#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <spawn.h>
#include <string.h>

#define KB              (1024UL)
#define MB              (1024UL * 1024UL)
#define GB              (1024UL * 1024UL * 1024UL)

#define TOTAL_BYTES     (2 * GB)
#define BUF_SIZE        (128 * KB)

#define MIN(x, y)       ((x) <= (y) ? (x) : (y))

int main(int argc, const char *argv[]) {
    // Create pipe
    int pipe_fds[2];
    if (pipe(pipe_fds) < 0) {
        printf("ERROR: failed to create a pipe\n");
        return -1;
    }
    int pipe_rd_fd = pipe_fds[0];
    int pipe_wr_fd = pipe_fds[1];

    // Spawn a child process that reads from the pipe
    posix_spawn_file_actions_t file_actions;
    posix_spawn_file_actions_init(&file_actions);
    posix_spawn_file_actions_adddup2(&file_actions, pipe_rd_fd, STDIN_FILENO);
    posix_spawn_file_actions_addclose(&file_actions, pipe_wr_fd);

    int child_pid;
    if (posix_spawn(&child_pid, "/bin/data_sink", &file_actions,
                    NULL, NULL, NULL) < 0) {
        printf("ERROR: failed to spawn a child process\n");
        return -1;
    }
    close(pipe_rd_fd);

    // Start the timer
    struct timeval tv_start, tv_end;
    gettimeofday(&tv_start, NULL);

    // Tell the reader how many data are to be transfered
    size_t remain_bytes = TOTAL_BYTES;
    if (write(pipe_wr_fd, &remain_bytes, sizeof(remain_bytes)) != sizeof(remain_bytes)) {
        printf("ERROR: failed to write to pipe\n");
        return -1;
    }

    // Tell the reader the buffer size that it should use
    size_t buf_size = BUF_SIZE;
    if (write(pipe_wr_fd, &buf_size, sizeof(buf_size)) != sizeof(buf_size)) {
        printf("ERROR: failed to write to pipe\n");
        return -1;
    }

    // Write a specified amount of data in a buffer of specified size
    char buf[BUF_SIZE] = {0};
    while (remain_bytes > 0) {
        size_t len = MIN(buf_size, remain_bytes);
        if ((len = write(pipe_wr_fd, &buf, len)) < 0) {
            printf("ERROR: failed to write to pipe\n");
            return -1;
        }
        remain_bytes -= len;
    }

    // Wait for the child process to read all data and exit
    int status = 0;
    if (wait4(child_pid, &status, 0, NULL) < 0) {
        printf("ERROR: failed to wait4 the child process\n");
        return -1;
    }

    // Stop the timer
    gettimeofday(&tv_end, NULL);

    // Calculate the throughput
    double total_s = (tv_end.tv_sec - tv_start.tv_sec)
                     + (double)(tv_end.tv_usec - tv_start.tv_usec) / 1000000;
    if (total_s < 1.0) {
        printf("WARNING: run long enough to get meaningful results\n");
        if (total_s == 0) { return 0; }
    }
    double total_mb = (double)TOTAL_BYTES / MB;
    double throughput = total_mb / total_s;
    printf("Throughput of pipe is %.2f MB/s\n", throughput);
    return 0;
}