/// @file dpf/experiment_note.hpp
/// @brief Lightweight seed registry hook (no Asio / PRG includes).
#ifndef LIBDPF_INCLUDE_DPF_EXPERIMENT_NOTE_HPP__
#define LIBDPF_INCLUDE_DPF_EXPERIMENT_NOTE_HPP__

#include <cstddef>
#include <cstdint>
#include <type_traits>

#include "hedley/hedley.h"

namespace dpf
{
namespace detail
{

/// @brief Optional sink installed by `experiment` (TLS).
struct experiment_seed_sink
{
    virtual ~experiment_seed_sink() = default;
    virtual void note(const char * name, const std::uint8_t * bytes,
        std::size_t n) = 0;
};

inline thread_local experiment_seed_sink * experiment_seed_sink_tls = nullptr;

}  // namespace detail

/// @brief Record a named seed when an `experiment` is installed on this thread.
HEDLEY_ALWAYS_INLINE
void note_experiment_seed(const char * name, const void * bytes,
    std::size_t n) noexcept
{
    if (detail::experiment_seed_sink_tls == nullptr || bytes == nullptr
        || n == 0 || name == nullptr)
        return;
    detail::experiment_seed_sink_tls->note(name,
        static_cast<const std::uint8_t *>(bytes), n);
}

template <typename T>
HEDLEY_ALWAYS_INLINE
void note_experiment_seed(const char * name, const T & seed) noexcept
{
    static_assert(std::is_trivially_copyable_v<T>,
        "note_experiment_seed requires a trivially copyable seed");
    note_experiment_seed(name, &seed, sizeof(seed));
}

}  // namespace dpf

#endif  // LIBDPF_INCLUDE_DPF_EXPERIMENT_NOTE_HPP__