#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>

GLFWwindow* StartGLU();
void CreateVBOVAO(GLuint& VAO, GLuint& VBO, const float* vertices, size_t vertexCount);
GLuint CreateShaderProgram(const char* vertexSource, const char* fragmentSource);

const char* vertexShaderSource = R"glsl(
    #version 330 core
    layout (location = 0) in vec3 aPos;
    void main() {
        gl_Position = vec4(aPos, 1.0);
    }
)glsl";

const char* fragmentShaderSource = R"glsl(
    #version 330 core
    out vec4 FragColor;
    void main() {
        FragColor = vec4(1.0, 0.5, 0.2, 1.0); // Orange color
    }
)glsl";

int main() {
    GLFWwindow* window = StartGLU();
    GLuint shaderProgram = CreateShaderProgram(vertexShaderSource, fragmentShaderSource);

    //vertex data
    float vertices[] = {
        -0.5f, -0.5f, 0.0f, // Bottom left
         0.5f, -0.5f, 0.0f, // Bottom right
         0.0f,  0.5f, 0.0f  // Top center
    };

    // Create VAO and VBO
    GLuint VAO, VBO;
    CreateVBOVAO(VAO, VBO, vertices, sizeof(vertices) / sizeof(float));

    while (!glfwWindowShouldClose(window)) {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glUseProgram(shaderProgram);

        glBindVertexArray(VAO);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteProgram(shaderProgram);

    glfwTerminate();
    return 0;
}

GLFWwindow* StartGLU() {
    if (!glfwInit()) {
        std::cout << "Failed to initialize GLFW, panic" << std::endl;
        return nullptr;
    }
    GLFWwindow* window = glfwCreateWindow(800, 600, "3D_TEST", NULL, NULL);
    if (!window) {
        std::cerr << "Failed to create GLFW window." << std::endl;
        glfwTerminate();
        return nullptr;
    }
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK) {
        std::cerr << "Failed to initialize GLEW." << std::endl;
        glfwTerminate();
        return nullptr;
    }

    glEnable(GL_DEPTH_TEST);

    return window;
}

GLuint CreateShaderProgram(const char* vertexSource, const char* fragmentSource) {
    // Vertex shader
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexSource, nullptr);
    glCompileShader(vertexShader);

    GLint success;
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        char infoLog[512];
        glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
        std::cerr << "Vertex shader compilation failed: " << infoLog << std::endl;
    }

    // Fragment shader
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentSource, nullptr);
    glCompileShader(fragmentShader);

    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        char infoLog[512];
        glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
        std::cerr << "Fragment shader compilation failed: " << infoLog << std::endl;
    }

    // Shader program
    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);

    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        char infoLog[512];
        glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
        std::cerr << "Shader program linking failed: " << infoLog << std::endl;
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    return shaderProgram;
}

void CreateVBOVAO(GLuint& VAO, GLuint& VBO, const float* vertices, size_t vertexCount) {
    //VAO
    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    //VBO
    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, vertexCount * sizeof(float), vertices, GL_STATIC_DRAW);

    //vertex attribute pointers
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glBindVertexArray(0);
}