#include "test_utils.h"

static int test_dual_open_same_file(const char *path)
{
    printf("\n=== test_dual_open_same_file ===\n");

    int fd_init = open(path, O_CREAT | O_RDWR | O_TRUNC, 0644);
    if (fd_init < 0) { perror("open init"); return 1; }
    const char *init = "0123456789";
    if (write(fd_init, init, 10) != 10) { perror("write init"); return 2; }
    close(fd_init);

    int fd_w = open(path, O_WRONLY);
    if (fd_w < 0) { perror("open W"); return 3; }

    int fd_r = open(path, O_RDONLY);
    if (fd_r < 0) { perror("open R"); return 4; }

    printf("fd_w=%d  fd_r=%d\n", fd_w, fd_r);

    if (write(fd_w, "HELLO", 5) != 5) { perror("write"); return 5; }
    printf("write via fd_w: HELLO (overwrite first 5 bytes)\n");

    char buf[32] = {0};
    lseek(fd_r, 0, SEEK_SET);
    ssize_t r = read(fd_r, buf, sizeof(buf));
    printf("read via fd_r: %zd bytes: %.*s  (expect: HELLO56789)\n", r, (int)r, buf);

    lseek(fd_w, 0, SEEK_END);
    if (write(fd_w, "!!!", 3) != 3) { perror("write append"); return 6; }
    printf("write append via fd_w: !!!\n");

    lseek(fd_r, 10, SEEK_SET);
    memset(buf, 0, sizeof(buf));
    r = read(fd_r, buf, sizeof(buf));
    printf("read appended via fd_r: %zd bytes: %.*s  (expect: !!!)\n", r, (int)r, buf);

    close(fd_w);
    close(fd_r);
    unlink(path);
    return 0;
}

int main(int argc, char **argv)
{
    char path[PATH_MAX];
    make_path(path, sizeof(path), argc >= 2 ? argv[1] : NULL, "file.dat");
    int rc = test_dual_open_same_file(path);
    return report_result("test_dual_open_same_file", rc);
}