completion.cpp

/*-
 * Copyright (C) Pietro Cerutti <gahr@gahr.ch>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>

#include <algorithm>
#include <iostream>
#include <iterator>
#include <stdexcept>
#include <sstream>
using namespace std;

#include "completion.h"
#include "util.h"

Completion::Completion()
{
    struct stat sb;
    uid_t uid { getuid() };
    gid_t gid { getgid() };

    /* get PATH env */
    string path { Util::getEnv("PATH") };

    /* tokenize path */
    string elem;
    stringstream ss { path };
    vector<string> pathElements;
    while (ss.good()) {
        getline(ss, elem, ':');
        pathElements.push_back(move(elem));
    }

    for (const auto& pathElem : pathElements) {

        /* open the directory pointed to by path */
        DIR * dirp { opendir(pathElem.c_str()) };
        if (dirp == nullptr) {
            continue;
        }

        /* traverse directory */
        struct dirent * dp;
        while ((dp = readdir(dirp))) {

            string currentPath { pathElem + "/" + dp->d_name };
            /* create a 'path/file' string and check whether we can access meta-information */
            if (stat(currentPath.c_str(), &sb) == -1) {
                continue;
            }

            /* a regular, executable file*/
            if (((sb.st_mode & S_IFREG) == S_IFREG) &&
                ((sb.st_uid == uid && (sb.st_mode & S_IXUSR) == S_IXUSR) ||
                 (sb.st_gid == gid && (sb.st_mode & S_IXGRP) == S_IXGRP) ||
                 ((sb.st_mode & S_IXOTH) == S_IXOTH)))
            {
                m_elements.push_back(dp->d_name);
            }
        }
        closedir(dirp);
    }

    sort(begin(m_elements), end(m_elements));

    /* initialize iterator to the begin */
    m_iter = begin(m_elements);
}

Completion::~Completion()
{
    // nothing to do...
}

string
Completion::next(string command)
{
    if (command.empty()) {
        return command;
    }

    if (m_prefix.empty()) {
        m_prefix = command;
    }

    auto matchPrefix = [this] (string e) { return e.compare(0, m_prefix.size(), m_prefix) == 0; };

    /* start from where we left off last time */
    auto iter1 = find_if(m_iter, m_elements.cend(), matchPrefix);
    if (iter1 != end(m_elements)) {
        m_iter = iter1 + 1;
        return *iter1;
    }

    /* start over */
    auto iter2 = find_if(begin(m_elements), end(m_elements), matchPrefix);
    if (iter2 != begin(m_elements)) {
        m_iter = iter2 + 1;
        return *iter2;
    }

    m_iter = begin(m_elements);

    return command;
}

void
Completion::reset()
{
    m_prefix.clear();
    m_iter = begin(m_elements);
}