//
// Copyright (c) 2014 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

//            Based on Hello_Triangle.c from
// Book:      OpenGL(R) ES 2.0 Programming Guide
// Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
// ISBN-10:   0321502795
// ISBN-13:   9780321502797
// Publisher: Addison-Wesley Professional
// URLs:      http://safari.informit.com/9780321563835
//            http://www.opengles-book.com

#include "SampleApplication.h"
#include "shader_utils.h"
#include "texture_utils.h"

#include <cstring>
#include <iostream>

// This sample demonstrates the differences in rendering efficiency when
// drawing with already-created textures whose dimensions have been altered
// versus drawing with newly created textures.
//
// In order to support GL's per-level texture creation semantics over the
// D3D API in particular, which requires textures' full mip chains to be
// created at texture object creation time, ANGLE maintains copies of the
// constituent texture images in system memory until the texture is used in
// a draw call, at which time, if the texture passes GL's mip completeness
// rules, the D3D texture is created and the contents of the texture are
// uploaded. Once the texture is created, redefinition of the dimensions or
// format of the texture is costly-- a new D3D texture needs to be created,
// and ANGLE may need to read the contents back into system memory.
//
// Creating an entirely new texture also requires that a new D3D texture be
// created, but any overhead associated with tracking the already-present
// texture images is eliminated, as it's a novel texture. This sample
// demonstrates the contrast in draw call time between these two situations.
//
// The resizing & creation of a new texture is delayed until several frames
// after startup, to eliminate draw time differences caused by caching of
// rendering state subsequent to the first frame.

class TexRedefBenchSample : public SampleApplication
{
  public:
    TexRedefBenchSample(int argc, char **argv)
        : SampleApplication("Microbench", argc, argv, 2, 0, 1280, 1280),
          mPixelsResize(nullptr),
          mPixelsNewTex(nullptr),
          mTimeFrame(false),
          mFrameCount(0)
    {
    }

    void defineSquareTexture2D(GLuint texId, GLsizei baseDimension, GLenum format, GLenum type, void* data)
    {
        glBindTexture(GL_TEXTURE_2D, texId);
        GLsizei curDim = baseDimension;
        GLuint level = 0;

        while (curDim >= 1)
        {
            glTexImage2D(GL_TEXTURE_2D, level, format, curDim, curDim, 0, format, type, data);
            curDim /= 2;
            level++;
        }
    }

    void createPixelData()
    {
        mPixelsResize = new GLubyte[512 * 512 * 4];
        mPixelsNewTex = new GLubyte[512 * 512 * 4];
        GLubyte *pixPtr0 = mPixelsResize;
        GLubyte *pixPtr1 = mPixelsNewTex;
        GLubyte zeroPix[] = { 0, 192, 192, 255 };
        GLubyte onePix[] = { 192, 0, 0, 255 };
        for (int i = 0; i < 512 * 512; ++i)
        {
            memcpy(pixPtr0, zeroPix, 4 * sizeof(GLubyte));
            memcpy(pixPtr1, onePix, 4 * sizeof(GLubyte));
            pixPtr0 += 4;
            pixPtr1 += 4;
        }
    }

    virtual bool initialize()
    {
        const std::string vs =
            R"(attribute vec4 a_position;
            attribute vec2 a_texCoord;
            varying vec2 v_texCoord;
            void main()
            {
                gl_Position = a_position;
                v_texCoord = a_texCoord;
            })";

        const std::string fs =
            R"(precision mediump float;
            varying vec2 v_texCoord;
            uniform sampler2D s_texture;
            void main()
            {
                gl_FragColor = texture2D(s_texture, v_texCoord);
            })";

        mProgram = CompileProgram(vs, fs);
        if (!mProgram)
        {
            return false;
        }

        // Get the attribute locations
        mPositionLoc = glGetAttribLocation(mProgram, "a_position");
        mTexCoordLoc = glGetAttribLocation(mProgram, "a_texCoord");

        // Get the sampler location
        mSamplerLoc = glGetUniformLocation(mProgram, "s_texture");

        // Generate texture IDs, and create texture 0
        glGenTextures(3, mTextureIds);

        createPixelData();
        defineSquareTexture2D(mTextureIds[0], 256, GL_RGBA, GL_UNSIGNED_BYTE, mPixelsResize);

