// A naive suffix tree implementation

sclass SuffixTree {

  Node root;

  S fullText;

  int nodeCount;

  bool useTailOptimization; // doesn't work yet

  Comparator<IFirstChar> childComparator = (a, b) -> a.firstCharOrMinus1(this)-b.firstCharOrMinus1(this);

  new DummyNode dummyNode;

  new Map<Int, Node> tailMap; // position -> node already made

  sinterface IFirstChar {

    int firstCharOrMinus1(SuffixTree tree);

  }

  sclass DummyNode implements IFirstChar {

    int firstChar;

    public int firstCharOrMinus1(SuffixTree tree) { ret firstChar; }

  }

  sclass Node implements IFirstChar {

    int from, to; // our range in fullText

    O children; // null, a Node or Node[] sorted by first character

    *() {}

    *(int *from, int *to) {}

    *(Substring s) { from = s.startIndex(); to = s.endIndex(); }

    Substring text(SuffixTree tree) { ret Substring(tree.fullText, from, to); }

    int lText() { ret to-from; }

    bool isTerminal(SuffixTree tree) { ret to == l(tree.fullText); }

    void addChild(SuffixTree tree, Node n) {

      if (children == null) children = n;

      else if (children cast Node)

        children = sortArrayInPlace(new Node[] {children, n}, tree.childComparator);

      else {

        Node[] c = cast children;

        Node[] x = new[l(c)+1];

        arraycopy(c, 0, x, 0, l(c));

        x[l(x)-1] = n;

        children = sortArrayInPlace(x, tree.childComparator);

      }

    }

    Cl<Node> children() {

      if (children == null) ret emptyList();

      if (children cast Node) ret ll(children);

      ret wrapArrayAsList((Node[]) children);

    }

    public int firstCharOrMinus1(SuffixTree tree) {

      ret charToIntOrMinus1(text(tree));

    }

    Node getChild(SuffixTree tree, int c) {

      if (children == null) null;

      if (children cast Node)

        ret children.firstCharOrMinus1(tree) == c ? children : null;

      tree.dummyNode.firstChar = c;

      Node[] x = cast children;

      int i = Arrays.binarySearch(x, tree.dummyNode, tree.childComparator);

      ret i >= 0 ? x[i] : null;

    }

  }

  *() {}

  *(S fullText) {

    processText(fullText);

  }

  void processText(S fullText) {

    this.fullText = fullText;

    root = new Node(0, 0);

    ++nodeCount;

    for i over fullText: {

    //for (int i = l(fullText)-1; i >= 0; i--) {

      addSuffix(Substring(fullText, i));

      if (((i+1) % 1000000) == 0)

        print((i+1) + " suffixes added (" + nNodes(nodeCount) + ")");

    }

    doneBuilding();

  }

  void doneBuilding {

    tailMap = null;

  }

  void addSuffix(Substring s) {

    Node node = root;

    while (!empty(s)) {

      int _n = lCommonPrefix_CharSequence(node.text(SuffixTree.this), s);

      s = s.substring(_n);

      if (_n >= node.lText()) { // node text exhausted

        if (empty(s)) { // pattern also exhausted - done

          //print("Exhausted: " + node.from + "/" + node.to);

          // add a new termination node

          Node nNew = newNode(s);

          node.addChild(SuffixTree.this, nNew);

          ret;

        } else { // node text exhausted, pattern not exhausted

          Node n = node.getChild(SuffixTree.this, charToIntOrMinus1(s));

          if (n == null) {

            n = newNode(s);

            node.addChild(SuffixTree.this, n);

            ret;

          } else

            node = n;

        }

      } else { // node text not exhausted, pattern not exhausted

        // split node. first, move all the node's vitals to a new node nOld

        Node nOld = newNode(node.from+_n, node.to);

        nOld.children = node.children;

        node.children = null;

        node.to = node.from+_n;

        node.addChild(SuffixTree.this, nOld);

        // now add a new node

        Node nNew = newNode(s);

        node.addChild(SuffixTree.this, nNew);

        ret;

      }

    }

  }

  public L<Int> indicesOf(S pattern) {

    ret asList(indicesOf_iterator(pattern));

  }

  public ItIt<Int> indicesOf_iterator(S pattern) {

    ret mapI_notNull(allNodesUnder(scanDown(root, pattern)),

      nad -> nad.node.isTerminal(this) ? nad.position() : null);

  }

  srecord NodeAndDepth(Node node, int depth) {

    int position() {

      int position = node.from-depth;

      //print("from=" + node.from + ", to=" + node.to + ", depth=" + depth + ", position=" + position);

      ret position;

    }

    Cl<NodeAndDepth> children() {

      ret lmap wrapChild(node.children());

    }

    NodeAndDepth wrapChild(Node n) {

      ret n == null ? null : new NodeAndDepth(n, depth+node.lText());

    }

    NodeAndDepth getChild(SuffixTree tree, int c) {

      ret wrapChild(node.getChild(tree, c));

    }

  }

  NodeAndDepth scanDown(Node node, S pattern) {

    int lPattern = l(pattern), iPattern = 0;

    NodeAndDepth nad = new(node, 0);

    while true {

      int n = lCommonPrefix_CharSequence(nad.node.text(this), Substring(pattern, iPattern));

      iPattern += n;

      if (iPattern >= lPattern) break; // pattern exhausted - done

      if (n < nad.node.lText()) null; // mismatch, exit

      NodeAndDepth child = nad.getChild(SuffixTree.this, charAtAsIntOrMinus1(pattern, iPattern));

      if (child != null) continue with nad = child;

      null;

    }

    ret nad;

  }

  void printMe() {

    printNode("", "", new NodeAndDepth(root, 0));

  }

  void printNode(S indent, S pre, NodeAndDepth nad) {

    print(indent + pre + quote(shorten(20, nad.node.text(this))) + (!nad.node.isTerminal(this) ? "" : " [" + nad.position() + "]"));

    fOr (NodeAndDepth n : nad.children()) {

      printNode(indent + "  ", "[" + (n.node.lText() == 0 ? "end" : quote(n.node.text(this).charAt(0))) + "] ", n);

    }

  }

  ItIt<NodeAndDepth> allNodes() {

    ret allNodesUnder(new NodeAndDepth(root, 0));

  }

  // includes the node itself

  ItIt<NodeAndDepth> allNodesUnder(NodeAndDepth nad) {

    new L<Iterator<NodeAndDepth>> stack;

    if (nad != null)

      stack.add(iteratorLL(nad));

    ret iteratorFromFunction_if0(() -> {

      while (nempty(stack)) {

        if (!last(stack).hasNext())

          popLast(stack);

        else {

          NodeAndDepth n = last(stack).next();

          stack.add((Iterator) iterator(n.children()));

          ret n;

        }

      }

      null;

    });

  }

  // also query & update tailMap

  Node newNode(Substring s) {  

    Node nNew = useTailOptimization && s.endIndex() == l(fullText) ? mapGet(tailMap, s.startIndex()) : null;

    if (nNew == null) {

      nNew = new Node(s);

      ++nodeCount;

      if (useTailOptimization)

        mapPut(tailMap, s.startIndex(), nNew);

    } else {

      print("Using existing node for index " + s.startIndex() + ":");

      printNode("  ", "", new NodeAndDepth(nNew, 0));

    }

    ret nNew;

  }

  Node newNode(int from, int to) {  

    ret newNode(Substring(fullText, from, to));

  }

}