sclass DialogOptimizer {

  OccTree2 tree, botTree;

  bool walkTree_debug;

  bool useAdapter = true;

  O engine;

  *(S theme, S engineID) {

    engine = run(engineID);

    L<Dialog> dialogs = loadDialogs(theme);

    callOpt(mc(), "expandDialogs", dialogs); // hmm.

    expandEllipsis(tree = makeOccTree(dialogs));

    expandEllipsis(botTree = makeOccTree(withoutSecretDialogs(dialogs)));

    printOccTree2(botTree);

    print("Tree size: " + tree.size() + ", bot tree size: " + botTree.size());

    //walkTree_debug = true;

    try {

      walkTree();

    } catch e {

      print("Engine not working, abort.");

      printStackTrace(e);

      ret;

    }

    print("Tree walked! " + inputFed + " -> " + outputGot);

    int origSize = botTree.size()-1;

    print("Engine works! Trying to shrink the tree.");

    while (canShrinkTree()) {

      print("Tree shrunk, trying it again.");

    }

    int newSize = botTree.size()-1;

    printOccTree2(botTree);

    if (newSize < origSize) {

      long percent = newSize == 0 ? 9999 : round(origSize*100.0/newSize-100);

      print("Done shrinking tree (" + origSize + " -> " + newSize + " entries - " + percent + "% shrinkage!)");

    } else

      print("Tree unshrinkable.");

  }

  int inputFed, outputGot;

  bool canShrinkTree() {

    L<OccTree2> leaves = botTree.allLeaves();

    print("Leaves found: " + l(leaves));

    bool anyChange = false;

    for (OccTree2 leaf : leaves) {

      print("Trying to remove leaf: " + leaf.e + " (level " + leaf.level() + ")");

      Reattach reattach = removeLeaf(leaf);

      //printOccTree2(botTree);

      if (canWalkTree()) {

        print("Leaf removed successfully!");

        anyChange = true;

      } else

        reattach.reattach();

    }

    ret anyChange;

  }

  class Reattach {

    OccTree2 node, leaf;

    int idx;

    void reattach() {

      leaf.parent = node;

      node.next.add(idx, leaf);

    }

  }

  Reattach removeLeaf(OccTree2 leaf) {

    new Reattach r;

    r.leaf = leaf;

    r.node = leaf.parent;

    r.idx = leaf.parent.next.indexOf(leaf);

    leaf.parent.next.remove(r.idx);

    leaf.parent = null;

    ret r;

  }

  bool canWalkTree() {

    ret canWalkTree(tree, makeBot());

  }

  bool canWalkTree(OccTree2 tree, O bot) {

    try { walkTree(tree, bot); true; } catch e {

      if (walkTree_debug)

        printStackTrace(e);

      ret false;

    }

  }

  void walkTree() {

    walkTree(tree, makeBot());

  }

  L<S> statesToIgnore = ll("good", "bad", "end");

  void walkTree(OccTree2 tree, O bot) {

    if (tree.isLeaf())

      assertNull(getOutput(bot));

    else

      for (E e : tree.followUpKeys()) {

        if (!contains(statesToIgnore, e.state)) {

          bool input = isInput(e);

          if (walkTree_debug)

            print((input ? "FEED " : "CHECK ") + structure(e));

          if (input) {

            assertNull(getOutput(bot));

            feed(bot, e);

          } else

            checkOutput(e, getOutput(bot), bot);

          walkTree(tree.followUp(e), bot);

          if (walkTree_debug)

            print("Rewind " + structure(e));

          rewind(bot);

        }

      }

  }

  void rewind(O bot) {

    call(bot, "rewind"); // rewind one step

  }

  void feed(O bot, E e) {

    call(bot, "take", quickExport(e, bot));

    ++inputFed;

  }

  E getOutput(O bot) {

    E e = cast quickImport(call(bot, "getSingleOutput"));

    if (e != null) ++outputGot;

    ret e;

  }

  void checkOutput(E e, E output, O bot) {

    //if (e.state() && matchStart("result is", e.text())) ret;

    //assertEquals(e, output);

    if (neq(e, output)) {

      print(asciiHeading("THOUGHTS"));

      print(callOpt(bot, "thoughts"));

      print();

      fail("Bot fail: Expected " + e + ", got: " + output);

    }

  }

  // should match isCommand() in LooseBot

  bool isInput(E e) {

    ret e.q()

      || e.state() && matchStart("result is ", e.text());

  }

  O makeBot() {

    setOpt(engine, "botTree", quickExport(botTree, engine));

    ret callF(get(engine, "makeBot"));

  }

}