#!/usr/bin/env python

"""
Mellanox

Module contains an implementation of SONiC Platform Base API and
provides access to hardware watchdog on Mellanox platforms
"""

import os
import fcntl
import array
import time

from sonic_platform_base.watchdog_base import WatchdogBase

""" ioctl constants """
IO_WRITE = 0x40000000
IO_READ = 0x80000000
IO_READ_WRITE = 0xC0000000
IO_SIZE_INT = 0x00040000
IO_SIZE_40 = 0x00280000
IO_TYPE_WATCHDOG = ord('W') << 8

WDR_INT = IO_READ | IO_SIZE_INT | IO_TYPE_WATCHDOG
WDR_40 = IO_READ | IO_SIZE_40 | IO_TYPE_WATCHDOG
WDWR_INT = IO_READ_WRITE | IO_SIZE_INT | IO_TYPE_WATCHDOG

""" Watchdog ioctl commands """
WDIOC_GETSUPPORT = 0 | WDR_40
WDIOC_GETSTATUS = 1 | WDR_INT
WDIOC_GETBOOTSTATUS = 2 | WDR_INT
WDIOC_GETTEMP = 3 | WDR_INT
WDIOC_SETOPTIONS = 4 | WDR_INT
WDIOC_KEEPALIVE = 5 | WDR_INT
WDIOC_SETTIMEOUT = 6 | WDWR_INT
WDIOC_GETTIMEOUT = 7 | WDR_INT
WDIOC_SETPRETIMEOUT = 8 | WDWR_INT
WDIOC_GETPRETIMEOUT = 9 | WDR_INT
WDIOC_GETTIMELEFT = 10 | WDR_INT

""" Watchdog status constants """
WDIOS_DISABLECARD = 0x0001
WDIOS_ENABLECARD = 0x0002

""" Mellanox main watchdog identity string """
WD_MLNX_MAIN_IDENTITY = "mlx-wdt-main"
""" watchdog sysfs """
WD_SYSFS_PATH = "/sys/class/watchdog/"


WD_COMMON_ERROR = -1


class WatchdogImplBase(WatchdogBase):
    """
    Base class that implements common logic for interacting
    with watchdog using ioctl commands
    """

    def __init__(self, wd_device_path):
        """
        Open a watchdog handle
        @param wd_device_path Path to watchdog device
        """

        self.watchdog_path = wd_device_path
        self.watchdog = os.open(self.watchdog_path, os.O_WRONLY)

        # Opening a watchdog descriptor starts
        # watchdog timer;
        # by default it should be stopped
        self._disablecard()
        self.armed = False

        self.timeout = self._gettimeout()

    def _enablecard(self):
        """
        Turn on the watchdog timer
        """

        req = array.array('h', [WDIOS_ENABLECARD])
        fcntl.ioctl(self.watchdog, WDIOC_SETOPTIONS, req, False)

    def _disablecard(self):
        """
        Turn off the watchdog timer
        """

        req = array.array('h', [WDIOS_DISABLECARD])
        fcntl.ioctl(self.watchdog, WDIOC_SETOPTIONS, req, False)

    def _keepalive(self):
        """
        Keep alive watchdog timer
        """

        fcntl.ioctl(self.watchdog, WDIOC_KEEPALIVE)

    def _settimeout(self, seconds):
        """
        Set watchdog timer timeout
        @param seconds - timeout in seconds
        @return is the actual set timeout
        """

        req = array.array('I', [seconds])
        fcntl.ioctl(self.watchdog, WDIOC_SETTIMEOUT, req, True)

        return int(req[0])

    def _gettimeout(self):
        """
        Get watchdog timeout
        @return watchdog timeout
        """

        req = array.array('I', [0])
        fcntl.ioctl(self.watchdog, WDIOC_GETTIMEOUT, req, True)

        return int(req[0])

    def _gettimeleft(self):
        """
        Get time left before watchdog timer expires
        @return time left in seconds
        """

        req = array.array('I', [0])
        fcntl.ioctl(self.watchdog, WDIOC_GETTIMELEFT, req, True)

        return int(req[0])

    def arm(self, seconds):
        """
        Implements arm WatchdogBase API
        """

        ret = WD_COMMON_ERROR
        if seconds < 0:
            return ret

        try:
            if self.timeout != seconds:
                self.timeout = self._settimeout(seconds)
            if self.armed:
                self._keepalive()
            else:
                self._enablecard()
                self.armed = True
            ret = self.timeout
        except IOError:
            pass

        return ret

    def disarm(self):
        """
        Implements disarm WatchdogBase API
        """

        disarmed = False
        if self.armed:
            try:
                self._disablecard()
                self.armed = False
                disarmed = True
            except IOError:
                pass

        return disarmed

    def is_armed(self):
        """
        Implements is_armed WatchdogBase API
        """

        return self.armed

    def get_remaining_time(self):
        """
        Implements get_remaining_time WatchdogBase API
        """

        timeleft = WD_COMMON_ERROR

        if self.armed:
            try:
                timeleft = self._gettimeleft()
            except IOError:
                pass

        return timeleft

    def __del__(self):
        """
        Close watchdog
        """

        os.close(self.watchdog)


class WatchdogType1(WatchdogImplBase):
    """
    Watchdog type 1
    """

    def arm(self, seconds):
        """
        Call arm from WatchdgoImplBase and save the timestamp
        when the watchdog was armed
        """

        ret = WatchdogImplBase.arm(self, seconds)
        # Save the watchdog arm timestamp
        # requiered for get_remaining_time()
        self.arm_timestamp = time.time()

        return ret

    def get_remaining_time(self):
        """
        Watchdog Type 1 does not support timeleft
        operation, we will calculate timeleft based
        on timeout and arm timestamp
        """

        timeleft = WD_COMMON_ERROR

        if self.armed:
            timeleft = int(self.timeout - (time.time() - self.arm_timestamp))

        return timeleft

class WatchdogType2(WatchdogImplBase):
    """
    Watchdog type 2
    """

    pass


def is_mlnx_wd_main(dev):
    """
    Checks if dev is Mellanox main watchdog
    """

    try:
        with open("{}/{}/identity".format(WD_SYSFS_PATH, dev)) as identity_file:
            identity = identity_file.read().strip()
            if identity == WD_MLNX_MAIN_IDENTITY:
                return True
    except IOError:
        pass

    return False


def is_wd_type2(dev):
    """
    Checks if dev is Mellanox type 2 watchdog
    """

    return os.path.exists("{}/{}/timeleft".format(WD_SYSFS_PATH, dev))


def get_watchdog():
    """
    Return WatchdogType1 or WatchdogType2 based on system
    """

    watchdog_main_device_name = None

    for device in os.listdir("/dev/"):
        if device.startswith("watchdog") and is_mlnx_wd_main(device):
            watchdog_main_device_name = device

    watchdog_device_path = "/dev/{}".format(watchdog_main_device_name)

    watchdog = None

    if is_wd_type2(watchdog_main_device_name):
        watchdog = WatchdogType2(watchdog_device_path)
    else:
        watchdog = WatchdogType1(watchdog_device_path)

    return watchdog