/*
 * 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.ignite.internal.sql.engine.exec.rel;

import static org.apache.ignite.internal.util.CollectionUtils.nullOrEmpty;

import java.util.function.Function;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.ignite.internal.sql.engine.exec.ExecutionContext;

/**
 * ProjectNode.
 * TODO Documentation https://issues.apache.org/jira/browse/IGNITE-15859
 */
public class ProjectNode<RowT> extends AbstractNode<RowT> implements SingleNode<RowT>, Downstream<RowT> {
    private final Function<RowT, RowT> prj;

    /**
     * Constructor.
     * TODO Documentation https://issues.apache.org/jira/browse/IGNITE-15859
     *
     * @param ctx Execution context.
     * @param rowType Rel data type.
     * @param prj Projection.
     */
    public ProjectNode(ExecutionContext<RowT> ctx, RelDataType rowType, Function<RowT, RowT> prj) {
        super(ctx, rowType);

        this.prj = prj;
    }

    /** {@inheritDoc} */
    @Override
    protected void rewindInternal() {
        // No-op.
    }

    /** {@inheritDoc} */
    @Override
    public void request(int rowsCnt) throws Exception {
        assert !nullOrEmpty(sources()) && sources().size() == 1;
        assert rowsCnt > 0;

        checkState();

        source().request(rowsCnt);
    }

    /** {@inheritDoc} */
    @Override
    public void push(RowT row) throws Exception {
        assert downstream() != null;

        checkState();

        downstream().push(prj.apply(row));
    }

    /** {@inheritDoc} */
    @Override
    public void end() throws Exception {
        assert downstream() != null;

        checkState();

        downstream().end();
    }

    /** {@inheritDoc} */
    @Override
    protected Downstream<RowT> requestDownstream(int idx) {
        if (idx != 0) {
            throw new IndexOutOfBoundsException();
        }

        return this;
    }
}
