//
//  ToneMappingEffect.cpp
//  libraries/render-utils/src
//
//  Created by Sam Gateau on 12/7/2015.
//  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 "ToneMappingEffect.h"

#include <gpu/Context.h>
#include <gpu/StandardShaderLib.h>

#include <RenderArgs.h>

#include "FramebufferCache.h"


ToneMappingEffect::ToneMappingEffect() {
    Parameters parameters;
    _parametersBuffer = gpu::BufferView(std::make_shared<gpu::Buffer>(sizeof(Parameters), (const gpu::Byte*) &parameters));
}

void ToneMappingEffect::init() {
    const char BlitTextureGamma_frag[] = R"SCRIBE(#version 410 core
        //  Generated on Sat Oct 24 09:34:37 2015
        //
        //  Draw texture 0 fetched at texcoord.xy
        //
        //  Created by Sam Gateau on 6/22/2015
        //  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
        //

        struct ToneMappingParams {
            vec4 _exp_2powExp_s0_s1;
            ivec4 _toneCurve_s0_s1_s2;
        };

        const float INV_GAMMA_22 = 1.0 / 2.2;
        const int ToneCurveNone = 0;
        const int ToneCurveGamma22 = 1;
        const int ToneCurveReinhard = 2;
        const int ToneCurveFilmic = 3;

        uniform toneMappingParamsBuffer {
            ToneMappingParams params;
        };
        float getTwoPowExposure() {
            return params._exp_2powExp_s0_s1.y;
        }
        int getToneCurve() {
            return params._toneCurve_s0_s1_s2.x;
        }

        uniform sampler2D colorMap;
        
        in vec2 varTexCoord0;
        out vec4 outFragColor;
        
        void main(void) {
            vec4 fragColorRaw = texture(colorMap, varTexCoord0);
            vec3 fragColor = fragColorRaw.xyz;

            vec3 srcColor = fragColor * getTwoPowExposure();

            int toneCurve = getToneCurve();
            vec3 tonedColor = srcColor;
            if (toneCurve == ToneCurveFilmic) {
                vec3 x = max(vec3(0.0), srcColor-0.004);
                tonedColor = (x * (6.2 * x + 0.5)) / (x * (6.2 * x + 1.7) + 0.06);
            } else if (toneCurve == ToneCurveReinhard) {
                tonedColor = srcColor/(1.0 + srcColor);
                tonedColor = pow(tonedColor, vec3(INV_GAMMA_22));
            } else if (toneCurve == ToneCurveGamma22) {
                tonedColor = pow(srcColor, vec3(INV_GAMMA_22));
            } // else None toned = src

            outFragColor = vec4(tonedColor, 1.0);
        }
        
        )SCRIBE";
    auto blitPS = gpu::ShaderPointer(gpu::Shader::createPixel(std::string(BlitTextureGamma_frag)));

    auto blitVS = gpu::StandardShaderLib::getDrawViewportQuadTransformTexcoordVS();
    auto blitProgram = gpu::ShaderPointer(gpu::Shader::createProgram(blitVS, blitPS));

    gpu::Shader::BindingSet slotBindings;
    slotBindings.insert(gpu::Shader::Binding(std::string("toneMappingParamsBuffer"), 3));
    gpu::Shader::makeProgram(*blitProgram, slotBindings);
    auto blitState = std::make_shared<gpu::State>();
    blitState->setColorWriteMask(true, true, true, true);
    _blitLightBuffer = gpu::PipelinePointer(gpu::Pipeline::create(blitProgram, blitState));
}

void ToneMappingEffect::setExposure(float exposure) {
    _parametersBuffer.edit<Parameters>()._exposure = exposure;
    _parametersBuffer.edit<Parameters>()._twoPowExposure = pow(2.0, exposure);
}

void ToneMappingEffect::setToneCurve(ToneCurve curve) {
    _parametersBuffer.edit<Parameters>()._toneCurve = curve;
}

void ToneMappingEffect::render(RenderArgs* args) {
    if (!_blitLightBuffer) {
        init();
    }
    auto framebufferCache = DependencyManager::get<FramebufferCache>();
    gpu::doInBatch(args->_context, [=](gpu::Batch& batch) {
        batch.enableStereo(false);
        QSize framebufferSize = framebufferCache->getFrameBufferSize();

        auto lightingBuffer = framebufferCache->getLightingTexture();
        auto destFbo = framebufferCache->getPrimaryFramebuffer();
        batch.setFramebuffer(destFbo);

        // FIXME: Generate the Luminosity map
        //batch.generateTextureMips(lightingBuffer);

        batch.setViewportTransform(args->_viewport);
        batch.setProjectionTransform(glm::mat4());
        batch.setViewTransform(Transform());
        {
            float sMin = args->_viewport.x / (float)framebufferSize.width();
            float sWidth = args->_viewport.z / (float)framebufferSize.width();
            float tMin = args->_viewport.y / (float)framebufferSize.height();
            float tHeight = args->_viewport.w / (float)framebufferSize.height();
            Transform model;
            batch.setPipeline(_blitLightBuffer);
            model.setTranslation(glm::vec3(sMin, tMin, 0.0));
            model.setScale(glm::vec3(sWidth, tHeight, 1.0));
            batch.setModelTransform(model);
        }

        batch.setUniformBuffer(3, _parametersBuffer);
        batch.setResourceTexture(0, lightingBuffer);
        batch.draw(gpu::TRIANGLE_STRIP, 4);
    });
}