////////////////////////////////////////////////////////////
//~ Key types

#define UI_NilKey ((UI_Key) { 0 })
#define UI_RootKey ((UI_Key) { 0xa3deb3749ef35a7aUll })

Struct(UI_Key)
{
    u64 hash;
};

////////////////////////////////////////////////////////////
//~ Build flags

Enum(UI_BuildFlag)
{
    UI_BuildFlag_None  = 0,
    UI_BuildFlag_Debug = (1 << 0),
};

////////////////////////////////////////////////////////////
//~ Size types

Enum(UI_SizeKind)
{
    UI_SizeKind_Pixel,  /* Exact size */
    UI_SizeKind_Fill,   /* Size as percent of parent size */
    UI_SizeKind_Fit,    /* Size to contents */
};

Struct(UI_Size)
{
    UI_SizeKind kind;
    f32 v;
    f32 strictness;
};

////////////////////////////////////////////////////////////
//~ Rounding types

Enum(UI_RoundKind)
{
    UI_RoundKind_Pixel,  /* Exact radius */
    UI_RoundKind_Fill,    /* Radius as percent of size */
};

Struct(UI_Round)
{
    UI_RoundKind kind;
    f32 v;
};

////////////////////////////////////////////////////////////
//~ Alignment types

Enum(UI_Alignment)
{
    UI_Alignment_Center,
    UI_Alignment_Left,
    UI_Alignment_Right,
};

////////////////////////////////////////////////////////////
//~ Padding types

Struct(UI_Pad)
{
    UI_Size top;
    UI_Size bottom;
    UI_Size left;
    UI_Size right;
};

////////////////////////////////////////////////////////////
//~ Checkpoint types

Struct(UI_Checkpoint)
{
    UI_Checkpoint *next;
    u64 v;
};

////////////////////////////////////////////////////////////
//~ Box flags

Enum(UI_BoxFlag)
{
    UI_BoxFlag_None                     = 0,
    UI_BoxFlag_DrawText                 = (1 << 0),
    UI_BoxFlag_NoTextTruncation         = (1 << 1),
    UI_BoxFlag_Floating                 = (1 << 2),
    UI_BoxFlag_NoFloatingClamp          = (1 << 3),
};

////////////////////////////////////////////////////////////
//~ Style types

#define UI_StyleKindsXMacro(x)                  \
    x(Flags,                UI_BoxFlag)         \
    x(Parent,               struct UI_Box *)    \
    x(Tag,                  UI_Tag)             \
    x(LayoutAxis,           Axis)               \
    x(Width,                UI_Size)            \
    x(Height,               UI_Size)            \
    x(Size,                 UI_Size)            \
    x(BackgroundColor,      u32)                \
    x(BorderColor,          u32)                \
    x(Tint,                 u32)                \
    x(Border,               f32)                \
    x(FloatingPos,          Vec2)               \
    x(Rounding,             UI_Round)           \
    x(Font,                 ResourceKey)        \
    x(FontSize,             u32)                \
    x(Text,                 String)             \
    x(TextAlignment,        UI_Alignment)       \
    x(LeftPadding,          UI_Size)            \
    x(RightPadding,         UI_Size)            \
    x(TopPadding,           UI_Size)            \
    x(BottomPadding,        UI_Size)            \
    /*  ----------------------------------- */  \
    /*  --------- Virtual styles  --------- */  \
    /*  ----------------------------------- */  \
    x(BeginVirtualStyles_,  i8)                 \
    x(Padding,              UI_Pad)             \
/* ------------------------------------------- */

Struct(UI_Tag)
{
    String name;
    u64 hash;
};

Enum(UI_StyleKind)
{
    #define X(name, type) UI_StyleKind_##name,
        UI_StyleKind_None,
        UI_StyleKindsXMacro(X)
        UI_StyleKind_Count,
    #undef X
};

Struct(UI_Style)
{
    UI_StyleKind kind;
    b32 pop_when_used;
    b32 forced;
    /* Union of all style fields */
    union
    {
        #define X(name, type) type name;
            UI_StyleKindsXMacro(X)
        #undef X
    };
};

