"""Utility functions for icalendar-searcher."""

from __future__ import annotations

from collections.abc import Iterable, Iterator
from datetime import date, datetime
from itertools import tee

from icalendar.prop import TypesFactory

## We need an instance of the icalendar.prop.TypesFactory class.
## We'll make a global instance rather than instantiate it for
## every loop iteration
types_factory = TypesFactory()


## Helper to normalize date/datetime for comparison
## (I feel this one is duplicated over many projects ...)
def _normalize_dt(dt_value: date | datetime) -> datetime:
    """Convert date to datetime for comparison, or return datetime as-is with timezone."""
    if dt_value is None:
        return None
    ## If it's a date (not datetime), convert to datetime at midnight
    if hasattr(dt_value, "year") and not hasattr(dt_value, "hour"):
        from datetime import time

        return datetime.combine(dt_value, time.min).astimezone()
    ## TODO: we should probably do some research on the default calendar timezone,
    ## which may not be the same as the local timezone ... uh ... timezones are
    ## difficult.
    return dt_value.astimezone()


## Helper - generators are generally more neat than lists,
## but bool(x) will always return True.  I'd like to verify
## that a generator is not empty, without side effects.
def _iterable_or_false(g: Iterable, _debug_print_peek: bool = False) -> bool | Iterable:
    """This method will return False if it's not possible to get an
    item from the iterable (which can only be done by utilizing
    `next`).  It will then return a new iterator that behaves like
    the original iterator (like if `next` wasn't used).

    Uses itertools.tee to create two independent iterators: one for
    checking if the iterator is empty, and one to return.
    """
    if not isinstance(g, Iterator):
        return bool(g) and g

    # Create two independent iterators from the input
    check_it, result_it = tee(g)

    try:
        my_value = next(check_it)
        if _debug_print_peek:
            print(my_value)
        return result_it  # Return the untouched iterator
    except StopIteration:
        return False