#include <cstdio>
#include "../include/RenderBackend/OpenGL/opengl.hpp"
#include "../include/RenderBackend/OpenGL/Shader.hpp"
#include "../include/RenderBackend/OpenGL/ShaderProgram.hpp"
#include "../include/RenderBackend/OpenGL/DeviceMemory.hpp"
#include "../include/RenderBackend/OpenGL/DeviceFrame.hpp"
#include "../include/Triangle2D.hpp"

// TODO: Disallow shader variables that begin with "gl_" as reserved variables
// start with that. What about hlsl?

// TODO: Creating buffers etc should be somehow created/drawn using the window object, since they are associated with the window
// opengl context

using namespace amalgine;
using namespace std;

static void glfwErrorHandler(int errorCode, const char *errorDescription);
static void initGlfw();
static void initGlew();
static GLFWwindow *createWindow();
static std::unique_ptr<Shader> load_shader_from_file(const char *filepath, Shader::Type shader_type);

int main()
{
    initGlfw();
    glfwSetErrorCallback(glfwErrorHandler);
    GLFWwindow *window = createWindow();
    
    DeviceFrame frame;
    
    Triangle2D cpuTriangle(
        Vertex2D(0.0f, 0.5f),
        Vertex2D(0.5f, -0.5f),
        Vertex2D(-0.5f, -0.5f)
    );
    DataView<Triangle2D> cpuTriangles(&cpuTriangle, 1);
    DeviceMemory *gpuTriangle = frame.alloc();
    gpuTriangle->copy(cpuTriangles, DeviceMemory::StorageType::STATIC);

    std::unique_ptr<Shader> vertex_shader = load_shader_from_file("shaders/vertex.vert", Shader::Type::VERTEX);
    std::unique_ptr<Shader> pixel_shader = load_shader_from_file("shaders/fragment.frag", Shader::Type::PIXEL);
    
    Result<std::unique_ptr<ShaderProgram>> shader_program_result = ShaderProgram::build({ vertex_shader.get(), pixel_shader.get() });
    if(!shader_program_result) {
        fprintf(stderr, "Failed to link shaders, error: %s\n", shader_program_result.getErrorMsg().c_str());
        exit(13);
    }
    std::unique_ptr<ShaderProgram> shader_program = std::move(shader_program_result.unwrap());
    
    shader_program->set_vertex_input("position", *gpuTriangle);
    shader_program->set_uniform("triangle_color", vec3f{ 1.0f, 0.0f, 0.0f });
    
    while(!glfwWindowShouldClose(window))
    {
        glfwPollEvents();
        if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
            glfwSetWindowShouldClose(window, GL_TRUE);

        // Set color for clearing
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        // Do the actual screen clearing, using the color set using glClearColor
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        frame.draw(shader_program.get());
        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}

void glfwErrorHandler(int errorCode, const char *errorDescription)
{
    printf("GLFW error code: %d, description: %s\n", errorCode, errorDescription);
}

void initGlfw()
{
    if(!glfwInit())
    {
        fprintf(stderr, "Failed to initialize GLFW\n");
        exit(-1);
    }

    glfwWindowHint(GLFW_SAMPLES, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 5);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
}

void initGlew()
{
    glewExperimental = true;
    if(glewInit() != GLEW_OK)
    {
        fprintf(stderr, "Failed to initialize GLEW\n");
        glfwTerminate();
        exit(-1);
    }
}

GLFWwindow* createWindow()
{
    GLFWwindow *window = glfwCreateWindow(1280, 720, "Amalgine", nullptr, nullptr);
    if(!window)
    {
        fprintf(stderr, "Failed to open GLFW window\n");
        glfwTerminate();
        exit(10);
    }

    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    glfwMakeContextCurrent(window);
    glfwSwapInterval(0);
    initGlew();
    return window;
}

static int file_read_all(const char *filepath, std::string &result) {
    FILE *file = fopen(filepath, "rb");
    if(!file) {
        perror("file_read_all");
        return errno;
    }

    fseek(file, 0, SEEK_END);
    size_t file_size = ftell(file);
    fseek(file, 0, SEEK_SET);
    result.resize(file_size);
    fread(&result[0], 1, result.size(), file);
    fclose(file);
    return 0;
}

std::unique_ptr<Shader> load_shader_from_file(const char *filepath, Shader::Type shader_type) {
    std::string file_content;
    if(file_read_all(filepath, file_content) != 0)
        exit(13);

    Result<std::unique_ptr<Shader>> vertex_shader_result = Shader::compile(shader_type, file_content.data(), file_content.size());
    if(!vertex_shader_result) {
        fprintf(stderr, "Failed to compile shader, error: %s\n", vertex_shader_result.getErrorMsg().c_str());
        exit(12);
    }
    return std::move(vertex_shader_result.unwrap());
}