/*
 * 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.trait;

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

import java.util.Collection;
import java.util.Collections;
import java.util.Set;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelTrait;
import org.apache.calcite.plan.RelTraitDef;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.CorrelationId;
import org.apache.ignite.internal.sql.engine.rel.IgniteCorrelatedNestedLoopJoin;

/**
 * Correlation trait is created by node that creates and sets correlation variables {@link RelNode#getVariablesSet()}}
 * (e.g. {@link IgniteCorrelatedNestedLoopJoin}) and pass through this trait to input that uses correlation variable(s).
 *
 * <p>The correlation trait is used to prevent the insertion of nodes that cannot preserve correlation in the correlated
 * data stream. e.g. these nodes are IgniteExchange, IgniteTableSpool, etc.
 *
 * <p>Let's describe more details: IgniteExchange: current implementation is not rewindable and not send values of the
 * correlation variables to Senders. TableSpool: stores the input data stream and rewind it many times So. it cannot be
 * depends on the value of the correlation variables.
 */
public class CorrelationTrait implements RelTrait {
    public static final CorrelationTrait UNCORRELATED = canonize(new CorrelationTrait(Collections.emptyList()));

    private final Set<CorrelationId> correlations;

    public CorrelationTrait(Collection<CorrelationId> correlationIds) {
        correlations = Set.copyOf(correlationIds);
    }

    public boolean correlated() {
        return !nullOrEmpty(correlations);
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }

        if (!(o instanceof CorrelationTrait)) {
            return false;
        }

        return correlations.equals(((CorrelationTrait) o).correlations);
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        return correlations.hashCode();
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return correlated() ? "correlated" + correlations : "uncorrelated";
    }

    /** {@inheritDoc} */
    @Override
    public RelTraitDef<CorrelationTrait> getTraitDef() {
        return CorrelationTraitDef.INSTANCE;
    }

    /** {@inheritDoc} */
    @Override
    public boolean satisfies(RelTrait trait) {
        if (trait == this || this == UNCORRELATED) {
            return true;
        }

        if (!(trait instanceof CorrelationTrait)) {
            return false;
        }

        CorrelationTrait other = (CorrelationTrait) trait;

        return other.correlated() && other.correlationIds().containsAll(correlationIds());
    }

    /** {@inheritDoc} */
    @Override
    public void register(RelOptPlanner planner) {
        // no-op
    }

    private static CorrelationTrait canonize(CorrelationTrait trait) {
        return CorrelationTraitDef.INSTANCE.canonize(trait);
    }

    public Set<CorrelationId> correlationIds() {
        return correlations;
    }

    public static CorrelationTrait correlations(Collection<CorrelationId> correlationIds) {
        return canonize(new CorrelationTrait(correlationIds));
    }
}
