/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */
package org.elasticsearch.search.internal;

import org.apache.lucene.search.FieldDoc;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TotalHits;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.action.support.SubscribableListener;
import org.elasticsearch.common.breaker.CircuitBreaker;
import org.elasticsearch.core.Assertions;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.Releasable;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.index.cache.bitset.BitsetFilterCache;
import org.elasticsearch.index.mapper.IdLoader;
import org.elasticsearch.index.mapper.SourceLoader;
import org.elasticsearch.index.query.ParsedQuery;
import org.elasticsearch.index.query.QueryShardException;
import org.elasticsearch.index.query.SearchExecutionContext;
import org.elasticsearch.index.shard.IndexShard;
import org.elasticsearch.search.RescoreDocIds;
import org.elasticsearch.search.SearchExtBuilder;
import org.elasticsearch.search.SearchShardTarget;
import org.elasticsearch.search.aggregations.SearchContextAggregations;
import org.elasticsearch.search.collapse.CollapseContext;
import org.elasticsearch.search.dfs.DfsSearchResult;
import org.elasticsearch.search.fetch.FetchPhase;
import org.elasticsearch.search.fetch.FetchSearchResult;
import org.elasticsearch.search.fetch.StoredFieldsContext;
import org.elasticsearch.search.fetch.subphase.FetchDocValuesContext;
import org.elasticsearch.search.fetch.subphase.FetchFieldsContext;
import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
import org.elasticsearch.search.fetch.subphase.InnerHitsContext;
import org.elasticsearch.search.fetch.subphase.ScriptFieldsContext;
import org.elasticsearch.search.fetch.subphase.highlight.SearchHighlightContext;
import org.elasticsearch.search.lookup.SourceFilter;
import org.elasticsearch.search.profile.Profilers;
import org.elasticsearch.search.query.QueryPhase;
import org.elasticsearch.search.query.QuerySearchResult;
import org.elasticsearch.search.rank.context.QueryPhaseRankShardContext;
import org.elasticsearch.search.rank.feature.RankFeatureResult;
import org.elasticsearch.search.rescore.RescoreContext;
import org.elasticsearch.search.sort.SortAndFormats;
import org.elasticsearch.search.suggest.SuggestionSearchContext;
import org.elasticsearch.tasks.CancellableTask;
import org.elasticsearch.transport.LeakTracker;

import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * This class encapsulates the state needed to execute a search. It holds a reference to the
 * shards point in time snapshot (IndexReader / ContextIndexSearcher) and allows passing on
 * state from one query / fetch phase to another.
 */
public abstract class SearchContext implements Releasable {

    public static final int DEFAULT_TERMINATE_AFTER = 0;
    public static final int TRACK_TOTAL_HITS_ACCURATE = Integer.MAX_VALUE;
    public static final int TRACK_TOTAL_HITS_DISABLED = -1;
    public static final int DEFAULT_TRACK_TOTAL_HITS_UP_TO = 10000;

    protected final SubscribableListener<Void> closeFuture = new SubscribableListener<>();

    {
        if (Assertions.ENABLED) {
            closeFuture.addListener(ActionListener.releasing(LeakTracker.wrap(new Releasable() {
                @Override
                public void close() {
                    // empty instance that will actually get GC'ed so that the leak tracker works
                }
            })));
        }
    }
    private InnerHitsContext innerHitsContext;

    private Query rewriteQuery;

    protected SearchContext() {}

    public final List<Runnable> getCancellationChecks() {
        final Runnable timeoutRunnable = QueryPhase.getTimeoutCheck(this);
        if (lowLevelCancellation()) {
            // This searching doesn't live beyond this phase, so we don't need to remove query cancellation
            Runnable c = () -> {
                final CancellableTask task = getTask();
                if (task != null) {
                    task.ensureNotCancelled();
                }
            };
            return timeoutRunnable == null ? List.of(c) : List.of(c, timeoutRunnable);
        }
        return timeoutRunnable == null ? List.of() : List.of(timeoutRunnable);
    }

    public abstract void setTask(CancellableTask task);

    public abstract CancellableTask getTask();

    public abstract boolean isCancelled();

    @Override
    public final void close() {
        closeFuture.onResponse(null);
    }

    /**
     * Should be called before executing the main query and after all other parameters have been set.
     */
    public abstract void preProcess();

