator = extract_stream_indicator(req_to)

            # For legacy reasons check_send_message expects
            # a list of streams, instead of a single stream.
            #
            # Also, mypy can't detect that a single-item
            # list populated from a Union[int, str] is actually
            # a Union[Sequence[int], Sequence[str]].
            if isinstance(stream_indicator, int):
                message_to = [stream_indicator]
            else:
                message_to = [stream_indicator]
        else:
            message_to = extract_private_recipients(req_to)

    # Temporary hack: We're transitioning `forged` from accepting
    # `yes` to accepting `true` like all of our normal booleans.
    forged = forged_str is not None and forged_str in ["yes", "true"]

    client = RequestNotes.get_notes(request).client
    assert client is not None
    can_forge_sender = user_profile.can_forge_sender
    if forged and not can_forge_sender:
        raise JsonableError(_("User not authorized for this query"))

    realm = user_profile.realm

    if client.name in ["zephyr_mirror", "irc_mirror", "jabber_mirror", "JabberMirror"]:
        # Here's how security works for mirroring:
        #
        # For direct messages, the message must be (1) both sent and
        # received exclusively by users in your realm, and (2)
        # received by the forwarding user.
        #
        # For stream messages, the message must be (1) being forwarded
        # by an API superuser for your realm and (2) being sent to a
        # mirrored stream.
        #
        # The most important security checks are in
        # `create_mirrored_message_users` below, which checks the
        # same-realm constraint.
        if req_sender is None:
            raise JsonableError(_("Missing sender"))
        if recipient_type_name != "private" and not can_forge_sender:
            raise JsonableError(_("User not authorized for this query"))

        # For now, mirroring only works with recipient emails, not for
        # recipient user IDs.
        if not all(isinstance(to_item, str) for to_item in message_to):
            raise JsonableError(_("Mirroring not allowed with recipient user IDs"))

        # We need this manual cast so that mypy doesn't complain about
        # create_mirrored_message_users not being able to accept a Sequence[int]
        # type parameter.
        message_to = cast(Sequence[str], message_to)

        try:
            mirror_sender = create_mirrored_message_users(
                client, user_profile, message_to, req_sender, recipient_type_name
            )
        except InvalidMirrorInputError:
            raise JsonableError(_("Invalid mirrored message"))

        if client.name == "zephyr_mirror" and not user_profile.realm.is_zephyr_mirror_realm:
            raise JsonableError(_("Zephyr mirroring is not allowed in this organization"))
        sender = mirror_sender
    else:
        if req_sender is not None:
            raise JsonableError(_("Invalid mirrored message"))
        sender = user_profile

    ret = check_send_message(
        sender,
        client,
        recipient_type_name,
        message_to,
        topic_name,
        message_content,
        forged=forged,
        forged_timestamp=time,
        forwarder_user_profile=user_profile,
        realm=realm,
        local_id=local_id,
        sender_queue_id=queue_id,
        widget_content=widget_content,
    )
    return json_success(request, data={"id": ret})


@has_request_variables
def zcommand_backend(
    request: HttpRequest, user_profile: UserProfile, command: str = REQ("command")
) -> HttpResponse:
    return json_success(request, data=process_zcommands(command, user_profile))


@has_request_variables
def render_message_backend(
    request: HttpRequest, user_profile: UserProfile, content: str = REQ()
) -> HttpResponse:
    message = Message()
    message.sender = user_profile
    message.realm = user_profile.realm
    message.content = content
    client = RequestNotes.get_notes(request).client
    assert client is not None
    message.sending_client = client

    rendering_result = render_markdown(message, content, realm=user_profile.realm)
    return json_success(request, data={"rendered": rendering_result.rendered_content})