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A library for 2D OpenGL and OpenAL support based on LWJGL 3
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package io.github.mwttg.pixelartillery2d.graphic;

import org.lwjgl.glfw.GLFW;
import org.lwjgl.glfw.GLFWErrorCallback;
import org.lwjgl.glfw.GLFWKeyCallbackI;
import org.lwjgl.opengl.GL;
import org.lwjgl.opengl.GL41;
import org.lwjgl.system.MemoryUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/** This class is responsible for creating a game window. */
public final class GameWindow {

  private static final Logger LOG = LoggerFactory.getLogger(GameWindow.class);
  private static final int OPENGL_MAJOR_VERSION = 4;
  private static final int OPENGL_MINOR_VERSION = 1;

  private GameWindow() {}

  /**
   * Creates a window for all OpenGL operations (like rendering sprites).
   *
   * @param configuration the {@link OpenGlConfiguration} for the window
   * @return the OpenGL window ID
   */
  public static long create(final OpenGlConfiguration configuration) {
    LOG.info("create GameWindow with {}", configuration.prettyFormat());

    initializeGlfw();
    final var id = initializeGameWindow(configuration);
    OpenGlCleanUp.setGameWindowId(id);
    initializeKeyCallback(id);
    centerGameWindow(id, configuration);

    return id;
  }

  private static void initializeGlfw() {
    LOG.debug("... initialize GLFW");
    GLFWErrorCallback.createPrint(System.err).set();
    if (!GLFW.glfwInit()) {
      throw new RuntimeException("GLFW wasn't initialized correctly.");
    }
  }

  private static long initializeGameWindow(final OpenGlConfiguration config) {
    LOG.debug("... initialize GameWindow");
    GLFW.glfwWindowHint(GLFW.GLFW_VISIBLE, GL41.GL_TRUE);
    GLFW.glfwWindowHint(GLFW.GLFW_RESIZABLE, GL41.GL_TRUE);
    GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MAJOR, OPENGL_MAJOR_VERSION);
    GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MINOR, OPENGL_MINOR_VERSION);
    GLFW.glfwWindowHint(GLFW.GLFW_OPENGL_FORWARD_COMPAT, GL41.GL_TRUE);
    GLFW.glfwWindowHint(GLFW.GLFW_OPENGL_PROFILE, GLFW.GLFW_OPENGL_CORE_PROFILE);

    final var monitor = GLFW.glfwGetPrimaryMonitor();
    final var id =
        GLFW.glfwCreateWindow(
            config.width(), config.height(), config.title(), monitor, MemoryUtil.NULL);
    if (id == MemoryUtil.NULL) {
      throw new RuntimeException("An error occurred during initializing the GameWindow");
    }

    GLFW.glfwMakeContextCurrent(id);
    GL.createCapabilities();
    GL41.glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
    GLFW.glfwSwapInterval(config.vSync() ? 1 : 0);
    GLFW.glfwShowWindow(id);
    GLFW.glfwSetInputMode(id, GLFW.GLFW_STICKY_KEYS, GLFW.GLFW_TRUE);

    GL41.glEnable(GL41.GL_DEPTH_TEST);
    GL41.glEnable(GL41.GL_BLEND);
    GL41.glBlendFunc(GL41.GL_SRC_ALPHA, GL41.GL_ONE_MINUS_SRC_ALPHA);
    GL41.glEnable(GL41.GL_CULL_FACE);
    GL41.glCullFace(GL41.GL_BACK);

    return id;
  }

  private static void initializeKeyCallback(final long id) {
    LOG.debug("... initialize Key callback");

    final GLFWKeyCallbackI callback =
        (long windowId, int key, int scancode, int action, int mods) -> {
          if (key == GLFW.GLFW_KEY_ESCAPE && action == GLFW.GLFW_RELEASE) {
            GLFW.glfwSetWindowShouldClose(windowId, true);
          }
        };
    GLFW.glfwSetKeyCallback(id, callback);
  }

  private static void centerGameWindow(final long id, final OpenGlConfiguration config) {
    LOG.debug("... center GameWindow");

    final var primaryMonitor = GLFW.glfwGetPrimaryMonitor();
    final var videoMode = GLFW.glfwGetVideoMode(primaryMonitor);
    if (videoMode == null) {
      throw new RuntimeException(
          "An error occurred during fetching the video mode of the primary monitor");
    }
    final var xPos = (videoMode.width() - config.width()) / 2;
    final var yPos = (videoMode.height() - config.height()) / 2;
    GLFW.glfwSetWindowPos(id, xPos, yPos);
  }
}