#include <SDL2/SDL.h>
#include <GL/glew.h>
#include <SDL2/SDL_opengl.h>

const GLchar *source = (const GLchar *) "#version 330 core\n"
    "\n"
    "uint dosomething(int bits) {\n"
    "  const uint mask = 0xFFFFFFFFu >> (32 - bits);\n"
    "  return mask;\n"
    "}\n"
    "\n"
    "layout(location = 0)in vec4 vert;\n"
    "\n"
    "uniform mat4 projection;\n"
    "uniform mat4 view;\n"
    "uniform mat4 model;\n"
    "\n"
    "void main() {\n"
    "  gl_Position = projection * view * model * vert;\n"
    "}";

int main(int argc, char* args[]) {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("SDL init error: %s\n", SDL_GetError());
        return -1;
    }

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

    SDL_Window* window = SDL_CreateWindow("Shader test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
    if (!window) {
        printf("SDL window error: %s\n", SDL_GetError());
        return -1;
    }

    SDL_GLContext context = SDL_GL_CreateContext(window);
    if (!context) {
        printf("SDL context error: %s\n", SDL_GetError());
        return -1;
    }

    GLenum glewError = glewInit();
    if (glewError != GLEW_OK) {
        printf("GLEW error: %s\n", glewGetErrorString(glewError));
    }

    GLuint program = glCreateProgram();

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &source, 0);
    glCompileShader(vertexShader);

    GLint success = GL_TRUE;
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (success == GL_FALSE) {
        printf("Failed.\n");
        GLint maxLength = 0;
        glGetShaderiv(vertexShader, GL_INFO_LOG_LENGTH, &maxLength);
        printf("%i\n", (int) maxLength);

        GLchar* errorLog = (GLchar*) malloc(sizeof(GLchar) * maxLength);
        glGetShaderInfoLog(vertexShader, maxLength, &maxLength, errorLog);

        printf("%s\n", errorLog);
        free(errorLog);
    } else {
        printf("All OK.\n");
    }

    return 0;
}