#include "Logger.h"

#include <spdlog/sinks/stdout_color_sinks.h>

#include <array>
#include <atomic>
#include <chrono>
#include <mutex>

namespace simv::core {

namespace {

constexpr std::array<const char*, LogCategoryCount> kCategoryNames = {{
    "core", "vk", "mesh", "ui", "test",
}};
static_assert(kCategoryNames.size() == LogCategoryCount,
              "kCategoryNames must have one entry per LogCategory");

struct CategoryEntry {
    bool                              enabled    {true};
    LogLevel                          minLevel   {LogLevel::Info};
    double                            throttleSec{0.5};
    std::atomic<std::int64_t>         lastLogMs  {INT64_MIN};
};

struct LoggerImpl {
    std::array<CategoryEntry, LogCategoryCount> entries{};
    std::shared_ptr<spdlog::logger>             sink;
    std::chrono::steady_clock::time_point       epoch{std::chrono::steady_clock::now()};
    std::mutex                                  initMutex;
    bool                                        initialized{false};
};

LoggerImpl& Impl() {
    static LoggerImpl impl;
    return impl;
}

spdlog::level::level_enum ToSpd(LogLevel l) noexcept {
    switch (l) {
        case LogLevel::Trace:    return spdlog::level::trace;
        case LogLevel::Debug:    return spdlog::level::debug;
        case LogLevel::Info:     return spdlog::level::info;
        case LogLevel::Warn:     return spdlog::level::warn;
        case LogLevel::Error:    return spdlog::level::err;
        case LogLevel::Critical: return spdlog::level::critical;
        default:                 return spdlog::level::off;
    }
}

std::int64_t NowMs() noexcept {
    using namespace std::chrono;
    return duration_cast<milliseconds>(steady_clock::now() - Impl().epoch).count();
}

} // namespace

const char* CategoryName(LogCategory cat) noexcept {
    const auto idx = static_cast<std::size_t>(cat);
    return idx < LogCategoryCount ? kCategoryNames[idx] : "?";
}

Logger& Logger::Instance() noexcept {
    static Logger inst;
    return inst;
}

void Logger::Init() {
    auto& impl = Impl();
    std::lock_guard<std::mutex> lk(impl.initMutex);
    if (impl.initialized) return;

    impl.sink = spdlog::stdout_color_mt("simv");
    impl.sink->set_pattern("[%H:%M:%S.%e] [%^%l%$] %v");
    impl.sink->set_level(spdlog::level::trace);

    impl.initialized = true;
}

void Logger::Shutdown() {
    auto& impl = Impl();
    std::lock_guard<std::mutex> lk(impl.initMutex);
    if (!impl.initialized) return;
    impl.sink.reset();
    spdlog::drop("simv");
    impl.initialized = false;
}

void Logger::SetMinLevel(LogCategory cat, LogLevel lvl) noexcept {
    const auto idx = static_cast<std::size_t>(cat);
    if (idx < LogCategoryCount) Impl().entries[idx].minLevel = lvl;
}

void Logger::SetThrottle(LogCategory cat, double seconds) noexcept {
    const auto idx = static_cast<std::size_t>(cat);
    if (idx < LogCategoryCount) Impl().entries[idx].throttleSec = seconds;
}

void Logger::SetEnabled(LogCategory cat, bool enabled) noexcept {
    const auto idx = static_cast<std::size_t>(cat);
    if (idx < LogCategoryCount) Impl().entries[idx].enabled = enabled;
}

void Logger::LogRaw(LogCategory cat, LogLevel lvl, std::string_view msg) noexcept {
    auto& impl = Impl();
    if (!impl.initialized) Init();

    const auto idx = static_cast<std::size_t>(cat);
    if (idx >= LogCategoryCount) return;
    auto& e = impl.entries[idx];
    if (!e.enabled) return;
    if (static_cast<std::uint8_t>(lvl) < static_cast<std::uint8_t>(e.minLevel)) return;

    // Warnings/errors bypass throttling.
    const bool important = (lvl == LogLevel::Warn) || (lvl == LogLevel::Error)
                        || (lvl == LogLevel::Critical);
    if (!important && e.throttleSec > 0.0) {
        const std::int64_t nowMs    = NowMs();
        const std::int64_t throttle = static_cast<std::int64_t>(e.throttleSec * 1000.0);
        std::int64_t lastMs         = e.lastLogMs.load(std::memory_order_relaxed);
        if (lastMs != INT64_MIN && (nowMs - lastMs) < throttle) return;
        e.lastLogMs.store(nowMs, std::memory_order_relaxed);
    }

    impl.sink->log(ToSpd(lvl), "[{}] {}", CategoryName(cat), msg);
}

} // namespace simv::core