!7

!include #1006440 // Concepts

sclass EditRecorder {

  Session session;

  // editor state

  S text = "";

  int caret;

  bool verbose = true;

  // update the text

  void update(S newText) {

    S a = text, b = newText;

    int i = lCommonPrefix(a, b);

    a = substring(a, i);

    b = substring(b, i);

    int j = lCommonSuffix(a, b);

    a = substring(a, 0, l(a)-j);

    b = substring(b, 0, l(b)-j);

    // Now differing part remains in a and b;

    // i and j give length of unchanged beginning+end

    if (empty(a) && empty(b)) {

      if (verbose) print("no change");

      ret;

    }

    EChange change = cnew(EChange, +session,

      startIndex := i, endIndex := i+l(a), text := b);

    if (verbose) print("change: " + renderConcept(change));

    // Verify the change we made

    assertEquals(newText, replayEdit(change, text));

    text = newText;

  }

  void updateCaret(int pos) {

    if (pos != caret) {

      cnew(ECaret, +session, +pos);

      caret = pos;

    }

  }

}

static Session session;

static JTextArea ta;

static EditRecorder er;

p-substance {

  db(); // persistence

  session = new Session;

  print("Session: " + session.id);

  ta = showText("");

  er = nu(EditRecorder, +session);

  onUpdate(ta, r { er.update(ta.getText()) });

  onCaret(ta, r { er.updateCaret(ta.getCaretPosition()) });

}