"""
ClearPilot telemetry client library.

Usage from any process:
  from openpilot.selfdrive.clearpilot.telemetry import tlog
  tlog("canbus", {"speed": 45.2, "speed_limit": 60})

Sends JSON packets over ZMQ PUSH to telemetryd, which diffs and writes CSV.
Only sends when TelemetryEnabled memory param is set — zero cost when disabled.
"""
import json
import os
import time
import zmq

TELEMETRY_SOCK = "ipc:///tmp/clearpilot_telemetry"
_PARAM_PATH = "/dev/shm/params/d/TelemetryEnabled"

_ctx = None
_sock = None
_last_check = 0
_enabled = False


def tlog(group: str, data: dict):
  """Log a telemetry packet. Only changed values will be written to CSV by telemetryd."""
  global _ctx, _sock, _last_check, _enabled

  # Check param at most once per second to avoid filesystem overhead
  now = time.monotonic()
  if now - _last_check > 1.0:
    _last_check = now
    try:
      with open(_PARAM_PATH, 'r') as f:
        _enabled = f.read().strip() == "1"
    except (FileNotFoundError, IOError):
      _enabled = False

  if not _enabled:
    return

  if _sock is None:
    _ctx = zmq.Context.instance()
    _sock = _ctx.socket(zmq.PUSH)
    _sock.setsockopt(zmq.LINGER, 0)
    _sock.setsockopt(zmq.SNDHWM, 100)
    _sock.connect(TELEMETRY_SOCK)

  msg = json.dumps({"ts": time.time(), "group": group, "data": data})
  try:
    _sock.send_string(msg, zmq.NOBLOCK)
  except zmq.Again:
    pass  # drop if collector isn't running or queue full