"""Pure functions: device output in, typed values out. No I/O here."""

from __future__ import annotations

import re
from typing import TypedDict

#: "Key : value" lines of `show version`.
_FIELD = re.compile(r"^(?P<key>[^:\n]+?)\s*:\s*(?P<value>.*)$", re.MULTILINE)
#: "3 days, 4:05:06" or "4:05:06".
_UPTIME = re.compile(r"^(?:(?P<days>\d+) days?, )?(?P<h>\d+):(?P<m>\d\d):(?P<s>\d\d)$")
_SECONDS_PER_DAY = 86400


class VersionDict(TypedDict):
    model: str
    hostname: str
    os_version: str
    serial_number: str
    uptime: float


def parse_uptime(text: str) -> float:
    """Seconds from an uptime like ``3 days, 4:05:06``."""
    match = _UPTIME.match(text.strip())
    if not match:
        raise ValueError(f"unreadable uptime: {text!r}")
    days = int(match.group("days") or 0)
    hours, minutes, seconds = (int(match.group(k)) for k in ("h", "m", "s"))
    return float(days * _SECONDS_PER_DAY + hours * 3600 + minutes * 60 + seconds)


def parse_version(text: str) -> VersionDict:
    """Facts from ``show version``; a field the device did not print is an error."""
    fields = {m.group("key").strip(): m.group("value").strip() for m in _FIELD.finditer(text)}
    try:
        return {
            "model": text.splitlines()[0].removesuffix(" Switch").strip(),
            "hostname": fields["Hostname"],
            "os_version": fields["Firmware"],
            "serial_number": fields["Serial number"],
            "uptime": parse_uptime(fields["Uptime"]),
        }
    except KeyError as exc:
        raise ValueError(f"show version lacks {exc.args[0]}") from exc