Statistics.h

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//
// SourceInterests.h
//
// Created on August 27th 2018
//
// Copyright 2018 CFM (www.cfm.fr)
//
// 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.
//

#pragma once

#include <array>
#include <string_view>

using namespace std::literals;


namespace MetroCollect {
    class MetricsController;

    class Statistics {
        friend MetricsController;                               
        protected:
            enum StatsIndex : uint8_t {
                StatsIndexMin       = 0,                        
                StatsIndexMax       = 1,                        
                StatsIndexAverage   = 2,                        
                StatsIndexStdDev    = 3,                        

                // Private intermediate statistics
                StatsIndexIntermediateSum           = 4,        
                StatsIndexIntermediateSumSquared    = 5,        
            };

        public:
            static constexpr size_t count = 4;                                                                              
            static constexpr std::array<std::string_view, count> names = {"min"sv, "max"sv, "average"sv, "stdDev"sv};       
            static constexpr std::string_view nameStatsAll = "*"sv;

            enum Stats : uint64_t {
                StatsMin        = 1 << StatsIndexMin,                                       
                StatsMax        = 1 << StatsIndexMax,                                       
                StatsAverage    = 1 << StatsIndexAverage,                                   
                StatsStdDev     = 1 << StatsIndexStdDev,                                    

                StatsNone       = 0,                                                        
                StatsAll        = StatsMin | StatsMax | StatsAverage | StatsStdDev,         
            };
            static constexpr std::array<Stats, count> allStats = {StatsMin, StatsMax, StatsAverage, StatsStdDev};           

            static Stats statsFromName(const std::string_view& statName);                   
            static Stats statsRequiredForStat(Stats stat);                                  

        protected:
            static constexpr size_t extraCount = count + 2;                                 

            enum StatsDependency : uint64_t {
                StatsDependencyMin          = StatsMin,                                     
                StatsDependencyMax          = StatsMax,                                     
                StatsDependencyStdDev       = StatsStdDev,                                  
                StatsDependencyAverage      = StatsAverage | StatsDependencyStdDev,         
                StatsDependencySum          = StatsDependencyAverage,                       
                StatsDependencySumSquared   = StatsDependencyStdDev,                        
            };
            static constexpr std::array<StatsDependency, extraCount> StatsDependencies = {StatsDependencyMin, StatsDependencyMax, StatsDependencyAverage, StatsDependencyStdDev, StatsDependencySum, StatsDependencySumSquared};        
    };


    template<typename T>
    constexpr inline Statistics::Stats operator| (Statistics::Stats a, T b) {
        return static_cast<Statistics::Stats>(static_cast<uint64_t>(a) | static_cast<uint64_t>(b));
    }

    template<typename T>
    constexpr inline Statistics::Stats& operator|= (Statistics::Stats& a, T b) {
        a = a | b;
        return a;
    }
}