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 static java.util.Objects.requireNonNull;
  
  /**
   * Helper methods concerning {@link BlockStatement}s.
   *
   * @see BlockBuilder
   */
  public final class Blocks {
    private Blocks() {
      throw new AssertionError("no blocks for you!");
    }
  
    private static BlockStatement toFunctionBlock(Node body, boolean function) {
      if (body instanceof BlockStatement) {
        return (BlockStatement) body;
      }
      Statement statement;
      if (body instanceof Statement) {
        statement = (Statement) body;
      } else if (body instanceof Expression) {
        if (((Expression) body).getType() == Void.TYPE && function) {
          statement = Expressions.statement((Expression) body);
        } else {
          statement = Expressions.return_(null, (Expression) body);
        }
      } else {
        throw new AssertionError("block cannot contain node that is neither "
            + "statement nor expression: " + body);
      }
      return Expressions.block(statement);
    }
  
    public static BlockStatement toFunctionBlock(Node body) {
      return toFunctionBlock(body, true);
    }
  
    public static BlockStatement toBlock(Node body) {
      return toFunctionBlock(body, false);
    }
  
    /**
     * Prepends a statement to a block.
     */
    public static BlockStatement create(Statement statement,
        BlockStatement block) {
      return Expressions.block(
          Expressions.list(statement).appendAll(block.statements));
    }
  
    /**
     * Converts a simple "{ return expr; }" block into "expr"; otherwise
     * throws.
     */
    public static Expression simple(BlockStatement block) {
      if (block.statements.size() == 1) {
        Statement statement = block.statements.get(0);
        if (statement instanceof GotoStatement) {
          return requireNonNull(((GotoStatement) statement).expression);
        }
      }
      throw new AssertionError("not a simple block: " + block);
    }
  }
  