/*
 * mp3plot - Bitrate analysis tool
 *
 * Copyright (C) 2007 Toni Corvera
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

// $Id: spinner.cc 703 2007-05-17 20:07:32Z  $

#include "spinner.h"

#include <iostream>
#include <cassert>

#include <sys/wait.h>
#include <signal.h>
#include <errno.h>

extern int errno;

namespace net_outlyer {

const char * spinner::SYMS = "|/-\\";

void spinner::start() {
    if (-1 == pipe(pfd)) {
        perror("pipe");
        return; // FIXME: throw something
    }

    pid = fork();

    if (-1 == pid) {
        perror("fork");
        return; // FIXME: throw something
    }

    // Parent process
    if (0 != pid) {
        close(pfd[0]); // Close the unneeded (read) channel
        // Parent process, we're done here, return to the caller
        // the parent tasks are in step and stop
        return;
    }

    // Child process
    assert( 0 == pid );

    // see nice(2):
    // A call to nice that returns -1 might be successful (e.g. -11 + 10).
    // errno must be checked explicitly to be sure
    errno=0;
    if (-1 == nice(+10)) {
        if (errno != 0) {
            // FIXME: Do something more useful
            exit(1);
            assert( 0 );
            return;
        }
    }

    close(pfd[1]); // Close the write end, unneeded

    // Wait for the parent process to send something through the pipe
    // (for each byte received a spin will be made). When the cannel
    // is closed (EOF) process will stop and this thread end
    char devnull, idx=0;
    const char LEN=strlen(SYMS);
    while (read(pfd[0], &devnull, 1) > 0) {
        std::cerr << "\r[" << SYMS[idx] << "]";
        idx = ( idx + 1 ) % LEN;
    }
    close(pfd[0]);

    exit(0); // quite important...
}

// This is called from the parent thread, it writes a byte on the shared pipe
void spinner::step() {
    write(pfd[1], ".", 1);
}

// This is called from the parent thread, it sends the EOF (by closing the
// pipe) and hence the child should end.
void spinner::stop() {
    if (pid > 0 && !stopped) { // Parent
        close(pfd[1]); // If already closed, it will fail and errno set to EBADF
        stopped = true;

        // We can do the child stopping in two fashions:
        // * wait() for it to end, this is nicer but kind of kills the benefits
        //   of using separate processes as we'll be blocked by console I/O
        //   anyway (although we'll be blocked *after* the file is processed)
        // * kill() it. This prevents the child from finishing the spinner
        //   nicely so we need to finish it here (send \r to the err channel)
        // DISCARDED: wait(NULL); // wait for the buffer to flush
        kill(pid, SIGTERM);
        std::cerr << std::flush << "\r" << std::flush;
    }
}

spinner::~spinner() {
    stop();
}


} // namespace net_outlyer

/* vim:set ts=4 et ai: */