import unix.*;
import libc;

tail?(str, tail) {
    if (size(str) < size(tail))
        return false;
    else
        return slice(str, size(str) - size(tail)) == tail;
}

head?(str, head) {
    if (size(str) < size(head))
        return false;
    else
        return slice(str, 0, size(head)) == head;
}

alias pathSeparator = '/';

absolutePath?(path) = head?(path, pathSeparator);

all?(seq, predicate) {
    var res = true;
    var iter = iterator(seq);
    while (res and hasNext?(iter))
        res = predicate(next(iter));
    return res;
}

any?(seq, predicate) {
    var res = false;
    var iter = iterator(seq);
    while (not res and hasNext?(iter))
        res = predicate(next(iter));
    return res;
}

trimHead(seq, predicate) {
    var n = size(seq);
    if (n == 0)
        return slice(seq, 0);
    var i = 0;
    while (i < n and predicate(seq[i]))
        i += 1;
    return slice(seq, i);
}

trimTail(seq, predicate) {
    var n = size(seq);
    if (n == 0)
        return slice(seq, 0);
    while (n > 0 and predicate(seq[n-1]))
        n -= 1;
    return slice(seq, 0, n);
}

trim(seq, predicate) = trimHead(trimTail(seq, predicate), predicate);

rootDirectory?(path) = not empty?(path) and all?(path, block (x) { return x == pathSeparator; });

appendPath(path1, ...paths) = appendPath(path1, appendPath(...paths));

overload appendPath(path1, path2) {
    if (empty?(path2))
        return String(path1);
    else if (absolutePath?(path2))
        return String(path2);
    else if (head?(path2, "." + [pathSeparator])) {
        var path3 = trimHead(slice(path2, 2),
            block (x) { return x == pathSeparator; });
        return String(appendPath(path1, path3));
    }
    else if (head?(path2, ".." + [pathSeparator])) {
        var path3 = trimHead(slice(path2, 3),
            block (x) { return x == pathSeparator; });
        return String(appendPath(path1, path3));
    }
}



======

import io.directories.*;
main() {
    println(appendPath("a","b"));
}