ls.cpp

#include "headers.h"

static string permissionString(mode_t mode)
{
    string s(10, '-');
    switch (mode & S_IFMT)
    {
    case S_IFBLK:  s[0] = 'b'; break;
    case S_IFCHR:  s[0] = 'c'; break;
    case S_IFDIR:  s[0] = 'd'; break;
    case S_IFIFO:  s[0] = 'p'; break;
    case S_IFLNK:  s[0] = 'l'; break;
    case S_IFSOCK: s[0] = 's'; break;
    default:       s[0] = '-'; break;
    }
    const char *bits = "rwxrwxrwx";
    mode_t masks[9] = {S_IRUSR, S_IWUSR, S_IXUSR, S_IRGRP, S_IWGRP, S_IXGRP, S_IROTH, S_IWOTH, S_IXOTH};
    for (int i = 0; i < 9; ++i)
        if (mode & masks[i])
            s[i + 1] = bits[i];
    return s;
}

static void printLongEntry(const string &fullPath, const string &displayName)
{
    struct stat st;
    if (lstat(fullPath.c_str(), &st) != 0)
    {
        cerr << "ls: cannot access '" << displayName << "': " << strerror(errno) << endl;
        return;
    }

    struct passwd *pw = getpwuid(st.st_uid);
    struct group *gr = getgrgid(st.st_gid);

    string when = ctime(&st.st_mtime);
    if (!when.empty() && when.back() == '\n')
        when.pop_back();

    cout << permissionString(st.st_mode)
         << " " << st.st_nlink
         << " " << (pw ? pw->pw_name : to_string(st.st_uid))
         << " " << (gr ? gr->gr_name : to_string(st.st_gid))
         << " " << st.st_size
         << " " << when
         << " " << displayName << '\n';
}

static void collectNames(DIR *dir, bool showHidden, vector<string> &names)
{
    struct dirent *entry;
    while ((entry = readdir(dir)) != nullptr)
    {
        if (!showHidden && entry->d_name[0] == '.')
            continue;
        names.push_back(entry->d_name);
    }
    sort(names.begin(), names.end());
}

static long directoryBlocks(const string &path, const vector<string> &names)
{
    long blocks = 0;
    for (const string &name : names)
    {
        struct stat st;
        if (lstat((path + "/" + name).c_str(), &st) == 0)
            blocks += st.st_blocks;
    }
    return blocks / 2; // ls reports 1K blocks; st_blocks counts 512B units
}

static void printPath(const string &path, bool showHidden, bool showDetails, bool withHeader)
{
    struct stat st;
    if (stat(path.c_str(), &st) != 0)
    {
        cerr << "ls: cannot access '" << path << "': " << strerror(errno) << endl;
        return;
    }

    if (!S_ISDIR(st.st_mode))
    {
        if (showDetails)
            printLongEntry(path, path);
        else
            cout << path << '\n';
        return;
    }

    DIR *dir = opendir(path.c_str());
    if (!dir)
    {
        cerr << "ls: cannot open '" << path << "': " << strerror(errno) << endl;
        return;
    }

    if (withHeader)
        cout << path << ":\n";

    vector<string> names;
    collectNames(dir, showHidden, names);
    closedir(dir);

    if (showDetails)
    {
        cout << "total " << directoryBlocks(path, names) << '\n';
        for (const string &name : names)
            printLongEntry(path + "/" + name, name);
    }
    else
    {
        for (const string &name : names)
            cout << name << '\n';
    }
}

void listDirectory(vector<string> args)
{
    bool showHidden = false;
    bool showDetails = false;
    vector<string> paths;

    for (size_t i = 1; i < args.size(); ++i)
    {
        const string &arg = args[i];
        if (arg.size() > 1 && arg[0] == '-')
        {
            for (size_t j = 1; j < arg.size(); ++j)
            {
                if (arg[j] == 'a')
                    showHidden = true;
                else if (arg[j] == 'l')
                    showDetails = true;
                else
                    cerr << "ls: invalid option -- '" << arg[j] << "'" << endl;
            }
        }
        else
        {
            paths.push_back(arg == "~" ? string(SHELL_DIRECTORY_PATH) : arg);
        }
    }

    if (paths.empty())
    {
        printPath(".", showHidden, showDetails, false);
        return;
    }

    for (size_t i = 0; i < paths.size(); ++i)
    {
        printPath(paths[i], showHidden, showDetails, paths.size() > 1);
        if (i + 1 < paths.size())
            cout << '\n';
    }
}