/* -*- MODE: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 *     Copyright 2018-Present Couchbase, Inc.
 *
 *   Use of this software is governed by the Business Source License included
 *   in the file licenses/BSL-Couchbase.txt.  As of the Change Date specified
 *   in that file, in accordance with the Business Source License, use of this
 *   software will be governed by the Apache License, Version 2.0, included in
 *   the file licenses/APL2.txt.
 */

#include "logger.hxx"

#include "configuration.hxx"
#include "custom_rotating_file_sink.hxx"

#include <chrono>
#include <spdlog/async.h>
#include <spdlog/async_logger.h>
#include <spdlog/sinks/dist_sink.h>
#include <spdlog/sinks/null_sink.h>
#include <spdlog/sinks/stdout_color_sinks.h>
#include <spdlog/spdlog.h>

static const std::string logger_name{ "couchbase_cxx_client_file_logger" };

/**
 * Custom log pattern which the loggers will use.
 * This pattern is duplicated for some test cases. If you need to update it,
 * please also update in all relevant places.
 */
static const std::string log_pattern{ "[%Y-%m-%d %T.%e] [%P,%t] [%^%l%$] %oms, %v" };

/**
 * Instances of spdlog (async) file logger.
 * The files logger requires a rotating file sink which is manually configured
 * from the parsed settings.
 * The loggers act as a handle to the sinks. They do the processing of log
 * messages and send them to the sinks, which do the actual writing (to file,
 * to stream etc.) or further processing.
 */
static std::shared_ptr<spdlog::logger> file_logger;

namespace couchbase::core::logger
{
spdlog::level::level_enum
translate_level(level level)
{
    switch (level) {
        case level::trace:
            return spdlog::level::level_enum::trace;
        case level::debug:
            return spdlog::level::level_enum::debug;
        case level::info:
            return spdlog::level::level_enum::info;
        case level::warn:
            return spdlog::level::level_enum::warn;
        case level::err:
            return spdlog::level::level_enum::err;
        case level::critical:
            return spdlog::level::level_enum::critical;
        case level::off:
            return spdlog::level::level_enum::off;
    }
    return spdlog::level::level_enum::trace;
}

level
level_from_str(const std::string& str)
{
    switch (spdlog::level::from_str(str)) {
        case spdlog::level::level_enum::trace:
            return level::trace;
        case spdlog::level::level_enum::debug:
            return level::debug;
        case spdlog::level::level_enum::info:
            return level::info;
        case spdlog::level::level_enum::warn:
            return level::warn;
        case spdlog::level::level_enum::err:
            return level::err;
        case spdlog::level::level_enum::critical:
            return level::critical;
        case spdlog::level::level_enum::off:
            return level::off;
        default:
            break;
    }
    // return highest level if we don't understand
    return level::trace;
}

bool
should_log(level lvl)
{
    if (is_initialized()) {
        return file_logger->should_log(translate_level(lvl));
    }
    return false;
}

namespace detail
{
void
log(const char* file, int line, const char* function, level lvl, std::string_view msg)
{
    if (is_initialized()) {
        return file_logger->log(spdlog::source_loc{ file, line, function }, translate_level(lvl), msg);
    }
}
} // namespace detail

void
flush()
{
    if (is_initialized()) {
        file_logger->flush();
    }
}

void
shutdown()
{
    // Force a flush (posts a message to the async logger if we are not in unit
    // test mode)
    flush();

    /**
     * This will drop all spdlog instances from the registry, and destruct the
     * thread pool which will post terminate message(s) (one per thread) to the
     * thread pool message queue. The calling thread will then block until all
     * thread pool workers have joined. This ensures that any messages queued
     * before shutdown is called will be flushed to disk. Any messages that are
     * queued after the final terminate message will not be logged.
     *
     * If the logger is running in unit test mode (synchronous) then this is a
     * no-op.
     */
    file_logger.reset();
    spdlog::details::registry::instance().shutdown();
}

bool
is_initialized()
{
    return file_logger != nullptr;
}

/**
 * Initialises the loggers. Called if the logger configuration is
 * specified in a separate settings object.
 */
std::optional<std::string>
create_file_logger(const configuration& logger_settings)
{
    auto fname = logger_settings.filename;
    auto buffersz = logger_settings.buffer_size;
    auto cyclesz = logger_settings.cycle_size;

    if (!spdlog::details::os::getenv("COUCHBASE_CXX_CLIENT_MAXIMIZE_LOGGER_CYCLE_SIZE").empty()) {
        cyclesz = 1024LLU * 1024 * 1024; // use up to 1 GB log file size
    }

    try {
        // Initialise the loggers.
        //
        // The structure is as follows:
        //
        // file_logger = sends log messages to sink
        //   |__dist_sink_mt = Distribute log messages to multiple sinks
        //       |     |__custom_rotating_file_sink_mt = adds opening & closing
        //       |                                       hooks to the file
        //       |__ (color)__stderr_sink_mt = Send log messages to console
        //
        // When a new log message is being submitted to the file_logger it
        // is subject to the log level specified on the file_logger. If it
        // is to be included it is passed down to the dist_sink which will
        // evaluate if the message should be passed on based on its log level.
        // It'll then try to pass the message to the file sink and the
        // console sink and they will evaluate if the message should be
        // logged or not. This means that we should set the file sink
        // loglevel to TRACE so that all messages which goes all the way
        // will end up in the file. Due to the fact that ns_server can't
        // keep up with the rate we might produce log we want the console
        // sink to drop everything below WARNING (unless we're running
        // unit tests (through testapp).
        //
        // When the user change the verbosity level we'll modify the
        // level for the file_logger object causing it to allow more
        // messages to go down to the various sinks.

