#include "watch.hpp"

#include <sys/inotify.h>
#include <unistd.h>

#include <cstddef>
#include <cstring>
#include <filesystem>
#include <stdexcept>
#include <string>

namespace pldm
{

namespace fw_update
{

using namespace std::string_literals;
namespace fs = std::filesystem;

Watch::Watch(sd_event* loop,
             std::function<int(const std::string&)> imageCallback) :
    imageCallback(imageCallback)
{
    // Check if IMAGE DIR exists.
    fs::path imgDirPath("/tmp/images");
    if (!fs::is_directory(imgDirPath))
    {
        fs::create_directories(imgDirPath);
    }

    fd = inotify_init1(IN_NONBLOCK);
    if (-1 == fd)
    {
        // Store a copy of errno, because the string creation below will
        // invalidate errno due to one more system calls.
        auto error = errno;
        throw std::runtime_error(
            "inotify_init1 failed, errno="s + std::strerror(error));
    }

    wd = inotify_add_watch(fd, "/tmp/images", IN_CLOSE_WRITE);
    if (-1 == wd)
    {
        auto error = errno;
        close(fd);
        throw std::runtime_error(
            "inotify_add_watch failed, errno="s + std::strerror(error));
    }

    auto rc = sd_event_add_io(loop, nullptr, fd, EPOLLIN, callback, this);
    if (0 > rc)
    {
        inotify_rm_watch(fd, wd);
        close(fd);
        throw std::runtime_error(
            "failed to add to event loop, rc="s + std::strerror(-rc));
    }
}

Watch::~Watch()
{
    if (-1 != fd)
    {
        if (-1 != wd)
        {
            inotify_rm_watch(fd, wd);
        }
        close(fd);
    }
}

int Watch::callback(sd_event_source* /* s */, int fd, uint32_t revents,
                    void* userdata)
{
    if (!(revents & EPOLLIN))
    {
        return 0;
    }

    constexpr auto maxBytes = 1024;
    uint8_t buffer[maxBytes];
    auto bytes = read(fd, buffer, maxBytes);
    if (0 > bytes)
    {
        auto error = errno;
        throw std::runtime_error(
            "failed to read inotify event, errno="s + std::strerror(error));
    }

    auto offset = 0;
    while (offset < bytes)
    {
        auto event = reinterpret_cast<inotify_event*>(&buffer[offset]);
        if ((event->mask & IN_CLOSE_WRITE) && !(event->mask & IN_ISDIR))
        {
            auto tarballPath = std::string{"/tmp/images"} + '/' + event->name;
            static_cast<Watch*>(userdata)->imageCallback(tarballPath);
        }

        offset += offsetof(inotify_event, name) + event->len;
    }

    return 0;
}

} // namespace fw_update
} // namespace pldm