#pragma once
 #include <stdio.h>
 
//GLSLクラス
 class GLSL{
 public:
  GLuint ShaderProg;
  GLuint VertexShader, FragmentShader;
  void ReadShaderCompile(GLuint Shader, const char *File);//shader fileを読み込みコンパイルする
  void Link( GLuint Prog );//リンクする
  void InitGLSL(const char *VertexFile);//GLSLの初期化
  void InitGLSL(const char *VertexFile, const char *FragmentFile);//GLSLの初期化
  void ON();//シェーダー描画に切り替え
  void OFF();//シェーダー解除
  ~GLSL();
 };
 
 void GLSL::ReadShaderCompile(GLuint Shader, const char *File){
    FILE *fp;
    char *buf;
    GLsizei size, len;
    GLint compiled;
 
    fopen_s(&fp,File, "rb");
    if(!fp) printf("ファイルを開くことができません %s\n", File);
 
    fseek(fp, 0, SEEK_END);
    size = ftell(fp);
 
   buf = (GLchar *)malloc(size);
    if (buf == NULL) {
      printf("メモリが確保できませんでした \n");
    }
 
    fseek(fp, 0, SEEK_SET);
    fread(buf, 1, size, fp);
    glShaderSource(Shader, 1, (const GLchar **)&buf, &size);
    free(buf);
    fclose(fp);
 
    glCompileShader(Shader);
    glGetShaderiv( Shader, GL_COMPILE_STATUS, &compiled );
 
   if ( compiled == GL_FALSE )
    {
     printf( "コンパイルできませんでした!!: %s \n ", File);
     glGetProgramiv( Shader, GL_INFO_LOG_LENGTH, &size );
     if ( size > 0 )
     {
      buf = (char *)malloc(size);
      glGetShaderInfoLog( Shader, size, &len, buf);
      printf(buf);
      free(buf);
     }
    }
  }
 
 void GLSL::Link( GLuint Prog ){
    GLsizei size, len;
    GLint linked;
    char *infoLog ;
 
   glLinkProgram( Prog );
 
   glGetProgramiv( Prog, GL_LINK_STATUS, &linked );
 
   if ( linked == GL_FALSE ){
    printf("リンクできませんでした!! \n");
    
    glGetProgramiv( Prog, GL_INFO_LOG_LENGTH, &size );
    if ( size > 0 ){
     infoLog = (char *)malloc(size);
     glGetProgramInfoLog( Prog, size, &len, infoLog );
     printf(infoLog);
     free(infoLog);
    }
   }
 }
 
void GLSL::InitGLSL(const char *VertexFile){
    GLenum err = glewInit();
    if (err != GLEW_OK)
    {
     printf("Error: %s\n", glewGetErrorString(err));
    }
    printf("VENDOR= %s \n", glGetString(GL_VENDOR));
    printf("GPU= %s \n", glGetString(GL_RENDERER));
    printf("OpenGL= %s \n", glGetString(GL_VERSION));
    printf("GLSL= %s \n", glGetString(GL_SHADING_LANGUAGE_VERSION));
    VertexShader = glCreateShader(GL_VERTEX_SHADER);
    ReadShaderCompile(VertexShader, VertexFile);
    ShaderProg = glCreateProgram();
    glAttachShader(ShaderProg, VertexShader);
    glDeleteShader(VertexShader);
    Link(ShaderProg);
  }
 
 
void GLSL::InitGLSL(const char *VertexFile, const char *FragmentFile){
    GLenum err = glewInit();
    if (err != GLEW_OK)
    {
     printf("Error: %s\n", glewGetErrorString(err));
    }
    printf("VENDOR= %s \n", glGetString(GL_VENDOR));
    printf("GPU= %s \n", glGetString(GL_RENDERER));
    printf("OpenGL= %s \n", glGetString(GL_VERSION));
    printf("GLSL= %s \n", glGetString(GL_SHADING_LANGUAGE_VERSION));
 
   VertexShader = glCreateShader(GL_VERTEX_SHADER);
    FragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
 
   ReadShaderCompile(VertexShader, VertexFile);
    ReadShaderCompile(FragmentShader, FragmentFile);
 
   ShaderProg = glCreateProgram();
 
    glAttachShader(ShaderProg, VertexShader);
    glAttachShader(ShaderProg, FragmentShader);
 
    glDeleteShader(VertexShader);
    glDeleteShader(FragmentShader);
    Link(ShaderProg);
  }
 
void GLSL::ON(){
  glUseProgram(ShaderProg);
 }
 
void GLSL::OFF(){
  glUseProgram(0);
 }
 
GLSL::~GLSL(){
  glDeleteProgram(ShaderProg);
 }