paced_sender.h

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// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (c) 2026-present FERS Contributors (see AUTHORS.md).
//
// See the GNU GPLv2 LICENSE file in the FERS project root for more information.
 
#pragma once
 
#include <chrono>
#include <condition_variable>
#include <list>
#include <memory>
#include <mutex>
#include <optional>
#include <thread>
#include <unordered_map>
#include <vector>
 
#include "serial/vita49/udp_sender.h"
#include "serial/vita49/vita49_types.h"
 
namespace serial::vita49
{
    struct DroppedDatagram
    {
        std::uint32_t stream_id = 0;
        std::uint64_t sample_count = 0;
        bool data_packet = false;
        bool context_packet = false;
    };
 
    struct EnqueueResult
    {
        bool enqueued = false;
        std::optional<DroppedDatagram> dropped;
    };
 
    class PacedSender
    {
    public:
        PacedSender(std::unique_ptr<DatagramSender> sender, std::size_t queue_depth);
        ~PacedSender();
 
        PacedSender(const PacedSender&) = delete;
        PacedSender& operator=(const PacedSender&) = delete;
 
        void open(const std::string& host, std::uint16_t port);
        void start(RealType simulation_epoch_time = 0.0);
        [[nodiscard]] EnqueueResult enqueue(SerializedPacket packet);
        void flush();
        void stop();
 
        [[nodiscard]] std::uint64_t latePacketCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::uint64_t sentPacketCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::uint64_t sendFailureCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::uint64_t droppedDataPacketCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::uint64_t droppedContextPacketCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::uint64_t droppedSampleCount(std::uint32_t stream_id) const;
        [[nodiscard]] std::vector<DroppedDatagram> consumeDroppedDatagrams();
 
    private:
        void run();
        void waitUntilDue(std::unique_lock<std::mutex>& lock, std::chrono::steady_clock::time_point due);
        void sendOneUnlocked(SerializedPacket packet, std::chrono::steady_clock::time_point now);
        void recordDroppedUnlocked(const SerializedPacket& packet);
        [[nodiscard]] DroppedDatagram makeDroppedDatagram(const SerializedPacket& packet) const noexcept;
        [[nodiscard]] std::chrono::steady_clock::time_point dueTime(const SerializedPacket& packet) const;
        [[nodiscard]] std::size_t queuedOrSendingCount() const noexcept;
 
        std::unique_ptr<DatagramSender> _sender;
        std::size_t _queue_depth = 0;
        mutable std::mutex _mutex;
        std::condition_variable _cv;
        std::list<SerializedPacket> _queue;
        std::unordered_map<std::uint32_t, std::uint64_t> _late_packets;
        std::unordered_map<std::uint32_t, std::uint64_t> _sent_packets;
        std::unordered_map<std::uint32_t, std::uint64_t> _send_failures;
        std::unordered_map<std::uint32_t, std::uint64_t> _dropped_data_packets;
        std::unordered_map<std::uint32_t, std::uint64_t> _dropped_context_packets;
        std::unordered_map<std::uint32_t, std::uint64_t> _dropped_samples;
        std::vector<DroppedDatagram> _pending_dropped_datagrams;
        std::chrono::steady_clock::time_point _steady_epoch = std::chrono::steady_clock::now();
        RealType _simulation_epoch_time = 0.0;
        bool _started = false;
        bool _stopping = false;
        bool _send_in_progress = false;
        std::thread _thread;
    };
}