#pragma once
#include "vde/brep/assembly.h"
#include <unordered_map>
#include <string>
#include <vector>

namespace vde::brep {

/// Shared geometry instance (for repeated parts)
struct GeometryInstance {
    std::string part_name;
    BrepModel geometry;   ///< shared geometry data
    size_t use_count = 0; ///< number of references to this geometry
};

/**
 * @brief Instance manager for large assemblies.
 *
 * Deduplicates repeated parts by reusing shared geometry.
 * Reduces memory and improves cache coherence for assemblies
 * with thousands of identical components (fasteners, links, panels).
 *
 * @ingroup brep
 */
class AssemblyInstancer {
public:
    /**
     * @brief Register a geometry for instancing.
     * @param name  Part name identifier
     * @param geom  Geometry to register
     * @return instance ID, reuses existing if same name & geometry matches
     */
    int register_instance(const std::string& name, const BrepModel& geom);

    /**
     * @brief Create an occurrence of a registered instance.
     * @param assy       Target assembly
     * @param parent     Parent node (nullptr = root)
     * @param instance_id Instance to place
     * @param transform   Local transform for this occurrence
     */
    void place_instance(Assembly& assy, AssemblyNode* parent,
                       int instance_id, const Transform3D& transform);

    /// Total unique geometries
    [[nodiscard]] size_t unique_count() const { return instances_.size(); }

    /// Total placed occurrences
    [[nodiscard]] size_t total_placed() const { return total_placed_; }

private:
    std::vector<GeometryInstance> instances_;
    size_t total_placed_ = 0;
};

} // namespace vde::brep