# Copyright (c) 2014 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.cros.video import method_logger
from autotest_lib.client.cros.image_comparison import comparison_result

# TODO (mussa): We will use data generated by running tests using this class.
# If we can do with one comparer we may not need this class.

class UploadOnFailComparer(object):
    """
    Compares a test image against a golden image.

    Uses a local comparer first to do the comparison, for every comparison
    that return fail, it uses remote comparer.

    """


    @method_logger.log
    def __init__(self, local_comparer, remote_comparer, threshold=0):
        """
        @param local_comparer: object impementing compare(), local comparer.
        @param remote_comparer: object implementing compare(), remote comparer.
        @param threshold: int, a value which the pixel difference between test
                          image and golden image has to exceed before the
                          remote comparer is used.

        """
        self.local_comparer = local_comparer
        self.remote_comparer = remote_comparer
        self.threshold = threshold


    def __enter__(self):
        return self


    @method_logger.log
    def compare(self, golden_image_path, test_image_path, box=None):
        """
        Compares a test image against a golden image using up to two comparers.

        If the local comparer reports a fail, use the remote comparer to
        compare the same images.

        E.g of use case: You have two comparers, one is local and another is
        web-based. Web-based comparer has the advantage of storing information
        you need to look at the results later.
        Local comparer is fast and reduces the load on the web-based comparer.

        Use local comparer as primary comparer and only invoke the web-based
        comparer on test images that differ from their golden counterparts.

        @param golden_image_path: path, complete path to the golden image.
        @param test_image_path: path, complete path  to the test image.
        @param box: int tuple, left, upper, right, lower pixel coordinates
                    defining a box region within which the comparison is made.

        @return: int, differing pixels as per double check comparer.

        """
        logging.debug('Using primary comparer..')

        with self.local_comparer:
            res = self.local_comparer.compare(golden_image_path,
                                                 test_image_path,
                                                 box)
            diffpx = res.diff_pixel_count
        logging.debug('Primary comparison complete. Diff pixels = %d', diffpx)

        diffpx2 = -1
        comp_res = res.comparison_url

        if (diffpx > self.threshold):
            logging.debug('Threshold diff pixels is %d', self.threshold)
            logging.debug('Diff pxls > threshold. Using remote comparer.')

            with self.remote_comparer:
                res_remote = self.remote_comparer.compare(golden_image_path,
                                                          test_image_path,
                                                          box)
                diffpx2 = res_remote.diff_pixel_count

            if not comp_res:
                comp_res = res_remote.comparison_url

            logging.debug('Secondary comparison complete. Diff pixels = %d',
                          diffpx2)

        diffpx_return = diffpx2 if diffpx2 != -1 else diffpx


        return comparison_result.ComparisonResult(diffpx_return,
                                                  comp_res)


    def __exit__(self, exc_type, exc_val, exc_tb):
        pass