#include "filesystem_log_watcher.hpp"

#include "event_service_manager.hpp"
#include "logging.hpp"

#include <sys/inotify.h>

#include <boost/asio/buffer.hpp>
#include <boost/asio/error.hpp>
#include <boost/asio/io_context.hpp>
#include <boost/asio/posix/stream_descriptor.hpp>

#include <array>
#include <cstddef>
#include <cstring>
#include <optional>
#include <string>

namespace redfish
{

// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
static std::optional<boost::asio::posix::stream_descriptor> inotifyConn;
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
static int inotifyFd = -1;
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
static int dirWatchDesc = -1;
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
static int fileWatchDesc = -1;
// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
static std::array<char, 1024> readBuffer{};

static constexpr const char* redfishEventLogDir = "/var/log";
static constexpr const size_t iEventSize = sizeof(inotify_event);

static void watchRedfishEventLogFile()
{
    if (!inotifyConn)
    {
        BMCWEB_LOG_ERROR("inotify Connection is not present");
        return;
    }

    inotifyConn->async_read_some(
        boost::asio::buffer(readBuffer),
        [&](const boost::system::error_code& ec,
            const std::size_t& bytesTransferred) {
            if (ec == boost::asio::error::operation_aborted)
            {
                BMCWEB_LOG_DEBUG("Inotify was canceled (shutdown?)");
                return;
            }
            if (ec)
            {
                BMCWEB_LOG_ERROR("Callback Error: {}", ec.message());
                return;
            }

            BMCWEB_LOG_DEBUG("reading {} via inotify", bytesTransferred);

            std::size_t index = 0;
            while ((index + iEventSize) <= bytesTransferred)
            {
                struct inotify_event event
                {};
                std::memcpy(&event, &readBuffer[index], iEventSize);
                if (event.wd == dirWatchDesc)
                {
                    if ((event.len == 0) ||
                        (index + iEventSize + event.len > bytesTransferred))
                    {
                        index += (iEventSize + event.len);
                        continue;
                    }

                    std::string fileName(&readBuffer[index + iEventSize]);
                    if (fileName != "redfish")
                    {
                        index += (iEventSize + event.len);
                        continue;
                    }

                    BMCWEB_LOG_DEBUG(
                        "Redfish log file created/deleted. event.name: {}",
                        fileName);
                    if (event.mask == IN_CREATE)
                    {
                        if (fileWatchDesc != -1)
                        {
                            BMCWEB_LOG_DEBUG(
                                "Remove and Add inotify watcher on "
                                "redfish event log file");
                            // Remove existing inotify watcher and add
                            // with new redfish event log file.
                            inotify_rm_watch(inotifyFd, fileWatchDesc);
                            fileWatchDesc = -1;
                        }

                        fileWatchDesc = inotify_add_watch(
                            inotifyFd, redfishEventLogFile, IN_MODIFY);
                        if (fileWatchDesc == -1)
                        {
                            BMCWEB_LOG_ERROR("inotify_add_watch failed for "
                                             "redfish log file.");
                            return;
                        }

                        EventServiceManager::getInstance()
                            .resetRedfishFilePosition();
                        EventServiceManager::getInstance()
                            .readEventLogsFromFile();
                    }
                    else if ((event.mask == IN_DELETE) ||
                             (event.mask == IN_MOVED_TO))
                    {
                        if (fileWatchDesc != -1)
                        {
                            inotify_rm_watch(inotifyFd, fileWatchDesc);
                            fileWatchDesc = -1;
                        }
                    }
                }
                else if (event.wd == fileWatchDesc)
                {
                    if (event.mask == IN_MODIFY)
                    {
                        EventServiceManager::getInstance()
                            .readEventLogsFromFile();
                    }
                }
                index += (iEventSize + event.len);
            }

            watchRedfishEventLogFile();
        });
}

int startEventLogMonitor(boost::asio::io_context& ioc)
{
    BMCWEB_LOG_DEBUG("starting Event Log Monitor");

    inotifyConn.emplace(ioc);
    inotifyFd = inotify_init1(IN_NONBLOCK);
    if (inotifyFd == -1)
    {
        BMCWEB_LOG_ERROR("inotify_init1 failed.");
        return -1;
    }

    // Add watch on directory to handle redfish event log file
    // create/delete.
    dirWatchDesc = inotify_add_watch(inotifyFd, redfishEventLogDir,
                                     IN_CREATE | IN_MOVED_TO | IN_DELETE);
    if (dirWatchDesc == -1)
    {
        BMCWEB_LOG_ERROR("inotify_add_watch failed for event log directory.");
        return -1;
    }

    // Watch redfish event log file for modifications.
    fileWatchDesc =
        inotify_add_watch(inotifyFd, redfishEventLogFile, IN_MODIFY);
    if (fileWatchDesc == -1)
    {
        BMCWEB_LOG_ERROR("inotify_add_watch failed for redfish log file.");
        // Don't return error if file not exist.
        // Watch on directory will handle create/delete of file.
    }

    // monitor redfish event log file
    inotifyConn->assign(inotifyFd);
    watchRedfishEventLogFile();

    return 0;
}

void stopEventLogMonitor()
{
    inotifyConn.reset();
}
} // namespace redfish