#ifndef SHADER_CPP
#define SHADER_CPP
#include <glad/glad.h>
#include <fstream>
#include "shader.hpp"
#include "misc.hpp"

unsigned int Shader::linkShaderObjectsShaderProgram(const unsigned int vertexShaders, const unsigned int fragmentShader) const
{
    // link shader objects into shader program
    // will store shader program id
    // creates program
    const unsigned int shaderProgram = glCreateProgram();

    // attachShaders
    glAttachShader(shaderProgram, vertexShaders);
    glAttachShader(shaderProgram, fragmentShader);

    // link shaders
    glLinkProgram(shaderProgram);
    if (!shaderSuccessful(shaderProgram, false))
        return 0;

    // delete shaders (they are linked into shaderProgram and we do not need them anymore)
    glDeleteShader(vertexShaders);
    glDeleteShader(fragmentShader);
    if (shaderProgram == 0)
        print("Shader Program Linking Failed");
    return shaderProgram;
}

unsigned int Shader::compileShader(const GLenum shaderType, const char *shaderSource) const
{
    // we create vertex shader and assign its id to shader variable
    const unsigned int shaderID = glCreateShader(shaderType);

    // attach shader source code to shader object
    // from left: shader object to compile, how many strings as source code, actual source code (we leave the 4th as NULL)
    glShaderSource(shaderID, 1, &shaderSource, NULL);
    // compile shader
    glCompileShader(shaderID);
    if (!shaderSuccessful(shaderID, true))
        return 0;
    return shaderID;
}

const char* Shader::getSourceCode(const std::string_view sourcePath) const
{
    // 1. retrieve the vertex/fragment source code from filePath
    std::string sourceCode;
    std::ifstream sourceFile;
    // ensure ifstream objects can throw exceptions:
    sourceFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
    try 
    {
        sourceCode = fileBufferToString(sourcePath, sourceFile);	
    }
    // https://stackoverflow.com/a/62030396
    catch(std::ifstream::failure const& e)
    {
        std::cerr << "ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ for sourcePath: " << sourcePath << std::endl;
    }
    const char* cSourceCode = sourceCode.c_str();
    return cSourceCode;
}

void Shader::use() 
{ 
    glUseProgram(ID);
}  

void Shader::setBool(const std::string_view &name, const bool value) const
{         
    const int vertexColorLocation = glGetUniformLocation(ID, name.c_str());
    if(vertexColorLocation != -1) {
        glUniform1i(vertexColorLocation, (int)value); 
    }
}

void Shader::setInt(const std::string_view &name, const int value) const
{ 
    const int vertexColorLocation = glGetUniformLocation(ID, name.c_str());
    if(vertexColorLocation != -1) {
        glUniform1i(vertexColorLocation, value); 
    }
}

void Shader::setFloat(const std::string_view  &name, const float value) const
{ 
    const int vertexColorLocation = glGetUniformLocation(ID, name.c_str());
    if(vertexColorLocation != -1) {
        glUniform1f(vertexColorLocation, value); 
    }
} 



Shader::Shader(const std::string_view vertexPath, const std::string_view fragmentPath)
{
    const char* vShaderCode = getSourceCode(vertexPath);
    const char* fShaderCode = getSourceCode(fragmentPath);
    const int vectorShaderID = compileShader(GL_VERTEX_SHADER, vShaderCode);
    const int fragmentShaderID = compileShader(GL_FRAGMENT_SHADER, fShaderCode);
    ID = linkShaderObjectsShaderProgram(vectorShaderID, fragmentShaderID);
}

#endif // SHADER_CPP