"""A grouping of component properties that describe a to-do.

A todo component can represent an item of work assigned to an individual
such as "turn in a travel expense today".

A todo component without a start date or due date (or duration) specifies
a to-do that will be associated with each successive calendar date until it
is completed.
"""

from __future__ import annotations

from collections.abc import Iterable
import datetime
import enum
from typing import Annotated, Any, Optional, Self, Union
import logging

from pydantic import BeforeValidator, Field, field_serializer, model_validator

from ical.types.data_types import serialize_field

from .alarm import Alarm
from .component import (
    ComponentModel,
    validate_duration_unit,
    validate_until_dtstart,
    validate_recurrence_dates,
)
from .exceptions import CalendarParseError
from .iter import RulesetIterable, as_rrule
from .parsing.property import ParsedProperty
from .timespan import Timespan
from .types import (
    CalAddress,
    Classification,
    Geo,
    Priority,
    Recur,
    RecurrenceId,
    RequestStatus,
    Uri,
    RelatedTo,
)
from .util import (
    dtstamp_factory,
    normalize_datetime,
    parse_date_and_datetime,
    parse_date_and_datetime_list,
    uid_factory,
    local_timezone,
)


_LOGGER = logging.getLogger(__name__)


class TodoStatus(str, enum.Enum):
    """Status or confirmation of the to-do."""

    NEEDS_ACTION = "NEEDS-ACTION"
    COMPLETED = "COMPLETED"
    IN_PROCESS = "IN-PROCESS"
    CANCELLED = "CANCELLED"


class Todo(ComponentModel):
    """A calendar todo component."""

    dtstamp: Union[datetime.date, datetime.datetime] = Field(
        default_factory=dtstamp_factory
    )
    """Specifies the date and time the item was created."""

    uid: str = Field(default_factory=lambda: uid_factory())
    """A globally unique identifier for the item."""

    attendees: list[CalAddress] = Field(alias="attendee", default_factory=list)
    """Specifies participants in a group-scheduled calendar."""

    categories: list[str] = Field(default_factory=list)
    """Defines the categories for an item.

    Specifies a category or subtype. Can be useful for searching for a particular
    type of item.
    """

    classification: Optional[Classification] = Field(alias="class", default=None)
    """An access classification for a calendar to-do item.

    This provides a method of capturing the scope of access of a calendar, in
    conjunction with an access control system.
    """

    comment: list[str] = Field(default_factory=list)
    """Specifies a comment to the calendar user."""

    completed: Optional[datetime.datetime] = None

    contacts: list[str] = Field(alias="contact", default_factory=list)
    """Contact information associated with the item."""

    created: Optional[datetime.datetime] = None

    description: Optional[str] = None
    """A more complete description of the item than provided by the summary."""

    # Has alias of 'start'
    dtstart: Annotated[
        Union[datetime.date, datetime.datetime, None],
        BeforeValidator(parse_date_and_datetime),
    ] = None
    """The start time or start day of the item."""

    due: Annotated[
        Union[datetime.date, datetime.datetime, None],
        BeforeValidator(parse_date_and_datetime),
    ] = None

    duration: Optional[datetime.timedelta] = None
    """The duration of the item as an alternative to an explicit end date/time."""

    geo: Optional[Geo] = None
    """Specifies a latitude and longitude global position for the activity."""

    last_modified: Optional[datetime.datetime] = Field(
        alias="last-modified", default=None
    )

    location: Optional[str] = None
    """Defines the intended venue for the activity defined by this item."""

    organizer: Optional[CalAddress] = None
    """The organizer of a group-scheduled calendar entity."""

    percent: Optional[int] = None

    priority: Optional[Priority] = None
    """Defines the relative priority of the todo item."""

    recurrence_id: Optional[RecurrenceId] = Field(default=None, alias="recurrence-id")
    """Defines a specific instance of a recurring item.

    The full range of items specified by a recurrence set is referenced
    by referring to just the uid. The `recurrence_id` allows reference of an individual
    instance within the recurrence set.
    """

    related_to: list[RelatedTo] = Field(alias="related-to", default_factory=list)
    """Used to represent a relationship or reference between events."""

    request_status: Optional[RequestStatus] = Field(
        default=None,
        alias="request-status",
    )

    rrule: Optional[Recur] = None
    """A recurrence rule specification.

    Defines a rule for specifying a repeated event. The recurrence set is the complete
    set of recurrence instances for a calendar component (based on rrule, rdate, exdate).
    The recurrence set is generated by gathering the rrule and rdate properties then
    excluding any times specified by exdate. The recurrence is generated with the dtstart
    property defining the first instance of the recurrence set.

