// Copyright (c) 2022 Dominic Masters
// 
// This software is released under the MIT License.
// https://opensource.org/licenses/MIT

#pragma once
#include "display/Texture.hpp"

namespace Dawn {
  class Material;

  enum ShaderParameterType {
    SHADER_PARAMETER_TYPE_MATRIX,
    SHADER_PARAMETER_TYPE_BOOLEAN,
    SHADER_PARAMETER_TYPE_COLOR,
    SHADER_PARAMETER_TYPE_VECTOR3,
    SHADER_PARAMETER_TYPE_TEXTURE
  };

  template<typename T>
  class IShader {
    public:
      /**
       * Attaches the supplied shader as the current shader.
       */
      virtual void bind() = 0;

      /**
       * Requested by the Material to set the default parameters of the shader.
       * Each parameter really should have a default value set so that there is
       * no nullptr's or other issues.
       * 
       * @param material Material to set the default parameters on to.
       */
      virtual void setDefaultParameters(Material &material) = 0;

      /**
       * Requested by the render pipeline (typically) to set global level (once
       * per frame) parameters.
       * 
       * @param projection Projection matrix of the current viewport.
       * @param view View matrix of the current viewport.
       */
      virtual void setGlobalParameters(
        glm::mat4 projection,
        glm::mat4 view
      ) = 0;

      /**
       * Requested by the render pipeline (typically) to set mesh-level params.
       * This may be performed multiple times per frame.
       * 
       * @param position Matrix of the position of the mesh.
       */
      virtual void setMeshParameters(glm::mat4 position) = 0;

      /**
       * Retreives the list of all parameters that the shader supports. This 
       * should not include the GLOBAL shader parameters (listed above) since 
       * those will be modified by the engine directly.
       * 
       * @return Key-Value-Pair of Shader parameters and their type.
       */
      virtual std::map<T, enum ShaderParameterType> getParameters() = 0;

      /**
       * Set's a specific shader parameter to a matrix.
       * 
       * @param parameter parameter on the shader to set.
       * @param matrix Matrix to apply.
       */
      virtual void setMatrix(T parameter, glm::mat4 matrix) = 0;

      /**
       * Attaches a boolean to a shader.
       * 
       * @param parameter parameter to set.
       * @param value Value to set.
       */
      virtual void setBoolean(T parameter, bool_t value) = 0;

      /**
       * Set a color on to the shader.
       * 
       * @param parameter parameter to set the color to.
       * @param color Color to set.
       */
      virtual void setColor(T parameter, struct Color color) = 0;

      /**
       * Set a 3D vector on to the shader.
       * 
       * @param parameter parameter to set the vector to.
       * @param vector Vector to set.
       */
      virtual void setVector3(T parameter, glm::vec3 vector) = 0;

      /**
       * Attaches a texture to the currently bound shader.
       * 
       * @param parameter parameter to set the texture on to.
       * @param texture Texture to bind to the parameter.
       */
      virtual void setTexture(T parameter, std::shared_ptr<Texture> texture)=0;
  };
}