import time
from collections.abc import Callable
from functools import wraps
from typing import Annotated, Any, Concatenate, Literal

from django.core.exceptions import ValidationError
from django.db import transaction
from django.http import HttpRequest, HttpResponse
from django.utils.translation import gettext as _
from pydantic import BaseModel, ConfigDict
from typing_extensions import ParamSpec

from zerver.lib.addressee import get_user_profiles_by_ids
from zerver.lib.exceptions import JsonableError, ResourceNotFoundError
from zerver.lib.message import normalize_body, truncate_topic
from zerver.lib.recipient_users import recipient_for_user_profiles
from zerver.lib.streams import access_stream_by_id
from zerver.lib.timestamp import timestamp_to_datetime
from zerver.lib.typed_endpoint import RequiredStringConstraint
from zerver.models import Draft, UserProfile
from zerver.tornado.django_api import send_event_on_commit

ParamT = ParamSpec("ParamT")


class DraftData(BaseModel):
    model_config = ConfigDict(extra="forbid")

    type: Literal["private", "stream", ""]
    to: list[int]
    topic: str
    content: Annotated[str, RequiredStringConstraint()]
    timestamp: int | float | None = None


def further_validated_draft_dict(
    draft_dict: DraftData, user_profile: UserProfile
) -> dict[str, Any]:
    """Take a DraftData object that was already validated by the @typed_endpoint
    decorator then further sanitize, validate, and transform it.
    Ultimately return this "further validated" draft dict.
    It will have a slightly different set of keys the values
    for which can be used to directly create a Draft object."""

    content = normalize_body(draft_dict.content)

    timestamp = draft_dict.timestamp
    if timestamp is None:
        timestamp = time.time()
    timestamp = round(timestamp, 6)
    if timestamp < 0:
        # While it's not exactly an invalid timestamp, it's not something
        # we want to allow either.
        raise JsonableError(_("Timestamp must not be negative."))
    last_edit_time = timestamp_to_datetime(timestamp)

    topic_name = ""
    recipient_id = None
    to = draft_dict.to
    if draft_dict.type == "stream":
        topic_name = truncate_topic(draft_dict.topic)
        if "\0" in topic_name:
            raise JsonableError(_("Topic must not contain null bytes"))
        if len(to) != 1:
            raise JsonableError(_("Must specify exactly 1 channel ID for channel messages"))
        stream, sub = access_stream_by_id(user_profile, to[0])
        recipient_id = stream.recipient_id
    elif draft_dict.type == "private" and len(to) != 0:
        to_users = get_user_profiles_by_ids(set(to), user_profile.realm)
        try:
            recipient_id = recipient_for_user_profiles(to_users, False, None, user_profile).id
        except ValidationError as e:  # nocoverage
            raise JsonableError(e.messages[0])

    return {
        "recipient_id": recipient_id,
        "topic": topic_name,
        "content": content,
        "last_edit_time": last_edit_time,
    }


def draft_endpoint(
    view_func: Callable[Concatenate[HttpRequest, UserProfile, ParamT], HttpResponse],
) -> Callable[Concatenate[HttpRequest, UserProfile, ParamT], HttpResponse]:
    @wraps(view_func)
    def draft_view_func(
        request: HttpRequest,
        user_profile: UserProfile,
        /,
        *args: ParamT.args,
        **kwargs: ParamT.kwargs,
    ) -> HttpResponse:
        if not user_profile.enable_drafts_synchronization:
            raise JsonableError(_("User has disabled synchronizing drafts."))
        return view_func(request, user_profile, *args, **kwargs)

    return draft_view_func


def do_create_drafts(drafts: list[DraftData], user_profile: UserProfile) -> list[Draft]:
    """Create drafts in bulk for a given user based on the DraftData objects. Since
    currently, the only place this method is being used (apart from tests) is from
    the create_draft view, we assume that these are syntactically valid
    (i.e. they satisfy the @typed_endpoint validation for DraftData)."""
    draft_objects = []
    for draft in drafts:
        valid_draft_dict = further_validated_draft_dict(draft, user_profile)
        draft_objects.append(
            Draft(
                user_profile=user_profile,
                recipient_id=valid_draft_dict["recipient_id"],
                topic=valid_draft_dict["topic"],
                content=valid_draft_dict["content"],
                last_edit_time=valid_draft_dict["last_edit_time"],
            )
        )

    with transaction.atomic(durable=True):
        created_draft_objects = Draft.objects.bulk_create(draft_objects)

        event = {
            "type": "drafts",
            "op": "add",
            "drafts": [draft.to_dict() for draft in created_draft_objects],
        }
        send_event_on_commit(user_profile.realm, event, [user_profile.id])

    return created_draft_objects


def do_edit_draft(draft_id: int, draft: DraftData, user_profile: UserProfile) -> None:
    """Edit/update a single draft for a given user. Since the only place this method is being
    used from (apart from tests) is the edit_draft view, we assume that the DraftData object
    is syntactically valid (i.e. it satisfies the @typed_endpoint validation for DraftData)."""
    try:
        draft_object = Draft.objects.get(id=draft_id, user_profile=user_profile)
    except Draft.DoesNotExist:
        raise ResourceNotFoundError(_("Draft does not exist"))
    valid_draft_dict = further_validated_draft_dict(draft, user_profile)
    draft_object.content = valid_draft_dict["content"]
    draft_object.topic = valid_draft_dict["topic"]
    draft_object.recipient_id = valid_draft_dict["recipient_id"]
    draft_object.last_edit_time = valid_draft_dict["last_edit_time"]

    with transaction.atomic(durable=True):
        draft_object.save()

        event = {"type": "drafts", "op": "update", "draft": draft_object.to_dict()}
        send_event_on_commit(user_profile.realm, event, [user_profile.id])


@transaction.atomic(durable=True)
def do_delete_draft(draft_id: int, user_profile: UserProfile) -> None:
    """Delete a draft belonging to a particular user."""
    try:
        draft_object = Draft.objects.get(id=draft_id, user_profile=user_profile)
    except Draft.DoesNotExist:
        raise ResourceNotFoundError(_("Draft does not exist"))

    draft_id = draft_object.id
    draft_object.delete()

    event = {"type": "drafts", "op": "remove", "draft_id": draft_id}
    send_event_on_commit(user_profile.realm, event, [user_profile.id])