////////////////////////////////////////////////////////////
//~ 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_Fit,
    UI_SizeKind_Fill,
    UI_SizeKind_Pixel,
    UI_SizeKind_TextContents,
};

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

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

#define UI_StyleKindsXMacro(x)                  \
    x(Tag,                  u64)                \
    x(Parent,               struct UI_Box *)    \
    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(Font,                 ResourceKey)        \
    x(FontSize,             u32)                \
    x(Text,                 String)             \
    x(TextPadding,          f32)                \
    x(Rounding,             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;
    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;
};

////////////////////////////////////////////////////////////
//~ 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),
};

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 *background_texture;
    Vec2 background_texture_uv0;
    Vec2 background_texture_uv1;

    Axis layout_axis;

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

    ResourceKey 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;
};

////////////////////////////////////////////////////////////
//~ 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
    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

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 helpers

UI_StyleNode *UI_PushStyleNode(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_Style) { .kind = UI_StyleKind_##name, .name = v, .pop_when_used = 1 })
#define UI_Push(name, v)       UI_PushStyleNode((UI_Style) { .kind = UI_StyleKind_##name, .name = v })
#define UI_ForceNext(name, v)  UI_PushStyleNode((UI_Style) { .kind = UI_StyleKind_##name, .name = v, .pop_when_used = 1, .forced = 1 })
#define UI_ForcePush(name, v)  UI_PushStyleNode((UI_Style) { .kind = UI_StyleKind_##name, .name = v, .forced = 1 })
#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_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_TXT(_s)       UI_SIZE(UI_SizeKind_TextContents, 0, (_s))
#define UI_EM(_v, _s)    UI_SIZE(UI_SizeKind_Pixel, (f32)UI_PeekTop(FontSize) * (_v), (_s))

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

UI_Box *UI_BuildBox(UI_BoxFlag flags, UI_Key key);

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

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

void UI_BeginBuild(void);

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

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