content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.materialize;
  
  import org.apache.calcite.util.Litmus;
  
  import com.google.common.collect.ImmutableList;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /** Root node in a {@link Lattice}. It has no parent. */
  public class LatticeRootNode extends LatticeNode {
    /** Descendants, in prefix order. This root node is at position 0. */
    public final ImmutableList<LatticeNode> descendants;
    final ImmutableList<Path> paths;
  
    @SuppressWarnings("method.invocation.invalid")
    LatticeRootNode(LatticeSpace space, MutableNode mutableNode) {
      super(space, null, mutableNode);
  
      final ImmutableList.Builder<LatticeNode> b = ImmutableList.builder();
      flattenTo(b);
      this.descendants = b.build();
      this.paths = createPaths(space);
    }
  
    private ImmutableList<Path> createPaths(LatticeSpace space) {
      final List<Step> steps = new ArrayList<>();
      final List<Path> paths = new ArrayList<>();
      createPathsRecurse(space, steps, paths);
      assert steps.isEmpty();
      return ImmutableList.copyOf(paths);
    }
  
    @Override void use(List<LatticeNode> usedNodes) {
      if (!usedNodes.contains(this)) {
        usedNodes.add(this);
      }
    }
  
    /** Validates that nodes form a tree; each node except the first references
     * a predecessor. */
    boolean isValid(Litmus litmus) {
      for (int i = 0; i < descendants.size(); i++) {
        LatticeNode node = descendants.get(i);
        if (i == 0) {
          if (node != this) {
            return litmus.fail("node 0 should be root");
          }
        } else {
          if (!(node instanceof LatticeChildNode)) {
            return litmus.fail("node after 0 should be child");
          }
          final LatticeChildNode child = (LatticeChildNode) node;
          if (!descendants.subList(0, i).contains(child.parent)) {
            return litmus.fail("parent not in preceding list");
          }
        }
      }
      return litmus.succeed();
    }
  
  
    /** Whether this node's graph is a super-set of (or equal to) another node's
     * graph. */
    public boolean contains(LatticeRootNode node) {
      return paths.containsAll(node.paths);
    }
  
  }
  