import datetime
import random
import threading
import time
from statistics import mean

from cereal import log
from common.realtime import sec_since_boot
from selfdrive.swaglog import cloudlog

PANDA_OUTPUT_VOLTAGE = 5.28


# Parameters
def get_battery_capacity():
  return _read_param("/sys/class/power_supply/battery/capacity", int)


def get_battery_status():
  # This does not correspond with actual charging or not.
  # If a USB cable is plugged in, it responds with 'Charging', even when charging is disabled
  return _read_param("/sys/class/power_supply/battery/status", lambda x: x.strip(), '')


def get_battery_current():
  return _read_param("/sys/class/power_supply/battery/current_now", int)


def get_battery_voltage():
  return _read_param("/sys/class/power_supply/battery/voltage_now", int)


def get_usb_present():
  return _read_param("/sys/class/power_supply/usb/present", lambda x: bool(int(x)), False)


def get_battery_charging():
  # This does correspond with actually charging
  return _read_param("/sys/class/power_supply/battery/charge_type", lambda x: x.strip() != "N/A", False)


def set_battery_charging(on):
  with open('/sys/class/power_supply/battery/charging_enabled', 'w') as f:
    f.write(f"{1 if on else 0}\n")


# Helpers
def _read_param(path, parser, default=0):
  try:
    with open(path) as f:
      return parser(f.read())
  except Exception:
    return default


def panda_current_to_actual_current(panda_current):
  # From white/grey panda schematic
  return (3.3 - (panda_current * 3.3 / 4096)) / 8.25


class PowerMonitoring:
  def __init__(self):
    self.last_measurement_time = None           # Used for integration delta
    self.power_used_uWh = 0                     # Integrated power usage in uWh since going into offroad
    self.next_pulsed_measurement_time = None
    self.integration_lock = threading.Lock()

  # Calculation tick
  def calculate(self, health):
    try:
      now = sec_since_boot()

      # Check that time is valid
      if datetime.datetime.fromtimestamp(now).year < 2019:
        return

      # Only integrate when there is no ignition
      # If health is None, we're probably not in a car, so we don't care
      if health is None or (health.health.ignitionLine or health.health.ignitionCan) or \
         health.health.hwType == log.HealthData.HwType.unknown:
        with self.integration_lock:
          self.last_measurement_time = None
          self.next_pulsed_measurement_time = None
          self.power_used_uWh = 0
        return

      # First measurement, set integration time
      with self.integration_lock:
        if self.last_measurement_time is None:
          self.last_measurement_time = now
          return

      is_uno = health.health.hwType == log.HealthData.HwType.uno
      # Get current power draw somehow
      current_power = 0
      if get_battery_status() == 'Discharging':
        # If the battery is discharging, we can use this measurement
        # On C2: this is low by about 10-15%, probably mostly due to UNO draw not being factored in
        current_power = ((get_battery_voltage() / 1000000) * (get_battery_current() / 1000000))
      elif (health.health.hwType in [log.HealthData.HwType.whitePanda, log.HealthData.HwType.greyPanda]) and (health.health.current > 1):
        # If white/grey panda, use the integrated current measurements if the measurement is not 0
        # If the measurement is 0, the current is 400mA or greater, and out of the measurement range of the panda
        # This seems to be accurate to about 5%
        current_power = (PANDA_OUTPUT_VOLTAGE * panda_current_to_actual_current(health.health.current))
      elif (self.next_pulsed_measurement_time is not None) and (self.next_pulsed_measurement_time <= now):
        # TODO: Figure out why this is off by a factor of 3/4???
        FUDGE_FACTOR = 1.33

        # Turn off charging for about 10 sec in a thread that does not get killed on SIGINT, and perform measurement here to avoid blocking thermal
        def perform_pulse_measurement(now):
          try:
            set_battery_charging(False)
            time.sleep(5)

            # Measure for a few sec to get a good average
            voltages = []
            currents = []
            for _ in range(6):
              voltages.append(get_battery_voltage())
              currents.append(get_battery_current())
              time.sleep(1)
            current_power = ((mean(voltages) / 1000000) * (mean(currents) / 1000000))

            self._perform_integration(now, current_power * FUDGE_FACTOR)

            # Enable charging again
            set_battery_charging(True)
          except Exception:
            cloudlog.exception("Pulsed power measurement failed")

        # Start pulsed measurement and return
        threading.Thread(target=perform_pulse_measurement, args=(now,)).start()
        self.next_pulsed_measurement_time = None
        return

      elif self.next_pulsed_measurement_time is None and not is_uno:
        # On a charging EON with black panda, or drawing more than 400mA out of a white/grey one
        # Only way to get the power draw is to turn off charging for a few sec and check what the discharging rate is
        # We shouldn't do this very often, so make sure it has been some long-ish random time interval
        self.next_pulsed_measurement_time = now + random.randint(120, 180)
        return
      else:
        # Do nothing
        return

      # Do the integration
      self._perform_integration(now, current_power)
    except Exception:
      cloudlog.exception("Power monitoring calculation failed")

  def _perform_integration(self, t, current_power):
    with self.integration_lock:
      try:
        if self.last_measurement_time:
          integration_time_h = (t - self.last_measurement_time) / 3600
          power_used = (current_power * 1000000) * integration_time_h
          if power_used < 0:
            raise ValueError(f"Negative power used! Integration time: {integration_time_h} h Current Power: {power_used} uWh")
          self.power_used_uWh += power_used
          self.last_measurement_time = t
      except Exception:
        cloudlog.exception("Integration failed")

  # Get the power usage
  def get_power_used(self):
    return int(self.power_used_uWh)