    /** Automatically apply all required filters to the given query such as
     *  alias filters, types filters, etc. */
    public abstract Query buildFilteredQuery(Query query);

    public abstract ShardSearchContextId id();

    public abstract String source();

    public abstract ShardSearchRequest request();

    public abstract SearchType searchType();

    public abstract SearchShardTarget shardTarget();

    public abstract int numberOfShards();

    public abstract ScrollContext scrollContext();

    public abstract SearchContextAggregations aggregations();

    public abstract SearchContext aggregations(SearchContextAggregations aggregations);

    public abstract SearchExtBuilder getSearchExt(String name);

    public abstract SearchHighlightContext highlight();

    public abstract void highlight(SearchHighlightContext highlight);

    public InnerHitsContext innerHits() {
        if (innerHitsContext == null) {
            innerHitsContext = new InnerHitsContext();
        }
        return innerHitsContext;
    }

    public abstract SuggestionSearchContext suggest();

    public abstract QueryPhaseRankShardContext queryPhaseRankShardContext();

    public abstract void queryPhaseRankShardContext(QueryPhaseRankShardContext queryPhaseRankShardContext);

    /**
     * @return list of all rescore contexts.  empty if there aren't any.
     */
    public abstract List<RescoreContext> rescore();

    public abstract void addRescore(RescoreContext rescore);

    public final RescoreDocIds rescoreDocIds() {
        final List<RescoreContext> rescore = rescore();
        if (rescore == null) {
            return RescoreDocIds.EMPTY;
        }
        Map<Integer, Set<Integer>> rescoreDocIds = null;
        for (int i = 0; i < rescore.size(); i++) {
            final Set<Integer> docIds = rescore.get(i).getRescoredDocs();
            if (docIds != null && docIds.isEmpty() == false) {
                if (rescoreDocIds == null) {
                    rescoreDocIds = new HashMap<>();
                }
                rescoreDocIds.put(i, docIds);
            }
        }
        return rescoreDocIds == null ? RescoreDocIds.EMPTY : new RescoreDocIds(rescoreDocIds);
    }

    public final void assignRescoreDocIds(RescoreDocIds rescoreDocIds) {
        final List<RescoreContext> rescore = rescore();
        if (rescore != null) {
            for (int i = 0; i < rescore.size(); i++) {
                final Set<Integer> docIds = rescoreDocIds.getId(i);
                if (docIds != null) {
                    rescore.get(i).setRescoredDocs(docIds);
                }
            }
        }
    }

    public abstract boolean hasScriptFields();

    public abstract ScriptFieldsContext scriptFields();

    /**
     * A shortcut function to see whether there is a fetchSourceContext and it says the source is requested.
     */
    public abstract boolean sourceRequested();

    public abstract FetchSourceContext fetchSourceContext();

    public abstract SearchContext fetchSourceContext(FetchSourceContext fetchSourceContext);

    public abstract FetchDocValuesContext docValuesContext();

    public abstract SearchContext docValuesContext(FetchDocValuesContext docValuesContext);

    /**
     * The context related to retrieving fields.
     */
    public abstract FetchFieldsContext fetchFieldsContext();

    /**
     * Sets the context related to retrieving fields.
     */
    public abstract SearchContext fetchFieldsContext(FetchFieldsContext fetchFieldsContext);

    public abstract ContextIndexSearcher searcher();

    public abstract IndexShard indexShard();

    public abstract BitsetFilterCache bitsetFilterCache();

    public abstract TimeValue timeout();

    public abstract int terminateAfter();

    public abstract void terminateAfter(int terminateAfter);

    /**
     * Indicates if the current index should perform frequent low level search cancellation check.
     *
     * Enabling low-level checks will make long running searches to react to the cancellation request faster. However,
     * since it will produce more cancellation checks it might slow the search performance down.
     */
    public abstract boolean lowLevelCancellation();

    public abstract SearchContext minimumScore(float minimumScore);

    public abstract Float minimumScore();

    public abstract SearchContext sort(SortAndFormats sort);

    public abstract SortAndFormats sort();

    public abstract SearchContext trackScores(boolean trackScores);

    public abstract boolean trackScores();

    public abstract SearchContext trackTotalHitsUpTo(int trackTotalHits);

    /**
     * Indicates the total number of hits to count accurately.
     * Defaults to {@link #DEFAULT_TRACK_TOTAL_HITS_UP_TO}.
     */
    public abstract int trackTotalHitsUpTo();

    public abstract SearchContext searchAfter(FieldDoc searchAfter);

    public abstract FieldDoc searchAfter();

    public abstract CollapseContext collapse();

    public abstract SearchContext parsedPostFilter(ParsedQuery postFilter);

    public abstract ParsedQuery parsedPostFilter();

    public abstract SearchContext parsedQuery(ParsedQuery query);

    public abstract ParsedQuery parsedQuery();

    /**
     * The query to execute, not rewritten.
     */
    public abstract Query query();