        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

        mOrigTimer = CreateTimer();
        mResizeDrawTimer = CreateTimer();
        mResizeDefineTimer = CreateTimer();
        mNewTexDrawTimer = CreateTimer();
        mNewTexDefineTimer = CreateTimer();

        return true;
    }

    virtual void destroy()
    {
        glDeleteProgram(mProgram);

        delete [] mPixelsResize;
        delete [] mPixelsNewTex;
    }

    virtual void draw()
    {
        GLfloat vertices[] =
        {
            -0.5f, 0.5f, 0.0f,  // Position 0
            0.0f, 0.0f,        // TexCoord 0
            -0.5f, -0.5f, 0.0f,  // Position 1
            0.0f, 1.0f,        // TexCoord 1
            0.5f, -0.5f, 0.0f,  // Position 2
            1.0f, 1.0f,        // TexCoord 2
            0.5f, 0.5f, 0.0f,  // Position 3
            1.0f, 0.0f         // TexCoord 3
        };
        GLushort indices[] = { 0, 1, 2, 0, 2, 3 };

        // Set the viewport
        glViewport(0, 0, getWindow()->getWidth(), getWindow()->getHeight());

        // Clear the color buffer
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // Use the program object
        glUseProgram(mProgram);

        // Load the vertex position
        glVertexAttribPointer(mPositionLoc, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), vertices);
        // Load the texture coordinate
        glVertexAttribPointer(mTexCoordLoc, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), vertices + 3);

        glEnableVertexAttribArray(mPositionLoc);
        glEnableVertexAttribArray(mTexCoordLoc);

        // Bind the texture
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, mTextureIds[0]);

        // Set the texture sampler to texture unit to 0
        glUniform1i(mSamplerLoc, 0);

        // We delay timing of texture resize/creation until after the first frame, as
        // caching optimizations will reduce draw time for subsequent frames for reasons
        // unreleated to texture creation. mTimeFrame is set to true on the fifth frame.
        if (mTimeFrame)
        {
            mOrigTimer->start();
        }

        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
        
        if (mTimeFrame)
        { 
            mOrigTimer->stop();
            // This timer indicates draw time for an already-created texture resident on the GPU, which
            // needs no updates. It will be faster than the other draws.
            std::cout << "Original texture draw: " << mOrigTimer->getElapsedTime() * 1000 << "msec" << std::endl;

            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

            // Now, change the texture dimensions of the original texture
            mResizeDefineTimer->start();
            defineSquareTexture2D(mTextureIds[0], 512, GL_RGBA, GL_UNSIGNED_BYTE, mPixelsResize);
            mResizeDefineTimer->stop();

            mResizeDrawTimer->start();
            glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
            mResizeDrawTimer->stop();
            // This timer indicates draw time for a texture which has already been used in a draw, causing the
            // underlying resource to be allocated, and then resized, requiring resource reallocation and
            // related overhead.
            std::cout << "Resized texture definition: " << mResizeDefineTimer->getElapsedTime() * 1000 << "msec" << std::endl;
            std::cout << "Resized texture draw: " << mResizeDrawTimer->getElapsedTime() * 1000 << "msec" << std::endl;

            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

            // Create texure at same dimensions we resized previous texture to
            mNewTexDefineTimer->start();
            defineSquareTexture2D(mTextureIds[1], 512, GL_RGBA, GL_UNSIGNED_BYTE, mPixelsNewTex);
            mNewTexDefineTimer->stop();

            mNewTexDrawTimer->start();
            glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
            mNewTexDrawTimer->stop();
            // This timer indicates draw time for a texture newly created this frame. The underlying resource
            // will need to be created, but because it has not previously been used, there is no already-resident
            // texture object to manage. This draw is expected to be faster than the resized texture draw.
            std::cout << "Newly created texture definition: " << mNewTexDefineTimer->getElapsedTime() * 1000 << "msec" << std::endl;
            std::cout << "Newly created texture draw: " << mNewTexDrawTimer->getElapsedTime() * 1000 << "msec" << std::endl;
        }

        if (mFrameCount == 5)
            mTimeFrame = true;
        else
            mTimeFrame = false;

        mFrameCount++;
    }

  private:
    // Handle to a program object
    GLuint mProgram;

    // Attribute locations
    GLint mPositionLoc;
    GLint mTexCoordLoc;

    // Sampler location
    GLint mSamplerLoc;

    // Texture handle
    GLuint mTextureIds[2]; // 0: texture created, then resized
                           // 1: texture newly created with TexImage

    // Texture pixel data
    GLubyte *mPixelsResize;
    GLubyte *mPixelsNewTex;

    Timer *mOrigTimer;
    Timer *mResizeDrawTimer;
    Timer *mResizeDefineTimer;
    Timer *mNewTexDrawTimer;
    Timer *mNewTexDefineTimer;
    bool mTimeFrame;
    unsigned int mFrameCount;
};

int main(int argc, char **argv)
{
    TexRedefBenchSample app(argc, argv);
    return app.run();
}
