/**
 *    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 <vector>

#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/ops/write_ops.h"
#include "mongo/s/chunk_version.h"
#include "mongo/s/shard_id.h"
#include "mongo/s/stale_exception.h"
#include "mongo/s/write_ops/batched_command_request.h"

namespace mongo {

class OperationContext;

/**
 * Combines a shard, the shard version, and database version that the shard should be using
 */
struct ShardEndpoint {
    ShardEndpoint(const ShardId& shardName,
                  const ChunkVersion& shardVersion,
                  boost::optional<DatabaseVersion> dbVersion = boost::none)
        : shardName(shardName), shardVersion(shardVersion), databaseVersion(std::move(dbVersion)) {}

    ShardId shardName;
    ChunkVersion shardVersion;
    boost::optional<DatabaseVersion> databaseVersion;
};

/**
 * The NSTargeter interface is used by a WriteOp to generate and target child write operations
 * to a particular collection.
 *
 * The lifecyle of a NSTargeter is:
 *
 *   0. targetDoc/targetQuery as many times as is required
 *
 *   1a. On targeting failure we may need to refresh, note that it happened.
 *   1b. On stale config from a child write operation we may need to refresh, note the error.
 *
 *   2. refreshIfNeeded() to get newer targeting information
 *
 *   3. Goto 0.
 *
 * The refreshIfNeeded() operation must try to make progress against noted targeting or stale
 * config failures, see comments below.  No functions may block for shared resources or network
 * calls except refreshIfNeeded().
 *
 * Implementers are free to define more specific targeting error codes to allow more complex
 * error handling.
 *
 * The interface must not be used from multiple threads.
 */
class NSTargeter {
public:
    virtual ~NSTargeter() = default;

    /**
     * Returns the namespace targeted.
     */
    virtual const NamespaceString& getNS() const = 0;

    /**
     * Returns a ShardEndpoint for a single document write or throws ShardKeyNotFound if 'doc' is
     * malformed with respect to the shard key pattern of the collection.
     */
    virtual ShardEndpoint targetInsert(OperationContext* opCtx, const BSONObj& doc) const = 0;

    /**
     * Returns a vector of ShardEndpoints for a potentially multi-shard update or throws
     * ShardKeyNotFound if 'updateOp' misses a shard key, but the type of update requires it.
     */
    virtual std::vector<ShardEndpoint> targetUpdate(OperationContext* opCtx,
                                                    const BatchItemRef& itemRef) const = 0;

    /**
     * Returns a vector of ShardEndpoints for a potentially multi-shard delete or throws
     * ShardKeyNotFound if 'deleteOp' misses a shard key, but the type of delete requires it.
     */
    virtual std::vector<ShardEndpoint> targetDelete(OperationContext* opCtx,
                                                    const BatchItemRef& itemRef) const = 0;

    /**
     * Returns a vector of ShardEndpoints for all shards.
     */
    virtual std::vector<ShardEndpoint> targetAllShards(OperationContext* opCtx) const = 0;

    /**
     * Informs the targeter that a targeting failure occurred during one of the last targeting
     * operations.  If this is noted, we cannot note stale responses.
     */
    virtual void noteCouldNotTarget() = 0;

    /**
     * Informs the targeter of stale config responses for this namespace from an endpoint, with
     * further information available in the returned staleInfo.
     *
     * Any stale responses noted here will be taken into account on the next refresh.
     *
     * If stale responses are is noted, we must not have noted that we cannot target.
     */
    virtual void noteStaleShardResponse(const ShardEndpoint& endpoint,
                                        const StaleConfigInfo& staleInfo) = 0;

    /**
     * Informs the targeter of stale db routing version responses for this db from an endpoint,
     * with further information available in the returned staleInfo.
     *
     * Any stale responses noted here will be taken into account on the next refresh.
     *
     * If stale responses are is noted, we must not have noted that we cannot target.
     */
    virtual void noteStaleDbResponse(const ShardEndpoint& endpoint,
                                     const StaleDbRoutingVersion& staleInfo) = 0;

    /**
     * Refreshes the targeting metadata for the namespace if needed, based on previously-noted
     * stale responses and targeting failures.
     *
     * After this function is called, the targeter should be in a state such that the noted
     * stale responses are not seen again and if a targeting failure occurred it reloaded -
     * it should try to make progress.  If provided, wasChanged is set to true if the targeting
     * information used here was changed.
     *
     * NOTE: This function may block for shared resources or network calls.
     */
    virtual void refreshIfNeeded(OperationContext* opCtx, bool* wasChanged) = 0;

    /**
     * Returns whether this write targets the config server. Invariants if the write targets the
     * config server AND there is more than one endpoint, since there should be no namespaces that
     * target both config servers and shards.
     */
    virtual bool endpointIsConfigServer() const = 0;

    /**
     * Returns the number of shards that own one or more chunks for the targeted collection.
     */
    virtual int getNShardsOwningChunks() const = 0;
};

}  // namespace mongo