//
//  LODManager.cpp
//  interface/src/LODManager.h
//
//  Created by Clement on 1/16/15.
//  Copyright 2015 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#include "LODManager.h"

#include <SettingHandle.h>
#include <OctreeUtils.h>
#include <Util.h>

#include "Application.h"
#include "ui/DialogsManager.h"
#include "InterfaceLogging.h"


Setting::Handle<float> desktopLODDecreaseFPS("desktopLODDecreaseFPS", DEFAULT_DESKTOP_LOD_DOWN_FPS);
Setting::Handle<float> hmdLODDecreaseFPS("hmdLODDecreaseFPS", DEFAULT_HMD_LOD_DOWN_FPS);

LODManager::LODManager() {
}

float LODManager::getLODDecreaseFPS() const {
    if (qApp->isHMDMode()) {
        return getHMDLODDecreaseFPS();
    }
    return getDesktopLODDecreaseFPS();
}

float LODManager::getLODIncreaseFPS() const {
    if (qApp->isHMDMode()) {
        return getHMDLODIncreaseFPS();
    }
    return getDesktopLODIncreaseFPS();
}

// We use a "time-weighted running average" of the maxRenderTime and compare it against min/max thresholds
// to determine if we should adjust the level of detail (LOD).
//
// A time-weighted running average has a timescale which determines how fast the average tracks the measured
// value in real-time.  Given a step-function in the mesured value, and assuming measurements happen
// faster than the runningAverage is computed, the error between the value and its runningAverage will be
// reduced by 1/e every timescale of real-time that passes.
const float LOD_ADJUST_RUNNING_AVG_TIMESCALE = 0.08f; // sec
//
// Assuming the measured value is affected by logic invoked by the runningAverage bumping up against its
// thresholds, we expect the adjustment to introduce a step-function.  We want the runningAverage to settle
// to the new value BEFORE we test it aginst its thresholds again.  Hence we test on a period that is a few
// multiples of the running average timescale:
const uint64_t LOD_AUTO_ADJUST_PERIOD = 4 * (uint64_t)(LOD_ADJUST_RUNNING_AVG_TIMESCALE * (float)USECS_PER_MSEC); // usec

const float LOD_AUTO_ADJUST_DECREMENT_FACTOR = 0.8f;
const float LOD_AUTO_ADJUST_INCREMENT_FACTOR = 1.2f;

void LODManager::setRenderTimes(float presentTime, float engineRunTime, float batchTime, float gpuTime) {
    _presentTime = presentTime;
    _engineRunTime = engineRunTime;
    _batchTime = batchTime;
    _gpuTime = gpuTime;
}

void LODManager::autoAdjustLOD(float realTimeDelta) {
    // The "render time" is the worse of:
    // - engineRunTime: Time spent in the render thread in the engine producing the gpu::Frame N
    // - batchTime: Time spent in the present thread processing the batches of gpu::Frame N+1
    // - presentTime: Time spent in the present thread between the last 2 swap buffers considered the total time to submit gpu::Frame N+1
    // - gpuTime: Time spent in the GPU executing the gpu::Frame N + 2

    // But Present time is in reality synched with the monitor/display refresh rate, it s always longer than batchTime.
    // So if batchTime is fast enough relative to PResent Time we are using it, otherwise we are using presentTime. got it ?
    auto presentTime = (_presentTime - _batchTime > 3.0f ? _batchTime + 3.0f : _presentTime);
    float maxRenderTime = glm::max(glm::max(presentTime, _engineRunTime), _gpuTime);

    // compute time-weighted running average maxRenderTime
    // Note: we MUST clamp the blend to 1.0 for stability
    float blend = (realTimeDelta < LOD_ADJUST_RUNNING_AVG_TIMESCALE) ? realTimeDelta / LOD_ADJUST_RUNNING_AVG_TIMESCALE : 1.0f;
    _avgRenderTime = (1.0f - blend) * _avgRenderTime + blend * maxRenderTime; // msec

    float smoothBlend = (realTimeDelta <  LOD_ADJUST_RUNNING_AVG_TIMESCALE * _smoothScale) ? realTimeDelta / (LOD_ADJUST_RUNNING_AVG_TIMESCALE * _smoothScale) : 1.0f;
    _smoothRenderTime = (1.0f - smoothBlend) * _smoothRenderTime + smoothBlend * maxRenderTime; // msec


