"""
Definition of an asyncio compatible CalDAV calendar.

Caches events using `timed_alru_cache`.
"""

from dataclasses import dataclass
from datetime import datetime, timedelta
from functools import total_ordering
from logging import getLogger
from typing import Iterator

from cache import AsyncTTL
from caldav import Calendar
from caldav.lib.error import ReportError
from pydantic import BaseModel, validator
from vobject.base import Component

from .async_helpers import run_in_executor
from .config import Config
from .dav_common import caldav_principal
from .settings import SETTINGS

_logger = getLogger(__name__)


def _string_strip(in_str: str) -> str:
    """
    Wrapper for str.strip().

    Used to define `pydantic` validators.
    """
    return in_str.strip()


@total_ordering
class CalEvent(BaseModel):
    """
    A CalDAV calendar event.

    Properties are to be named as in the EVENT component of
    RFC5545 (iCalendar).

    https://icalendar.org/iCalendar-RFC-5545/3-6-1-event-component.html
    """

    summary: str = ""
    description: str = ""
    dtstart: datetime = datetime.utcnow()
    dtend: datetime = datetime.utcnow()

    class Config:
        frozen = True

    def __lt__(self, other: "CalEvent") -> bool:
        """
        Order Events by start time.
        """

        return self.dtstart < other.dtstart

    def __eq__(self, other: "CalEvent") -> bool:
        """
        Compare all properties.
        """

        return self.dict() == other.dict()

    _validate_summary = validator(
        "summary",
        allow_reuse=True,
    )(_string_strip)

    _validate_description = validator(
        "description",
        allow_reuse=True,
    )(_string_strip)

    @classmethod
    def from_vevent(cls, event: Component) -> "CalEvent":
        """
        Create a CalEvent instance from a `VObject.VEvent` object.
        """

        data = {}
        keys = ("summary", "description", "dtstart", "dtend", "duration")

        for key in keys:
            try:
                data[key] = event.contents[key][0].value  # type: ignore

            except KeyError:
                pass

        if "dtend" not in data:
            data["dtend"] = data["dtstart"]

            if "duration" in data:
                try:
                    data["dtend"] += data["duration"]

                except (ValueError, TypeError, AttributeError):
                    _logger.warn(
                        "Could not add duration %s to %s",
                        repr(data["duration"]),
                        repr(data["dtstart"]),
                    )

                del data["duration"]

        return cls.parse_obj(data)


@AsyncTTL(time_to_live=SETTINGS.cache_time, maxsize=SETTINGS.cache_size)
async def _get_calendar(
    calendar_name: str,
) -> Calendar:
    """
    Get a calendar by name using the CalDAV principal object.
    """

    @run_in_executor
    def _inner() -> Calendar:
        return caldav_principal().calendar(calendar_name)

    return await _inner()


@AsyncTTL(time_to_live=SETTINGS.cache_time, maxsize=SETTINGS.cache_size)
async def _get_calendar_events(
    calendar_name: str,
) -> list[CalEvent]:
    """
    Get a sorted list of events by CalDAV calendar name.

    Do not return an iterator here - this result is cached and
    an iterator would get consumed.
    """

    cfg = await Config.get()
    search_span = timedelta(days=cfg.calendar.future_days)

    @run_in_executor
    def _inner() -> Iterator[Component]:
        """
        Get events by CalDAV calendar name.

        This can return an iterator - only the outer function is
        cached.
        """
        _logger.info(f"downloading {calendar_name!r} ...")

        calendar = caldav_principal().calendar(calendar_name)

        date_start = datetime.utcnow().date()
        time_min = datetime.min.time()
        dt_start = datetime.combine(date_start, time_min)
        dt_end = dt_start + search_span

        try:
            search_result = calendar.date_search(
                start=dt_start,
                end=dt_end,
                expand=True,
                verify_expand=True,
            )

        except ReportError:
            _logger.warning("CalDAV server does not support expanded search")

            search_result = calendar.date_search(
                start=dt_start,
                end=dt_end,
                expand=False,
            )

        for event in search_result:
            vobject: Component = event.vobject_instance  # type: ignore
            yield from vobject.vevent_list

    return sorted([
        CalEvent.from_vevent(vevent)
        for vevent in await _inner()
    ])


@dataclass(frozen=True)
class DavCalendar:
    """
    Object representation of a CalDAV calendar.
    """

    calendar_name: str

    @property
    async def calendar(self) -> Calendar:
        """
        Calendar as `caldav` library representation.
        """

        return await _get_calendar(
            calendar_name=self.calendar_name,
        )

    @property
    async def events(self) -> list[CalEvent]:
        """
        Calendar events in object representation.
        """

        return await _get_calendar_events(
            calendar_name=self.calendar_name,
        )