// #define V_ParticlesCap Kibi(128)
// #define V_ParticlesCap Mebi(1)
#define V_ParticlesCap Mebi(2)
// #define V_ParticlesCap Mebi(16)

////////////////////////////////////////////////////////////
//~ Constant types

Enum(V_GpuFlag)
{
  V_GpuFlag_None = 0,
  V_GpuFlag_DebugDraw = (1 << 0),
};

G_DeclConstant(V_GpuFlag,                 V_ShaderConst_GpuFlags,             0);
G_DeclConstant(G_RWStructuredBufferRef,   V_ShaderConst_State,                1);
G_DeclConstant(G_StructuredBufferRef,     V_ShaderConst_Params,               2);
G_DeclConstant(G_Texture3DRef,            V_ShaderConst_NoiseTex,             3);

Enum(V_SelectionMode)
{
  V_SelectionMode_None,
  V_SelectionMode_Tile,
};

Struct(V_Affines)
{
  // World <-> screen
  Affine world_to_screen;
  Affine screen_to_world;

  // World <-> shade
  Affine world_to_shade;
  Affine shade_to_world;

  // Shade <-> screen
  Affine shade_to_screen;
  Affine screen_to_shade;

  // World <-> cell
  Affine world_to_cell;
  Affine cell_to_world;

  // World <-> tile
  Affine world_to_tile;
  Affine tile_to_world;
};

Struct(V_TileDesc)
{
  G_Texture2DRef tex;
};

Struct(V_GpuState)
{
  // u32 particle_seq;  // Atomic monotonically increasing allocation counter sequence for particle ring buffer
  i32 _;
};

Struct(V_GpuParams)
{
  // TODO: Use simulation dt
  f32 dt;
  u64 tick;
  u64 seed;
  V_Affines af;

  V_SelectionMode selection_mode;
  P_TileKind equipped_tile;

  b32 has_mouse_focus;
  b32 has_keyboard_focus;
  Vec2 screen_cursor;
  Vec2 shade_cursor;
  Vec2 world_cursor;
  Rng2 screen_selection;
  Rng2 shade_selection;
  Rng2 world_selection;

  Vec2 camera_pos;
  f32 camera_zoom;

  G_SamplerStateRef pt_clamp_sampler;
  G_SamplerStateRef pt_wrap_sampler;

  Vec2 screen_dims;

  Vec2 shade_dims;
  G_Texture2DRef shade_ro;
  G_RWTexture2DRef shade_rw;
  G_Texture2DRef albedo_ro;
  G_RWTexture2DRef albedo_rw;

  G_Texture2DRef tiles;
  G_StructuredBufferRef quads;
  G_StructuredBufferRef shape_verts;

  u32 emitters_count;
  G_StructuredBufferRef emitters;

  G_RWStructuredBufferRef particles;

  b32 should_clear_stains;
  G_RWTexture2DRef cells;
  G_RWTexture2DRef stains;
  G_RWTexture2DRef drynesses;

  V_TileDesc tile_descs[P_TileKind_COUNT];
};

////////////////////////////////////////////////////////////
//~ Particle types

Enum(V_ParticleFlag)
{
  V_ParticleFlag_None = 0,
  V_ParticleFlag_PruneWhenStill = (1 << 0),
  V_ParticleFlag_StainOnPrune   = (1 << 1),
  V_ParticleFlag_StainTrail     = (1 << 2),
};

Struct(V_Emitter)
{
  V_ParticleFlag flags;

  u32 first_particle_seq;
  u32 count;

  Vec2 start;
  Vec2 end;

  f32 lifetime;
  f32 lifetime_spread;

  f32 speed;
  f32 speed_spread;

  f32 angle;
  f32 angle_spread;

  f32 velocity_falloff;
  f32 velocity_falloff_spread;

  Vec4 color_lin;
  Vec4 color_spread;
};

// TODO: Pack this efficiently
Struct(V_Particle)
{
  u32 emitter_init_num;  // if != 0, then initialize using emitter at index [emitter_init_num - 1]
  u32 seq;

  V_ParticleFlag flags;

  Vec2 pos;
  Vec2 velocity;

  f32 exists;
  f32 lifetime;

  f32 velocity_falloff;
  Vec4 color;
};

#if IsLanguageC
  Struct(V_EmitterNode)
  {
    V_EmitterNode *next;
    V_Emitter emitter;
  };
#endif

////////////////////////////////////////////////////////////
//~ Quad types

Enum(V_QuadFlag)
{
  V_QuadFlag_None = 0,
};

Struct(V_Quad)
{
  V_QuadFlag flags;
  Affine to_shade_af;
  G_Texture2DRef tex;
  Rng2 uv_rect;
};

////////////////////////////////////////////////////////////
//~ Debug vert types

Struct(V_DVert)
{
  Vec2 pos;
  Vec4 color_lin;
};


////////////////////////////////////////////////////////////
//~ Helpers

#define V_ThreadGroupSizeFromBufferSize(buffer_size) VEC3I32((((buffer_size) + 63) / 64), 1, 1)
#define V_ThreadGroupSizeFromTexSize(tex_size) VEC3I32(((tex_size).x + 7) / 8, ((tex_size).y + 7) / 8, 1)