#define _GNU_SOURCE
#include <libaio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/eventfd.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>

#define FILE_SIZE 4096

int main(void)
{
    io_context_t ctx;
    int fd,fd_odirect,i,event_fd,epoll_fd;
    struct epoll_event ev;
    void *buf;
    size_t offset = 0;
    struct iocb cb;
    struct iocb * cbs[1] = { &cb };

    fd = open("/tmp/foo",O_RDWR|O_CREAT);
    if (fd == -1) {
        perror("open");
        return 1;
    }
    for (i = 0; i < FILE_SIZE; ++i) {
        char c = rand() % 255;
        write(fd, &c, 1);
    }
    close(fd);

    fd_odirect = open("/tmp/foo",O_RDONLY|O_DIRECT);
    if (fd_odirect == -1) {
        perror("open");
        return 1;
    }
    memset(&ctx, 0, sizeof(ctx));
    if (0 != io_queue_init(1, &ctx)) {
        perror("ctx");
        return 1;
    }
    event_fd = eventfd(0, EFD_CLOEXEC);
    if (event_fd == -1) {
        perror("eventfd");
        return -1;
    }

    epoll_fd = epoll_create(1);
    if (epoll_fd == -1) {
        perror("epoll_fd");
        return 1;
    }

    ev.events = EPOLLIN;

    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, event_fd, &ev) == -1) {
        perror("epoll_ctl");
        return 1;
    }

    posix_memalign(&buf, 512, 32768);

    while (1) {
        struct timespec ts = { 0, 0 };
        struct io_event ioev;
        int ret;
        long v;
        io_prep_pread(&cb, fd_odirect, buf + offset, 512, offset);
        io_set_eventfd(&cb, event_fd);
        if (1 != io_submit(ctx, 1, cbs)) {
            perror("io_submit");
            return 1;
        }

        ret = epoll_wait(epoll_fd, &ev, 1, -1);
        if (ret != 1) {
            perror("epoll_wait");
        }

        read(event_fd, &v, 8);
        
        printf("event_fd returned %ld\n", v);


        if (io_getevents(ctx, 1, 1, &ioev, &ts) != 1) {
            perror("io_getevents");
            return 1;
        }

        printf("Read 1 res %ld res2 %ld\n", ioev.res, ioev.res2);
        offset += ioev.res;

        if (ioev.res == 0) {
            break;
        } 
        if ((offset + 512) > 32768) {
            puts("ERROR - reading past buffer");
            return 1;
        }
    }

    free(buf);
    io_destroy(ctx);
    close(event_fd);
    close(epoll_fd);
    close(fd_odirect);

    return 0;
}