# Copyright 2015 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Facade to access the system-related functionality."""

import os

from autotest_lib.client.bin import utils, site_utils


class SystemFacadeNativeError(Exception):
    """Error in SystemFacadeNative."""
    pass


class SystemFacadeNative(object):
    """Facede to access the system-related functionality.

    The methods inside this class only accept Python native types.

    """
    SCALING_GOVERNOR_MODES = [
            'interactive',
            'performance',
            'ondemand',
            'powersave',
            ]

    def set_scaling_governor_mode(self, index, mode):
        """Set mode of CPU scaling governor on one CPU.

        @param index: CPU index starting from 0.

        @param mode: Mode of scaling governor, accept 'interactive' or
                     'performance'.

        @returns: The original mode.

        """
        if mode not in self.SCALING_GOVERNOR_MODES:
            raise SystemFacadeNativeError('mode %s is invalid' % mode)

        governor_path = os.path.join(
                '/sys/devices/system/cpu/cpu%d' % index,
                'cpufreq/scaling_governor')
        if not os.path.exists(governor_path):
            raise SystemFacadeNativeError(
                    'scaling governor of CPU %d is not available' % index)

        original_mode = utils.read_one_line(governor_path)
        utils.open_write_close(governor_path, mode)

        return original_mode


    def get_cpu_usage(self):
        """Returns machine's CPU usage.

        Returns:
            A dictionary with 'user', 'nice', 'system' and 'idle' values.
            Sample dictionary:
            {
                'user': 254544,
                'nice': 9,
                'system': 254768,
                'idle': 2859878,
            }
        """
        return site_utils.get_cpu_usage()


    def compute_active_cpu_time(self, cpu_usage_start, cpu_usage_end):
        """Computes the fraction of CPU time spent non-idling.

        This function should be invoked using before/after values from calls to
        get_cpu_usage().
        """
        return site_utils.compute_active_cpu_time(cpu_usage_start,
                                                  cpu_usage_end)


    def get_mem_total(self):
        """Returns the total memory available in the system in MBytes."""
        return site_utils.get_mem_total()


    def get_mem_free(self):
        """Returns the currently free memory in the system in MBytes."""
        return site_utils.get_mem_free()


    def get_ec_temperatures(self):
        """Uses ectool to return a list of all sensor temperatures in Celsius.
        """
        return site_utils.get_ec_temperatures()


    def get_current_board(self):
        """Returns the current device board name."""
        return utils.get_current_board()


    def get_chromeos_release_version(self):
        """Returns chromeos version in device under test as string. None on
        fail.
        """
        return utils.get_chromeos_release_version()