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/*
 * 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.trino.cost;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.inject.Inject;
import io.trino.matching.Pattern;
import io.trino.matching.pattern.TypeOfPattern;
import io.trino.sql.planner.plan.PlanNode;

import java.lang.reflect.Modifier;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.Multimaps.toMultimap;

public class ComposableStatsCalculator
        implements StatsCalculator
{
    private final ListMultimap, Rule> rulesByRootType;

    @Inject
    public ComposableStatsCalculator(List> rules)
    {
        this.rulesByRootType = rules.stream()
                .peek(rule -> {
                    if (!(rule.getPattern() instanceof TypeOfPattern pattern)) {
                        throw new IllegalArgumentException("Rule pattern must be TypeOfPattern but was: " + rule.getPattern().getClass().getSimpleName());
                    }
                    Class expectedClass = pattern.expectedClass();
                    checkArgument(!expectedClass.isInterface() && !Modifier.isAbstract(expectedClass.getModifiers()), "Rule must be registered on a concrete class");
                })
                .collect(toMultimap(
                        rule -> ((TypeOfPattern) rule.getPattern()).expectedClass(),
                        rule -> rule,
                        ArrayListMultimap::create));
    }

    private Stream> getCandidates(PlanNode node)
    {
        for (Class superclass = node.getClass().getSuperclass(); superclass != null; superclass = superclass.getSuperclass()) {
            // This is important because rule ordering, given in the constructor, is significant.
            // We can't check this fully in the constructor, since abstract class may lack `abstract` modifier.
            checkState(rulesByRootType.get(superclass).isEmpty(), "Cannot maintain rule order because there is rule registered for %s", superclass);
        }
        return rulesByRootType.get(node.getClass()).stream();
    }

    @Override
    public PlanNodeStatsEstimate calculateStats(PlanNode node, Context context)
    {
        Iterator> ruleIterator = getCandidates(node).iterator();
        while (ruleIterator.hasNext()) {
            Rule rule = ruleIterator.next();
            Optional calculatedStats = calculateStats(rule, node, context);
            if (calculatedStats.isPresent()) {
                return calculatedStats.get();
            }
        }
        return PlanNodeStatsEstimate.unknown();
    }

    private static  Optional calculateStats(Rule rule, PlanNode node, Context context)
    {
        @SuppressWarnings("unchecked")
        T typedNode = (T) node;
        return rule.calculate(typedNode, context);
    }

    public interface Rule
    {
        Pattern getPattern();

        Optional calculate(T node, Context context);
    }
}