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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.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);
  }
}