"""Request-driven Linux telemetry; adapted StarPilot producer (see LICENSE)."""

import math
import os
import pwd
import shutil
import threading
import time
from pathlib import Path


class SystemMonitor:
  def __init__(self, root=Path('/proc'), *, storage=Path('/data'), clock=time.monotonic,
               wall_clock=time.time, disk_usage=shutil.disk_usage, page_size=None):  # noqa: TID251 - Display capture date; intervals use monotonic.
    self.root = Path(root)
    self.storage = Path(storage)
    self.clock, self.wall_clock, self.disk_usage = clock, wall_clock, disk_usage
    self.page_size = os.sysconf('SC_PAGE_SIZE') if page_size is None else page_size
    self.lock = threading.Lock()
    self.previous = {}
    self.cpu_previous = {}
    self.previous_time = None

  def sample(self):
    with self.lock:
      try:
        return self._sample()
      except (OSError, ValueError, IndexError):
        # A failed sample breaks the comparison interval, including PID identity.
        self.previous, self.cpu_previous, self.previous_time = {}, {}, None
        raise OSError('System telemetry is unavailable') from None

  def _sample(self):
    now = self.clock()
    comparable = self.previous_time is not None and now > self.previous_time
    cpu_now, cores = {}, []
    overall = capacity = None
    for line in (self.root / 'stat').read_text().splitlines():
      values = line.split()
      if not values or not (values[0] == 'cpu' or values[0].startswith('cpu') and values[0][3:].isdigit()):
        continue
      ticks = [int(value) for value in values[1:9]]
      if len(ticks) < 5 or any(value < 0 for value in ticks):
        raise ValueError('Invalid CPU counters')
      pair = (sum(ticks), ticks[3] + ticks[4])
      key = values[0]
      cpu_now[key] = pair
      old = self.cpu_previous.get(key) if comparable else None
      percent = None
      if old and pair[0] > old[0] and 0 <= pair[1] - old[1] <= pair[0] - old[0]:
        percent = round(100 * (1 - (pair[1] - old[1]) / (pair[0] - old[0])), 1)
        if key == 'cpu':
          capacity = pair[0] - old[0]
      if key == 'cpu':
        overall = percent
      else:
        cores.append({'name': key, 'percent': percent})
    if 'cpu' not in cpu_now:
      raise ValueError('Missing CPU counters')

    rows, process_ticks = [], {}
    for path in sorted(self.root.iterdir()):
      if not path.name.isdigit() or int(path.name) <= 0:
        continue
      try:
        raw = (path / 'stat').read_text()
        end = raw.rindex(')')
        fields = raw[end + 2:].split()
        identity = (int(path.name), int(fields[19]))
        current = int(fields[11]) + int(fields[12])
        if current < 0:
          continue
        args = [part for part in (path / 'cmdline').read_bytes().decode(errors='replace').split('\0') if part]
        name = raw[raw.index('(') + 1:end]
        if args:
          name = args[0]
          if 'python' in Path(name).name and len(args) > 1:
            name = args[2] if args[1] == '-m' and len(args) > 2 else args[1] if not args[1].startswith('-') else Path(name).name
        uid = path.stat().st_uid
        try:
          user = pwd.getpwuid(uid).pw_name
        except KeyError:
          user = str(uid)
        cpu = None
        previous = self.previous.get(identity) if comparable else None
        if capacity and previous is not None and current >= previous:
          cpu = round(min(100, (current - previous) / capacity * 100), 1)
        rows.append({'pid': identity[0], 'name': name.removeprefix('/data/openpilot/'), 'user': user,
                     'kernel': not args, 'state': fields[0], 'cpu': cpu,
                     'memoryMiB': round(max(0, int(fields[21])) * self.page_size / 1048576, 1)})
        process_ticks[identity] = current
      except (OSError, ValueError, IndexError):
        # Processes may disappear between reading stat, cmdline and ownership.
        continue

    memory = {line.split(':')[0]: int(line.split()[1])
              for line in (self.root / 'meminfo').read_text().splitlines() if ':' in line}
    total = memory.get('MemTotal', 0)
    available = memory.get('MemAvailable')
    if total <= 0:
      raise ValueError('Missing total memory')
    # MemFree excludes reclaimable cache and cannot stand in for MemAvailable.
    if available is not None and not 0 <= available <= total:
      available = None
    used = total - available if available is not None else None
    storage = {'usedGiB': None, 'totalGiB': None}
    try:
      disk = self.disk_usage(self.storage)
      storage = {'usedGiB': round(disk.used / 1073741824, 1), 'totalGiB': round(disk.total / 1073741824, 1)}
    except OSError:
      pass
    uptime = float((self.root / 'uptime').read_text().split()[0])
    sampled_at = self.wall_clock()
    if not math.isfinite(uptime) or uptime < 0 or not math.isfinite(now) or not math.isfinite(sampled_at) or sampled_at <= 0:
      raise ValueError('Invalid sample time')
    result = {
      'schemaVersion': 1, 'mode': 'local-runtime', 'source': 'Local Linux system telemetry',
      'sampledAt': sampled_at, 'cpuPercent': overall, 'cores': cores,
      'memory': {'totalMiB': round(total / 1024, 1),
                 'usedMiB': round(used / 1024, 1) if used is not None else None,
                 'availableMiB': round(available / 1024, 1) if available is not None else None,
                 'percent': round(100 * used / total, 1) if used is not None else None},
      'storage': storage, 'uptimeSeconds': uptime, 'processCount': len(rows), 'processes': rows,
    }
    self.previous, self.cpu_previous, self.previous_time = process_ticks, cpu_now, now
    return result