// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <algorithm>
#include <atomic>
#include <chrono>
#include <climits>
#include <condition_variable>
#include <memory>
#include <mutex>
#include <thread>
#include <vector>
#ifdef _WIN32
#include <share.h> // For _SH_DENYWR
#else
#define _SH_DENYWR 0
#endif
#include "common/assert.h"
#include "common/logging/backend.h"
#include "common/logging/log.h"
#include "common/logging/text_formatter.h"
#include "common/string_util.h"
#include "common/threadsafe_queue.h"

namespace Log {

/**
 * Static state as a singleton.
 */
class Impl {
public:
    static Impl& Instance() {
        static Impl backend;
        return backend;
    }

    Impl(Impl const&) = delete;
    const Impl& operator=(Impl const&) = delete;

    void PushEntry(Entry e) {
        std::lock_guard<std::mutex> lock(message_mutex);
        message_queue.Push(std::move(e));
        message_cv.notify_one();
    }

    void AddBackend(std::unique_ptr<Backend> backend) {
        std::lock_guard<std::mutex> lock(writing_mutex);
        backends.push_back(std::move(backend));
    }

    void RemoveBackend(std::string_view backend_name) {
        std::lock_guard<std::mutex> lock(writing_mutex);
        const auto it =
            std::remove_if(backends.begin(), backends.end(),
                           [&backend_name](const auto& i) { return backend_name == i->GetName(); });
        backends.erase(it, backends.end());
    }

    const Filter& GetGlobalFilter() const {
        return filter;
    }

    void SetGlobalFilter(const Filter& f) {
        filter = f;
    }

    Backend* GetBackend(std::string_view backend_name) {
        const auto it =
            std::find_if(backends.begin(), backends.end(),
                         [&backend_name](const auto& i) { return backend_name == i->GetName(); });
        if (it == backends.end())
            return nullptr;
        return it->get();
    }

private:
    Impl() {
        backend_thread = std::thread([&] {
            Entry entry;
            auto write_logs = [&](Entry& e) {
                std::lock_guard<std::mutex> lock(writing_mutex);
                for (const auto& backend : backends) {
                    backend->Write(e);
                }
            };
            while (true) {
                {
                    std::unique_lock<std::mutex> lock(message_mutex);
                    message_cv.wait(lock, [&] { return !running || message_queue.Pop(entry); });
                }
                if (!running) {
                    break;
                }
                write_logs(entry);
            }
            // Drain the logging queue. Only writes out up to MAX_LOGS_TO_WRITE to prevent a case
            // where a system is repeatedly spamming logs even on close.
            const int MAX_LOGS_TO_WRITE = filter.IsDebug() ? INT_MAX : 100;
            int logs_written = 0;
            while (logs_written++ < MAX_LOGS_TO_WRITE && message_queue.Pop(entry)) {
                write_logs(entry);
            }
        });
    }

    ~Impl() {
        running = false;
        message_cv.notify_one();
        backend_thread.join();
    }

    std::atomic_bool running{true};
    std::mutex message_mutex, writing_mutex;
    std::condition_variable message_cv;
    std::thread backend_thread;
    std::vector<std::unique_ptr<Backend>> backends;
    Common::MPSCQueue<Log::Entry> message_queue;
    Filter filter;
};

void ConsoleBackend::Write(const Entry& entry) {
    PrintMessage(entry);
}

void ColorConsoleBackend::Write(const Entry& entry) {
    PrintColoredMessage(entry);
}

// _SH_DENYWR allows read only access to the file for other programs.
// It is #defined to 0 on other platforms
FileBackend::FileBackend(const std::string& filename)
    : file(filename, "w", _SH_DENYWR), bytes_written(0) {}

void FileBackend::Write(const Entry& entry) {
    // prevent logs from going over the maximum size (in case its spamming and the user doesn't
    // know)
    constexpr size_t MAX_BYTES_WRITTEN = 50 * 1024L * 1024L;
    if (!file.IsOpen() || bytes_written > MAX_BYTES_WRITTEN) {
        return;
    }
    bytes_written += file.WriteString(FormatLogMessage(entry) + '\n');
    if (entry.log_level >= Level::Error) {
        file.Flush();
    }
}

