/**
 *    Copyright (C) 2015 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    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 GNU Affero General 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 "mongo/base/disallow_copying.h"
#include "mongo/base/status_with.h"
#include "mongo/rpc/protocol.h"

namespace mongo {
class BSONObj;
class Message;

namespace rpc {
class DocumentRange;

/**
 * Constructs an RPC Reply.
 */
class ReplyBuilderInterface {
    MONGO_DISALLOW_COPYING(ReplyBuilderInterface);

public:
    /**
     * Reply builders must have their fields set in order as they are immediately written into
     * the underlying message buffer. This enum represents the next field that can be written
     * into the builder. Note that when the builder is in state 'kInputDocs', multiple input
     * docs can be added. After the builder's done() method is called it is in state 'kDone',
     * and no further methods can be called.
     */
    enum class State { kMetadata, kCommandReply, kOutputDocs, kDone };

    virtual ~ReplyBuilderInterface() = default;

    virtual ReplyBuilderInterface& setMetadata(BSONObj metadata) = 0;

    /**
     * Sets the raw command reply. This should probably not be used in favor of the
     * variants that accept a Status or StatusWith.
     */
    virtual ReplyBuilderInterface& setRawCommandReply(BSONObj reply) = 0;

    /**
     * Sets the reply for this command. If an engaged StatusWith<BSONObj> is passed, the command
     * reply will be set to the contained BSONObj, augmented with the element {ok, 1.0} if it
     * does not already have an "ok" field. If a disengaged StatusWith<BSONObj> is passed, the
     * command reply will be set to {ok: 0.0, code: <code of status>,
     *                               errmsg: <reason of status>}
     */
    ReplyBuilderInterface& setCommandReply(StatusWith<BSONObj> commandReply);

    /**
     * Sets the reply for this command. The status parameter must be non-OK. The reply for
     * this command will be set to an object containing all the fields in extraErrorInfo,
     * augmented with {ok: 0.0} , {code: <code of status>}, and {errmsg: <reason of status>}.
     * If any of the fields "ok", "code", or "errmsg" already exist in extraErrorInfo, they
     * will be left as-is in the command reply. This use of this form is intended for
     * interfacing with legacy code that adds additional data to a failed command reply and
     * its use is discouraged in new code.
     */
    ReplyBuilderInterface& setCommandReply(Status nonOKStatus, BSONObj extraErrorInfo);

    /**
     * Add a range of output documents to the reply. This method can be called multiple times
     * before calling done().
     */
    virtual ReplyBuilderInterface& addOutputDocs(DocumentRange outputDocs) = 0;

    /**
     * Add a single output document to the reply. This method can be called multiple times
     * before calling done().
     */
    virtual ReplyBuilderInterface& addOutputDoc(BSONObj outputDoc) = 0;

    /**
     * Gets the state of the builder. As the builder will simply crash the process if it is ever
     * put in an invalid state, it isn't neccessary to call this method for correctness. Rather
     * it may be helpful to explicitly assert that the builder is in a certain state to make
     * code that manipulates the builder more readable.
     */
    virtual State getState() const = 0;

    /**
     * Gets the protocol used to serialize this reply. This should be used for validity checks
     * only - runtime behavior changes should be implemented with polymorphism.
     */
    virtual Protocol getProtocol() const = 0;

    /**
     * Resets the state of the builder to kMetadata and clears any data that was previously
     * written.
     */
    virtual void reset() = 0;

    /**
     * Returns available space in bytes, should be used to verify that the message have enough
     * space for ouput documents.
     */
    virtual std::size_t availableSpaceForOutputDocs() const = 0;

    /**
     * Writes data then transfers ownership of the message to the caller. The behavior of
     * calling any methods on the builder is subsequently undefined.
     */
    virtual std::unique_ptr<Message> done() = 0;

protected:
    ReplyBuilderInterface() = default;
};

}  // namespace rpc
}  // namespace mongo