#ifndef ui_hpp
#define ui_hpp

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

#include <new>

struct Arena;
struct Heap;
struct UI {
	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 clip_src(const Rect& other, Rect& src);
		void shrink(int a);
		bool contains(int px, int py);
	};

	struct Renderer {
		static constexpr int grid_size = 16;
		static constexpr int cmd_buf_size = 1024 * 128;
		Rect bound;
		Rect clip;
		Colour* pixels;
		Heap* arena;
		uint8_t cmd_buf[cmd_buf_size];
		int cmd_buf_ptr;
		int grid_cell_size[2];
		uint64_t grid_a[grid_size * grid_size];
		uint64_t grid_b[grid_size * grid_size];
		uint64_t* grid;

		struct Cmd {
			enum {
				RECT,
				TEXT,
				CLIP
			};
			int type, size;
			Colour col;
			Rect r;
		};

		void blit_rect(int x, int y, int w, int h, Colour col);
		void blit_char(char ch, int x, int y, Colour col);

		Cmd* add_cmd(int size);
		void commit_cmd(Cmd* c);
		void add_rect(int x, int y, int w, int h, Colour col);
		void add_text(int x, int y, const char* txt, Colour col);
		void reset(const Rect& cl);
		void set_clip(const Rect& r);
		void clear(const Rect& r);
		void flush_cell(int x, int y);
		bool flush(void* target);
		void resize(int w, int h);
		void init(Heap* heap, int w, int h);
	} ren;

	struct Element;

	Heap* heap;
	const App* app;
	Element* root, * hot, * hovered, * active;
	Rect area;
	bool layout_dirty;

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

	static UI* create(
		const App* app,
		Arena* a
	);

	void init(
		const App* app,
		Heap* h
	);
	void destroy();
	void layout(int w, int h);
	void text_input(const char* buf);
	void update(Arena* s);
	bool render(Arena* s, void* pixels);

	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,
			input_changed,
			input_finalised,
			text_typed,
			text_backspaced
		} type;
		void* payload;
	};

	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, bool recurse = false);
		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 Table : Container {
		int* rows;
		Table(UI* ui, Element* parent, const int* rows);
		~Table();
		Rect layout(const Rect& avail) 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);
		void set_int(int v);
		void set_hex(uint64_t v);
		void set_float(float v);
	};

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

	typedef int (*Input_Filter)(char ch);

	struct Input : Element {
		Input_Filter filter;
		char* buf;
		int buf_size;
		Input(UI* ui, Element* parent, Input_Filter f);
		~Input();
		Rect layout(const Rect& avail) override;
		void on_render() override;
		void on_message(const Message& m) override;
		void set_text(const char* t);
		void add_text(const char* s);
	};

	struct Float_Input : Input {
		float val;
		Float_Input(UI* ui, Element* parent);
		void on_message(const Message& m) override;
		void set_val(float v);
	};

	struct Slider : Element {
		Float_Input* input;
		float minval, maxval;
		int drag_off;
		bool dragging;
		Slider(UI* ui, Element* parent, float miv, float mav);
		Rect layout(const Rect& avail) override;
		void on_message(const Message& m) override;
		void on_render() override;
		void on_update() override;

		int track_w();
		Rect handle_rect();
		Rect track_rect();
		float val_from_coord(int coord);
	};

	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