#!/usr/bin/env python3
# SPDX-License-Identifier: MPL-2.0
"""Low-overhead, read-only battery and thermal sampler for a RAM trial."""
import json
from pathlib import Path
import time


def values(directory, names):
    result = {}
    for name in names:
        try:
            result[name] = (directory / name).read_text().strip()
        except OSError:
            pass
    return result


def sample():
    supplies = {}
    for path in sorted(Path('/sys/class/power_supply').iterdir()):
        supplies[path.name] = values(path, (
            'type', 'status', 'online', 'capacity', 'current_now',
            'voltage_now', 'power_now', 'charge_now', 'energy_now', 'temp'))
    thermal = {}
    for path in sorted(Path('/sys/class/thermal').glob('thermal_zone*')):
        item = values(path, ('type', 'temp'))
        if item:
            thermal[path.name] = item
    idle = {}
    for path in sorted(Path('/sys/devices/system/cpu').glob('cpu[0-9]*/cpuidle/state*')):
        item = values(path, ('name', 'time', 'usage', 'disable'))
        if item:
            idle[str(path.relative_to('/sys/devices/system/cpu'))] = item
    return {'timeUnix': time.time(), 'timeMonotonic': time.monotonic(),
            'powerSupplies': supplies, 'thermalZones': thermal, 'cpuIdle': idle}


def main():
    output = Path('/run/tundra/battery-idle.jsonl')
    output.parent.mkdir(parents=True, exist_ok=True)
    with output.open('a', buffering=1) as stream:
        while True:
            stream.write(json.dumps(sample(), separators=(',', ':')) + '\n')
            time.sleep(30)


if __name__ == '__main__':
    main()