/**
 *    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 <iosfwd>

#include "mongo/logger/encoder.h"
#include "mongo/logger/message_event.h"
#include "mongo/util/time_support.h"

namespace mongo {
namespace logger {

typedef void (*DateFormatter)(std::ostream&, Date_t);

/**
 * This is the logging context for the MessageEventDetailsEncoder below.  It actively controls how
 * the output is encoded. As of now, there can be only one.
 */
struct LogContext {
    static constexpr int kDefaultMaxLogSizeKB = 10;

    LogContext();

    DateFormatter _dateFormatter;
    const AtomicWord<int>* _maxLogSizeSource;
};

/**
 * Encoder that writes log messages of the style that MongoDB writes to console and files.
 */
class MessageEventDetailsEncoder : public Encoder<MessageEventEphemeral> {
public:
    /**
     * Sets the date formatter function for all instances of MessageEventDetailsEncoder.
     *
     * Only and always safe to call during single-threaded execution, as in during start-up
     * intiailization.
     */
    static void setDateFormatter(DateFormatter dateFormatter);

    /**
     * Gets the date formatter function in use by instances of MessageEventDetailsEncoder.
     *
     * Always safe to call.
     */
    static DateFormatter getDateFormatter();

    /**
     * Sets a static wrapper to track an atomic variable reference
     *
     * Only safe to call once during single-threaded execution, as in during start-up
     * initialization.
     */
    static void setMaxLogSizeKBSource(const AtomicWord<int>& source);

    /**
     * Loads a max log size from the reference set above. If no reference has been set, it returns
     * the default. Note that this has to be an atomic operation, cache values when possible.
     *
     * Always safe to call.
     */
    static int getMaxLogSizeKB();

    virtual ~MessageEventDetailsEncoder();
    virtual std::ostream& encode(const MessageEventEphemeral& event, std::ostream& os);

private:
    /**
     * Grab the singleton LogContext
     */
    static LogContext& getGlobalLogContext();
};

/**
 * Encoder that generates log messages suitable for syslog.
 */
class MessageEventWithContextEncoder : public Encoder<MessageEventEphemeral> {
public:
    virtual ~MessageEventWithContextEncoder();
    virtual std::ostream& encode(const MessageEventEphemeral& event, std::ostream& os);
};


/**
 * Encoder that generates log messages containing only the raw text of the message.
 */
class MessageEventUnadornedEncoder : public Encoder<MessageEventEphemeral> {
public:
    virtual ~MessageEventUnadornedEncoder();
    virtual std::ostream& encode(const MessageEventEphemeral& event, std::ostream& os);
};

}  // namespace logger
}  // namespace mongo