    Typically a dtstart should be specified with a date local time and timezone to make
    sure all instances have the same start time regardless of time zone changing.
    """

    rdate: Annotated[
        list[Union[datetime.date, datetime.datetime]],
        BeforeValidator(parse_date_and_datetime_list),
    ] = Field(default_factory=list)
    """Defines the list of date/time values for recurring events.

    Can appear along with the rrule property to define a set of repeating occurrences of the
    event. The recurrence set is the complete set of recurrence instances for a calendar component
    (based on rrule, rdate, exdate). The recurrence set is generated by gathering the rrule
    and rdate properties then excluding any times specified by exdate.
    """

    exdate: Annotated[
        list[Union[datetime.date, datetime.datetime]],
        BeforeValidator(parse_date_and_datetime_list),
    ] = Field(default_factory=list)
    """Defines the list of exceptions for recurring events.

    The exception dates are used in computing the recurrence set. The recurrence set is
    the complete set of recurrence instances for a calendar component (based on rrule, rdate,
    exdate). The recurrence set is generated by gathering the rrule and rdate properties
    then excluding any times specified by exdate.
    """

    sequence: Optional[int] = None
    """The revision sequence number in the calendar component.

    When an event is created, its sequence number is 0. It is monotonically incremented
    by the organizer's calendar user agent every time a significant revision is made to
    the calendar event.
    """

    status: Optional[TodoStatus] = None
    """Defines the overall status or confirmation of the event.

    In a group-scheduled calendar, used by the organizer to provide a confirmation
    of the event to attendees.
    """

    summary: Optional[str] = None
    """Defines a short summary or subject for the event."""

    url: Optional[Uri] = None
    """Defines a url associated with the item.

    May convey a location where a more dynamic rendition of the item can be found.
    """

    alarms: list[Alarm] = Field(alias="valarm", default_factory=list)

    extras: list[ParsedProperty] = Field(default_factory=list)

    def __init__(self, **data: Any) -> None:
        """Initialize Todo."""
        if "start" in data:
            data["dtstart"] = data.pop("start")
        super().__init__(**data)

    @property
    def start(self) -> datetime.datetime | datetime.date | None:
        """Return the start time for the todo."""
        return self.dtstart

    @property
    def start_datetime(self) -> datetime.datetime | None:
        """Return the todos start as a datetime."""
        if not self.dtstart:
            return None
        return normalize_datetime(self.dtstart).astimezone(tz=datetime.timezone.utc)

    @property
    def end(self) -> datetime.datetime | datetime.date | None:
        """Return due if it's defined, or dtstart + duration if they're defined.

        RFC5545 doesn't define end time for other cases but this method implements the
        same rules as the one on VEVENT:
        if dtstart is a date, the next day is returned, otherwise the dtstart is returned.
        """

        if self.due:
            return self.due
        if self.duration is not None:
            assert self.dtstart is not None
            return self.dtstart + self.duration
        if type(self.dtstart) is datetime.date:
            return self.dtstart + datetime.timedelta(days=1)

        # whenever dtstart is not None, end is not None
        return self.dtstart

    @property
    def computed_duration(self) -> datetime.timedelta:
        """Return the event duration. If duration is set, return it;
        if dtstart is set, take due (set or calculated) and return the difference. Otherwise return 1 day.

        If dtstart is a datetime and neither due nor duration is set, due is assumed to be equal to dtstart
        and the result is zero."""
        if self.duration:
            return self.duration
        if self.dtstart:
            assert self.end
            return self.end - self.dtstart
        return datetime.timedelta(days=1)

    def is_due(self, tzinfo: datetime.tzinfo | None = None) -> bool:
        """Return true if the todo is due."""
        if tzinfo is None:
            tzinfo = local_timezone()
        now = datetime.datetime.now(tz=tzinfo)
        due = self.end
        return due is not None and normalize_datetime(due, tzinfo) < now

    @property
    def timespan(self) -> Timespan:
        """Return a timespan representing the item start and due date."""
        return self.timespan_of(local_timezone())

    def timespan_of(self, tzinfo: datetime.tzinfo) -> Timespan:
        """Return a timespan representing the item start and due date or start and duration if it's set."""
        dtstart = self.dtstart
        dtend = self.end
        if dtstart is None:
            if dtend is None:
                # A component without the DTSTART or DUE specifies a to-do that
                # will be associated with each successive calendar date, until
                # it is completed.
                dtstart = datetime.datetime.now(tzinfo).date()
                dtend = dtstart + datetime.timedelta(days=1)
            else:
                # Component with a DTSTART but no DUE date will be sorted next
                # to the due date.
                dtstart = dtend
        elif dtend is None:
            # Component with a DTSTART but not DUE date will be sorted next to the start date
            dtend = dtstart
        return Timespan.of(
            normalize_datetime(dtstart, tzinfo), normalize_datetime(dtend, tzinfo)
        )

    @property
    def recurring(self) -> bool:
        """Return true if this Todo is recurring.

