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package org.apache.doris.nereids.rules.rewrite;

import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.logical.LogicalFilter;
import org.apache.doris.nereids.trees.plans.logical.LogicalLimit;
import org.apache.doris.nereids.trees.plans.logical.LogicalProject;
import org.apache.doris.nereids.util.ExpressionUtils;

import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * Push down filter through project.
 * input:
 * filter(a>2, b=0) -> project(c+d as a, e as b)
 * output:
 * project(c+d as a, e as b) -> filter(c+d>2, e=0).
 */
public class PushdownFilterThroughProject implements RewriteRuleFactory {
    @Override
    public List<Rule> buildRules() {
        return ImmutableList.of(
            RuleType.PUSHDOWN_FILTER_THROUGH_PROJECT.build(
                    logicalFilter(logicalProject())
                            .then(PushdownFilterThroughProject::pushdownFilterThroughProject)
            ),
            // filter(project(limit)) will change to filter(limit(project)) by PushdownProjectThroughLimit,
            // then we should change filter(limit(project)) to project(filter(limit))
            RuleType.PUSHDOWN_FILTER_THROUGH_PROJECT_UNDER_LIMIT.build(
                    logicalFilter(logicalLimit(logicalProject())).then(filter -> {
                        LogicalLimit<LogicalProject<Plan>> limit = filter.child();
                        LogicalProject<Plan> project = limit.child();

                        return project.withProjectsAndChild(
                                project.getProjects(),
                                new LogicalFilter<>(
                                        ExpressionUtils.replace(filter.getConjuncts(), project.getAliasToProducer()),
                                        limit.withChildren(project.child())
                                )
                        );
                    })
            )
        );
    }

    /** pushdown Filter through project */
    public static Plan pushdownFilterThroughProject(LogicalFilter<LogicalProject<Plan>> filter) {
        LogicalProject<Plan> project = filter.child();
        return project.withChildren(
                new LogicalFilter<>(
                        ExpressionUtils.replace(filter.getConjuncts(), project.getAliasToProducer()),
                        project.child()
                )
        );
    }
}
