// adapters are immutable! (plus returns a modified clone)

abstract sclass Adapter {

  abstract bool canMatch(S in, S out);

  Adapter plus(S in, S out) { ret this; }

  S get(S in) { ret in; }

  double size() { ret 0; }

}

sclass WordAdapter extends Adapter {

  new Map<S, S> wordMap;

  L<S> tok(S s) {

    ret nlTok2(dropPunctuation2(s));

  }

  bool canMatch(S in, S out) {

    L<S> t1 = tok(in), t2 = tok(out);

    ret l(t1) == l(t2);

  }

  Adapter plus(S in, S out) {

    L<S> t1 = tok(in), t2 = tok(out);

    if (l(t1) != l(t2)) ret this;

    WordAdapter a = cast nuObject(getClass());

    a.wordMap = cloneMap(wordMap);

    for (int i = 1; i < l(t1); i += 2) {

      S w1 = t1.get(i), w2 = t2.get(i);

      if (!eqic(w1, w2))

        // just overwrite - be flexible!

        a.wordMap.put(w1.toLowerCase(), w2.toLowerCase());

    }

    ret a;

  }

  S get(S s) {

    L<S> tok = nlTok2(s);

    for (int i = 1; i < l(tok); i += 2) {

      S w = lookupToken(tok.get(i));

      if (nempty(w))

        tok.set(i, w);

    }

    ret join(tok);

  }

  S lookupToken(S s) {

    ret wordMap.get(s.toLowerCase());

  }

  double size() {

    ret l(wordMap);

  }

  public S toString() {

    ret structure(wordMap);

  }

}