        A recurring event is typically evaluated specially on the list. The
        data model has a single todo, but the timeline evaluates the recurrence
        to expand and copy the event to multiple places on the timeline
        using `as_rrule`.
        """
        if self.rrule or self.rdate:
            return True
        return False

    def as_rrule(self) -> Iterable[datetime.datetime | datetime.date] | None:
        """Return an iterable containing the occurrences of a recurring todo.

        A recurring todo is typically evaluated specially on the todo list. The
        data model has a single todo item, but the timeline evaluates the recurrence
        to expand and copy the item to multiple places on the timeline.

        This is only valid for events where `recurring` is True.
        """
        if not self.rrule and not self.rdate:
            return None
        if not self.due and not self.duration:
            raise CalendarParseError("Event must have a due date or duration to be recurring")
        return as_rrule(self.rrule, self.rdate, self.exdate, self.dtstart)

    _validate_until_dtstart = model_validator(mode="after")(validate_until_dtstart)
    _validate_recurrence_dates = model_validator(mode="after")(
        validate_recurrence_dates
    )
    _validate_duration_unit = model_validator(mode="after")(validate_duration_unit)

    @model_validator(mode="after")
    def _validate_one_due_or_duration(self) -> Self:
        """Validate that only one of duration or end date may be set."""
        if self.due and self.duration:
            raise ValueError("Only one of due or duration may be set.")
        return self

    @model_validator(mode="after")
    def _validate_duration_requires_start(self) -> Self:
        """Validate that a duration requires the dtstart."""
        if self.duration and not self.dtstart:
            raise ValueError("Duration requires that dtstart is specified")
        return self

    @model_validator(mode="after")
    def _validate_date_types(self) -> Self:
        """Validate and repair due vs start values to ensure they are the same date or datetime type."""
        dtstart = self.dtstart
        due = self.due
        if not dtstart or not due:
            return self
        if isinstance(due, datetime.datetime):
            if not isinstance(dtstart, datetime.datetime):
                _LOGGER.debug(
                    "Repairing unexpected dtstart value '%s' as date with due value '%s' as datetime",
                    dtstart,
                    due,
                )
                self.dtstart = datetime.datetime.combine(
                    dtstart, datetime.time.min, tzinfo=due.tzinfo
                )
        elif isinstance(due, datetime.date):
            if isinstance(dtstart, datetime.datetime):
                _LOGGER.debug(
                    "Repairing unexpected dtstart value '%s' as date with due value '%s' as datetime",
                    dtstart,
                    due,
                )
                self.dtstart = dtstart.date()
                _LOGGER.debug("values=%s", self)
        return self

    @model_validator(mode="after")
    def _validate_datetime_timezone(self) -> Self:
        """Validate that start and due values have the same timezone information."""
        if (
            not (dtstart := self.dtstart)
            or not (due := self.due)
            or not isinstance(dtstart, datetime.datetime)
            or not isinstance(due, datetime.datetime)
        ):
            return self
        if dtstart.tzinfo is None and due.tzinfo is not None:
            raise ValueError(f"Expected due datetime value in localtime but was {due}")
        if dtstart.tzinfo is not None and due.tzinfo is None:
            raise ValueError(f"Expected due datetime with timezone but was {due}")
        return self

    @model_validator(mode="after")
    def _validate_due_later(self) -> Self:
        """Validate that the due property is later than dtstart."""
        if not (due := self.due) or not (dtstart := self.dtstart):
            return self
        if due <= dtstart:
            _LOGGER.debug(
                "Due date %s is earlier than start date %s, adjusting start date",
                due,
                dtstart,
            )
            self.dtstart = due - datetime.timedelta(days=1)
        return self

    @classmethod
    def _parse_single_property(cls, field_type: type, prop: ParsedProperty) -> Any:
        """Parse an individual field as a single type."""
        try:
            return super()._parse_single_property(field_type, prop)
        except ValueError as err:
            if (
                prop.name == "dtstart"
                and field_type == datetime.datetime
                and prop.params is not None
            ):
                _LOGGER.debug(
                    "Applying todo dtstart repair for invalid timezone; Removing dtstart",
                )
                return None
            raise err

    serialize_fields = field_serializer("*")(serialize_field)  # type: ignore[pydantic-field]