import os
import sys
import tarfile


def is_exe(fpath):
    return os.path.isfile(fpath) and os.access(fpath, os.X_OK)


def main(args):
    if len(args) < 2 or len(args) > 3:
        raise Exception(
            "Illegal usage: `tar_directory.py archive.tar directory [skip prefix]` or `tar_directory.py archive.tar output_directory --extract`"
        )
    tar, directory, prefix, extract = args[0], args[1], None, False
    if len(args) == 3:
        if args[2] == '--extract':
            extract = True
        else:
            prefix = args[2]
    for tar_exe in ('/usr/bin/tar', '/bin/tar'):
        if not is_exe(tar_exe):
            continue
        if extract:
            dest = os.path.abspath(directory)
            if not os.path.exists(dest):
                os.makedirs(dest)
            os.execv(tar_exe, [tar_exe, '-xf', tar, '-C', dest])
        else:
            source = os.path.relpath(directory, prefix) if prefix else directory
            os.execv(tar_exe, [tar_exe, '-cf', tar] + (['-C', prefix] if prefix else []) + [source])
        break
    else:
        if extract:
            dest = os.path.abspath(directory)
            if not os.path.exists(dest):
                os.makedirs(dest)
            with tarfile.open(tar, 'r') as tar_file:
                tar_file.extractall(dest)
        else:
            source = directory
            with tarfile.open(tar, 'w') as out:
                out.add(os.path.abspath(source), arcname=os.path.relpath(source, prefix) if prefix else source)


if __name__ == '__main__':
    main(sys.argv[1:])