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/*
 * 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.test;

import org.apache.calcite.DataContexts;
import org.apache.calcite.plan.AbstractRelOptPlanner;
import org.apache.calcite.plan.Context;
import org.apache.calcite.plan.RelHintsPropagator;
import org.apache.calcite.plan.RelOptCostImpl;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.plan.RelOptRuleOperand;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rex.RexExecutorImpl;
import org.apache.calcite.util.Pair;

import com.google.common.collect.ImmutableList;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

/**
 * MockRelOptPlanner is a mock implementation of the {@link RelOptPlanner}
 * interface.
 */
public class MockRelOptPlanner extends AbstractRelOptPlanner {
  //~ Instance fields --------------------------------------------------------

  private RelNode root;

  private RelOptRule rule;

  private RelNode transformationResult;

  private long metadataTimestamp = 0L;

  //~ Methods ----------------------------------------------------------------

  /** Creates MockRelOptPlanner. */
  public MockRelOptPlanner(Context context) {
    super(RelOptCostImpl.FACTORY, context);
    setExecutor(new RexExecutorImpl(DataContexts.EMPTY));
  }

  @Override public void setRoot(RelNode rel) {
    this.root = rel;
  }

  @Override public @Nullable RelNode getRoot() {
    return root;
  }

  @Override public void clear() {
    super.clear();
    this.rule = null;
  }

  @Override public List getRules() {
    return rule == null
        ? ImmutableList.of() : ImmutableList.of(rule);
  }

  @Override public boolean addRule(RelOptRule rule) {
    assert this.rule == null
        : "MockRelOptPlanner only supports a single rule";
    this.rule = rule;

    return false;
  }

  @Override public boolean removeRule(RelOptRule rule) {
    return false;
  }

  @Override public RelNode changeTraits(RelNode rel, RelTraitSet toTraits) {
    return rel;
  }

  @Override public RelNode findBestExp() {
    if (rule != null) {
      matchRecursive(root, null, -1);
    }
    return root;
  }

  /**
   * Recursively matches a rule.
   *
   * @param rel             Relational expression
   * @param parent          Parent relational expression
   * @param ordinalInParent Ordinal of relational expression among its
   *                        siblings
   * @return whether match occurred
   */
  private boolean matchRecursive(
      RelNode rel,
      RelNode parent,
      int ordinalInParent) {
    List bindings = new ArrayList();
    if (match(
        rule.getOperand(),
        rel,
        bindings)) {
      MockRuleCall call =
          new MockRuleCall(
              this,
              rule.getOperand(),
              bindings.toArray(new RelNode[0]));
      if (rule.matches(call)) {
        rule.onMatch(call);
      }
    }

    if (transformationResult != null) {
      if (parent == null) {
        root = transformationResult;
      } else {
        parent.replaceInput(ordinalInParent, transformationResult);
      }
      return true;
    }

    List children = rel.getInputs();
    for (int i = 0; i < children.size(); ++i) {
      if (matchRecursive(children.get(i), rel, i)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Matches a relational expression to a rule.
   *
   * @param operand  Root operand of rule
   * @param rel      Relational expression
   * @param bindings Bindings, populated on successful match
   * @return whether relational expression matched rule
   */
  private static boolean match(RelOptRuleOperand operand, RelNode rel,
      List bindings) {
    if (!operand.matches(rel)) {
      return false;
    }
    bindings.add(rel);
    switch (operand.childPolicy) {
    case ANY:
      return true;
    default:
      // fall through
    }
    List childOperands = operand.getChildOperands();
    List childRels = rel.getInputs();
    if (childOperands.size() != childRels.size()) {
      return false;
    }
    for (Pair pair
        : Pair.zip(childOperands, childRels)) {
      if (!match(pair.left, pair.right, bindings)) {
        return false;
      }
    }
    return true;
  }

  @Override public RelNode register(RelNode rel, @Nullable RelNode equivRel) {
    return rel;
  }

  @Override public RelNode ensureRegistered(RelNode rel, RelNode equivRel) {
    return rel;
  }

  @Override public boolean isRegistered(RelNode rel) {
    return true;
  }

  @Deprecated // to be removed before 2.0
  @Override public long getRelMetadataTimestamp(RelNode rel) {
    return metadataTimestamp;
  }

  @Deprecated // to be removed before 2.0
  /** Allow tests to tweak the timestamp. */
  public void setRelMetadataTimestamp(long metadataTimestamp) {
    this.metadataTimestamp = metadataTimestamp;
  }

  //~ Inner Classes ----------------------------------------------------------

  /** Mock call to a planner rule. */
  private class MockRuleCall extends RelOptRuleCall {
    /**
     * Creates a MockRuleCall.
     *
     * @param planner Planner
     * @param operand Operand
     * @param rels    List of matched relational expressions
     */
    MockRuleCall(
        RelOptPlanner planner,
        RelOptRuleOperand operand,
        RelNode[] rels) {
      super(
          planner,
          operand,
          rels,
          Collections.emptyMap());
    }

    @Override public void transformTo(RelNode rel, Map equiv,
        RelHintsPropagator handler) {
      transformationResult = rel;
    }
  }
}