#define GL_GLEXT_PROTOTYPES
#include <GL/gl.h>
#include <GL/glext.h>
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define TEX_W 256
#define TEX_H 256

#define CHECK_GLERROR()                                     \
{                                                           \
    GLenum err = glGetError();                              \
    while (err != GL_NO_ERROR)                              \
    {                                                       \
        fprintf(stderr, "GL Error %#x, %s, line %d\n",      \
                err, __FILE__, __LINE__);                   \
        err = glGetError();                                 \
    }                                                       \
}

void init(void)
{
    GLuint tex, fbo_dst, rb, fbo_src;
    GLenum status;
    unsigned int mem[TEX_W][TEX_H];

    /* Generate a destination texture */
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_SRGB8_ALPHA8, TEX_W, TEX_H, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, mem);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SRGB_DECODE_EXT, GL_SKIP_DECODE_EXT);
    glBindTexture(GL_TEXTURE_2D, 0);
    CHECK_GLERROR();

    /* Source renderbuffer */
    glGenRenderbuffers(1, &rb);
    glBindRenderbuffer(GL_RENDERBUFFER, rb);
    glRenderbufferStorageMultisample(GL_RENDERBUFFER, 2, GL_RGBA8, TEX_W, TEX_H);
    CHECK_GLERROR();

    glGenFramebuffers(1, &fbo_src);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo_src);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, rb);
    status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE) fprintf(stderr, "FBO status %#x\n", status);
    CHECK_GLERROR();

    glDrawBuffer(GL_COLOR_ATTACHMENT0);
    glViewport(0, 0, TEX_W, TEX_H);
    glClearColor(0.0, 1.0, 0.5, 0);
    glClear(GL_COLOR_BUFFER_BIT);
    CHECK_GLERROR();

    /* Prepare a fbo with the texture as color attachment */
    glGenFramebuffers(1, &fbo_dst);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo_dst);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0);
    status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE) fprintf(stderr, "FBO status %#x\n", status);
    CHECK_GLERROR();

    glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo_src);
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_dst);
    printf("Going to blit\n");
    glBlitFramebuffer(0, 0, TEX_W, TEX_H, 0, 0, TEX_W, TEX_H, GL_COLOR_BUFFER_BIT, GL_NEAREST);
    printf("Blit done\n");
    CHECK_GLERROR();

    glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
    CHECK_GLERROR();

    glBindTexture(GL_TEXTURE_2D, tex);
    glGetTexImage(GL_TEXTURE_2D, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, mem);
    printf("read result: %08x\n", mem[16][16]);
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_ACCUM);
    glutInitWindowSize(200, 200);
    glutCreateWindow(argv[0]);
    init();

    return 0;
}