First Light

#pragma once

#include <cstddef>
#include <cstdint>
#include <expected>
#include <string>
#include <vector>

namespace prism {

// World-space coordinates. Colors are linear-light RGB, each component in [0, 1].
struct Vec3 { double x{}, y{}, z{}; };
struct Color { double r{}, g{}, b{}; };
struct Camera { Vec3 position; Vec3 look_at; double vertical_fov_degrees{}; };
struct Sphere { Vec3 center; double radius{}; Color color; };

// These values own their strings and containers. References to a Scene borrow it.
struct Scene {
    std::uint32_t version{};
    std::string title;
    std::uint32_t width{}, height{};
    Camera camera;
    Color background;
    Vec3 light_direction; // Direction FROM a surface TOWARD the light.
    double ground_y{};
    Color ground_color;
    std::vector<Sphere> spheres;
};

enum class ErrorCode { invalid_scene, allocation, io };
struct Error {
    ErrorCode code;
    std::string message; // Fixed diagnostics: never echo arbitrary input or file contents.
};

inline constexpr std::uint32_t max_dimension = 2048;
inline constexpr std::size_t max_pixels = 2'097'152;
inline constexpr std::size_t max_spheres = 32;
inline constexpr std::size_t max_intersection_work = 33'554'432;

[[nodiscard]] Scene demo_scene();
[[nodiscard]] std::expected<void, Error> validate_scene(const Scene& scene);

} // namespace prism