#!/usr/bin/env python3
# -*- coding: utf-8 -*-

__author__ = "Christian Heider Nielsen"

import statistics

__all__ = ["MetricSummary"]


class MetricSummary:
    """description"""

    def __init__(self):
        self._values = []
        self.length = 0
        self.running_mean = 0
        self.running_variance = 0

    def append(self, val):
        """

        :param val:
        :type val:"""
        self._values.append(val)
        self.length += 1

    @property
    def values(self):
        """

        :return:
        :rtype:"""
        return self._values

    def moving_average(self, window_size=100):
        """

        :param window_size:
        :type window_size:
        :return:
        :rtype:"""
        if self.length >= window_size:
            return statistics.mean(self._values[-window_size:])
        elif self.length > 0:
            return statistics.mean(self._values)
        else:
            return 0

    def running_average(self, data):
        """
        Computes new running mean and variances.
        :param data: New piece of data.
        :return: New mean and variance values."""
        mean, var, steps = self.running_mean, self.running_variance, self.length
        current_x = statistics.mean(data)

        new_mean = mean + (current_x - mean) / (steps + 1)
        new_variance = var + (current_x - new_mean) * (current_x - mean)

        self.running_mean, self.running_variance = new_mean, new_variance
        return new_mean, new_variance

    def __len__(self):
        return len(self._values)


if __name__ == "__main__":
    MetricSummary()
