////////////////////////////////
//~ Opaque types

Struct(G_Resource);
Struct(G_RenderSig);
Struct(G_Swapchain);

////////////////////////////////
//~ Render

Struct(G_Indices)
{
    u32 count;
    u32 *indices;
};

typedef i32 G_RenderCmdKind; enum
{
    GP_RENDER_CMD_KIND_NONE,
    GP_RENDER_CMD_KIND_DRAW_MATERIAL,
    GP_RENDER_CMD_KIND_DRAW_UI_RECT,
    GP_RENDER_CMD_KIND_DRAW_UI_SHAPE,
    GP_RENDER_CMD_KIND_PUSH_GRID,

    NUM_GP_RENDER_CMD_KINDS
};

Struct(G_RenderCmdDesc)
{
    G_RenderCmdKind kind;
    union
    {
        struct
        {
            Xform xf;
            G_Resource *texture;
            ClipRect clip;
            u32 tint;
            b32 is_light;
            Vec3 light_emittance;
            u32 grid_cmd_id;
        } material;
        struct
        {
            Xform xf;
            G_Resource *texture;
            ClipRect clip;
            u32 tint;
        } ui_rect;
        struct
        {
            Vec2Array vertices;
            G_Indices indices;
            u32 color;
        } ui_shape;
        struct
        {
            f32 line_thickness;
            f32 line_spacing;
            Vec2 offset;
            u32 bg0_color;
            u32 bg1_color;
            u32 line_color;
            u32 x_color;
            u32 y_color;
        } grid;
    };
};

Struct(G_RenderParams)
{
    Vec2I32 ui_size;
    Vec2I32 render_size;
    Xform world_to_render_xf;
    Xform render_to_ui_xf;
    b32 effects_disabled;
};

////////////////////////////////
//~ Texture

typedef i32 G_TextureFormat; enum
{
    GP_TEXTURE_FORMAT_NONE,
    GP_TEXTURE_FORMAT_R8_UNORM,
    GP_TEXTURE_FORMAT_R8G8B8A8_UNORM,
    GP_TEXTURE_FORMAT_R8G8B8A8_UNORM_SRGB,
    GP_TEXTURE_FORMAT_R16G16B16A16_FLOAT,

    NUM_GP_TEXTURE_FORMATS
};

typedef i32 G_TextureFlag; enum
{
    GP_TEXTURE_FLAG_NONE        = (0),
    GP_TEXTURE_FLAG_TARGETABLE  = (1 << 0)
};

////////////////////////////////
//~ Memory info

Struct(G_MemoryInfo)
{
    u64 local_used;
    u64 local_budget;
    u64 non_local_used;
    u64 non_local_budget;
};

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

void gp_startup(void);

////////////////////////////////
//~ Resource operations

/* NOTE: Internally, the layer will make sure to not release any resources
 * until after any in-flight GPU runs finish using them. However, it is up to
 * the caller to make sure the released resources aren't then referenced in
 * any runs
 */
void gp_resource_release(G_Resource *resource);

////////////////////////////////
//~ Texture operations

G_Resource *gp_texture_alloc(G_TextureFormat format, u32 flags, Vec2I32 size, void *initial_data);

Vec2I32 gp_texture_get_size(G_Resource *texture);

////////////////////////////////
//~ Render operations

G_RenderSig *gp_render_sig_alloc(void);

/* Returns a cmd id internal to the sig */
u32 gp_push_render_cmd(G_RenderSig *render_sig, G_RenderCmdDesc *desc);

G_Resource *gp_run_render(G_RenderSig *gp_render_sig, G_RenderParams render_params);

////////////////////////////////
//~ Memory query

G_MemoryInfo gp_query_memory_info(void);

////////////////////////////////
//~ Swapchain

G_Swapchain *gp_swapchain_alloc(P_Window *window, Vec2I32 resolution);

void gp_swapchain_release(G_Swapchain *gp_swapchain);

/* Waits until a new backbuffer is ready to be written to.
 * This should be called before rendering for minimum latency. */
void gp_swapchain_wait(G_Swapchain *gp_swapchain);

////////////////////////////////
//~ Present

/* 1. Clears the backbuffer and ensures it's at size `backbuffer_resolution`
 * 2. Blits `texture` to the backbuffer using `texture_xf`
 * 3. Presents the backbuffer */
void gp_present(G_Swapchain *gp_swapchain, Vec2I32 backbuffer_resolution, G_Resource *texture, Xform texture_xf, i32 vsync);