module Render.Debug.Pipeline
  ( Pipeline
  , allocate
  , Mode(..)
  ) where

import RIO

import Control.Monad.Trans.Resource (ResourceT)
import Data.Tagged (Tagged(..))
import Vulkan.Core10 qualified as Vk

import Engine.Vulkan.Pipeline qualified as Pipeline
import Engine.Vulkan.Shader qualified as Shader
import Engine.Vulkan.Types (HasVulkan, HasRenderPass(..), DsBindings)
import Render.Code (compileVert, compileFrag, glsl)
import Render.Debug.Model qualified as Model
import Render.DescSets.Set0 (Scene, vertexPos, instanceTransform)
import Render.DescSets.Set0.Code (set0binding0, set0binding1, set0binding2, set0binding3, set0binding5color)

type Pipeline = Pipeline.Pipeline '[Scene] Model.VertexAttrs Model.InstanceAttrs

data Mode
  = UV
  | Texture
  | Shadow Word32
  deriving (Eq, Ord, Show)

instance Shader.Specialization Mode where
  specializationData = \case
    UV ->
      [0]
    Texture ->
      [1]
    Shadow bits ->
      [2, bits]

allocate
  :: ( HasVulkan env
     , HasRenderPass renderpass
     )
  => Mode
  -> Vk.SampleCountFlagBits
  -> Tagged Scene DsBindings
  -> renderpass
  -> ResourceT (RIO env) Pipeline
allocate mode multisample (Tagged set0) = do
  fmap snd . Pipeline.allocate Nothing multisample config
  where
    config = Pipeline.baseConfig
      { Pipeline.cDescLayouts    = Tagged @'[Scene] [set0]
      , Pipeline.cVertexCode     = Just vertCode
      , Pipeline.cVertexInput    = vertexInput
      , Pipeline.cFragmentCode   = Just fragCode
      , Pipeline.cSpecialization = mode
      }

    vertexInput = Pipeline.vertexInput
      [ vertexPos -- vPosition
      , (Vk.VERTEX_INPUT_RATE_VERTEX,   Model.vkVertexAttrs)
      , (Vk.VERTEX_INPUT_RATE_INSTANCE, Model.vkInstanceTexture)
      , instanceTransform
      ]

vertCode :: ByteString
vertCode =
  $(compileVert [glsl|
    #version 450
    #extension GL_ARB_separate_shader_objects : enable

    ${set0binding0}

    // vertexPos
    layout(location = 0) in vec3 vPosition;
    // vertexAttrs
    layout(location = 1) in vec2 vTexCoord;
    // textureParams
    layout(location = 2) in  vec4 iTextureScaleOffset;
    layout(location = 3) in  vec4 iTextureGamma;
    layout(location = 4) in ivec2 iTextureIds;

    // transformMat
    layout(location = 5) in mat4 iModel;

    layout(location = 0)      out  vec2 fTexCoord;
    layout(location = 1) flat out  vec4 fTextureGamma;
    layout(location = 2) flat out ivec2 fTextureIds;

    void main() {
      vec4 fPosition = iModel * vec4(vPosition, 1.0);

      gl_Position
        = scene.projection
        * scene.view
        * fPosition;

      fTexCoord     = vTexCoord * iTextureScaleOffset.st + iTextureScaleOffset.pq;
      fTextureGamma = iTextureGamma;
      fTextureIds   = iTextureIds;
    }
  |])

fragCode :: ByteString
fragCode =
  $(compileFrag [glsl|
    #version 450
    #extension GL_ARB_separate_shader_objects : enable
    #extension GL_EXT_nonuniform_qualifier : enable

    ${set0binding1}
    ${set0binding2}
    ${set0binding3}
    ${set0binding5color}

    layout(location = 0)      in  vec2 fTexCoord;
    layout(location = 1) flat in  vec4 fTextureGamma;
    layout(location = 2) flat in ivec2 fTextureIds;

    layout(location = 0) out vec4 oColor;

    layout (constant_id=0) const uint mode = 0;
    layout (constant_id=1) const uint shadow_mask = 0;

    void main() {
      vec4 texel = vec4(0);

      switch(mode) {
        case 0:
          texel = vec4(fTexCoord, 0, 1);
          break;

        case 1:
          if ((fTextureIds.t < 0) || (fTextureIds.s < 0)) break;

          texel = texture(
            sampler2D(
              textures[nonuniformEXT(fTextureIds.t)],
              samplers[nonuniformEXT(fTextureIds.s)]
            ),
            fTexCoord
          );
          break;

        case 2:
          float d0 = 1.0;
          if ((shadow_mask & 1) == 1)
            d0 = texture(
              shadowmaps,
              vec3(fTexCoord, 0.0)
            ).x;

          float d1 = 1.0;
          if ((shadow_mask & 2) == 2)
            d1 = texture(
              shadowmaps,
              vec3(fTexCoord, 1.0)
            ).x;

          float d2 = 1.0;
          if ((shadow_mask & 4) == 4)
            d2 = texture(
              shadowmaps,
              vec3(fTexCoord, 2.0)
            ).x;

          texel = vec4(1-d0, 1-d1, 1-d2, 1.0);
          break;

        default:
          break;
      }

      vec3 color = pow(texel.rgb, fTextureGamma.rgb);
      float combinedAlpha = texel.a * fTextureGamma.a;

      // XXX: premultiply alpha due to additive blending
      oColor = vec4(color * combinedAlpha, combinedAlpha);
    }
  |])