snapcast/client/metadata.hpp

/***
    This file is part of snapcast
    Copyright (C) 2014-2020  Johannes Pohl

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
***/

#ifndef METADATA_H
#define METADATA_H

#include "common/json.hpp"

// Prefix used in output
#define METADATA std::string("metadata")

/*
 * Implement a generic metadata output handler
 */
using json = nlohmann::json;

/*
 * Base class, prints to stdout
 */
class MetadataAdapter
{
public:
    MetadataAdapter()
    {
        reset();
    }

    virtual ~MetadataAdapter() = default;

    void reset()
    {
        msg_ = json{};
    }

    std::string serialize()
    {
        return METADATA + ":" + msg_.dump();
    }

    void tag(const std::string& name, const std::string& value)
    {
        msg_[name] = value;
    }

    std::string operator[](const std::string& key)
    {
        try
        {
            return msg_[key];
        }
        catch (std::domain_error&)
        {
            return std::string();
        }
    }

    virtual int push()
    {
        std::cout << serialize() << "\n";
        return 0;
    }

    int push(const json& jtag)
    {
        msg_ = jtag;
        return push();
    }

protected:
    json msg_;
};

/*
 * Send metadata to stderr as json
 */
class MetaStderrAdapter : public MetadataAdapter
{
public:
    using MetadataAdapter::push;

    int push() override
    {
        std::cerr << serialize() << "\n";
        return 0;
    }
};

#endif