--- a/src/vertex.nim	Fri Dec 30 15:56:17 2022 +0700
+++ b/src/vertex.nim	Sun Jan 01 01:00:50 2023 +0700
@@ -1,5 +1,179 @@
+import std/macros
+import std/strutils
+import std/strformat
+import std/typetraits
+
+import ./math/vector
+import ./vulkan
+
 type
-  VertexAttribute = object
+  VertexAttributeType = SomeNumber|Vec
+  VertexAttribute*[T:VertexAttributeType] = object
+
+
+# from https://registry.khronos.org/vulkan/specs/1.3-extensions/html/chap15.html
+func nLocationSlots[T: VertexAttributeType](): int =
+  when (T is Vec3[float64] or T is Vec3[uint64] or T is Vec4[float64] or T is Vec4[float64]):
+    2
+  else:
+    1
+
+# numbers
+func getVkFormat[T: VertexAttributeType](): VkFormat =
+  when T is uint8:         VK_FORMAT_R8_UINT
+  elif T is int8:          VK_FORMAT_R8_SINT
+  elif T is uint16:        VK_FORMAT_R16_UINT
+  elif T is int16:         VK_FORMAT_R16_SINT
+  elif T is uint32:        VK_FORMAT_R32_UINT
+  elif T is int32:         VK_FORMAT_R32_SINT
+  elif T is uint64:        VK_FORMAT_R64_UINT
+  elif T is int64:         VK_FORMAT_R64_SINT
+  elif T is float32:       VK_FORMAT_R32_SFLOAT
+  elif T is float64:       VK_FORMAT_R64_SFLOAT
+  elif T is Vec2[uint8]:   VK_FORMAT_R8G8_UINT
+  elif T is Vec2[int8]:    VK_FORMAT_R8G8_SINT
+  elif T is Vec2[uint16]:  VK_FORMAT_R16G16_UINT
+  elif T is Vec2[int16]:   VK_FORMAT_R16G16_SINT
+  elif T is Vec2[uint32]:  VK_FORMAT_R32G32_UINT
+  elif T is Vec2[int32]:   VK_FORMAT_R32G32_SINT
+  elif T is Vec2[uint64]:  VK_FORMAT_R64G64_UINT
+  elif T is Vec2[int64]:   VK_FORMAT_R64G64_SINT
+  elif T is Vec2[float32]: VK_FORMAT_R32G32_SFLOAT
+  elif T is Vec2[float64]: VK_FORMAT_R64G64_SFLOAT
+  elif T is Vec3[uint8]:   VK_FORMAT_R8G8B8_UINT
+  elif T is Vec3[int8]:    VK_FORMAT_R8G8B8_SINT
+  elif T is Vec3[uint16]:  VK_FORMAT_R16G16B16_UINT
+  elif T is Vec3[int16]:   VK_FORMAT_R16G16B16_SINT
+  elif T is Vec3[uint32]:  VK_FORMAT_R32G32B32_UINT
+  elif T is Vec3[int32]:   VK_FORMAT_R32G32B32_SINT
+  elif T is Vec3[uint64]:  VK_FORMAT_R64G64B64_UINT
+  elif T is Vec3[int64]:   VK_FORMAT_R64G64B64_SINT
+  elif T is Vec3[float32]: VK_FORMAT_R32G32B32_SFLOAT
+  elif T is Vec3[float64]: VK_FORMAT_R64G64B64_SFLOAT
+  elif T is Vec4[uint8]:   VK_FORMAT_R8G8B8A8_UINT
+  elif T is Vec4[int8]:    VK_FORMAT_R8G8B8A8_SINT
+  elif T is Vec4[uint16]:  VK_FORMAT_R16G16B16A16_UINT
+  elif T is Vec4[int16]:   VK_FORMAT_R16G16B16A16_SINT
+  elif T is Vec4[uint32]:  VK_FORMAT_R32G32B32A32_UINT
+  elif T is Vec4[int32]:   VK_FORMAT_R32G32B32A32_SINT
+  elif T is Vec4[uint64]:  VK_FORMAT_R64G64B64A64_UINT
+  elif T is Vec4[int64]:   VK_FORMAT_R64G64B64A64_SINT
+  elif T is Vec4[float32]: VK_FORMAT_R32G32B32A32_SFLOAT
+  elif T is Vec4[float64]: VK_FORMAT_R64G64B64A64_SFLOAT
+
+func getGLSLType[T: VertexAttributeType](): string =
+  # todo: likely not correct as we would need to enable some 
+  # extensions somewhere (Vulkan/GLSL compiler?) to have 
+  # everything work as intended. Or maybe the GPU driver does
+  # some automagic conversion stuf..