  // _avgRenderTime = maxRenderTime;
    if (!_automaticLODAdjust || _avgRenderTime == 0.0f) {
        // early exit
        return;
    }

    float oldOctreeSizeScale = _octreeSizeScale;
    float oldSolidAngle = getLODAngleDeg();

    float targetFPS = 0.5 * (getLODDecreaseFPS() + getLODIncreaseFPS());
    float targetPeriod = 1.0f / targetFPS;

    float currentFPS = (float)MSECS_PER_SECOND / _avgRenderTime;
    float currentSmoothFPS = (float)MSECS_PER_SECOND / _smoothRenderTime;
    float currentVarianceFPS = (currentSmoothFPS - currentFPS);
    currentVarianceFPS *= currentVarianceFPS;

    auto dt = realTimeDelta;

    auto previous_error = _pidHistory.x;
    auto previous_integral = _pidHistory.y;

    auto smoothError = (targetFPS - currentSmoothFPS);

    auto fpsError = smoothError;

    auto errorSquare = smoothError * smoothError;

    auto noiseCoef = (errorSquare <  _pidCoefs.w * currentVarianceFPS ? 0.0f : 1.0f);

    auto normalizedError = noiseCoef * smoothError / targetFPS;

    auto error = glm::clamp(normalizedError, -1.0f, 1.0f);

    auto integral = previous_integral + error * dt;
    glm::clamp(integral, -1.0f, 1.0f);

    auto derivative = (error - previous_error) / dt;

    _pidHistory.x = error;
    _pidHistory.y = integral;
    _pidHistory.z = derivative;

    auto Kp = _pidCoefs.x;
    auto Ki = _pidCoefs.y;
    auto Kd = _pidCoefs.z;

    _pidOutputs.x = Kp * error;
    _pidOutputs.y = Ki * integral;
    _pidOutputs.z = Kd * derivative;

    auto output = _pidOutputs.x + _pidOutputs.y + _pidOutputs.z;

    _pidOutputs.w = output;

    auto newSolidAngle = oldSolidAngle + output;

    setLODAngleDeg(newSolidAngle);

    if (oldOctreeSizeScale != _octreeSizeScale) {
        auto lodToolsDialog = DependencyManager::get<DialogsManager>()->getLodToolsDialog();
        if (lodToolsDialog) {
            lodToolsDialog->reloadSliders();
        }
    }
}

void LODManager::resetLODAdjust() {
    _decreaseFPSExpiry = _increaseFPSExpiry = usecTimestampNow() + LOD_AUTO_ADJUST_PERIOD;
}

void LODManager::setAutomaticLODAdjust(bool value) {
    _automaticLODAdjust = value;
    emit autoLODChanged();
}

float LODManager::getLODLevel() const {
    // simpleLOD is a linearized and normalized number that represents how much LOD is being applied.
    // It ranges from:
    //    1.0 = normal (max) level of detail
    //    0.0 = min level of detail
    // In other words: as LOD "drops" the value of simpleLOD will also "drop", and it cannot go lower than 0.0.
    const float LOG_MIN_LOD_RATIO = logf(ADJUST_LOD_MIN_SIZE_SCALE / ADJUST_LOD_MAX_SIZE_SCALE);
    float power = logf(_octreeSizeScale / ADJUST_LOD_MAX_SIZE_SCALE);
    float simpleLOD = (LOG_MIN_LOD_RATIO - power) / LOG_MIN_LOD_RATIO;
    return simpleLOD;
}

void LODManager::setLODLevel(float level) {
    float simpleLOD = level;
    if (!_automaticLODAdjust) {
        const float LOG_MIN_LOD_RATIO = logf(ADJUST_LOD_MIN_SIZE_SCALE / ADJUST_LOD_MAX_SIZE_SCALE);

        float power = LOG_MIN_LOD_RATIO - (simpleLOD * LOG_MIN_LOD_RATIO);
        float sizeScale = expf(power) * ADJUST_LOD_MAX_SIZE_SCALE;
        setOctreeSizeScale(sizeScale);
    }
}

