//
//  main.c
//  testsdlgl
//
//  Created by Daniel Bokser on 9/26/18.
//  Copyright © 2018 dan. All rights reserved.
//
#include <stdio.h>
#include <SDL2/SDL.h>
#include <OpenGL/gl.h>

#define USE_RENDERER 0
#define LATE_INIT 1

typedef struct ThreadContext {
    SDL_Window *window;
    SDL_GLContext context;
    float r;
    float g;
    float b;
} ThreadContext;

static SDL_bool isRunning = SDL_TRUE;
static SDL_atomic_t stopflag;
static SDL_mutex *mutex = NULL;
static void (*mark)(GLsizei, const void *) = NULL;

void renderWindow(const char *title, ThreadContext *tc) {
    char buf[128];
    SDL_snprintf(buf, sizeof (buf), "Starting %s render", title);

    SDL_LockMutex(mutex);
    if (mark) mark(0, buf);

    SDL_Window *curwin = SDL_GL_GetCurrentWindow();
    SDL_GLContext curctx = SDL_GL_GetCurrentContext();
    if ((curwin != tc->window) || (curctx != tc->context)) {
        printf("%s: %p %p vs %p %p\n", title, curwin, curctx, tc->window, tc->context);
    }

    SDL_GL_MakeCurrent(tc->window, tc->context);
    glClearColor(tc->r, tc->g, tc->b, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    tc->r += 1.0f / 255.0f;
    if (tc->r > 1.0f) {
        tc->r = 0;
    }

    SDL_GL_SwapWindow(tc->window);
    SDL_snprintf(buf, sizeof (buf), "Ending %s render", title);
    if (mark) mark(0, buf);
    SDL_UnlockMutex(mutex);
SDL_Delay(10);
}

static int threntry(void *arg) {
    ThreadContext *tc = (ThreadContext *) arg;
    while (!SDL_AtomicGet(&stopflag)) {
        renderWindow("window 2", tc);
    }
    return 0;
}

int initWindow(const char *title, ThreadContext *tc) {
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    tc->window = SDL_CreateWindow(title, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 300, 300, SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL);
    tc->context = SDL_GL_CreateContext(tc->window);
    SDL_GL_MakeCurrent(tc->window, tc->context);

    printf("Create %s\n", title);

    return 0;
}
int main(int argc, const char * argv[]) {
    SDL_Init(SDL_INIT_EVERYTHING);

    mutex = SDL_CreateMutex();

#if USE_RENDERER
    SDL_Window *window = SDL_CreateWindow("Test SDL Renderer", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 300, 300, SDL_WINDOW_SHOWN );
    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    Uint8 r = 0;
#else
    ThreadContext tc1;
    if (initWindow("window 1", &tc1)) {
        return 1;
    }
    tc1.r = 1; tc1.g = 0; tc1.b = 0;
#endif

    mark = (void (*)(GLsizei, const void *)) SDL_GL_GetProcAddress("glStringMarkerGREMEDY");

    ThreadContext tc2;
    SDL_Thread *thr = NULL;

#if LATE_INIT
    int isInited = 0;
    int count = 30;
#else
    if (initWindow("window 2", &tc2)) {
        return 1;
    }
    tc2.r = 0; tc2.g = 0; tc2.b = 1;
    thr = SDL_CreateThread(threntry, "2ndContext", &tc2);
#endif

    while (isRunning) {
        SDL_Event e;
        while (SDL_PollEvent(&e)) {
            switch (e.type) {
                case SDL_QUIT:
                    isRunning = SDL_FALSE;
                    break;

                case SDL_WINDOWEVENT:
                    if (e.window.event == SDL_WINDOWEVENT_CLOSE) {
                        isRunning = SDL_FALSE;
                        break;
                    }
                    break;
            }
        }

#if LATE_INIT
        if (!isInited && count <= 0) {
            if (initWindow("window 2", &tc2)) {
                return 1;
            }
            tc2.r = 0; tc2.g = 0; tc2.b = 1;
            isInited = 1;
            thr = SDL_CreateThread(threntry, "2ndContext", &tc2);
        } else {
            count--;
        }
#endif

#if USE_RENDERER
        SDL_SetRenderDrawColor(renderer, r++, 0, 0, 255);
        SDL_RenderClear(renderer);
        SDL_RenderPresent(renderer);
#else
        renderWindow("window 1", &tc1);
#endif
    }

    if (thr) {
        SDL_AtomicSet(&stopflag, 1);
        SDL_WaitThread(thr, NULL);
    }

    SDL_Quit();

    return 0;
}