// Shader.cpp
#include "Shader.h"
#include <fstream>
#include <sstream>
#include <iostream>
#include <filesystem> // C++17 feature for file existence

namespace fs = std::filesystem;

Shader::Shader(const char* vertexPath, const char* fragmentPath)
{
    // 1. Retrieve the vertex/fragment source code from filePath
    std::string vertexCode;
    std::string fragmentCode;
    std::ifstream vShaderFile;
    std::ifstream fShaderFile;

    // Check if shader files exist
    if (!fs::exists(vertexPath)) {
        std::cerr << "ERROR::SHADER::VERTEX_SHADER_FILE_NOT_FOUND: " << vertexPath << "\n";
        return;
    }
    if (!fs::exists(fragmentPath)) {
        std::cerr << "ERROR::SHADER::FRAGMENT_SHADER_FILE_NOT_FOUND: " << fragmentPath << "\n";
        return;
    }

    // Ensure ifstream objects can throw exceptions:
    vShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
    fShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
    try 
    {
        // Open files
        vShaderFile.open(vertexPath);
        fShaderFile.open(fragmentPath);
        std::stringstream vShaderStream, fShaderStream;
        
        // Read file's buffer contents into streams
        vShaderStream << vShaderFile.rdbuf();
        fShaderStream << fShaderFile.rdbuf();		

        // Close file handlers
        vShaderFile.close();
        fShaderFile.close();

        // Convert stream into string
        vertexCode = vShaderStream.str();
        fragmentCode = fShaderStream.str();			
    }
    catch (std::ifstream::failure& e)
    {
        std::cerr << "ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ\n";
        std::cerr << "Failed to read shader files: " << vertexPath << " and " << fragmentPath << "\n";
        return;
    }
    const char* vShaderCode = vertexCode.c_str();
    const char * fShaderCode = fragmentCode.c_str();

    // 2. Compile shaders
    GLuint vertex, fragment;
    GLint success;
    GLchar infoLog[1024];

    // Vertex Shader
    vertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex, 1, &vShaderCode, NULL);
    glCompileShader(vertex);
    // Print compile errors if any
    glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(vertex, 1024, NULL, infoLog);
        std::cerr << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << "\n";
    }

    // Fragment Shader
    fragment = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment, 1, &fShaderCode, NULL);
    glCompileShader(fragment);
    // Print compile errors if any
    glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(fragment, 1024, NULL, infoLog);
        std::cerr << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << "\n";
    }

    // Shader Program
    ID = glCreateProgram();
    glAttachShader(ID, vertex);
    glAttachShader(ID, fragment);
    glLinkProgram(ID);
    // Print linking errors if any
    glGetProgramiv(ID, GL_LINK_STATUS, &success);
    if(!success)
    {
        glGetProgramInfoLog(ID, 1024, NULL, infoLog);
        std::cerr << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << "\n";
    }

    // Delete the shaders as they're linked into our program now and no longer necessary
    glDeleteShader(vertex);
    glDeleteShader(fragment);
}



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

void Shader::SetBool(const std::string &name, bool value) const
{         
    glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value); 
}

void Shader::SetInt(const std::string &name, int value) const
{ 
    glUniform1i(glGetUniformLocation(ID, name.c_str()), value); 
}

void Shader::SetFloat(const std::string &name, float value) const
{ 
    glUniform1f(glGetUniformLocation(ID, name.c_str()), value); 
}

void Shader::SetVec3(const std::string &name, const glm::vec3 &value) const
{ 
    glUniform3fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]); 
}

void Shader::SetMat4(const std::string &name, const glm::mat4 &mat) const
{
    glUniformMatrix4fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}