import time
from typing import Any, Dict, List, Set

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

from zerver.lib.actions import recipient_for_user_profiles
from zerver.lib.addressee import get_user_profiles_by_ids
from zerver.lib.exceptions import JsonableError
from zerver.lib.message import truncate_body, truncate_topic
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_error, json_success
from zerver.lib.streams import access_stream_by_id
from zerver.lib.timestamp import timestamp_to_datetime
from zerver.lib.validator import (
    check_dict_only,
    check_float,
    check_int,
    check_list,
    check_required_string,
    check_string,
    check_string_in,
    check_union,
)
from zerver.models import Draft, UserProfile

VALID_DRAFT_TYPES: Set[str] = {"", "private", "stream"}

# A validator to verify if the structure (syntax) of a dictionary
# meets the requirements to be a draft dictionary:
draft_dict_validator = check_dict_only(
    required_keys=[
        ("type", check_string_in(VALID_DRAFT_TYPES)),
        ("to", check_list(check_int)),  # The ID of the stream to send to, or a list of user IDs.
        ("topic", check_string),  # This string can simply be empty for private type messages.
        ("content", check_required_string),
    ],
    optional_keys=[
        ("timestamp", check_union([check_int, check_float])),  # A Unix timestamp.
    ]
)

def further_validated_draft_dict(draft_dict: Dict[str, Any],
                                 user_profile: UserProfile) -> Dict[str, Any]:
    """ Take a draft_dict that was already validated by draft_dict_validator 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 = truncate_body(draft_dict["content"])
    if "\x00" in content:
        raise JsonableError(_("Content must not contain null bytes"))

    timestamp = draft_dict.get("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 = ""
    recipient = None
    to = draft_dict["to"]
    if draft_dict["type"] == "stream":
        topic = truncate_topic(draft_dict["topic"])
        if "\x00" in topic:
            raise JsonableError(_("Topic must not contain null bytes"))
        if len(to) != 1:
            raise JsonableError(_("Must specify exactly 1 stream ID for stream messages"))
        stream, recipient, sub = access_stream_by_id(user_profile, to[0])
    elif draft_dict["type"] == "private" and len(to) != 0:
        to_users = get_user_profiles_by_ids(set(to), user_profile.realm)
        try:
            recipient = recipient_for_user_profiles(to_users, False, None, user_profile)
        except ValidationError as e:  # nocoverage
            raise JsonableError(e.messages[0])

    return {
        "recipient": recipient,
        "topic": topic,
        "content": content,
        "last_edit_time": last_edit_time,
    }

def fetch_drafts(request: HttpRequest, user_profile: UserProfile) -> HttpResponse:
    user_drafts = Draft.objects.filter(user_profile=user_profile).order_by("last_edit_time")
    draft_dicts = {str(draft.id): draft.to_dict() for draft in user_drafts}
    return json_success({"count": user_drafts.count(), "drafts": draft_dicts})

@has_request_variables
def create_drafts(request: HttpRequest, user_profile: UserProfile,
                  draft_dicts: List[Dict[str, Any]]=REQ("drafts",
                                                        validator=check_list(draft_dict_validator)),
                  ) -> HttpResponse:
    draft_objects = []
    for draft_dict in draft_dicts:
        valid_draft_dict = further_validated_draft_dict(draft_dict, user_profile)
        draft_objects.append(Draft(
            user_profile=user_profile,
            recipient=valid_draft_dict["recipient"],
            topic=valid_draft_dict["topic"],
            content=valid_draft_dict["content"],
            last_edit_time=valid_draft_dict["last_edit_time"],
        ))

    created_draft_objects = Draft.objects.bulk_create(draft_objects)
    draft_ids = [draft_object.id for draft_object in created_draft_objects]
    return json_success({"ids": draft_ids})

@has_request_variables
def edit_draft(request: HttpRequest, user_profile: UserProfile, draft_id: int,
               draft_dict: Dict[str, Any]=REQ("draft", validator=draft_dict_validator),
               ) -> HttpResponse:
    try:
        draft_object = Draft.objects.get(id=draft_id, user_profile=user_profile)
    except Draft.DoesNotExist:
        return json_error(_("Draft does not exist"), status=404)

    valid_draft_dict = further_validated_draft_dict(draft_dict, user_profile)
    draft_object.content = valid_draft_dict["content"]
    draft_object.topic = valid_draft_dict["topic"]
    draft_object.recipient = valid_draft_dict["recipient"]
    draft_object.last_edit_time = valid_draft_dict["last_edit_time"]
    draft_object.save()

    return json_success()

def delete_draft(request: HttpRequest, user_profile: UserProfile, draft_id: int) -> HttpResponse:
    try:
        draft_object = Draft.objects.get(id=draft_id, user_profile=user_profile)
    except Draft.DoesNotExist:
        return json_error(_("Draft does not exist"), status=404)

    draft_object.delete()
    return json_success()