# Copyright (c) 2018 Cisco and/or its affiliates.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Module holding BitCountingMetadataFactory class."""

import math

from AvgStdevMetadata import AvgStdevMetadata
from AvgStdevMetadataFactory import AvgStdevMetadataFactory
from BitCountingMetadata import BitCountingMetadata


class BitCountingMetadataFactory(object):
    """Class for factory which creates bit counting metadata from data.

    TODO: Summarize the methods?
    """

    @staticmethod
    def find_max_value(values):
        """Return the max value.

        This is a separate helper method,
        because the whole set of values is usually larger than in from_data().

        :param values: Run values to be processed.
        :type values: Iterable of float
        :returns: 0.0 or the biggest value found.
        :rtype: float
        """
        max_value = 0.0
        for value in values:
            if isinstance(value, AvgStdevMetadata):
                value = value.avg
            if value > max_value:
                max_value = value
        return max_value

    def __init__(self, max_value, prev_avg=None):
        """Construct the factory instance with given arguments.

        :param max_value: Maximal expected value.
        :param prev_avg: Population average of the previous group.
            If None, no previous average is taken into account.
            If not None, the given previous average is used to discourage
            consecutive groups with similar averages
            (opposite triangle distribution is assumed).
        :type max_value: float
        :type prev_avg: float or None
        """
        self.max_value = max_value
        self.prev_avg = prev_avg

    def from_avg_stdev_metadata(self, metadata):
        """Return new metadata object by adding bits to existing metadata.

        :param metadata: Metadata to count bits for.
        :type metadata: AvgStdevMetadata
        :returns: The metadata with bits counted.
        :rtype: BitCountingMetadata
        """
        return BitCountingMetadata(
            max_value=self.max_value, size=metadata.size,
            avg=metadata.avg, stdev=metadata.stdev, prev_avg=self.prev_avg)

    def from_data(self, values):
        """Return new metadata object fitting the values.

        :param values: Run values to be processed.
        :type values: Iterable of float or of AvgStdevMetadata
        :returns: The metadata matching the values.
        :rtype: BitCountingMetadata
        """
        metadata = AvgStdevMetadataFactory.from_data(values)
        return self.from_avg_stdev_metadata(metadata)