#include <assert.h>

#include <stdio.h>

#include <fcntl.h>

#include <unistd.h>

#include <uv.h>

void on_read(uv_fs_t *req);

uv_fs_t open_req;

uv_fs_t read_req;

uv_fs_t write_req;

static char buffer[1024];

static uv_buf_t iov;

void on_write(uv_fs_t *req) {

    if (req->result < 0) {

        fprintf(stderr, "Write error: %s\n", uv_strerror((int)req->result));

    }

    else {

        uv_fs_read(uv_default_loop(), &read_req, open_req.result, &iov, 1, -1, on_read);

    }

}

void on_read(uv_fs_t *req) {

    if (req->result < 0) {

        fprintf(stderr, "Read error: %s\n", uv_strerror(req->result));

    }

    else if (req->result == 0) {

        uv_fs_t close_req;

        // synchronous

        uv_fs_close(uv_default_loop(), &close_req, open_req.result, NULL);

    }

    else if (req->result > 0) {

        iov.len = req->result;

        uv_fs_write(uv_default_loop(), &write_req, 1, &iov, 1, -1, on_write);

    }

}

void on_open(uv_fs_t *req) {

    // The request passed to the callback is the same as the one the call setup

    // function was passed.

    assert(req == &open_req);

    if (req->result >= 0) {

        iov = uv_buf_init(buffer, sizeof(buffer));

        uv_fs_read(uv_default_loop(), &read_req, req->result,

                   &iov, 1, -1, on_read);

    }

    else {

        fprintf(stderr, "error opening file: %s\n", uv_strerror((int)req->result));

    }

}

int main(int argc, char **argv) {

    uv_fs_open(uv_default_loop(), &open_req, argv[1], O_RDONLY, 0, on_open);

    uv_run(uv_default_loop(), UV_RUN_DEFAULT);

    uv_fs_req_cleanup(&open_req);

    uv_fs_req_cleanup(&read_req);

    uv_fs_req_cleanup(&write_req);

    return 0;

}