const float MIN_DECREASE_FPS = 0.5f;

void LODManager::setDesktopLODDecreaseFPS(float fps) {
    if (fps < MIN_DECREASE_FPS) {
        // avoid divide by zero
        fps = MIN_DECREASE_FPS;
    }
    _desktopMaxRenderTime = (float)MSECS_PER_SECOND / fps;
}

float LODManager::getDesktopLODDecreaseFPS() const {
    return (float)MSECS_PER_SECOND / _desktopMaxRenderTime;
}

float LODManager::getDesktopLODIncreaseFPS() const {
    return glm::min(((float)MSECS_PER_SECOND / _desktopMaxRenderTime) + INCREASE_LOD_GAP_FPS, MAX_LIKELY_DESKTOP_FPS);
}

void LODManager::setHMDLODDecreaseFPS(float fps) {
    if (fps < MIN_DECREASE_FPS) {
        // avoid divide by zero
        fps = MIN_DECREASE_FPS;
    }
    _hmdMaxRenderTime = (float)MSECS_PER_SECOND / fps;
}

float LODManager::getHMDLODDecreaseFPS() const {
    return (float)MSECS_PER_SECOND / _hmdMaxRenderTime;
}

float LODManager::getHMDLODIncreaseFPS() const {
    return glm::min(((float)MSECS_PER_SECOND / _hmdMaxRenderTime) + INCREASE_LOD_GAP_FPS, MAX_LIKELY_HMD_FPS);
}

QString LODManager::getLODFeedbackText() {
    // determine granularity feedback
    int boundaryLevelAdjust = getBoundaryLevelAdjust();
    QString granularityFeedback;
    switch (boundaryLevelAdjust) {
        case 0: {
            granularityFeedback = QString(".");
        } break;
        case 1: {
            granularityFeedback = QString(" at half of standard granularity.");
        } break;
        case 2: {
            granularityFeedback = QString(" at a third of standard granularity.");
        } break;
        default: {
            granularityFeedback = QString(" at 1/%1th of standard granularity.").arg(boundaryLevelAdjust + 1);
        } break;
    }
    // distance feedback
    float octreeSizeScale = getOctreeSizeScale();
    float relativeToDefault = octreeSizeScale / DEFAULT_OCTREE_SIZE_SCALE;
    int relativeToTwentyTwenty = 20 / relativeToDefault;

    QString result;
    if (relativeToDefault > 1.01f) {
        result = QString("20:%1 or %2 times further than average vision%3").arg(relativeToTwentyTwenty).arg(relativeToDefault,0,'f',2).arg(granularityFeedback);
    } else if (relativeToDefault > 0.99f) {
        result = QString("20:20 or the default distance for average vision%1").arg(granularityFeedback);
    } else if (relativeToDefault > 0.01f) {
        result = QString("20:%1 or %2 of default distance for average vision%3").arg(relativeToTwentyTwenty).arg(relativeToDefault,0,'f',3).arg(granularityFeedback);
    } else {
        result = QString("%2 of default distance for average vision%3").arg(relativeToDefault,0,'f',3).arg(granularityFeedback);
    }
    return result;
}

bool LODManager::shouldRender(const RenderArgs* args, const AABox& bounds) {
    // FIXME - eventually we want to use the render accuracy as an indicator for the level of detail
    // to use in rendering.
  //  float renderAccuracy = calculateRenderAccuracy(args->getViewFrustum().getPosition(), bounds, args->_sizeScale, args->_boundaryLevelAdjust);
  //  return (renderAccuracy > 0.0f);

    auto pos = args->getViewFrustum().getPosition() - bounds.calcCenter();
    auto dim = bounds.getDimensions();
    auto halfTanSq = 0.25f * glm::dot(dim, dim) / glm::dot(pos, pos);
    return (halfTanSq >= args->_solidAngleHalfTanSq);

