shader.hpp

// SPDX-License-Identifier: MIT
// Author:  Giovanni Santini
// Mail:    giovanni.santini@proton.me
// Github:  @San7o
 
#pragma once
 
#include <algorithm>
#include <brenta/logger.hpp>
#include <fstream>
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>
#include <sstream>
#include <string>
#include <unordered_map>
#include <vector>
 
namespace brenta
{
 
class shader
{
public:
 
  using name_t = std::string;
 
  enum type
  {
    vertex,
    fragment,
    geometry,
    compute,
  };
  
  static std::unordered_map<shader::name_t, unsigned int> shaders;
 
  template <typename... Args>
  static bool create(const std::string &shader_name,
                     shader::type type, const std::string &path,
                     Args... args)
  {
    std::vector<unsigned int> compiled_shaders = {};
    if (!compile_shaders(compiled_shaders, type, path, args...))
    {
      ERROR("shader: error compiling shader {}", path);
      return false;
    }
 
    /* shader Program */
    unsigned int ID = glCreateProgram();
    std::for_each(compiled_shaders.begin(), compiled_shaders.end(),
                  [&ID](auto shader) { glAttachShader(ID, shader); });
 
    glLinkProgram(ID);
    if (!shader::check_compile_errors(ID, "PROGRAM"))
    {
      return false;
    }
 
    shader::shaders.insert({shader_name, ID});
    std::for_each(compiled_shaders.begin(), compiled_shaders.end(),
                  [](auto shader) { glDeleteShader(shader); });
    return true;
  }
 
  template <typename... Args>
  static bool create(const GLchar **feedback_varyings, int num_varyings,
                     const std::string &shader_name,
                     shader::type type, const std::string &path,
                     Args... args)
  {
    std::vector<unsigned int> compiled_shaders = {};
    if (!compile_shaders(compiled_shaders, type, path, args...))
    {
      ERROR("shader: error compiling shader {}", path)
      return false;
    }
 
    /* shader Program */
    unsigned int ID = glCreateProgram();
    std::for_each(compiled_shaders.begin(), compiled_shaders.end(),
                  [&ID](auto shader) { glAttachShader(ID, shader); });
 
    if (feedback_varyings != nullptr)
    {
      glTransformFeedbackVaryings(ID, num_varyings, feedback_varyings,
                                  GL_INTERLEAVED_ATTRIBS);
    }
 
    glLinkProgram(ID);
    if (!shader::check_compile_errors(ID, "PROGRAM"))
    {
      return false;
    }
 
    shader::shaders.insert({shader_name, ID});
    std::for_each(compiled_shaders.begin(), compiled_shaders.end(),
                  [](auto shader) { glDeleteShader(shader); });
 
    return true;
  }
 
  static bool
  compile_shaders([[maybe_unused]] std::vector<unsigned int> &compiled)
  {
    return true;
  }
 
  template <typename... Args>
  static bool compile_shaders(std::vector<unsigned int> &compiled,
                              shader::type type, const std::string &path,
                              Args... args)
  {
    std::string code;
    std::ifstream file;
    file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
 
    try
    {
      file.open(path);
      if (!file.is_open()) throw "Cannot open file";
      std::stringstream stream;
      stream << file.rdbuf();
      file.close();
      code = stream.str();
    }
    catch (std::ifstream::failure &e)
    {
      ERROR("shader: error reading shader file: {}", path);
      return false;
    }
 
    if (code.empty())
    {
      ERROR("shader: file is empty: {}", path);
      return false;
    }
 
    const char *shader_code = code.c_str();
    
    GLenum shader_type_gl;
    switch(type)
    {
    case fragment: shader_type_gl = GL_FRAGMENT_SHADER; break;
    case vertex: shader_type_gl = GL_VERTEX_SHADER; break;
    case geometry: shader_type_gl = GL_GEOMETRY_SHADER; break;
    case compute: shader_type_gl = GL_COMPUTE_SHADER; break;
    default: shader_type_gl = 0; break;
    }
    
    unsigned int shader = glCreateShader(shader_type_gl);
    glShaderSource(shader, 1, &shader_code, NULL);
    glCompileShader(shader);
    if (!shader::check_compile_errors(shader, "SHADER"))
    {
      return false;
    }
 
    compiled.push_back(shader);
    return compile_shaders(compiled, args...);
  }
 
  static unsigned int get_id(shader::name_t shader_name);
 
  static bool use(shader::name_t shader_name);
 
  // Utility uniform functions
 
  static bool set_bool(shader::name_t shader_name,
                       const GLchar *name, bool value);
  static bool set_int(shader::name_t shader_name, const GLchar *name,
                      int value);
  static bool set_float(shader::name_t shader_name,
                        const GLchar *name, float value);
  static bool set_mat4(shader::name_t shader_name, const GLchar *name,
                       glm::mat4 value);
  static bool set_vec3(shader::name_t shader_name, const GLchar *name,
                       float x, float y, float z);
  static bool set_vec3(shader::name_t shader_name, const GLchar *name,
                       glm::vec3 value);
 
private:
  
  static bool check_compile_errors(unsigned int shader, std::string type);
  
};
 
} // namespace brenta