"""NormalizedDateTime module."""

from datetime import date, datetime
from typing import Any

from sqlalchemy.engine import Dialect
from sqlalchemy.types import DateTime as SADateTime, TypeDecorator

from abacus_common_logic.constants.constants import SYSTEM_TIMEZONE

_FORMATS = [
    '%Y/%m/%d',
    '%m/%d/%Y',
    '%d-%m-%Y',
    '%Y-%m-%d %H:%M',
    '%Y-%m-%d %H:%M:%S',
    '%Y-%m-%d %H:%M:%S.%f',
]


class NormalizedDateTime(TypeDecorator):
    """Normalize inputs to a datetime."""

    impl = SADateTime(timezone=True)
    cache_ok = True

    def process_bind_param(self, value: Any, dialect: Dialect) -> datetime | None:
        """Process params."""
        return to_datetime(value)

    def process_result_value(self, value: Any, dialect: Dialect) -> datetime | None:
        """Process results."""
        return to_datetime(value)


def to_datetime(value: Any) -> datetime | None:
    """Normalize inputs to a datetime."""
    # None / '' -> None
    if value is None or value == '':
        return None

    # datetime
    if isinstance(value, datetime):
        return _to_naive_datetime(value)

    # date -> datetime at midnight
    if isinstance(value, date):
        return datetime(value.year, value.month, value.day)

    # Epoch seconds
    if isinstance(value, (int, float)):
        return datetime.fromtimestamp(value)

    # bytes -> decode (utf-8)
    if isinstance(value, (bytes, bytearray)):
        value = value.decode('utf-8', errors='strict')

    # Convert to string
    s = str(value).strip()
    if not s:
        return None

    # Handle trailing 'Z' (UTC)
    if s.endswith(('Z', 'z')):
        s = s[:-1] + '+00:00'

    # ISO 8601
    try:
        return _to_naive_datetime(datetime.fromisoformat(s))
    except ValueError:
        pass

    # ISO date-only ('YYYY-MM-DD')
    try:
        d = date.fromisoformat(s)
        return datetime(d.year, d.month, d.day)
    except ValueError:
        pass

    # Try fallback formats
    for fmt in _FORMATS:
        try:
            return _to_naive_datetime(datetime.strptime(s, fmt))
        except ValueError:
            continue

    raise TypeError(f'Unsupported datetime value: {value!r}')


def _to_naive_datetime(dt: datetime) -> datetime:
    if dt.tzinfo is None:
        return dt
    return dt.astimezone(SYSTEM_TIMEZONE).replace(tzinfo=None)