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

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

Struct(UI_Key)
{
    u64 hash;
};

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

Enum(UI_SizeKind)
{
    UI_SizeKind_Children,
    UI_SizeKind_Ratio,
    UI_SizeKind_Pixel,
    UI_SizeKind_Text,
};

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

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

/* NOTE: UI flags are located here since they are shared between application & shader code */

Enum(UI_BoxFlag)
{
    UI_BoxFlag_None        = 0,
    UI_BoxFlag_DrawText    = (1 << 0),
    UI_BoxFlag_DrawImage   = (1 << 1),
};

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;

    //- Per-build data
    UI_BoxFlag flags;

    String display_text;
    GPU_Resource *display_image;

    Axis layout_axis;

    UI_Size pref_size[Axis_CountXY];
    u32 background_color;
    u32 border_color;
    f32 border;
    f32 text_padding;

    Resource font_resource;
    f32 font_size;

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

    //- Post-solve data
    Vec2 p0;
    Vec2 p1;
};
Struct(UI_BoxBin)
{
    UI_Box *first;
    UI_Box *last;
};

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

#define UI_StyleKindsXMacro(x)          \
    x(Tag,                  u64)        \
    x(Parent,               UI_Box *)   \
    x(LayoutAxis,           Axis)       \
    x(Width,                UI_Size)    \
    x(Height,               UI_Size)    \
    x(BackgroundColor,      u32)        \
    x(BorderColor,          u32)        \
    x(Border,               f32)        \
    x(Font,                 Resource)   \
    x(FontSize,             u32)        \
    x(TextPadding,          f32)        \
/* ----------------------------------- */

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;
    /* Union of all style fields */
    union
    {
        #define X(name, type) type name;
            UI_StyleKindsXMacro(X)
        #undef X
    };
};

Struct(UI_StyleNode)
{
    UI_StyleNode *next;
    b32 pop_when_used;
    u64 checkpoint;
    UI_Style style;
};

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

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

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

#define UI_NumBoxLookupBins 16384

Struct(UI_SharedState)
{
    //- Build state
    Arena *build_arena;
    Arena *back_build_arena;

    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_Checkpoint *top_checkpoint;
    UI_Checkpoint *first_free_checkpoint;

    UI_StyleNode *style_tops[UI_StyleKind_Count];
    UI_StyleNode *first_free_style_node;

    //- Render state
    GPU_Resource *render_target;
    i64 render_fence_target;

    GPU_TransientBuffer draw_rects_tbuff;
    Arena *draw_rects_arena;

} extern UI_shared_state;

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

void UI_Startup(void);

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

Resource UI_GetDefaultFontResource(void);

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

u64 UI_HashFromTop(void);
u64 UI_HashFromString(u64 seed, String str);
UI_Key UI_KeyFromString(u64 seed, String str);

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

void UI_PushCheckpoint(void);
void UI_PopCheckpoint(void);

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

UI_StyleNode *UI_PushStyleNode(UI_StyleKind kind, b32 pop_when_used, UI_Style desc);
UI_Style UI_PopStyleNode(UI_StyleKind kind);
UI_StyleNode *UI_PeekTopStyleNode(UI_StyleKind kind);
UI_Style UI_StyleFromTopNode(UI_StyleKind kind, b32 use);

#define UI_SetNext(name, v)    UI_PushStyleNode(UI_StyleKind_##name, 1, (UI_Style) { .name = v })
#define UI_Push(name, v)       UI_PushStyleNode(UI_StyleKind_##name, 0, (UI_Style) { .name = v })
#define UI_Pop(name, v)        UI_PopStyleNode(UI_StyleKind_##name).name
#define UI_UseTop(name)        UI_StyleFromTopNode(UI_StyleKind_##name, 1).name
#define UI_PeekTop(name)       UI_StyleFromTopNode(UI_StyleKind_##name, 0).name

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

#define UI_ChildrenSize(_strictness)             ((UI_Size) { .kind = UI_SizeKind_Children, .strictness = strictness_ })
#define UI_RatioSize(_ratio, _strictness)        ((UI_Size) { .kind = UI_SizeKind_Ratio, .v = _ratio, .strictness = _strictness })
#define UI_PixelSize(_pixels, _strictness)       ((UI_Size) { .kind = UI_SizeKind_Pixel, .v = _pixels, .strictness = _strictness })
#define UI_TextSize(_strictness)                 ((UI_Size) { .kind = UI_SizeKind_Text, .strictness = _strictness })

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

UI_Box *UI_BuildBox(UI_BoxFlag flags, UI_Key key);

void UI_SetDisplayText(UI_Box *box, String str);
void UI_SetDisplayImage(UI_Box *box, GPU_Resource *img);

////////////////////////////////////////////////////////////
//~ Image

void UI_SetDisplayImage(UI_Box *box, GPU_Resource *img);

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

void UI_BeginBuild(void);

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

GPU_Resource *UI_EndBuild(Rect render_viewport);