"""Battery presence + percentage via sysfs — no upower dependency (that daemon
isn't guaranteed running; sysfs always is on real hardware). Mirrors the icon
tiers already established in scripts/batteryperc (the eww bar's battery poll)
so a laptop that switches between hyprlua and hyprdrive sees the same glyphs.
"""

from __future__ import annotations

from pathlib import Path
from typing import NamedTuple, Optional

_POWER_SUPPLY = Path("/sys/class/power_supply")

# (floor percentage, glyph) — first match wins, checked high to low.
_DISCHARGING_TIERS = [
    (95, "󰁹"), (90, "󰂂"), (80, "󰂁"), (70, "󰂀"), (60, "󰁿"),
    (50, "󰁾"), (40, "󰁽"), (30, "󰁼"), (20, "󰁻"), (10, "󰁺"), (0, "󰂎"),
]
_CHARGING_ICON = "󰂄"


class BatteryState(NamedTuple):
    percent: int
    charging: bool
    icon: str


def _find_battery() -> Optional[Path]:
    if not _POWER_SUPPLY.is_dir():
        return None
    for entry in sorted(_POWER_SUPPLY.iterdir()):
        if entry.name.startswith("BAT"):
            return entry
    return None


def read() -> Optional[BatteryState]:
    """Returns None when no battery is present (desktop machine) — callers
    should hide the widget entirely in that case, per spec."""
    bat = _find_battery()
    if bat is None:
        return None
    try:
        percent = int((bat / "capacity").read_text().strip())
        status = (bat / "status").read_text().strip().lower()
    except (OSError, ValueError):
        return None

    charging = status == "charging"
    if charging:
        icon = _CHARGING_ICON
    else:
        icon = next(g for floor, g in _DISCHARGING_TIERS if percent >= floor)
    return BatteryState(percent=percent, charging=charging, icon=icon)