// Copyright (c) 2023 Dominic Masters
// 
// This software is released under the MIT License.
// https://opensource.org/licenses/MIT

#include "SimpleBillboardedShader.hpp"
#include "scene/components/display/mesh/MeshRenderer.hpp"
#include "scene/components/display/Camera.hpp"

using namespace Dawn;

void SimpleBillboardedShaderProgram::compile() {
  #if DAWN_OPENGL_GLSL
    this->compileShader(
      {
        { "aPos", 0 },
        { "aTexCoord", 1 }
      },
      // Vertex Shader
      "#version 330 core\n"
      "layout (location = 0) in vec3 aPos;\n"
      "layout (location = 1) in vec2 aTexCoord;\n"

      "uniform mat4 u_Proj;\n"
      "uniform mat4 u_View;\n"
      "uniform mat4 u_Model;\n"

      "out vec2 o_TextCoord;\n"
      "void main() {\n"
        "vec3 camRight = vec3(u_View[0][0], u_View[1][0], u_View[2][0]);\n"
        "vec3 camUp = vec3(u_View[0][1], u_View[1][1], u_View[2][1]);\n"
        "vec3 billboardPos = u_View[3].xyz + aPos.x * camRight + aPos.y * camUp;\n"
        "gl_Position = u_Proj * u_View * u_Model * vec4(billboardPos, 1.0);\n"
        "o_TextCoord = vec2(aTexCoord.x, aTexCoord.y);\n"
      "}",

      // Fragment Shader
      "#version 330 core\n"
      "in vec2 o_TextCoord;\n"
      "out vec4 o_Color;\n"
      "uniform vec4 u_Color;\n"
      "uniform bool u_HasTexture;\n"
      "uniform sampler2D u_Text;\n"

      "void main() {\n"
        "if(u_HasTexture) {\n"
          "o_Color = texture(u_Text, o_TextCoord) * u_Color;\n"
        "} else {\n"
          "o_Color = u_Color;"
        "}\n"
      "}\n"
    );
  #endif

  this->paramProjection = this->getParameterByName("u_Proj");
  this->paramView = this->getParameterByName("u_View");
  this->paramModel = this->getParameterByName("u_Model");
  this->paramColor = this->getParameterByName("u_Color");
  this->paramTexture = this->getParameterByName("u_Text");
  this->paramHasTexture = this->getParameterByName("u_HasTexture");
}



void SimpleBillboardedShader::compile() {
  this->program.compile();
}

std::vector<struct ShaderPassItem> SimpleBillboardedShader::getPassItems(
  Mesh *mesh,
  Material *material,
  Camera *camera
) {
  auto simpleMaterial = dynamic_cast<SimpleBillboardedMaterial*>(material);
  assertNotNull(simpleMaterial);

  struct ShaderPassItem onlyPass;
  onlyPass.mesh = mesh;
  onlyPass.shaderProgram = &program;
  onlyPass.colorValues[program.paramColor] = simpleMaterial->color;
  onlyPass.matrixValues[program.paramModel] = material->transform->getWorldTransform();
  onlyPass.matrixValues[program.paramView] = camera->transform->getWorldTransform();
  onlyPass.matrixValues[program.paramProjection] = camera->getProjection();
  onlyPass.renderFlags = (
    RENDER_MANAGER_RENDER_FLAG_BLEND |
    RENDER_MANAGER_RENDER_FLAG_DEPTH_TEST
  );

  if(simpleMaterial->texture != nullptr) {
    onlyPass.boolValues[program.paramHasTexture] = true;
    onlyPass.textureSlots[0] = simpleMaterial->texture;
    onlyPass.textureValues[program.paramTexture] = 0;
  } else {
    onlyPass.boolValues[program.paramHasTexture] = false;
  }

  std::vector<struct ShaderPassItem> passes;
  passes.push_back(onlyPass);
  return passes;
}