const char *DefaultVertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec2 aTexCoord;\n"
"out vec2 TexCoord;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos, 1.0);\n"
" TexCoord = aTexCoord;\n"
"}\0";
const char *MaskVertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec2 aTexCoord;\n"
"out vec2 TexCoord;\n"
"uniform vec3 CompDimensions;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(vec2(aPos.x / CompDimensions.x, aPos.y / CompDimensions.y) * 2 - 1.0f, 0.0f, 1.0);\n"
" TexCoord = aTexCoord;\n"
"}\0";
const char *DefaultFragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec2 TexCoord;\n"
"uniform sampler2D Texture;\n"
"void main()\n"
"{\n"
"vec4 ColTest = texture(Texture, TexCoord);\n"
"ColTest.r += 0.5f;\n"
"FragColor = ColTest;\n"
"}\0";
#if 0
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec2 TexCoord;\n"
"uniform float Start;\n"
"uniform float Mid;\n"
"uniform float End;\n"
"uniform vec4 StartCol;\n"
"uniform vec4 MidCol;\n"
"uniform vec4 EndCol;\n"
"uniform sampler2D ourTexture;\n"
"void main()\n"
"{\n"
"vec4 OutCol = texture(ourTexture, TexCoord);\n"
// individual channels
"vec4 ColorI = pow(OutCol, MidCol);\n"
"vec4 ValI = 1.0f / (EndCol - StartCol) * (ColorI - StartCol);\n"
// global channel
"vec4 ColorG = pow(ValI, vec4(Mid));\n"
"vec4 ValG = 1.0f / (End - Start) * (ColorG - Start);\n"
"FragColor = clamp(ValG, 0.0f, 1.0f);\n"
"}\0";
const char *fragmentShaderSource = "#version 330 core\n"
"uniform float Radius;\n"
"uniform vec2 Direction;\n"
"uniform sampler2D ourTexture;\n"
"out vec4 FragColor;\n"
"in vec2 TexCoord;\n"
"\n"
"vec4 blur(sampler2D image, vec2 uv, vec2 resolution, vec2 direction) {\n"
"    vec4 color = vec4(0.0f);\n"
"    float Omega = Radius / 3;\n"
"    float Divisor = 2*Omega*Omega;\n"
"    float A2 = 1.0f / (Omega * sqrt(2*3.141592));\n"
"    for (float Span = -round(Radius); Span < round(Radius); Span++) {\n"
"        float Dividend = -Span * Span;\n"
"        float Multiplier =  A2 * exp(Dividend/Divisor);\n"
"        vec2 Dir = Span*direction;\n"
"        color += texture2D(image, uv + (Dir / resolution)) * Multiplier;\n"
"    }\n"
"    return color;\n"
"}\n"
"void main(void) {\n"
"    gl_FragColor = blur(ourTexture, TexCoord, vec2(1280, 720),  Direction);\n"
"}\0";
#endif


static void TestGL_InitDefaultShader() {
    DefaultVertexShader = glCreateShader(GL_VERTEX_SHADER);

    glShaderSource(DefaultVertexShader, 1, &DefaultVertexShaderSource, NULL);
    glCompileShader(DefaultVertexShader);

    int success;
    char infoLog[512];
    glGetShaderiv(DefaultVertexShader, GL_COMPILE_STATUS, &success);

    if(!success)
    {
        glGetShaderInfoLog(DefaultVertexShader, 512, NULL, infoLog);
        printf("Vertex shader fail:\n %s", infoLog);
    }

    uint32 DefaultFragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

    glShaderSource(DefaultFragmentShader, 1, &DefaultFragmentShaderSource, NULL);
    glCompileShader(DefaultFragmentShader);

    glGetShaderiv(DefaultFragmentShader, GL_COMPILE_STATUS, &success);

    if(!success)
    {
        glGetShaderInfoLog(DefaultFragmentShader, 512, NULL, infoLog);
        printf("Fragment shader fail:\n %s", infoLog);
    }

