/*
 * 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.jackrabbit.oak.plugins.index.elastic.query;

import org.apache.jackrabbit.oak.commons.PathUtils;
import org.apache.jackrabbit.oak.plugins.index.elastic.query.async.ElasticResultRowAsyncIterator;
import org.apache.jackrabbit.oak.plugins.index.search.IndexNode;
import org.apache.jackrabbit.oak.plugins.index.search.SizeEstimator;
import org.apache.jackrabbit.oak.plugins.index.search.spi.query.FulltextIndex;
import org.apache.jackrabbit.oak.plugins.index.search.spi.query.FulltextIndexPlanner;
import org.apache.jackrabbit.oak.plugins.index.search.util.LMSEstimator;
import org.apache.jackrabbit.oak.spi.query.Cursor;
import org.apache.jackrabbit.oak.spi.query.Filter;
import org.apache.jackrabbit.oak.spi.state.NodeState;
import org.elasticsearch.common.Strings;

import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.function.BiFunction;
import java.util.function.Predicate;

import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.TYPE_PROPERTY_NAME;
import static org.apache.jackrabbit.oak.plugins.index.elastic.ElasticIndexDefinition.TYPE_ELASTICSEARCH;

class ElasticIndex extends FulltextIndex {
    private static final Predicate<NodeState> ELASTICSEARCH_INDEX_DEFINITION_PREDICATE =
            state -> TYPE_ELASTICSEARCH.equals(state.getString(TYPE_PROPERTY_NAME));
    private static final Map<String, LMSEstimator> ESTIMATORS = new WeakHashMap<>();

    // no concept of rewound in ES (even if it might be doing it internally, we can't do much about it
    private static final IteratorRewoundStateProvider REWOUND_STATE_PROVIDER_NOOP = () -> 0;

    // # OAK-9419 
    private static final double MIN_COST = 2.2;

    private final ElasticIndexTracker elasticIndexTracker;

    ElasticIndex(ElasticIndexTracker elasticIndexTracker) {
        this.elasticIndexTracker = elasticIndexTracker;
    }

    @Override
    protected String getType() {
        return TYPE_ELASTICSEARCH;
    }

    @Override
    protected FulltextIndexPlanner getPlanner(IndexNode indexNode, String path, Filter filter, List<OrderEntry> sortOrder) {
        return new ElasticIndexPlanner(indexNode, path, filter, sortOrder);
    }

    @Override
    protected SizeEstimator getSizeEstimator(IndexPlan plan) {
        return () -> getEstimator(plan.getPlanName()).estimate(plan.getFilter());
    }

    @Override
    protected Predicate<NodeState> getIndexDefinitionPredicate() {
        return ELASTICSEARCH_INDEX_DEFINITION_PREDICATE;
    }

    @Override
    public double getMinimumCost() {
        return MIN_COST;
    }

    @Override
    public String getIndexName() {
        return "elasticsearch";
    }

    @Override
    protected ElasticIndexNode acquireIndexNode(IndexPlan plan) {
        return (ElasticIndexNode) super.acquireIndexNode(plan);
    }

    @Override
    protected IndexNode acquireIndexNode(String indexPath) {
        return elasticIndexTracker.acquireIndexNode(indexPath, TYPE_ELASTICSEARCH);
    }

    @Override
    protected String getFulltextRequestString(IndexPlan plan, IndexNode indexNode, NodeState rootState) {
        return Strings.toString(new ElasticRequestHandler(plan, getPlanResult(plan), rootState).baseQuery());
    }

    @Override
    public Cursor query(IndexPlan plan, NodeState rootState) {
        final Filter filter = plan.getFilter();
        final FulltextIndexPlanner.PlanResult planResult = getPlanResult(plan);

        final ElasticRequestHandler requestHandler = new ElasticRequestHandler(plan, planResult, rootState);
        final ElasticResponseHandler responseHandler = new ElasticResponseHandler(planResult, filter);

        final Iterator<FulltextResultRow> itr;
        ElasticIndexNode indexNode = acquireIndexNode(plan);
        try {
            if (requestHandler.requiresSpellCheck()) {
                itr = new ElasticSpellcheckIterator(indexNode, requestHandler, responseHandler);
            } else if (requestHandler.requiresSuggestion()) {
                itr = new ElasticSuggestIterator(indexNode, requestHandler, responseHandler);
            } else {
                // this function is called for each extracted row. Passing FulltextIndex::shouldInclude means that for each
                // row we evaluate getPathRestriction(plan) & plan.getFilter().getPathRestriction(). Providing a partial
                // function (https://en.wikipedia.org/wiki/Partial_function) we can evaluate them once and still use a predicate as before
                BiFunction<String, Filter.PathRestriction, Predicate<String>> partialShouldInclude = (path, pathRestriction) -> docPath ->
                        shouldInclude(path, pathRestriction, docPath);

                itr = new ElasticResultRowAsyncIterator(
                        indexNode,
                        requestHandler,
                        responseHandler,
                        plan,
                        partialShouldInclude.apply(getPathRestriction(plan), filter.getPathRestriction()),
                        getEstimator(plan.getPlanName())
                );

            }
        } finally {
            indexNode.release();
        }
        return new FulltextPathCursor(itr, REWOUND_STATE_PROVIDER_NOOP, plan, filter.getQueryLimits(), getSizeEstimator(plan));
    }

    private LMSEstimator getEstimator(String path) {
        ESTIMATORS.putIfAbsent(path, new LMSEstimator());
        return ESTIMATORS.get(path);
    }

    private static boolean shouldInclude(String path, Filter.PathRestriction pathRestriction, String docPath) {
        boolean include = true;
        switch (pathRestriction) {
            case EXACT:
                include = path.equals(docPath);
                break;
            case DIRECT_CHILDREN:
                include = PathUtils.getParentPath(docPath).equals(path);
                break;
            case ALL_CHILDREN:
                include = PathUtils.isAncestor(path, docPath);
                break;
        }

        return include;
    }

    @Override
    protected boolean filterReplacedIndexes() {
        return true;
    }
}
