/*
 * 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 io.prestosql.sql.planner.iterative.rule;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import io.prestosql.matching.Captures;
import io.prestosql.matching.Pattern;
import io.prestosql.sql.planner.iterative.Rule;
import io.prestosql.sql.planner.optimizations.PlanNodeDecorrelator;
import io.prestosql.sql.planner.optimizations.PlanNodeDecorrelator.DecorrelatedNode;
import io.prestosql.sql.planner.plan.JoinNode;
import io.prestosql.sql.planner.plan.LateralJoinNode;
import io.prestosql.sql.planner.plan.PlanNode;
import io.prestosql.sql.tree.Expression;

import java.util.Optional;

import static io.prestosql.matching.Pattern.nonEmpty;
import static io.prestosql.sql.ExpressionUtils.combineConjuncts;
import static io.prestosql.sql.planner.plan.Patterns.LateralJoin.correlation;
import static io.prestosql.sql.planner.plan.Patterns.lateralJoin;
import static io.prestosql.sql.tree.BooleanLiteral.TRUE_LITERAL;

/**
 * Tries to decorrelate subquery and rewrite it using normal join.
 * Decorrelated predicates are part of join condition.
 */
public class TransformCorrelatedLateralJoinToJoin
        implements Rule<LateralJoinNode>
{
    private static final Pattern<LateralJoinNode> PATTERN = lateralJoin()
            .with(nonEmpty(correlation()));

    @Override
    public Pattern<LateralJoinNode> getPattern()
    {
        return PATTERN;
    }

    @Override
    public Result apply(LateralJoinNode lateralJoinNode, Captures captures, Context context)
    {
        PlanNode subquery = lateralJoinNode.getSubquery();

        PlanNodeDecorrelator planNodeDecorrelator = new PlanNodeDecorrelator(context.getIdAllocator(), context.getLookup());
        Optional<DecorrelatedNode> decorrelatedNodeOptional = planNodeDecorrelator.decorrelateFilters(subquery, lateralJoinNode.getCorrelation());

        return decorrelatedNodeOptional
                .map(decorrelatedNode -> {
                    Expression joinFilter = combineConjuncts(
                            decorrelatedNode.getCorrelatedPredicates().orElse(TRUE_LITERAL),
                            lateralJoinNode.getFilter());
                    return Result.ofPlanNode(new JoinNode(
                            context.getIdAllocator().getNextId(),
                            lateralJoinNode.getType().toJoinNodeType(),
                            lateralJoinNode.getInput(),
                            decorrelatedNode.getNode(),
                            ImmutableList.of(),
                            lateralJoinNode.getOutputSymbols(),
                            joinFilter.equals(TRUE_LITERAL) ? Optional.empty() : Optional.of(joinFilter),
                            Optional.empty(),
                            Optional.empty(),
                            Optional.empty(),
                            Optional.empty(),
                            ImmutableMap.of()));
                })
                .orElseGet(Result::empty);
    }
}
