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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.sql;

import org.apache.calcite.sql.parser.SqlParserPos;
import org.apache.calcite.sql.type.SqlTypeName;
import org.apache.calcite.util.ImmutableNullableList;
import org.apache.calcite.util.Util;

import com.google.common.base.Preconditions;

import java.util.List;
import java.util.Objects;

/**
 * Parse tree node representing a {@code JOIN} clause.
 */
public class SqlJoin extends SqlCall {
  public static final SqlJoinOperator OPERATOR = new SqlJoinOperator();

  SqlNode left;

  /**
   * Operand says whether this is a natural join. Must be constant TRUE or
   * FALSE.
   */
  SqlLiteral natural;

  /**
   * Value must be a {@link SqlLiteral}, one of the integer codes for
   * {@link JoinType}.
   */
  SqlLiteral joinType;
  SqlNode right;

  /**
   * Value must be a {@link SqlLiteral}, one of the integer codes for
   * {@link JoinConditionType}.
   */
  SqlLiteral conditionType;
  SqlNode condition;

  //~ Constructors -----------------------------------------------------------

  public SqlJoin(SqlParserPos pos, SqlNode left, SqlLiteral natural,
      SqlLiteral joinType, SqlNode right, SqlLiteral conditionType,
      SqlNode condition) {
    super(pos);
    this.left = left;
    this.natural = Objects.requireNonNull(natural);
    this.joinType = Objects.requireNonNull(joinType);
    this.right = right;
    this.conditionType = Objects.requireNonNull(conditionType);
    this.condition = condition;

    Preconditions.checkArgument(natural.getTypeName() == SqlTypeName.BOOLEAN);
    Objects.requireNonNull(conditionType.symbolValue(JoinConditionType.class));
    Objects.requireNonNull(joinType.symbolValue(JoinType.class));
  }

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

  public SqlOperator getOperator() {
    return OPERATOR;
  }

  @Override public SqlKind getKind() {
    return SqlKind.JOIN;
  }

  public List getOperandList() {
    return ImmutableNullableList.of(left, natural, joinType, right,
        conditionType, condition);
  }

  @Override public void setOperand(int i, SqlNode operand) {
    switch (i) {
    case 0:
      left = operand;
      break;
    case 1:
      natural = (SqlLiteral) operand;
      break;
    case 2:
      joinType = (SqlLiteral) operand;
      break;
    case 3:
      right = operand;
      break;
    case 4:
      conditionType = (SqlLiteral) operand;
      break;
    case 5:
      condition = operand;
      break;
    default:
      throw new AssertionError(i);
    }
  }

  public final SqlNode getCondition() {
    return condition;
  }

  /** Returns a {@link JoinConditionType}, never null. */
  public final JoinConditionType getConditionType() {
    return conditionType.symbolValue(JoinConditionType.class);
  }

  public SqlLiteral getConditionTypeNode() {
    return conditionType;
  }

  /** Returns a {@link JoinType}, never null. */
  public final JoinType getJoinType() {
    return joinType.symbolValue(JoinType.class);
  }

  public SqlLiteral getJoinTypeNode() {
    return joinType;
  }

  public final SqlNode getLeft() {
    return left;
  }

  public void setLeft(SqlNode left) {
    this.left = left;
  }

  public final boolean isNatural() {
    return natural.booleanValue();
  }

  public final SqlLiteral isNaturalNode() {
    return natural;
  }

  public final SqlNode getRight() {
    return right;
  }

  public void setRight(SqlNode right) {
    this.right = right;
  }

  /**
   * SqlJoinOperator describes the syntax of the SQL 
   * JOIN operator. Since there is only one such operator, this class is
   * almost certainly a singleton.
   */
  public static class SqlJoinOperator extends SqlOperator {
    private static final SqlWriter.FrameType FRAME_TYPE =
        SqlWriter.FrameTypeEnum.create("USING");

    //~ Constructors -----------------------------------------------------------

    private SqlJoinOperator() {
      super("JOIN", SqlKind.JOIN, 16, true, null, null, null);
    }

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

    public SqlSyntax getSyntax() {
      return SqlSyntax.SPECIAL;
    }

    public SqlCall createCall(
        SqlLiteral functionQualifier,
        SqlParserPos pos,
        SqlNode... operands) {
      assert functionQualifier == null;
      return new SqlJoin(pos, operands[0], (SqlLiteral) operands[1],
          (SqlLiteral) operands[2], operands[3], (SqlLiteral) operands[4],
          operands[5]);
    }

    @Override public void unparse(
        SqlWriter writer,
        SqlCall call,
        int leftPrec,
        int rightPrec) {
      final SqlJoin join = (SqlJoin) call;

      final SqlWriter.Frame joinFrame =
          writer.startList(SqlWriter.FrameTypeEnum.JOIN);
      join.left.unparse(
          writer,
          leftPrec,
          getLeftPrec());
      String natural = "";
      if (join.isNatural()) {
        natural = "NATURAL ";
      }
      switch (join.getJoinType()) {
      case COMMA:
        writer.sep(",", true);
        break;
      case CROSS:
        writer.sep(natural + "CROSS JOIN");
        break;
      case FULL:
        writer.sep(natural + "FULL JOIN");
        break;
      case INNER:
        writer.sep(natural + "INNER JOIN");
        break;
      case LEFT:
        writer.sep(natural + "LEFT JOIN");
        break;
      case LEFT_SEMI_JOIN:
        writer.sep(natural + "LEFT SEMI JOIN");
        break;
      case RIGHT:
        writer.sep(natural + "RIGHT JOIN");
        break;
      default:
        throw Util.unexpected(join.getJoinType());
      }
      join.right.unparse(writer, getRightPrec(), rightPrec);
      if (join.condition != null) {
        switch (join.getConditionType()) {
        case USING:
          // No need for an extra pair of parens -- the condition is a
          // list. The result is something like "USING (deptno, gender)".
          writer.keyword("USING");
          assert join.condition instanceof SqlNodeList;
          final SqlWriter.Frame frame =
              writer.startList(FRAME_TYPE, "(", ")");
          join.condition.unparse(writer, 0, 0);
          writer.endList(frame);
          break;

        case ON:
          writer.keyword("ON");
          join.condition.unparse(writer, leftPrec, rightPrec);
          break;

        default:
          throw Util.unexpected(join.getConditionType());
        }
      }
      writer.endList(joinFrame);
    }
  }
}

// End SqlJoin.java