EmptyExpression.java

/*
 * Copyright (c) 2015 Spotify AB.
 *
 * 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 com.spotify.heroic.grammar;

import com.fasterxml.jackson.annotation.JsonTypeName;
import lombok.Data;

import java.util.Optional;

@Data
@JsonTypeName("empty")
public class EmptyExpression implements Expression {
    private final Context context;

    @Override
    public <R> R visit(final Visitor<R> visitor) {
        return visitor.visitEmpty(this);
    }

    @Override
    public <T extends Expression> T cast(Class<T> to) {
        if (to.equals(Expression.class) || to.equals(EmptyExpression.class)) {
            return (T) this;
        }

        throw context.castError(this, to);
    }

    @Override
    public Optional<Expression> toOptional() {
        return Optional.empty();
    }

    @Override
    public String toRepr() {
        return "empty";
    }
}