//
//  PerfStat.h
//  libraries/shared/src
//
//  Created by Brad Hefta-Gaub on 3/29/13.
//  Copyright 2013 High Fidelity, Inc.
//
//  Poor-man's performance stats collector class. Useful for collecting timing
//  details from various portions of the code.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#ifndef hifi_PerfStat_h
#define hifi_PerfStat_h

#include <stdint.h>
#include "SharedUtil.h"
#include "SimpleMovingAverage.h"

#include <atomic>
#include <cstring>
#include <string>
#include <map>

using AtomicUIntStat = std::atomic<uintmax_t>;

class PerformanceWarning {
private:
    quint64 _start;
    const char* _message;
    bool _renderWarningsOn;
    bool _alwaysDisplay;
    AtomicUIntStat* _runningTotal;
    AtomicUIntStat* _totalCalls;
    static bool _suppressShortTimings;
public:

    PerformanceWarning(bool renderWarnings, const char* message, bool alwaysDisplay = false,
                       AtomicUIntStat* runningTotal = NULL, AtomicUIntStat* totalCalls = NULL) :
        _start(usecTimestampNow()),
        _message(message),
        _renderWarningsOn(renderWarnings),
        _alwaysDisplay(alwaysDisplay),
        _runningTotal(runningTotal),
        _totalCalls(totalCalls) { }

    quint64 elapsed() const { return (usecTimestampNow() - _start); };

    ~PerformanceWarning();

    static void setSuppressShortTimings(bool suppressShortTimings) { _suppressShortTimings = suppressShortTimings; }
};

class PerformanceTimerRecord {
public:
    PerformanceTimerRecord() : _runningTotal(0), _lastTotal(0), _numAccumulations(0), _numTallies(0), _expiry(0) {}

    void accumulateResult(const quint64& elapsed) { _runningTotal += elapsed; ++_numAccumulations; }
    void tallyResult(const quint64& now);
    bool isStale(const quint64& now) const { return now > _expiry; }
    quint64 getAverage() const { return (_numTallies == 0) ? 0 : _runningTotal / _numTallies; }
    quint64 getMovingAverage() const { return (_numTallies == 0) ? 0 : _movingAverage.getAverage(); }
    quint64 getCount() const { return _numTallies; }

private:
    quint64 _runningTotal;
    quint64 _lastTotal;
    quint64 _numAccumulations;
    quint64 _numTallies;
    quint64 _expiry;
    SimpleMovingAverage _movingAverage;
};

class PerformanceTimer {
public:

    PerformanceTimer(const QString& name);
    ~PerformanceTimer();

    static bool isActive();
    static void setActive(bool active);

    static QString getContextName();
    static void addTimerRecord(const QString& fullName, quint64 elapsedUsec);
    static QMap<QString, PerformanceTimerRecord> getAllTimerRecords();
    static void tallyAllTimerRecords();
    static void dumpAllTimerRecords();

private:
    quint64 _start = 0;
    QString _name;
    static std::atomic<bool> _isActive;

    static std::mutex _mutex;  // used to guard multi-threaded access to _fullNames and _records
    static QHash<QThread*, QString> _fullNames;
    static QMap<QString, PerformanceTimerRecord> _records;
};

// uncomment WANT_DETAILED_PERFORMANCE_TIMERS definition to enable performance timers in high-frequency contexts
//#define WANT_DETAILED_PERFORMANCE_TIMERS
#ifdef WANT_DETAILED_PERFORMANCE_TIMERS
    #define DETAILED_PERFORMANCE_TIMER(name) PerformanceTimer detailedPerformanceTimer(name);
#else // WANT_DETAILED_PERFORMANCE_TIMERS
    #define DETAILED_PERFORMANCE_TIMER(name) ; // no-op
#endif // WANT_DETAILED_PERFORMANCE_TIMERS

#endif // hifi_PerfStat_h