#pragma once

#include <chrono>
#include <functional>
#include <memory>
#include <systemd/sd-event.h>

#include "sdevent/source.hpp"
#include "sdevent/event.hpp"

// TODO: openbmc/openbmc#1720 - add error handling for sd_event API failures

namespace sdevent
{
namespace event
{
namespace timer
{

/** @class Timer
 *  @brief Provides C++ bindings to the sd_event_source* timer functions.
 */
class Timer
{
  public:
    /* Define all of the basic class operations:
     *     Not allowed:
     *         - Default constructor to avoid nullptrs.
     *         - Copy operations due to internal unique_ptr.
     *     Allowed:
     *         - Move operations.
     *         - Destructor.
     */
    Timer() = delete;
    Timer(const Timer&) = delete;
    Timer& operator=(const Timer&) = delete;
    Timer(Timer&&) = default;
    Timer& operator=(Timer&&) = default;
    ~Timer() = default;

    using Callback = std::function<void(source::Source&)>;

    /** @brief Register a timer callback.
     *
     *  @param[in] event - The event to register on.
     *  @param[in] expires - The initial timer expiration time.
     *  @param[in] callback - The callback method.
     */
    Timer(sdevent::event::Event& event,
          const std::chrono::steady_clock::time_point& expires,
          Callback callback) :
        src(nullptr),
        cb(std::make_unique<Callback>(std::move(callback)))
    {
        using namespace std::chrono;
        auto epoch = expires.time_since_epoch();
        auto time = duration_cast<microseconds>(epoch);
        sd_event_source* source = nullptr;
        sd_event_add_time(event.get(), &source, CLOCK_MONOTONIC, time.count(),
                          0, callCallback, cb.get());
        // **INDENT-OFF**
        src = decltype(src){source, std::false_type()};
        // **INDENT-ON**
    }

    /** @brief Register a disabled timer callback.
     *
     *  @param[in] event - The event to register on.
     *  @param[in] callback - The callback method.
     */
    Timer(sdevent::event::Event& event, Callback callback) :
        src(nullptr), cb(std::make_unique<Callback>(std::move(callback)))
    {
        sd_event_source* source = nullptr;
        sd_event_add_time(event.get(), &source, CLOCK_MONOTONIC, ULLONG_MAX, 0,
                          callCallback, cb.get());
        // **INDENT-OFF**
        src = decltype(src){source, std::false_type()};
        // **INDENT-ON**
    }

    /** @brief Set the timer expiration time. */
    void setTime(const std::chrono::steady_clock::time_point& expires)
    {
        src.setTime(expires);
    }

    /** @brief Get the timer expiration time. */
    auto getTime()
    {
        return src.getTime();
    }

    /** @brief Set the timer source enable state. */
    void enable(int enable)
    {
        src.enable(enable);
    }

    /** @brief Query timer state. */
    auto enabled()
    {
        return src.enabled();
    }

  private:
    source::Source src;
    std::unique_ptr<Callback> cb = nullptr;

    static int callCallback(sd_event_source* s, uint64_t usec, void* context)
    {
        source::Source source(s);
        auto c = static_cast<Callback*>(context);
        (*c)(source);

        return 0;
    }
};
} // namespace timer
} // namespace event
} // namespace sdevent