    // Shader programs link both types of shaders together.
    DefaultShaderProgram = glCreateProgram();

    glAttachShader(DefaultShaderProgram, DefaultVertexShader);
    glAttachShader(DefaultShaderProgram, DefaultFragmentShader);
    glLinkProgram(DefaultShaderProgram);

    glGetProgramiv(DefaultShaderProgram, GL_LINK_STATUS, &success);
    if(!success) {
        glGetProgramInfoLog(DefaultShaderProgram, 512, NULL, infoLog);
        printf("Shader linkage fail:\n %s", infoLog);
    }

    uint32 MaskVertexShader = glCreateShader(GL_VERTEX_SHADER);

    glShaderSource(MaskVertexShader, 1, &MaskVertexShaderSource, NULL);
    glCompileShader(MaskVertexShader);

    glGetShaderiv(MaskVertexShader, GL_COMPILE_STATUS, &success);
    if(!success) {
        glGetProgramInfoLog(DefaultShaderProgram, 512, NULL, infoLog);
        printf("Shader linkage fail:\n %s", infoLog);
    }

    MaskShaderProgram = glCreateProgram();

    glAttachShader(MaskShaderProgram, MaskVertexShader);
    glAttachShader(MaskShaderProgram, DefaultFragmentShader);
    glLinkProgram(MaskShaderProgram);

    glGetProgramiv(MaskShaderProgram, GL_LINK_STATUS, &success);
    if(!success) {
        glGetProgramInfoLog(MaskShaderProgram, 512, NULL, infoLog);
        printf("Shader linkage fail:\n %s", infoLog);
    }

    // Default vertex shader is still needed to link to other effects.
    glDeleteShader(DefaultFragmentShader);
    glDeleteShader(MaskVertexShader);
}

static void TestGL_InitDefaultVerts() {

    unsigned int GLIndices[] = {
        0, 1, 3,
        1, 2, 3
    };

    glEnable(GL_MULTISAMPLE);

    // Indices!
    glGenVertexArrays(1, &DefaultVerts.VertexArrayObject);

    glGenBuffers(1, &DefaultVerts.ElementBufferObject);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, DefaultVerts.ElementBufferObject);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLIndices), GLIndices,
                 GL_STATIC_DRAW);
    glGenBuffers(1, &DefaultVerts.VertexBufferObject);

    // Our vertices need to be stored in this buffer.
    glBindBuffer(GL_ARRAY_BUFFER, DefaultVerts.VertexBufferObject);
    glBufferData(GL_ARRAY_BUFFER, sizeof(DefaultVertices), DefaultVertices, GL_STATIC_DRAW);

    // position attribute
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);
    // texture coordinate (note the last parameter's offset)
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);
}

void
TestGL_InitTexture(gl_effect_layer *Test, void *Data, uint16 Width, uint16 Height)
{
    glGenTextures(1, &Test->Texture);
    glBindTexture(GL_TEXTURE_2D, Test->Texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    glViewport(0, 0, Width, Height);

    glGenFramebuffers(1, &Test->FramebufferObject);

    glGenRenderbuffers(1, &Test->Color_Renderbuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, Test->Color_Renderbuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, Width, Height);

    GLuint Stencil_Renderbuffer = 0;
    glGenRenderbuffers(1, &Stencil_Renderbuffer);
    glBindRenderbuffer( GL_RENDERBUFFER, (GLuint)Stencil_Renderbuffer );
    glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, Width, Height );

    glBindFramebuffer(GL_FRAMEBUFFER, Test->FramebufferObject);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, Test->Color_Renderbuffer);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, Stencil_Renderbuffer);

    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE) {
        printf("incomplete framebuffer");
        Assert(0);
    }

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Width, Height, 0, GL_RGBA,
                 GL_UNSIGNED_BYTE, Data);

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}