/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <memory>
#include <utility>

#include "mongo/client/connpool.h"
#include "mongo/db/matcher/matcher.h"
#include "mongo/db/pipeline/document_source.h"

namespace mongo {

class DocumentSourceMatch : public DocumentSource {
public:
    static constexpr StringData kStageName = "$match"_sd;
    /**
     * Convenience method for creating a $match stage.
     */
    static boost::intrusive_ptr<DocumentSourceMatch> create(
        BSONObj filter, const boost::intrusive_ptr<ExpressionContext>& expCtx);

    /**
     * Parses a $match stage from 'elem'.
     */
    static boost::intrusive_ptr<DocumentSource> createFromBson(
        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pCtx);

    /**
     * Returns a new DocumentSourceMatch with a MatchExpression that, if executed on the
     * sub-document at 'path', is equivalent to 'expression'.
     *
     * For example, if the original expression is {$and: [{'a.b': {$gt: 0}}, {'a.d': {$eq: 3}}]},
     * the new $match will have the expression {$and: [{b: {$gt: 0}}, {d: {$eq: 3}}]} after
     * descending on the path 'a'.
     *
     * Should be called _only_ on a MatchExpression that is a predicate on 'path', or subfields of
     * 'path'. It is also invalid to call this method on an expression including a $elemMatch on
     * 'path', for example: {'path': {$elemMatch: {'subfield': 3}}}
     */
    static boost::intrusive_ptr<DocumentSourceMatch> descendMatchOnPath(
        MatchExpression* matchExpr,
        const std::string& path,
        const boost::intrusive_ptr<ExpressionContext>& expCtx);

    virtual ~DocumentSourceMatch() = default;

    /**
     * Parses 'filter' and resets the member of this source to be consistent with the new
     * MatchExpression. Takes ownership of 'filter'.
     */
    void rebuild(BSONObj filter);

    boost::intrusive_ptr<DocumentSource> optimize() final;

    const char* getSourceName() const override;

    StageConstraints constraints(Pipeline::SplitState pipeState) const override {
        return {StreamType::kStreaming,
                PositionRequirement::kNone,
                HostTypeRequirement::kNone,
                DiskUseRequirement::kNoDiskUse,
                FacetRequirement::kAllowed,
                TransactionRequirement::kAllowed,
                LookupRequirement::kAllowed,
                ChangeStreamRequirement::kWhitelist};
    }

    Value serialize(
        boost::optional<ExplainOptions::Verbosity> explain = boost::none) const override;

    /**
     * Attempts to combine with any subsequent $match stages, joining the query objects with a
     * $and.
     */
    Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
                                                     Pipeline::SourceContainer* container) final;

    DepsTracker::State getDependencies(DepsTracker* deps) const final;

    GetModPathsReturn getModifiedPaths() const final {
        // This stage does not modify or rename any paths.
        return {GetModPathsReturn::Type::kFiniteSet, std::set<std::string>{}, {}};
    }

    /**
     * Access the MatchExpression stored inside the DocumentSourceMatch. Does not release ownership.
     */
    MatchExpression* getMatchExpression() const {
        return _expression.get();
    }

    /**
     * Combines the filter in this $match with the filter of 'other' using a $and, updating this
     * match in place.
     */
    void joinMatchWith(boost::intrusive_ptr<DocumentSourceMatch> other);

    /**
     * Returns the query in MatchExpression syntax.
     */
    BSONObj getQuery() const;

    /** Returns the portion of the match that can safely be promoted to before a $redact.
     *  If this returns an empty BSONObj, no part of this match may safely be promoted.
     *
     *  To be safe to promote, removing a field from a document to be matched must not cause
     *  that document to be accepted when it would otherwise be rejected. As an example,
     *  {name: {$ne: "bob smith"}} accepts documents without a name field, which means that
     *  running this filter before a redact that would remove the name field would leak
     *  information. On the other hand, {age: {$gt:5}} is ok because it doesn't accept documents
     *  that have had their age field removed.
     */
    BSONObj redactSafePortion() const;

    static bool isTextQuery(const BSONObj& query);
    bool isTextQuery() const {
        return _isTextQuery;
    }

    /**
     * Attempt to split this $match into two stages, where the first is not dependent upon any path
     * from 'fields', and where applying them in sequence is equivalent to applying this stage once.
     *
     * Will return two intrusive_ptrs to new $match stages, where the first pointer is independent
     * of 'fields', and the second is dependent. Either pointer may be null, so be sure to check the
     * return value.
     *
     * For example, {$match: {a: "foo", "b.c": 4}} split by "b" will return pointers to two stages:
     * {$match: {a: "foo"}}, and {$match: {"b.c": 4}}.
     *
     * The 'renames' structure maps from a field to an alias that should be used in the independent
     * portion of the match. For example, suppose that we split by fields "a" with the rename "b" =>
     * "c". The match {$match: {a: "foo", b: "bar", z: "baz"}} will split into {$match: {c: "bar",
     * z: "baz"}} and {$match: {a: "foo"}}.
     */
    std::pair<boost::intrusive_ptr<DocumentSourceMatch>, boost::intrusive_ptr<DocumentSourceMatch>>
    splitSourceBy(const std::set<std::string>& fields, const StringMap<std::string>& renames);

    boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
        return boost::none;
    }

protected:
    GetNextResult doGetNext() override;
    DocumentSourceMatch(const BSONObj& query,
                        const boost::intrusive_ptr<ExpressionContext>& expCtx);

    BSONObj _predicate;

private:
    std::unique_ptr<MatchExpression> _expression;

    bool _isTextQuery;

    // Cache the dependencies so that we know what fields we need to serialize to BSON for matching.
    DepsTracker _dependencies;
};

}  // namespace mongo