"""Read-only Linux collector, executed via SSH stdin; never imports router code."""
import csv
import json
import time
import subprocess
from pathlib import Path


def read(path):
    try:
        return Path(path).read_text().strip()
    except OSError:
        return ''


def number(value):
    try:
        return float(value)
    except (ValueError, TypeError):
        return None


def ticks():
    values = list(map(int, read('/proc/stat').splitlines()[0].split()[1:9]))
    return sum(values), sum(values[3:5])


def collect():
    errors = []
    cpu = {'name': None, 'percent': None, 'temperature_c': None}
    try:
        a, ai = ticks()
        time.sleep(.25)
        b, bi = ticks()
        cpu['percent'] = round(100 * (1 - (bi-ai)/(b-a)), 1) if b > a else None
    except (ValueError, IndexError):
        errors.append('CPU-Auslastung nicht verfügbar')
    for line in read('/proc/cpuinfo').splitlines():
        if line.startswith('model name'):
            cpu['name'] = line.split(':', 1)[1].strip()
            break
    for path in Path('/sys/class/hwmon').glob('hwmon*'):
        if read(path / 'name') in ('k10temp', 'coretemp'):
            value = number(read(path / 'temp1_input'))
            cpu['temperature_c'] = value / 1000 if value is not None else None
            break
    mem = {}
    for line in read('/proc/meminfo').splitlines():
        parts = line.split()
        if parts[0] in ('MemTotal:', 'MemAvailable:'):
            mem[parts[0][:-1]] = int(parts[1]) * 1024
    total, available = mem.get('MemTotal'), mem.get('MemAvailable')
    ram = {'total_bytes': total, 'used_bytes': total-available if total is not None and available is not None else None}
    gpus = []
    try:
        result = subprocess.run(['nvidia-smi', '--query-gpu=index,name,uuid,memory.total,memory.used,utilization.gpu,temperature.gpu', '--format=csv,noheader,nounits'], capture_output=True, text=True, timeout=4, check=True)
        for row in csv.reader(result.stdout.splitlines(), skipinitialspace=True):
            index, name, uuid, total, used, usage, temp = row
            gpus.append(dict(index=int(index), name=name, uuid=uuid, total_mib=number(total), used_mib=number(used), percent=number(usage), temperature_c=number(temp)))
    except (OSError, subprocess.SubprocessError, ValueError):
        errors.append('GPU-Messwerte nicht verfügbar')
    return dict(source='Debian-Server · /proc + hwmon + nvidia-smi', sampled_at=time.time(), cpu=cpu, ram=ram, gpus=gpus, errors=errors)


if __name__ == '__main__':
    print(json.dumps(collect()))