/**
 *    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 <functional>
#include <memory>
#include <vector>

#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/aggregate_command_gen.h"
#include "mongo/db/pipeline/lite_parsed_document_source.h"
#include "mongo/db/read_concern_support_result.h"

namespace mongo {

/**
 * A semi-parsed version of a Pipeline, parsed just enough to determine information like what
 * foreign collections are involved.
 */
class LiteParsedPipeline {
public:
    /**
     * Constructs a LiteParsedPipeline from the raw BSON stages given in 'request'.
     *
     * May throw a AssertionException if there is an invalid stage specification, although full
     * validation happens later, during Pipeline construction.
     */
    LiteParsedPipeline(const AggregateCommandRequest& request)
        : LiteParsedPipeline(request.getNamespace(), request.getPipeline()) {}

    LiteParsedPipeline(const NamespaceString& nss, const std::vector<BSONObj>& pipelineStages) {
        _stageSpecs.reserve(pipelineStages.size());
        for (auto&& rawStage : pipelineStages) {
            _stageSpecs.push_back(LiteParsedDocumentSource::parse(nss, rawStage));
        }
    }

    /**
     * Returns all foreign namespaces referenced by stages within this pipeline, if any.
     */
    stdx::unordered_set<NamespaceString> getInvolvedNamespaces() const {
        stdx::unordered_set<NamespaceString> involvedNamespaces;
        for (auto&& spec : _stageSpecs) {
            auto stagesInvolvedNamespaces = spec->getInvolvedNamespaces();
            involvedNamespaces.insert(stagesInvolvedNamespaces.begin(),
                                      stagesInvolvedNamespaces.end());
        }
        return involvedNamespaces;
    }

    /**
     * Returns a vector of the foreign collections(s) referenced by this stage that potentially will
     * be involved in query execution, if any. For example, consider the pipeline:
     *
     * [{$lookup: {from: "bar", localField: "a", foreignField: "b", as: "output"}},
     *  {$unionWith: {coll: "foo", pipeline: [...]}}].
     *
     * Here, "foo" is not considered a foreign execution namespace because "$unionWith" cannot be
     * pushed down into the execution subsystem underneath the leading cursor stage, while "bar"
     * is considered one because "$lookup" can be pushed down in certain cases.
     */
    std::vector<NamespaceStringOrUUID> getForeignExecutionNamespaces() const {
        stdx::unordered_set<NamespaceString> nssSet;
        for (auto&& spec : _stageSpecs) {
            spec->getForeignExecutionNamespaces(nssSet);
        }
        return {nssSet.begin(), nssSet.end()};
    }

    /**
     * Returns a list of the priviliges required for this pipeline.
     */
    PrivilegeVector requiredPrivileges(bool isMongos, bool bypassDocumentValidation) const {
        PrivilegeVector requiredPrivileges;
        for (auto&& spec : _stageSpecs) {
            Privilege::addPrivilegesToPrivilegeVector(
                &requiredPrivileges, spec->requiredPrivileges(isMongos, bypassDocumentValidation));
        }

        return requiredPrivileges;
    }

    /**
     * Returns true if the pipeline begins with a $collStats stage.
     */
    bool startsWithCollStats() const {
        return !_stageSpecs.empty() && _stageSpecs.front()->isCollStats();
    }

    /**
     * Returns true if the pipeline begins with a $indexStats stage.
     */
    bool startsWithIndexStats() const {
        return !_stageSpecs.empty() && _stageSpecs.front()->isIndexStats();
    }

    /**
     * Returns true if the pipeline begins with a $documents stage.
     */
    bool startsWithDocuments() const {
        return !_stageSpecs.empty() && _stageSpecs.front()->isDocuments();
    }

    /**
     * Returns true if the pipeline has a $changeStream stage.
     */
    bool hasChangeStream() const {
        return std::any_of(_stageSpecs.begin(), _stageSpecs.end(), [](auto&& spec) {
            return spec->isChangeStream();
        });
    }

    /**
     * Returns false if the pipeline has any stages which cannot be passed through to the shards.
     */
    bool allowedToPassthroughFromMongos() const {
        return std::all_of(_stageSpecs.cbegin(), _stageSpecs.cend(), [](const auto& spec) {
            return spec->allowedToPassthroughFromMongos();
        });
    }

    /**
     * Returns false if at least one of the stages does not allow the involved namespace 'nss' to be
     * sharded.
     */
    bool allowShardedForeignCollection(NamespaceString nss, bool isMultiDocumentTransaction) const {
        return std::all_of(_stageSpecs.begin(),
                           _stageSpecs.end(),
                           [&nss, isMultiDocumentTransaction](auto&& spec) {
                               return spec->allowShardedForeignCollection(
                                   nss, isMultiDocumentTransaction);
                           });
    }

    /**
     * Verifies that this pipeline is allowed to run with the specified read concern level.
     */
    ReadConcernSupportResult supportsReadConcern(repl::ReadConcernLevel level,
                                                 bool isImplicitDefault,
                                                 boost::optional<ExplainOptions::Verbosity> explain,
                                                 bool enableMajorityReadConcern) const;

    /**
     * Checks that all of the stages in this pipeline are allowed to run with the specified read
     * concern level. Does not do any pipeline global checks.
     */
    ReadConcernSupportResult sourcesSupportReadConcern(repl::ReadConcernLevel level,
                                                       bool isImplicitDefault) const;

    /**
     * Verifies that this pipeline is allowed to run in a multi-document transaction. This ensures
     * that each stage is compatible, and throws a UserException if not. This should only be called
     * if the caller has determined the current operation is part of a transaction.
     */
    void assertSupportsMultiDocumentTransaction(
        boost::optional<ExplainOptions::Verbosity> explain) const;

    /**
     * Verifies that this pipeline is allowed to run with the read concern from the provided opCtx.
     * Used only when asserting is the desired behavior, otherwise use supportsReadConcern instead.
     */
    void assertSupportsReadConcern(OperationContext* opCtx,
                                   boost::optional<ExplainOptions::Verbosity> explain) const;

    /**
     * Perform checks that verify that the LitePipe is valid. Note that this function must be called
     * before forwarding an aggregation command on an unsharded collection, in order to verify that
     * the involved namespaces are allowed to be sharded.
     */
    void verifyIsSupported(OperationContext* opCtx,
                           std::function<bool(OperationContext*, const NamespaceString&)> isSharded,
                           boost::optional<ExplainOptions::Verbosity> explain,
                           bool enableMajorityReadConcern) const;

    /**
     * Returns true if the first stage in the pipeline does not require an input source.
     */
    bool startsWithInitialSource() const {
        return !_stageSpecs.empty() && _stageSpecs.front()->isInitialSource();
    }

    /**
     * Increments global stage counters corresponding to the stages in this lite parsed pipeline.
     */
    void tickGlobalStageCounters() const;

    /**
     * Verifies that the pipeline contains valid stages. Optionally calls
     * 'validatePipelineStagesforAPIVersion' with 'opCtx'.
     */
    void validate(const OperationContext* opCtx, bool performApiVersionChecks = true) const;

private:
    std::vector<std::unique_ptr<LiteParsedDocumentSource>> _stageSpecs;
};

}  // namespace mongo