/*
 * Licensed 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 edu.stanford.futuredata.macrobase.sql.tree;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.collect.ImmutableList;
import java.util.List;
import java.util.Optional;

public class FieldReference extends Expression {

    private final int fieldIndex;

    public FieldReference(int fieldIndex) {
        super(Optional.empty());
        checkArgument(fieldIndex >= 0, "fieldIndex must be >= 0");

        this.fieldIndex = fieldIndex;
    }

    public int getFieldIndex() {
        return fieldIndex;
    }

    @Override
    public <R, C> R accept(AstVisitor<R, C> visitor, C context) {
        return visitor.visitFieldReference(this, context);
    }

    @Override
    public List<Node> getChildren() {
        return ImmutableList.of();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        FieldReference that = (FieldReference) o;

        return fieldIndex == that.fieldIndex;
    }

    @Override
    public int hashCode() {
        return fieldIndex;
    }
}
