#pragma once

#include <glm/glm.hpp>
#include <functional>
#include <string>
#include <vector>

namespace Donut
{
    // A placeable/editable sphere in the world-builder scene view. Backend-
    // agnostic: the app owns the list, every backend renders it the same way.
    struct SceneObject
    {
        glm::vec3 position = { 0.0f, 2.0f, 0.0f };
        float     radius   = 2.0f;
        glm::vec3 color    = { 0.85f, 0.35f, 0.2f };
    };

    // Live-tunable black-hole / accretion-disk parameters. Radii are in
    // Schwarzschild radii; the inner edge is clamped to the ISCO (3 r_s).
    struct BlackHoleParams
    {
        float disk_inner_rs = 3.0f;      // inner edge (x r_s)
        float disk_outer_rs = 12.0f;     // outer edge (x r_s)
        float temperature   = 4800.0f;   // Kelvin at the flux peak (disk colour)
        float brightness    = 0.9f;      // disk exposure
        float turbulence    = 0.4f;      // 0 = smooth physical disk
        int   quality_steps = 15000;     // geodesic integration steps
        float fov_degrees   = 60.0f;     // camera field of view
    };

    // The swappable high-level renderer. Each graphics backend (OpenGL, Vulkan,
    // and later Metal / D3D12) implements this one interface; the Application,
    // states and UI drive it identically, so the app behaves the same no matter
    // which backend is active. Backends own their own device/swapchain/pipelines
    // and translate these high-level calls into their native API.
    class RendererBackend
    {
    public:
        virtual ~RendererBackend() = default;

        // glfwWindow is an opaque GLFW handle (created NO_API for Vulkan/Metal,
        // with a GL context for OpenGL). Returns false on failure.
        virtual auto init(void* glfwWindow, int width, int height) -> bool = 0;

        // Creates the ImGui context + this backend's ImGui platform/render impl.
        virtual auto init_ui() -> bool = 0;
        virtual auto shutdown() -> void = 0;
        virtual auto resize(int width, int height) -> void = 0;

        // Renders one frame: draws the current view (black hole or scene) from
        // the shared state, then invokes build_ui to draw the ImGui panel on top.
        virtual auto draw_frame(const glm::vec4& clear_color,
                                const std::function<void()>& build_ui) -> void = 0;

        // --- shared view / camera state ------------------------------------
        virtual auto set_scene_mode(bool enabled) -> void = 0;  // black hole vs scene view
        virtual auto is_scene_mode() const -> bool = 0;
        virtual auto set_free_fly(bool enabled) -> void = 0;    // free-fly vs orbital camera
        virtual auto is_free_fly() const -> bool = 0;
        virtual auto reset_camera() -> void = 0;

        // --- shared content ------------------------------------------------
        virtual auto set_hdri(const std::string& path) -> void = 0;
        virtual auto current_hdri() const -> const std::string& = 0;
        virtual auto scene_objects() -> std::vector<SceneObject>& = 0;
        virtual auto set_selected_object(int index) -> void = 0;
        virtual auto black_hole_params() -> BlackHoleParams& = 0;

        // --- introspection for the UI --------------------------------------
        virtual auto device_name() const -> const std::string& = 0;
    };
}