state_tree_sync.hpp

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#pragma once
 
// StateTreeSynchroniser — delta-based sync of StateTree over IPC.
// Encodes property changes and child mutations as compact deltas,
// sends over an InterprocessConnection, and applies on the remote side.
 
#include <pulp/state/state_tree.hpp>
#include <vector>
#include <cstdint>
#include <functional>
#include <utility>
 
namespace pulp::state {

enum class SyncDeltaType : uint8_t {
    PropertySet = 1,
    PropertyRemove = 2,
    ChildAdd = 3,
    ChildRemove = 4,
    ChildMove = 5 
};

struct SyncDelta {
    SyncDeltaType type;
    std::string path;        // Dot-separated path to the node
    std::string key;         // Property name (for property ops) or child type (for child ops)
    PropertyValue value;     // New value (for PropertySet)
    int child_index = -1;    // Index (for ChildAdd/ChildRemove; source index for ChildMove)
};

class StateTreeSynchroniser {
public:
    StateTreeSynchroniser() = default;

    void attach(StateTree::Ptr tree);

    void detach();

    std::vector<SyncDelta> take_deltas();

    static std::vector<uint8_t> encode(const std::vector<SyncDelta>& deltas);

    static std::vector<SyncDelta> decode(const uint8_t* data, size_t size);

    static void apply(StateTree& tree, const std::vector<SyncDelta>& deltas);
 
private:
    void attach_node(StateTree& node);

    void attach_subtree(StateTree& node);

    void detach_subtree(StateTree& node);
 
    StateTree::Ptr tree_;
    std::vector<SyncDelta> pending_;
 
    // Per-node listener registrations — recorded so detach() can remove
    // listeners from every observed node, not just the root.
    std::vector<std::pair<StateTree*, int>> property_listener_ids_;
    std::vector<std::pair<StateTree*, int>> child_added_listener_ids_;
    std::vector<std::pair<StateTree*, int>> child_removed_listener_ids_;
    std::vector<std::pair<StateTree*, int>> child_moved_listener_ids_;
};
 
}  // namespace pulp::state