        auto sink = std::make_shared<spdlog::sinks::dist_sink_mt>();
        sink->set_level(spdlog::level::trace);

        if (!fname.empty()) {
            auto fsink = std::make_shared<custom_rotating_file_sink_mt>(fname, cyclesz, log_pattern);
            fsink->set_level(spdlog::level::trace);
            sink->add_sink(fsink);
        }

        if (logger_settings.console) {
            auto stderrsink = std::make_shared<spdlog::sinks::stderr_color_sink_mt>();

            // Set the formatting pattern of this sink
            stderrsink->set_pattern(log_pattern);
            if (logger_settings.unit_test) {
                stderrsink->set_level(spdlog::level::trace);
            } else {
                stderrsink->set_level(spdlog::level::err);
            }
            sink->add_sink(stderrsink);
        }
        if (nullptr != logger_settings.sink) {
            logger_settings.sink->set_pattern(log_pattern);
            sink->add_sink(logger_settings.sink);
        }

        spdlog::drop(logger_name);

        if (logger_settings.unit_test) {
            file_logger = std::make_shared<spdlog::logger>(logger_name, sink);
        } else {
            // Create the default thread pool for async logging
            spdlog::init_thread_pool(buffersz, 1);

            // Get the thread pool so that we can actually construct the
            // object with already created sinks...
            auto tp = spdlog::thread_pool();
            file_logger = std::make_shared<spdlog::async_logger>(logger_name, sink, tp, spdlog::async_overflow_policy::block);
        }

        file_logger->set_pattern(log_pattern);
        file_logger->set_level(translate_level(logger_settings.log_level));

        // Set the flushing interval policy
        spdlog::flush_every(std::chrono::seconds(1));

        spdlog::register_logger(file_logger);
    } catch (const spdlog::spdlog_ex& ex) {
        std::string msg = std::string{ "Log initialization failed: " } + ex.what();
        return std::optional<std::string>{ msg };
    }
    return {};
}

spdlog::logger*
get()
{
    return file_logger.get();
}

void
reset()
{
    spdlog::drop(logger_name);
    file_logger.reset();
}

void
create_blackhole_logger()
{
    // delete if already exists
    spdlog::drop(logger_name);

    file_logger = std::make_shared<spdlog::logger>(logger_name, std::make_shared<spdlog::sinks::null_sink_mt>());

    file_logger->set_level(spdlog::level::off);
    file_logger->set_pattern(log_pattern);

    spdlog::register_logger(file_logger);
}

void
create_console_logger()
{
    // delete if already exists
    spdlog::drop(logger_name);

    auto stderrsink = std::make_shared<spdlog::sinks::stderr_color_sink_mt>();

    file_logger = std::make_shared<spdlog::logger>(logger_name, stderrsink);
    file_logger->set_level(spdlog::level::info);
    file_logger->set_pattern(log_pattern);

    spdlog::register_logger(file_logger);
}

void
register_spdlog_logger(std::shared_ptr<spdlog::logger> l)
{
    try {
        file_logger->debug("Registering logger {}", l->name());
        spdlog::register_logger(l);
    } catch (const spdlog::spdlog_ex& e) {
        file_logger->warn("Exception caught when attempting to register the logger {} in the spdlog registry. The verbosity of this logger "
                          "cannot be changed at runtime. e.what()={}",
                          l->name(),
                          e.what());
    }
}

void
unregister_spdlog_logger(const std::string& n)
{
    spdlog::drop(n);
}

bool
check_log_levels(level lvl)
{
    auto level = translate_level(lvl);
    bool correct = true;
    spdlog::apply_all([level, &correct](std::shared_ptr<spdlog::logger> l) {
        if (l->level() != level) {
            correct = false;
        }
    });
    return correct;
}

void
set_log_levels(level lvl)
{
    auto level = translate_level(lvl);
    // Apply the function to each registered spdlog::logger
    spdlog::apply_all([level](std::shared_ptr<spdlog::logger> l) {
        try {
            l->set_level(level);
        } catch (const spdlog::spdlog_ex& e) {
            l->warn("Exception caught when attempting to change the verbosity "
                    "of logger {} to spdlog level {}. e.what()={}",
                    l->name(),
                    to_short_c_str(level),
                    e.what());
        }
    });

    flush();
}
} // namespace couchbase::core::logger