/// Macro listing all log classes. Code should define CLS and SUB as desired before invoking this.
#define ALL_LOG_CLASSES()                                                                          \
    CLS(Log)                                                                                       \
    CLS(Common)                                                                                    \
    SUB(Common, Filesystem)                                                                        \
    SUB(Common, Memory)                                                                            \
    CLS(Core)                                                                                      \
    SUB(Core, ARM)                                                                                 \
    SUB(Core, Timing)                                                                              \
    CLS(Config)                                                                                    \
    CLS(Debug)                                                                                     \
    SUB(Debug, Emulated)                                                                           \
    SUB(Debug, GPU)                                                                                \
    SUB(Debug, Breakpoint)                                                                         \
    SUB(Debug, GDBStub)                                                                            \
    CLS(Kernel)                                                                                    \
    SUB(Kernel, SVC)                                                                               \
    CLS(Service)                                                                                   \
    SUB(Service, ACC)                                                                              \
    SUB(Service, Audio)                                                                            \
    SUB(Service, AM)                                                                               \
    SUB(Service, AOC)                                                                              \
    SUB(Service, APM)                                                                              \
    SUB(Service, BCAT)                                                                             \
    SUB(Service, Fatal)                                                                            \
    SUB(Service, Friend)                                                                           \
    SUB(Service, FS)                                                                               \
    SUB(Service, HID)                                                                              \
    SUB(Service, LBL)                                                                              \
    SUB(Service, LDN)                                                                              \
    SUB(Service, LM)                                                                               \
    SUB(Service, MM)                                                                               \
    SUB(Service, NCM)                                                                              \
    SUB(Service, NFC)                                                                              \
    SUB(Service, NFP)                                                                              \
    SUB(Service, NIFM)                                                                             \
    SUB(Service, NS)                                                                               \
    SUB(Service, NVDRV)                                                                            \
    SUB(Service, PCTL)                                                                             \
    SUB(Service, PREPO)                                                                            \
    SUB(Service, SET)                                                                              \
    SUB(Service, SM)                                                                               \
    SUB(Service, SPL)                                                                              \
    SUB(Service, SSL)                                                                              \
    SUB(Service, Time)                                                                             \
    SUB(Service, VI)                                                                               \
    CLS(HW)                                                                                        \
    SUB(HW, Memory)                                                                                \
    SUB(HW, LCD)                                                                                   \
    SUB(HW, GPU)                                                                                   \
    SUB(HW, AES)                                                                                   \
    CLS(IPC)                                                                                       \
    CLS(Frontend)                                                                                  \
    CLS(Render)                                                                                    \
    SUB(Render, Software)                                                                          \
    SUB(Render, OpenGL)                                                                            \
    CLS(Audio)                                                                                     \
    SUB(Audio, DSP)                                                                                \
    SUB(Audio, Sink)                                                                               \
    CLS(Input)                                                                                     \
    CLS(Network)                                                                                   \
    CLS(Loader)                                                                                    \
    CLS(WebService)

// GetClassName is a macro defined by Windows.h, grrr...
const char* GetLogClassName(Class log_class) {
    switch (log_class) {
#define CLS(x)                                                                                     \
    case Class::x:                                                                                 \
        return #x;
#define SUB(x, y)                                                                                  \
    case Class::x##_##y:                                                                           \
        return #x "." #y;
        ALL_LOG_CLASSES()
#undef CLS
#undef SUB
    case Class::Count:
        UNREACHABLE();
    }
}

const char* GetLevelName(Level log_level) {
#define LVL(x)                                                                                     \
    case Level::x:                                                                                 \
        return #x
    switch (log_level) {
        LVL(Trace);
        LVL(Debug);
        LVL(Info);
        LVL(Warning);
        LVL(Error);
        LVL(Critical);
    case Level::Count:
        UNREACHABLE();
    }
#undef LVL
}

Entry CreateEntry(Class log_class, Level log_level, const char* filename, unsigned int line_nr,
                  const char* function, std::string message) {
    using std::chrono::duration_cast;
    using std::chrono::steady_clock;

    static steady_clock::time_point time_origin = steady_clock::now();

    Entry entry;
    entry.timestamp = duration_cast<std::chrono::microseconds>(steady_clock::now() - time_origin);
    entry.log_class = log_class;
    entry.log_level = log_level;
    entry.filename = Common::TrimSourcePath(filename);
    entry.line_num = line_nr;
    entry.function = function;
    entry.message = std::move(message);

    return entry;
}

void SetGlobalFilter(const Filter& filter) {
    Impl::Instance().SetGlobalFilter(filter);
}

void AddBackend(std::unique_ptr<Backend> backend) {
    Impl::Instance().AddBackend(std::move(backend));
}

void RemoveBackend(std::string_view backend_name) {
    Impl::Instance().RemoveBackend(backend_name);
}

Backend* GetBackend(std::string_view backend_name) {
    return Impl::Instance().GetBackend(backend_name);
}

void FmtLogMessageImpl(Class log_class, Level log_level, const char* filename,
                       unsigned int line_num, const char* function, const char* format,
                       const fmt::format_args& args) {
    auto filter = Impl::Instance().GetGlobalFilter();
    if (!filter.CheckMessage(log_class, log_level))
        return;

    Entry entry =
        CreateEntry(log_class, log_level, filename, line_num, function, fmt::vformat(format, args));

    Impl::Instance().PushEntry(std::move(entry));
}
} // namespace Log