#include <boost/log/sources/record_ostream.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/utility/setup/console.hpp>
#include <iomanip>

namespace logging = boost::log;
namespace keywords = boost::log::keywords;
namespace expr = boost::log::expressions;

namespace my {
	enum severity { trace, info, warning, error };
}


// Unclear as to this line's intended benefit, but it makes code shorter too.
BOOST_LOG_ATTRIBUTE_KEYWORD(severity, "Severity", my::severity);


template <typename Stream>
void output_severity_to (Stream& output, const my::severity& level)
{
    switch (level) {
        case my::severity::error:   output << "ERROR";   break;
        case my::severity::warning: output << "WARNING"; break;
        case my::severity::info:    output << "INFO";    break;
        case my::severity::trace:   output << "TRACE";   break;
        default:                    output << "???";     break;
    }
}


// Handle regular stream output.
std::ostream& operator<< (std::ostream& output, const my::severity& level)
{
	output_severity_to(output, level);
    return output;
}


// Special output handling for log
logging::formatting_ostream& operator<< (logging::formatting_ostream& output, const logging::to_log_manip<my::severity, tag::severity>& level)
{
    output_severity_to(output, level.get());
    return output;
}


int main ()
{
	logging::register_simple_formatter_factory<my::severity, char>("Severity");
	logging::add_console_log
    (
    	std::cout,
        keywords::format = expr::stream << severity << ": " << expr::smessage
    );

    logging::sources::severity_logger_mt<my::severity> logger;
    BOOST_LOG_SEV(logger, my::info) << "Booo!";
    return -1;
}