Renderer Engineering

#pragma once
#include "prism_engineering/asset_pipeline.hpp"
#include <cstddef>
#include <cstdint>
#include <memory_resource>

namespace prism_engineering {
struct AllocationCounts {
  std::size_t calls{}, requested_bytes{}, live_bytes{}, peak_live_bytes{};
};
// Single-threaded instrumentation. Equality is identity, not upstream equality:
// allocating through one counter and deallocating through another loses accounting.
class CountingResource final : public std::pmr::memory_resource {
public:
  explicit CountingResource(std::pmr::memory_resource& upstream) noexcept : upstream_{upstream} {}
  CountingResource(const CountingResource&)=delete;
  CountingResource& operator=(const CountingResource&)=delete;
  [[nodiscard]] AllocationCounts counts() const noexcept { return counts_; }
private:
  void* do_allocate(std::size_t bytes, std::size_t alignment) override;
  void do_deallocate(void* pointer, std::size_t bytes, std::size_t alignment) override;
  bool do_is_equal(const std::pmr::memory_resource& other) const noexcept override { return this==&other; }
  std::pmr::memory_resource& upstream_;
  AllocationCounts counts_;
};

enum class ResourceChoice { ordinary, monotonic, pool };
struct RenderMeasurement {
  PreparedImage image; // Ordinary owning allocation, outside scratch accounting.
  AllocationCounts requests;
  AllocationCounts upstream_before_release;
  AllocationCounts upstream_after_release;
  std::int64_t elapsed_nanoseconds{};
};

// Same 64x64, four-samples-per-pixel integer scene under each resource policy.
// All temporary tile objects die before returning; result pixels own their bytes.
[[nodiscard]] PreparedImage render_tiles(std::pmr::memory_resource& scratch);
[[nodiscard]] PreparedImage render_plain();
[[nodiscard]] RenderMeasurement measure_render(ResourceChoice choice);
[[nodiscard]] std::uint64_t image_checksum(const PreparedImage& image) noexcept;
} // namespace prism_engineering