# Copyright (c) 2010 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.
import logging

from autotest_lib.client.bin import test
from autotest_lib.client.common_lib import error
from autotest_lib.client.cros import power_utils, service_stopper


class hardware_Backlight(test.test):
    version = 1

    def initialize(self):
        """Perform necessary initialization prior to test run.

        Private Attributes:
          _backlight: power_utils.Backlight object
          _services: service_stopper.ServiceStopper object
        """
        super(hardware_Backlight, self).initialize()
        self._backlight = None
        # Stop powerd to avoid it adjusting backlight levels
        self._services = service_stopper.ServiceStopper(['powerd'])
        self._services.stop_services()


    def run_once(self):
        # optionally test keyboard backlight
        kblight = None
        kblight_errs = 0
        try:
            kblight = power_utils.KbdBacklight()
        except power_utils.KbdBacklightException as e:
            logging.info("Assuming no keyboard backlight due to %s", str(e))

        if kblight:
            init_percent = kblight.get()
            try:
                for i in xrange(100, -1, -1):
                    kblight.set(i)
                    result = int(kblight.get())
                    if i != result:
                        logging.error('keyboard backlight set %d != %d get',
                                      i, result)
                        kblight_errs += 1
            finally:
                kblight.set(init_percent)

        if kblight_errs:
            raise error.TestFail("%d errors testing keyboard backlight." % \
                                 kblight_errs)

        self._backlight = power_utils.Backlight()
        backlight_errs = 0
        backlight_max = self._backlight.get_max_level()
        for i in xrange(backlight_max + 1):
            self._backlight.set_level(i)
            result = self._backlight.get_level()
            if i != result:
                # The kernel Documentation/ABI/stable/sysfs-class-backlight
                # states that the requested brightness may not be the
                # actual_brightness.
                # Although not specified in the docs, let's allow the difference
                # between requested brightness and actual_brightness percent be
                # within a tolerance of 1 of each other.
                actual_percent = self._backlight.get_percent()
                expected_percent = float(i) / float(backlight_max) * 100.0
                diff_percent = abs(actual_percent - expected_percent)
                log_level_func = logging.warn
                if diff_percent > 1:
                    backlight_errs += 1
                    log_level_func = logging.error
                    log_level_func('backlight expected vs. actual exceeds error'
                                   'tolerance')
                log_level_func('backlight set %d != %d get', i, result)
                log_level_func('backlight percent difference is %f%%',
                               diff_percent)

        if backlight_errs:
            raise error.TestFail("%d errors testing backlight." % \
                                 backlight_errs)


    def cleanup(self):
        if self._backlight:
            self._backlight.restore()
        self._services.restore_services()
        super(hardware_Backlight, self).cleanup()