Struct(UI_StyleNode)
{
    UI_StyleNode *next;
    u64 checkpoint;
    UI_Style style;
};

Struct(UI_Stack)
{
    UI_Stack *next;

    UI_Checkpoint *top_checkpoint;
    UI_StyleNode *style_tops[UI_StyleKind_Count];
};

////////////////////////////////////////////////////////////
//~ Event types

Enum(UI_EventFlag)
{
    UI_EventFlag_None           = 0,
    UI_EventFlag_Active         = (1 << 0),
    UI_EventFlag_Hovered        = (1 << 1),
};

Struct(UI_Event)
{
    UI_EventFlag flags;
    Vec2 activation_offset;
};

////////////////////////////////////////////////////////////
//~ Box types

Struct(UI_Box)
{
    //- Hash list
    UI_Box *next_in_bin;
    UI_Box *prev_in_bin;

    //- Tree
    UI_Box *parent;
    UI_Box *first;
    UI_Box *last;
    UI_Box *next;
    UI_Box *prev;
    u64 count;

    //- Persistent data
    UI_Key key;
    UI_Event event;

    //- Per-build data
    UI_BoxFlag flags;

    GPU_Resource *background_texture;
    Vec2 background_texture_uv0;
    Vec2 background_texture_uv1;

    UI_Size pref_size[Axis_CountXY];
    UI_Round rounding;
    u32 background_color;
    u32 border_color;
    u32 text_color;
    u32 tint;
    f32 border;
    Vec2 floating_pos;
    String text;
    UI_Alignment text_alignment;
    ResourceKey font_resource;
    f32 font_size;
    Axis layout_axis;

    //- Pre-layout data
    u64 pre_index;
    u64 post_index;

    //- Layout data
    F_Run glyph_run;
    F_Font *font;
    f32 solved_dims[Axis_CountXY];
    f32 layout_cursor;

    //- Post-layout data
    Vec2 p0;
    Vec2 p1;
    f32 rounding_tl;
    f32 rounding_tr;
    f32 rounding_br;
    f32 rounding_bl;
};

Struct(UI_BoxBin)
{
    UI_Box *first;
    UI_Box *last;
};

////////////////////////////////////////////////////////////
//~ State types

#define UI_NumBoxLookupBins 16384

Struct(UI_SharedState)
{
    //- Control state
    Vec2 cursor_pos;
    Xform ui_to_screen_xf;

    //- Build state
    Arena *build_arena;
    Arena *back_build_arena;

    UI_BuildFlag build_flags;
    UI_BuildFlag back_build_flags;

    UI_BoxBin *box_bins;
    UI_BoxBin *back_box_bins;

    UI_Box *root_box;
    UI_Box *back_root_box;

    u64 boxes_count;
    u64 back_boxes_count;

    UI_Stack *top_stack;
    UI_Stack *first_free_stack;
    UI_Checkpoint *first_free_checkpoint;
    UI_StyleNode *first_free_style_node;

    //- Layout state
    UI_Box **boxes_pre;
    UI_Box **boxes_post;
    UI_Box **back_boxes_pre;
    UI_Box **back_boxes_post;

    //- Render state
    i64 gpu_submit_fence_target;
    GPU_TransientBuffer draw_rects_tbuff;
    Arena *draw_rects_arena;

} extern UI_shared_state;

////////////////////////////////////////////////////////////
//~ Startup

void UI_Startup(void);

////////////////////////////////////////////////////////////
//~ Font helpers

ResourceKey UI_GetDefaultFontResource(void);

////////////////////////////////////////////////////////////
//~ Key helpers

UI_Box *UI_BackBoxFromKey(UI_Key key);
UI_Box *UI_FrontBoxFromKey(UI_Key key);

////////////////////////////////////////////////////////////
//~ Checkpoint helpers

void UI_PushCP(UI_Box *parent);
void UI_PopCP(void);

