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.linq4j.tree;
  
  import org.checkerframework.checker.initialization.qual.UnderInitialization;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Type;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Objects;
  import java.util.Set;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Represents a block that contains a sequence of expressions where variables
   * can be defined.
   */
  public class BlockStatement extends Statement {
    public final List<Statement> statements;
    /** Cached hash code for the expression. */
    private int hash;
  
    BlockStatement(List<Statement> statements, Type type) {
      super(ExpressionType.Block, type);
      this.statements = requireNonNull(statements, "statements");
      assert distinctVariables(true);
    }
  
    private boolean distinctVariables(
        @UnderInitialization(BlockStatement.class) BlockStatement this,
        boolean fail) {
      Set<String> names = new HashSet<>();
      for (Statement statement : statements) {
        if (statement instanceof DeclarationStatement) {
          String name = ((DeclarationStatement) statement).parameter.name;
          if (!names.add(name)) {
            assert !fail : "duplicate variable " + name;
            return false;
          }
        }
      }
      return true;
    }
  
    @Override public BlockStatement accept(Shuttle shuttle) {
      shuttle = shuttle.preVisit(this);
      List<Statement> newStatements =
          Expressions.acceptStatements(statements, shuttle);
      return shuttle.visit(this, newStatements);
    }
  
    @Override public <R> R accept(Visitor<R> visitor) {
      return visitor.visit(this);
    }
  
    @Override void accept0(ExpressionWriter writer) {
      if (statements.isEmpty()) {
        writer.append("{}");
        return;
      }
      writer.begin("{\n");
      for (Statement node : statements) {
        node.accept(writer, 0, 0);
      }
      writer.end("}\n");
    }
  
    @Override public @Nullable Object evaluate(Evaluator evaluator) {
      Object o = null;
      for (Statement statement : statements) {
        o = statement.evaluate(evaluator);
      }
      return o;
    }
  
    @Override public boolean equals(@Nullable Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      if (!super.equals(o)) {
        return false;
      }
  
      BlockStatement that = (BlockStatement) o;
  
      if (!statements.equals(that.statements)) {
        return false;
      }
  
      return true;
    }
  
    @Override public int hashCode() {
      int result = hash;
      if (result == 0) {
        result = Objects.hash(nodeType, type, statements);
        if (result == 0) {
          result = 1;
        }
        hash = result;
      }
      return result;
    }
  }
  