from __future__ import annotations

from datetime import datetime


class Time:
    @staticmethod
    def _get_date_format() -> str:
        """date format as used by zpool status

        %a: day of week, short version
        %b: month, short version
        %d: day of month, zero-padded
        %H, %M, %S: hour, minute, second, zero-padded
        %Y: year
        """
        return "%a %b %d %H:%M:%S %Y"

    @classmethod
    def _extract_datetime_segment(cls, line_with_datetime: str) -> str:
        """From the line in `zpool status` that includes the date and time, extract only the part with date and time."""
        return line_with_datetime.split(" errors on ")[-1]

    @classmethod
    def _get_line_with_datetime_from_status_output(cls, output: str) -> str:
        """From `zpool status`, extract the line that contains the date and time of the last scrub."""
        lines = output.split("\n")
        for line in lines:
            if line.startswith("  scan: scrub repaired"):
                return line.strip()
        else:
            raise ValueError("Could not find the correct line")

    @classmethod
    def get_last_scrub_from_status_output(cls, output: str) -> datetime:
        """Given the output of `zfs status`, return the `datetime` object of the last scrub."""
        line_with_datetime = cls._get_line_with_datetime_from_status_output(output)
        date_str = cls._extract_datetime_segment(line_with_datetime)
        return datetime.strptime(date_str, cls._get_date_format())