    /**
     * The query to execute in its rewritten form.
     */
    public Query rewrittenQuery() {
        if (query() == null) {
            throw new IllegalStateException("preProcess must be called first");
        }
        if (rewriteQuery == null) {
            try {
                this.rewriteQuery = searcher().rewrite(query());
            } catch (IOException exc) {
                throw new QueryShardException(getSearchExecutionContext(), "rewrite failed", exc);
            }
        }
        return rewriteQuery;
    }

    public abstract int from();

    public abstract SearchContext from(int from);

    public abstract int size();

    public abstract SearchContext size(int size);

    public abstract boolean hasStoredFields();

    public abstract StoredFieldsContext storedFieldsContext();

    public abstract SearchContext storedFieldsContext(StoredFieldsContext storedFieldsContext);

    public abstract boolean explain();

    public abstract void explain(boolean explain);

    @Nullable
    public abstract List<String> groupStats();

    public abstract boolean version();

    public abstract void version(boolean version);

    /** indicates whether the sequence number and primary term of the last modification to each hit should be returned */
    public abstract boolean seqNoAndPrimaryTerm();

    /** controls whether the sequence number and primary term of the last modification to each hit should be returned */
    public abstract void seqNoAndPrimaryTerm(boolean seqNoAndPrimaryTerm);

    public abstract DfsSearchResult dfsResult();

    /**
     * Indicates that the caller will be using, and thus owning, a {@link DfsSearchResult} object.  It is the caller's responsibility
     * to correctly cleanup this result object.
     */
    public abstract void addDfsResult();

    public abstract QuerySearchResult queryResult();

    /**
     * Indicates that the caller will be using, and thus owning, a {@link QuerySearchResult} object.  It is the caller's responsibility
     * to correctly cleanup this result object.
     */
    public abstract void addQueryResult();

    public abstract TotalHits getTotalHits();

    public abstract float getMaxScore();

    public abstract void addRankFeatureResult();

    public abstract RankFeatureResult rankFeatureResult();

    public abstract FetchPhase fetchPhase();

    public abstract FetchSearchResult fetchResult();

    /**
     * Indicates that the caller will be using, and thus owning, a {@link FetchSearchResult} object.  It is the caller's responsibility
     * to correctly cleanup this result object.
     */
    public abstract void addFetchResult();

    /**
     * Return a handle over the profilers for the current search request, or {@code null} if profiling is not enabled.
     */
    public abstract Profilers getProfilers();

    /**
     * The circuit breaker used to account for the search operation.
     */
    public abstract CircuitBreaker circuitBreaker();

    /**
     * Return the amount of memory to buffer locally before accounting for it in the breaker.
     */
    public abstract long memAccountingBufferSize();

    /**
     * Checks if the accumulated bytes are greater than the buffer size and if so, checks the available memory in the parent breaker
     * (the real memory breaker).
     * @param locallyAccumulatedBytes the number of bytes accumulated locally
     * @param label the label to use in the breaker
     * @return true if the real memory breaker is called and false otherwise
     */
    public final boolean checkRealMemoryCB(int locallyAccumulatedBytes, String label) {
        if (locallyAccumulatedBytes >= memAccountingBufferSize()) {
            circuitBreaker().addEstimateBytesAndMaybeBreak(0, label);
            return true;
        }
        return false;
    }

    /**
     * Adds a releasable that will be freed when this context is closed.
     */
    public void addReleasable(Releasable releasable) {   // TODO most Releasables are managed by their callers. We probably don't need this.
        assert closeFuture.isDone() == false;
        closeFuture.addListener(ActionListener.releasing(releasable));
    }

    /**
     * @return true if the request contains only suggest
     */
    public final boolean hasOnlySuggest() {
        var source = request().source();
        return source != null && source.isSuggestOnly();
    }

    /**
     * Returns time in milliseconds that can be used for relative time calculations.
     * WARN: This is not the epoch time.
     */
    public abstract long getRelativeTimeInMillis();

    public abstract SearchExecutionContext getSearchExecutionContext();

    @Override
    public String toString() {
        StringBuilder result = new StringBuilder().append(shardTarget());
        if (searchType() != SearchType.DEFAULT) {
            result.append("searchType=[").append(searchType()).append("]");
        }
        if (scrollContext() != null) {
            if (scrollContext().scroll != null) {
                result.append("scroll=[").append(scrollContext().scroll).append("]");
            } else {
                result.append("scroll=[null]");
            }
        }
        result.append(" query=[").append(query()).append("]");
        return result.toString();
    }

    public abstract ReaderContext readerContext();

    /**
     * Build something to load source {@code _source}.
     */
    public abstract SourceLoader newSourceLoader(@Nullable SourceFilter sourceFilter);

    public abstract IdLoader newIdLoader();
}