/*
 * 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 java.util.Objects.requireNonNull;

import java.util.List;
import java.util.Optional;

public abstract class Node {

    private final Optional<NodeLocation> location;

    protected Node(Optional<NodeLocation> location) {
        this.location = requireNonNull(location, "location is null");
    }

    /**
     * Accessible for {@link AstVisitor}, use {@link AstVisitor#process(Node, Object)} instead.
     */
    protected <R, C> R accept(AstVisitor<R, C> visitor, C context) {
        return visitor.visitNode(this, context);
    }

    public Optional<NodeLocation> getLocation() {
        return location;
    }

    public abstract List<? extends Node> getChildren();

    // Force subclasses to have a proper equals and hashcode implementation
    @Override
    public abstract int hashCode();

    @Override
    public abstract boolean equals(Object obj);

    @Override
    public abstract String toString();
}
