#ifndef ui_hpp
#define ui_hpp

#include "app.hpp"
#include "maths.hpp"
#include "video.hpp"

#include <new>

struct Arena;
struct UI {
	struct Vertex {
		float x, y, u, v, r, g, b, a;
	};

	struct Colour {
		uint8_t r, g, b, a;
		Colour(unsigned rgb, uint8_t a = 0xff);
		float r_f() { return (float)r / 255.0f; };
		float g_f() { return (float)g / 255.0f; };
		float b_f() { return (float)b / 255.0f; };
		float a_f() { return (float)a / 255.0f; };
	};

	struct Rect {
		int x, y, w, h;

		Rect() = default;
		Rect(int x, int y, int w, int h);

		void clip(const Rect& other);
		void shrink(int a);
		bool contains(int px, int py);
	};

	struct Vertex_Buffer {
		Rect clip;
		bool dirty;
		Staged_Buffer buf;
		Buffer_Id indices;
		int start, usage;

		void init(Device* dev);
		void init_indices(Device* dev);
		void destroy(UI* ui);
		void update_buffer(Context& ctx);
		void reset(const Rect& clip);
		void set_clip(const Rect& clip);

		void add_quad(
			UI* ui,
			int x,
			int y,
			int w,
			int h,
			float u0,
			float v0,
			float u1,
			float v1,
			Colour col
		);
		void add_rect(
			UI* ui,
			int x,
			int y,
			int w,
			int h,
			Colour col
		);
		void add_char(UI* ui, int x, int y, char ch, Colour col);
		void add_text(
			UI* ui,
			int x,
			int y,
			const char* txt,
			Colour col
		);
		void draw(
			UI* ui,
			Context& ctx,
			Pipeline& pip,
			Render_Pass& rp
		);
		Vertex_Buffer* next;
	};

	struct Element;

	Heap* heap;
	Device* device;
	const App* app;
	Texture_Id atlas;
	Shader_Id shader;
	Vertex_Format_Id vertex_format;
	Sampler_Id sampler;
	Staged_Buffer cbuffer;
	Vertex_Buffer mesh;
	Pipeline* pipeline;
	Render_Pass* render_pass;
	Element* root, * hot, * hovered;
	Rect area;
	bool layout_dirty;

	struct UI_CBuffer {
		m4f projection;
	};
	struct {
		int vert_binding;
		int atlas_binding;
		int config_binding;
	} shader_info;

	static int text_width(const char* t);
	static int text_height(const char* t);

	static UI* create(
		Device* dev,
		const App* app,
		Arena* a,
		Shader_Id sh
	);

	void init(
		Device* dev,
		const App* app,
		Heap* h,
		Texture_Id atlas,
		Shader_Id sh
	);
	void destroy();
	void layout(int w, int h);
	void update(Arena* s);
	void render(Arena* s, Texture_Id target);

	void draw_container(const Rect& r, Colour c);
	void draw_containeri(const Rect& r, Colour c);

	Element* alloc_element(size_t size);
	template <typename T, typename... Args>
	T* create_element(Element* parent, Args... args) {
		T* e = (T*)alloc_element(sizeof(T));
		new (e) T(this, parent, args...);
		return e;
	}

	struct Message {
		enum class Type {
			click,
			destroy,
			activate,
			deactivate
		} type;
	};

	typedef int (*Message_Handler)(Element* e, const Message& m);

	struct Element {
		struct Flags {
			enum {
				disabled = 1 << 0
			};
		};

		UI* ui;
		Element* parent;
		Element* children, * next;
		Message_Handler handler;
		Rect bound, clip;
		int flags;

		Element(UI* ui, Element* parent);
		virtual ~Element();

		void destroy();

		virtual Rect layout(const Rect& avail);
		void update();
		virtual void on_update();
		virtual void on_render();
		virtual void on_add_child(Element* nch);
		virtual void on_message(const Message& msg);

		void add_child(Element* ch);
		void remove_child(Element* ch);
		void message(const Message& msg);
		void render();

		bool enabled();
		void disable();
		void enable();
	};

	struct Container : Element {
		int padding;
		Container(UI* ui, Element* parent);

		Rect layout(const Rect& avail) override;
		void on_render() override;
	};

	struct Toolbar : Element {
		int padding;
		Toolbar(UI* ui, Element* parent);
		Rect layout(const Rect& avail) override;
		void on_render() override;
	};

	struct Label : Element {
		char* text;
		Label(UI* ui, Element* parent, const char* label);
		~Label();
		Rect layout(const Rect& avail) override;
		void on_render() override;

		void set_text(const char* s);
	};

	struct Button : Label {
		Button(UI* ui, Element* parent, const char* label);
		Rect layout(const Rect& avail) override;
		void on_render() override;
	};

	struct Modal : Element {
		Container* contents;
		Toolbar* title_bar;
		Label* title;
		Button* close;
		int drag_offset[2];
		int pos[2];
		bool dragging;
		Modal(UI* ui, Element* parent, const char* title);
		Rect layout(const Rect& avail) override;
		void on_render() override;
		void on_update() override;
		void bring_to_front();
	};

	struct Tree : Element {
		Element* collapsed; /* <- children are moved here when it's collapsed so they stop layout'ing and rendering! */
		Button* expandbtn;
		Label* text;
		Tree(UI* ui, Element* parent, const char* text);
		Rect layout(const Rect& avail) override;
		void on_render() override;
		void on_update() override;
		void on_add_child(Element* child) override;
		void expand();
		void collapse();
		bool is_leaf() const;
	};
};

#endif