import os
import re
from datetime import date, datetime, time


def extract_datetime_from_file_name(file_name: str) -> datetime | None:
    FILE_NAME_REGEX = r"^(?P<date>\d{8})(?:-(?P<time>\d{4,6}))?.+.md$"
    base_name = os.path.basename(file_name)
    match = re.match(FILE_NAME_REGEX, base_name)

    if match:
        date_str = match.group("date")
        time_str = match.group("time") or ""
        time_str = time_str.ljust(6, "0")
        datetime_str = f"{date_str} {time_str[:2]}:{time_str[2:4]}:{time_str[4:]}"
        return datetime.strptime(datetime_str, "%Y%m%d %H:%M:%S")
    return None


def extract_datetime_from_marker(marker: str) -> datetime | None:
    """
    Extract a datetime from a marker string in the exact format: YYYYMMDDHHMMSS.

    Returns:
        Parsed datetime if the format is fulfilled and values are valid, else None.
    """
    if not re.fullmatch(r"\d{14}", marker or ""):
        return None
    try:
        return datetime.strptime(marker, "%Y%m%d%H%M%S")
    except ValueError:
        return None


def extract_date_from_marker(marker: str) -> date | None:
    """
    Extract a date from a marker string in the exact format: YYYYMMDD.

    Returns:
        Parsed date if the format is fulfilled and values are valid, else None.
    """
    if not re.fullmatch(r"\d{8}", marker or ""):
        return None
    try:
        return datetime.strptime(marker, "%Y%m%d").date()
    except ValueError:
        return None


def extract_time_from_marker(marker: str) -> time | None:  # noqa: F821
    """
    Extract a time from a marker string in the exact format: HHMMSS.

    Returns:
        Parsed time if the format is fulfilled and values are valid, else None.
    """
    if not re.fullmatch(r"\d{6}", marker or ""):
        return None
    try:
        return datetime.strptime(marker, "%H%M%S").time()
    except ValueError:
        return None


def extract_datetime_from_marker_list(markers: list[str], inherited_datetime: datetime):
    shard_time: time | None = None
    shard_date: date | None = None

    for marker in markers[::-1]:
        if parsed_time := extract_time_from_marker(marker):
            shard_time = parsed_time
        if parsed_date := extract_date_from_marker(marker):
            shard_date = parsed_date
        if parsed_datetime := extract_datetime_from_marker(marker):
            shard_date = parsed_datetime.date()
            shard_time = parsed_datetime.time()

    if shard_date and not shard_time:
        return datetime.combine(shard_date, time(0, 0, 0))

    return datetime.combine(
        shard_date or inherited_datetime.date(), shard_time or inherited_datetime.time()
    )


__all__ = [
    "extract_datetime_from_file_name",
    "extract_datetime_from_marker",
    "extract_date_from_marker",
    "extract_time_from_marker",
    "extract_datetime_from_marker_list",
]