import glob
import re
import shutil
import subprocess
from typing import Any

_name_cache: str | None = None


def _read(path: str) -> str | None:
    try:
        with open(path) as f:
            return f.read().strip()
    except OSError:
        return None


def _shorten(name: str) -> str:
    name = re.sub(r"\s*\(rev.*\)$", "", name).strip()
    groups = re.findall(r"\[([^\]]+)\]", name)
    if len(groups) >= 2:
        brand = groups[0]
        series = groups[-1].split(" / ")[0]
        model = name.split("]", 1)[1].split("[", 1)[0].strip()
        return f"{brand} {model} ({series})".strip()
    return name[:50]


def _gpu_name() -> str:
    global _name_cache
    if _name_cache is None:
        _name_cache = "GPU"
        if shutil.which("lspci"):
            try:
                out = subprocess.run(
                    ["lspci"], capture_output=True, text=True, timeout=5, check=False
                ).stdout
                for line in out.splitlines():
                    if "VGA" in line or "3D controller" in line:
                        _name_cache = _shorten(line.split(":", 2)[-1].strip())
                        break
            except (OSError, subprocess.SubprocessError):
                pass
    return _name_cache


def _amd_sample() -> dict[str, Any] | None:
    devices = sorted(glob.glob("/sys/class/drm/card[0-9]*/device/gpu_busy_percent"))
    if not devices:
        return None
    busy_sum = 0
    count = 0
    vram_used = 0
    vram_total = 0
    temps: list[float] = []
    for busy_path in devices:
        dev = busy_path.rsplit("/", 1)[0]
        try:
            busy_sum += int(_read(busy_path) or 0)
            count += 1
        except ValueError:
            continue
        vram_used += int(_read(f"{dev}/mem_info_vram_used") or 0)
        vram_total += int(_read(f"{dev}/mem_info_vram_total") or 0)
        for hwmon in glob.glob(f"{dev}/hwmon/hwmon*"):
            t = _read(f"{hwmon}/temp1_input")
            if t:
                try:
                    temps.append(int(t) / 1000.0)
                except ValueError:
                    pass
    if count == 0:
        return None
    return {
        "gpu": round(busy_sum / count, 1),
        "vram_used": vram_used,
        "vram_total": vram_total,
        "vram_pct": round(vram_used / vram_total * 100, 1) if vram_total else None,
        "gpu_temp": max(temps) if temps else None,
        "gpu_name": _gpu_name(),
    }


def _nvidia_sample() -> dict[str, Any] | None:
    if not shutil.which("nvidia-smi"):
        return None
    try:
        out = subprocess.run(
            [
                "nvidia-smi",
                "--query-gpu=utilization.gpu,memory.used,memory.total,temperature.gpu,name",
                "--format=csv,noheader,nounits",
            ],
            capture_output=True,
            text=True,
            timeout=5,
            check=True,
        ).stdout
    except (OSError, subprocess.SubprocessError):
        return None
    lines = [l for l in out.splitlines() if l.strip()]
    if not lines:
        return None
    busy = used = total = 0
    temp = 0
    for line in lines:
        parts = [p.strip() for p in line.split(",")]
        try:
            busy += int(parts[0])
            used += int(parts[1])
            total += int(parts[2])
            temp = max(temp, int(parts[3]))
        except ValueError:
            continue
    name = lines[0].split(",")[-1].strip()
    vram_used = used * 1024 * 1024
    vram_total = total * 1024 * 1024
    return {
        "gpu": round(busy / len(lines), 1),
        "vram_used": vram_used,
        "vram_total": vram_total,
        "vram_pct": round(vram_used / vram_total * 100, 1) if vram_total else None,
        "gpu_temp": float(temp),
        "gpu_name": name,
    }


def sample() -> dict[str, Any]:
    return (
        _amd_sample()
        or _nvidia_sample()
        or {
            "gpu": None,
            "vram_used": None,
            "vram_total": None,
            "vram_pct": None,
            "gpu_temp": None,
            "gpu_name": "no GPU detected",
        }
    )