};

void LODManager::setOctreeSizeScale(float sizeScale) {
    _octreeSizeScale = sizeScale;
}

void LODManager::setBoundaryLevelAdjust(int boundaryLevelAdjust) {
    _boundaryLevelAdjust = boundaryLevelAdjust;
}

void LODManager::loadSettings() {
    setDesktopLODDecreaseFPS(desktopLODDecreaseFPS.get());
    setHMDLODDecreaseFPS(hmdLODDecreaseFPS.get());
}

void LODManager::saveSettings() {
    desktopLODDecreaseFPS.set(getDesktopLODDecreaseFPS());
    hmdLODDecreaseFPS.set(getHMDLODDecreaseFPS());
}


void LODManager::setSmoothScale(float t) {
    _smoothScale = glm::max(1.0f, t);
}

void LODManager::setWorldDetailQuality(float quality) {

    static const float MAX_DESKTOP_FPS = 60;
    static const float MAX_HMD_FPS = 90;
    static const float MIN_FPS = 10;
    static const float LOW = 0.25f;
    static const float MEDIUM = 0.5f;
    static const float HIGH = 0.75f;
    static const float THRASHING_DIFFERENCE = 10;

    bool isLowestValue = quality == LOW;
    bool isHMDMode = qApp->isHMDMode();

    float maxFPS = isHMDMode ? MAX_HMD_FPS : MAX_DESKTOP_FPS;
    float desiredFPS = maxFPS /* - THRASHING_DIFFERENCE*/;

    if (!isLowestValue) {
        float calculatedFPS = (maxFPS - (maxFPS * quality))/* - THRASHING_DIFFERENCE*/;
        desiredFPS = calculatedFPS < MIN_FPS ? MIN_FPS : calculatedFPS;
    }

    if (isHMDMode) {
        setHMDLODDecreaseFPS(desiredFPS);
    }
    else {
        setDesktopLODDecreaseFPS(desiredFPS);
    }

    emit worldDetailQualityChanged();
}

float LODManager::getWorldDetailQuality() const {


    static const float MAX_DESKTOP_FPS = 60;
    static const float MAX_HMD_FPS = 90;
    static const float MIN_FPS = 10;
    static const float LOW = 0.25f;
    static const float MEDIUM = 0.5f;
    static const float HIGH = 0.75f;

    bool inHMD = qApp->isHMDMode();

    float increaseFPS = 0;
    if (inHMD) {
        increaseFPS = getHMDLODDecreaseFPS();
    } else {
        increaseFPS = getDesktopLODDecreaseFPS();
    }
    float maxFPS = inHMD ? MAX_HMD_FPS : MAX_DESKTOP_FPS;
    float percentage = 1.0 - increaseFPS / maxFPS;

    if (percentage <= LOW) {
        return LOW;
    }
    else if (percentage <= MEDIUM) {
        return MEDIUM;
    }

    return HIGH;
}


float LODManager::getLODAngleHalfTan() const {
    return getPerspectiveAccuracyAngleTan(_octreeSizeScale, _boundaryLevelAdjust);
}
float LODManager::getLODAngle() const {
    return 2.0f * atan(getLODAngleHalfTan());
}
float LODManager::getLODAngleDeg() const {
    return glm::degrees(getLODAngle());
}

void LODManager::setLODAngleDeg(float lodAngle) {
    auto newSolidAngle = std::max(0.5f, std::min(lodAngle, 90.f));
    auto halTan = glm::tan(glm::radians(newSolidAngle * 0.5f));
    auto octreeSizeScale = TREE_SCALE * OCTREE_TO_MESH_RATIO / halTan;
    setOctreeSizeScale(octreeSizeScale);
}

float LODManager::getPidKp() const {
    return _pidCoefs.x;
}
float LODManager::getPidKi() const {
    return _pidCoefs.y;
}
float LODManager::getPidKd() const {
    return _pidCoefs.z;
}
float LODManager::getPidKv() const {
    return _pidCoefs.w;
}
void LODManager::setPidKp(float k) {
    _pidCoefs.x = k;
}
void LODManager::setPidKi(float k) {
    _pidCoefs.y = k;
}
void LODManager::setPidKd(float k) {
    _pidCoefs.z = k;
}
void LODManager::setPidKv(float t) {
    _pidCoefs.w = t;
}

float LODManager::getPidOp() const {
    return _pidOutputs.x;
}
float LODManager::getPidOi() const {
    return _pidOutputs.y;
}
float LODManager::getPidOd() const {
    return _pidOutputs.z;
}
float LODManager::getPidO() const {
    return _pidOutputs.w;
}