////////////////////////////////////////////////////////////
//~ Style stack helpers

void UI_PushStack(void);
void UI_PopStack(void);

void     UI_PushStyle(UI_Style desc);
UI_Style UI_PopStyle(UI_StyleKind kind);
UI_Style UI_FetchStyle(UI_StyleKind kind, b32 use);

#define UI_SetNext(name, ...)       UI_PushStyle((UI_Style) { .kind = UI_StyleKind_##name, .name = __VA_ARGS__, .pop_when_used = 1 })
#define UI_Push(name, ...)          UI_PushStyle((UI_Style) { .kind = UI_StyleKind_##name, .name = __VA_ARGS__ })
#define UI_ForceNext(name, ...)     UI_PushStyle((UI_Style) { .kind = UI_StyleKind_##name, .name = __VA_ARGS__, .pop_when_used = 1, .forced = 1 })
#define UI_ForcePush(name, ...)     UI_PushStyle((UI_Style) { .kind = UI_StyleKind_##name, .name = __VA_ARGS__, .forced = 1 })
#define UI_Pop(name)                UI_PopStyle(UI_StyleKind_##name).name
#define UI_FetchTop(name, use)      UI_FetchStyle(UI_StyleKind_##name, use).name
#define UI_PeekTop(name)            UI_FetchTop(name, 0)
#define UI_UseTop(name)             UI_FetchTop(name, 1)

#define UI_PushCopy(name, src, ...) do {  \
    UI_Style _new = src;                  \
    _new.kind = UI_StyleKind_##name;      \
    _new.name = __VA_ARGS__;              \
    UI_PushStyle(_new);                   \
} while (0)

////////////////////////////////////////////////////////////
//~ Size helpers

#define UI_SIZE(_kind, _v, _s) (UI_Size) { .kind = (_kind), .v = (_v), .strictness = (_s) }

#define UI_PIX(_v, _s)   UI_SIZE(UI_SizeKind_Pixel, (_v), (_s))
#define UI_FIT(_s)       UI_SIZE(UI_SizeKind_Fit, 0, (_s))
#define UI_FILL(_v, _s)  UI_SIZE(UI_SizeKind_Fill, (_v), (_s))
#define UI_FNT(_v, _s)   UI_SIZE(UI_SizeKind_Pixel, (f32)UI_PeekTop(FontSize) * (_v), (_s))

////////////////////////////////////////////////////////////
//~ Rounding helpers

#define UI_ROUND(_kind, _v) (UI_Round) { .kind = (_kind), .v = (_v)}

#define UI_RPIX(_v) UI_ROUND(UI_RoundKind_Pixel, (_v))
#define UI_RFILL(_v) UI_ROUND(UI_RoundKind_Fill, (_v))

////////////////////////////////////////////////////////////
//~ Padding helpers

#define UI_PAD(...)   ((UI_Pad) { __VA_ARGS__ })
#define UI_PADALL(size)    ((UI_Pad) { .top = size, .bottom = size, .left = size, .right = size })

UI_Box *UI_BuildPadAlongAxis(UI_Box *parent, UI_Size start, UI_Size end, Axis final_layout_axis);
UI_Box *UI_BuildPad(UI_Box *parent, UI_Pad padding);

////////////////////////////////////////////////////////////
//~ Box

UI_Box *UI_BuildBox(String seed);

void UI_SetBackgroundTexture(UI_Box *box, GPU_Resource *texture, Vec2 uv0, Vec2 uv1);
b32 UI_IsPointInBox(UI_Box *box, Vec2 point);

////////////////////////////////////////////////////////////
//~ Event

UI_Event UI_EventFromKey(UI_Key key);

////////////////////////////////////////////////////////////
//~ Begin build

void UI_BeginBuild(ControllerEventsArray controller_events, UI_BuildFlag flags);

////////////////////////////////////////////////////////////
//~ End build

GPU_ResourceDesc UI_GetRenderTargetDesc(Vec2I32 size);
i64 UI_EndBuild(GPU_Resource *render_target, Xform ui_to_screen_xf);