KPN/include/kpn/python/object_variant_node.hpp

#pragma once
// ObjectVariantNodeWrapper — variant-node adapter for *stateful* functors.
//
// VariantNodeWrapper (variant_node.hpp) wraps Node<Func,...>, where Func is a
// default-constructible NTTP callable. That doesn't fit nodes whose functor must
// be constructed with runtime state (a Config, a loaded gallery, etc.) — those use
// ObjectNode<Obj>, which takes `Obj& obj` at construction.
//
// This wrapper owns an Obj instance and exposes the same IVariantNode surface so a
// stateful C++ node can live inside a PyNetwork. Build one via a factory that
// constructs the functor from Python-supplied config, e.g.:
//
//   auto n = std::make_shared<ObjectVariantNodeWrapper<
//                IdentityMatcherFunc, Variant, in<"tracked">, out<"matched">>>(
//                fifo_cap, gallery, cfg);            // Obj ctor args forwarded
//   net.add("identity_matcher", n);
//
// The wrapper mirrors VariantNodeWrapper's channel plumbing exactly; only the
// underlying node type (PoolObjectNode, holding Obj&) differs.

#include "../channel.hpp"
#include "../node.hpp"
#include "../variant_node.hpp"

#include <memory>
#include <stdexcept>
#include <string>
#include <tuple>
#include <typeindex>
#include <utility>
#include <vector>

namespace kpn {

template<typename Obj, typename Variant,
         typename InputTag  = in<>,
         typename OutputTag = out<>>
class ObjectVariantNodeWrapper;

template<typename Obj, typename Variant,
         fixed_string... InNames, fixed_string... OutNames>
class ObjectVariantNodeWrapper<Obj, Variant, in<InNames...>, out<OutNames...>>
    : public IVariantNode<Variant>
{
    using NodeT = ObjectNode<Obj, in<InNames...>, out<OutNames...>>;

public:
    using args_tuple   = typename NodeT::args_tuple;
    using return_tuple = typename NodeT::return_tuple;

    static constexpr std::size_t n_in  = NodeT::input_count;
    static constexpr std::size_t n_out = NodeT::output_count;

    // Owns the functor; forwards remaining args to Obj's constructor.
    template<typename... ObjArgs>
    explicit ObjectVariantNodeWrapper(std::size_t fifo_capacity, ObjArgs&&... obj_args)
        : obj_(std::forward<ObjArgs>(obj_args)...)
        , node_(obj_, fifo_capacity)
        , in_channels_(n_in)
        , out_channels_(n_out)
        , out_type_indices_(n_out, std::type_index(typeid(void)))
    {
        init_inputs(std::make_index_sequence<n_in>{}, fifo_capacity);
        init_out_types(std::make_index_sequence<n_out>{});
    }

    // Access the owned functor so callers can invoke its runtime setters (e.g. to
    // change a threshold on a persistent pipeline without rebuilding the node).
    Obj& functor() { return obj_; }

    // ── INode ─────────────────────────────────────────────────────────────────
    void start() override { node_.start(); }
    void stop()  override { node_.stop(); }
    bool running() const override { return node_.running(); }
    const NodeStats& stats() const override { return node_.stats(); }
    void set_name(std::string name) override { node_.set_name(std::move(name)); }
    NodeSnapshot node_snapshot(const std::string& name, double elapsed_s) const override {
        return node_.node_snapshot(name, elapsed_s);
    }

    // ── IVariantNode ──────────────────────────────────────────────────────────
    std::size_t input_count()  const override { return n_in; }
    std::size_t output_count() const override { return n_out; }

    std::type_index input_type(std::size_t i) const override {
        return in_channels_[i]->type_index();
    }
    std::type_index output_type(std::size_t i) const override {
        return out_type_indices_[i];
    }

    std::shared_ptr<IVariantChannel<Variant>> input_channel(std::size_t i) override {
        return in_channels_[i];
    }

    void set_output_channel(std::size_t i,
                            std::shared_ptr<IVariantChannel<Variant>> ch) override {
        set_output_impl(i, std::move(ch), std::make_index_sequence<n_out>{});
    }

private:
    template<std::size_t... Is>
    void init_inputs(std::index_sequence<Is...>, std::size_t cap) {
        ((init_one_input<Is>(cap)), ...);
    }

    template<std::size_t I>
    void init_one_input(std::size_t cap) {
        using T = std::tuple_element_t<I, args_tuple>;
        auto shared_ch = std::make_shared<Channel<T>>(cap);
        node_.template set_input_channel<I>(shared_ch);
        in_channels_[I] = std::make_shared<VariantChannel<T, Variant>>(std::move(shared_ch));
    }

    template<std::size_t... Is>
    void init_out_types(std::index_sequence<Is...>) {
        ((out_type_indices_[Is] =
              std::type_index(typeid(std::tuple_element_t<Is, return_tuple>))), ...);
    }

    template<std::size_t... Is>
    void set_output_impl(std::size_t port,
                         std::shared_ptr<IVariantChannel<Variant>> ch,
                         std::index_sequence<Is...>) {
        bool matched = false;
        ((Is == port && (set_output_at<Is>(std::move(ch)), matched = true)), ...);
        if (!matched)
            throw std::out_of_range("set_output_channel: port index out of range");
    }

    template<std::size_t I>
    void set_output_at(std::shared_ptr<IVariantChannel<Variant>> ch) {
        using T = std::tuple_element_t<I, return_tuple>;
        auto* typed = dynamic_cast<VariantChannel<T, Variant>*>(ch.get());
        if (!typed)
            throw std::runtime_error(
                "set_output_channel: type mismatch at output port " + std::to_string(I));
        node_.template set_output_channel<I>(typed->raw_ptr());
        out_channels_[I] = std::move(ch);
    }

    Obj   obj_;    // owned; node_ holds Obj& — declaration order keeps obj_ alive first
    NodeT node_;
    std::vector<std::shared_ptr<IVariantChannel<Variant>>> in_channels_;
    std::vector<std::shared_ptr<IVariantChannel<Variant>>> out_channels_;
    std::vector<std::type_index>                           out_type_indices_;
};

} // namespace kpn