+  when T is uint8:         "uint"
+  elif T is int8:          "int"
+  elif T is uint16:        "uint"
+  elif T is int16:         "int"
+  elif T is uint32:        "uint"
+  elif T is int32:         "int"
+  elif T is uint64:        "uint"
+  elif T is int64:         "int"
+  elif T is float32:       "float"
+  elif T is float64:       "double"
+
+  elif T is Vec2[uint8]:   "uvec2"
+  elif T is Vec2[int8]:    "ivec2"
+  elif T is Vec2[uint16]:  "uvec2"
+  elif T is Vec2[int16]:   "ivec2"
+  elif T is Vec2[uint32]:  "uvec2"
+  elif T is Vec2[int32]:   "ivec2"
+  elif T is Vec2[uint64]:  "uvec2"
+  elif T is Vec2[int64]:   "ivec2"
+  elif T is Vec2[float32]: "vec2"
+  elif T is Vec2[float64]: "dvec2"
 
-  VertexType = object
+  elif T is Vec3[uint8]:   "uvec3"
+  elif T is Vec3[int8]:    "ivec3"
+  elif T is Vec3[uint16]:  "uvec3"
+  elif T is Vec3[int16]:   "ivec3"
+  elif T is Vec3[uint32]:  "uvec3"
+  elif T is Vec3[int32]:   "ivec3"
+  elif T is Vec3[uint64]:  "uvec3"
+  elif T is Vec3[int64]:   "ivec3"
+  elif T is Vec3[float32]: "vec3"
+  elif T is Vec3[float64]: "dvec3"
+
+  elif T is Vec4[uint8]:   "uvec4"
+  elif T is Vec4[int8]:    "ivec4"
+  elif T is Vec4[uint16]:  "uvec4"
+  elif T is Vec4[int16]:   "ivec4"
+  elif T is Vec4[uint32]:  "uvec4"
+  elif T is Vec4[int32]:   "ivec4"
+  elif T is Vec4[uint64]:  "uvec4"
+  elif T is Vec4[int64]:   "ivec4"
+  elif T is Vec4[float32]: "vec4"
+  elif T is Vec4[float64]: "dvec4"
+
+template rawAttributeType(v: VertexAttribute): auto = get(genericParams(typeof(v)), 0)
+
+func generateGLSL[T](): string =
+  var stmtList: seq[string]
+  var i = 0
+  for name, value in T().fieldPairs:
+    when typeof(value) is VertexAttribute:
+      let glsltype = getGLSLType[rawAttributeType(value)]()
+      let n = name
+      stmtList.add(&"layout(location = {i}) in {glsltype} {n};")
+      i += nLocationSlots[rawAttributeType(value)]()
+
+  return stmtList.join("\n")
 
+func generateInputVertexBinding*[T](bindingoffset: int = 0, locationoffset: int = 0): seq[VkVertexInputBindingDescription] =
+  # packed attribute data, not interleaved (aks "struct of arrays")
+  var binding = bindingoffset
+  for name, value in T().fieldPairs:
+    when typeof(value) is VertexAttribute:
+      result.add(
+        VkVertexInputBindingDescription(
+          binding: uint32(binding),
+          stride: uint32(sizeof(rawAttributeType(value))),
+          inputRate: VK_VERTEX_INPUT_RATE_VERTEX, # VK_VERTEX_INPUT_RATE_INSTANCE for instances
+        )
+      )
+      binding += 1
+
+func generateInputAttributeBinding*[T](bindingoffset: int = 0, locationoffset: int = 0): seq[VkVertexInputAttributeDescription] =
+  # packed attribute data, not interleaved (aks "struct of arrays")
+  var location = 0
+  var binding = bindingoffset
+  for name, value in T().fieldPairs:
+    when typeof(value) is VertexAttribute:
+      result.add(
+        VkVertexInputAttributeDescription(
+          binding: uint32(binding),
+          location: uint32(location),
+          format: getVkFormat[rawAttributeType(value)](),
+          offset: 0,
+        )
+      )
+      location += nLocationSlots[rawAttributeType(value)]()
+      binding += 1
+
+func getBindingDescription(binding: int): auto =
+  VkVertexInputBindingDescription(
+    binding: uint32(binding),
+    stride: 0, # either sizeof of vertex (array of structs) or of attribute (struct of arrays)
+    inputRate: VK_VERTEX_INPUT_RATE_VERTEX, # VK_VERTEX_INPUT_RATE_INSTANCE for instances
+  )
+
+func getAttributeDescriptions(binding: int): auto =
+  [
+    VkVertexInputAttributeDescription(
+      binding: 0'u32,
+      location: 0,
+      format: VK_FORMAT_R32G32_SFLOAT,
+      offset: 0,
+    ),
+    VkVertexInputAttributeDescription(
+      binding: 0'u32,
+      location: 1,
+      format: VK_FORMAT_R32G32B32_SFLOAT,
+      offset: uint32(sizeof(Vec2)), # use offsetOf?
+    ),
+  ]