hadean/src/main/java/xyz/valnet/engine/graphics/ImmediateUI.java

package xyz.valnet.engine.graphics;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Stack;

import xyz.valnet.engine.math.Box;
import xyz.valnet.engine.math.Vector4f;
import xyz.valnet.engine.math.Vector4i;
import xyz.valnet.engine.scenegraph.GameObject;
import xyz.valnet.engine.scenegraph.IMouseCaptureArea;
import xyz.valnet.hadean.input.Button;
import xyz.valnet.hadean.util.Assets;
import xyz.valnet.hadean.util.Layers;

public abstract class ImmediateUI extends GameObject implements IMouseCaptureArea {

  @SuppressWarnings("unused")
  private boolean active;
  @SuppressWarnings("unused")
  private boolean mouseDown;

  public void render() {
    begin();
    gui();
    end();
  }

  @Override
  public void mouseEnter() {
    active = true;
  }

  @Override
  public void mouseLeave() {
    active = false;
  }

  @Override
  public void mouseDown(int button) {
    if(button == 0) mouseDown = true;
  }

  @Override
  public void mouseUp(int button) {
    if(button == 0) mouseDown = false;
  }

  @Override
  public float getLayer() {
    return Layers.GENERAL_UI_INTERACTABLE;
  }

  protected abstract void gui();

  private record StackingContext(
    boolean fixedSize,
    Box box,
    Box occlusionBox,
    boolean hasRegisteredGuiArea,
    boolean horizontal
    // layout manager?
  ) {
    public boolean vertical() {
      return !horizontal;
    }
  }

  private transient StackingContext context;
  private transient Stack<StackingContext> contextStack = new Stack<StackingContext>();;

  private transient Map<String, Button> buttons = new HashMap<String, Button>();
  private transient Set<String> usedButtonId = new HashSet<String>();
  private transient Map<Button, Integer> clicks = new HashMap<Button, Integer>();
  private transient int buttonCount;

  private String genButtonId() {
    buttonCount ++;
    return "DefaultButton-" + buttonCount;
  }

  private boolean hasButton(String id) {
    usedButtonId.add(id);
    return buttons.containsKey(id);
  }

  private Button getButton(String id) {
    if(hasButton(id)) return buttons.get(id);
    System.out.println("Created new Button");
    Button btn = new Button(Assets.uiFrame, "", 0, 0, 0, 0, 0);
    btn.registerClickListener((target) -> {
      if(!clicks.containsKey(target)) clicks.put(target, 0);
      clicks.put(target, clicks.get(target) + 1);
    });
    buttons.put(id, add(btn));
    return btn;
  }

  private boolean getClick(Button btn) {
    if(clicks.containsKey(btn)) {
      int clickCount = clicks.get(btn);
      if(clickCount > 0) {
        clicks.put(btn, clickCount - 1);
        return true;
      }
    }
    return false;
  }

  private void modifyBox(float x, float y, float w, float h) {
    context = new StackingContext(
      context.fixedSize,
      new Box(context.box.x + x, context.box.y + y, context.box.w + w, context.box.h + h),
      context.occlusionBox,
      context.hasRegisteredGuiArea,
      context.horizontal
    );
  }

  private void adjustBox(float w, float h) {
    if(context.vertical()) {
      if(context.fixedSize) {
        modifyBox(0, h, 0, -h);
      } else {
        modifyBox(0, 0, 0, h);
      }
    } else {
      if(context.fixedSize) {
        modifyBox(w, 0, -w, 0);
      } else {
        modifyBox(0, 0, w, 0);
        if (h - context.box.h > 0)
          modifyBox(0, 0, 0, h - context.box.h);
      }
    }
  }

  @Override
  public final List<Box> getGuiBoxes() {
    return guiAreas;
  }

  private transient List<Box> guiAreas = new ArrayList<Box>();

  @FunctionalInterface
  public interface RenderCallback {
    public void apply();
  }

  private float getCurrentLayer() {
    return getLayer() + contextStack.size() * 0.001f;
  }

  private float getPreviousLayer() {
    return getLayer() + contextStack.size() * 0.001f;
  }

  // === ELEMENTS ===
  // 

  protected void begin() {
    buttonCount = 0;
    usedButtonId.clear();
    contextStack.clear();
    guiAreas.clear();
  }

  protected void root(int x, int y, int w, int h, RenderCallback cb) {
    root(x, y, w, h);
    cb.apply();
    rootEnd();
  }

  protected void window(int x, int y, int w, int h, RenderCallback cb) {
    root(x, y, w, h);
    fixedFrame(w, h);
    pad();
    cb.apply();
    padEnd();
    frameEnd();
    rootEnd();
  }

  protected void root(int x, int y, int w, int h) {
    assert context == null : "root can only be a root element";
    Box box = new Box(x, y, w, h);
    context = new StackingContext(true, box, box, false, false);
  }

  protected void rootEnd() {
    assert contextStack.size() == 0 : "cannot end fixedFrame with un-ended elements inside";
    context = null;
  }

  protected void fixedFrame(int w, int h) {
    contextStack.push(context);
    context = new StackingContext(
      true,
      new Box(context.box.x, context.box.y, w, h),
      context.occlusionBox.copy(),
      true,
      context.horizontal
    );
  }

  protected void dynamicFrame() {
    contextStack.push(context);
    context = new StackingContext(
      false,
      new Box(context.box.x, context.box.y, context.box.w, 0),
      context.occlusionBox.copy(),
      true,
      context.horizontal
    );
  }

  // TODO this will add _all_ frames, not just root frames to guiareas.
  // not a problem, but not efficient. revisit.
  protected void frameEnd() {
    Drawing.setLayer(getPreviousLayer());
    if(!context.fixedSize) {
      Assets.uiFrame.draw(context.box);
      guiAreas.add(context.box);
    } else {
      Assets.uiFrame.draw(context.occlusionBox);
      guiAreas.add(context.occlusionBox);
    }
    context = contextStack.pop();
  }

  protected boolean button(String text) {
    return button(genButtonId(), text, false);
  }

  protected boolean button(String text, boolean expand) {
    return button(genButtonId(), text, expand);
  }

  protected boolean button(String id, String text) {
    return button(id, text, false);
  }

  protected boolean button(String id, String text, boolean expand) {
    int h = 32;
    if(expand && context.fixedSize) {
      h = (int) context.box.h;
    }
    int w = (int) context.box.w;
    if(context.horizontal && !context.fixedSize) {
      w = 100;
    }
    
    int x = (int) context.box.x;
    int y = (int) context.box.y;

    if(!context.fixedSize) {
      if(context.vertical()) {
        y += (int) context.box.h;
      } else {
        x += (int) context.box.w;
      }
    }

    Box buttonBox = new Box(x, y, w, h);
    Button btn = getButton(id);

    if(!context.hasRegisteredGuiArea) {
      guiAreas.add(buttonBox);
    }

    btn.setText(text);
    btn.setPosition(x, y);
    btn.setSize(w, h);
    btn.setLayer(getCurrentLayer());

    adjustBox(buttonBox.w, buttonBox.h);

    return getClick(btn);
  }

  protected void group(RenderCallback cb) {
    group();
    cb.apply();
    groupEnd();
  }

  protected void group() {
    contextStack.push(context);
    context = new StackingContext(false,
      new Box(
        context.box.x, context.box.y, context.box.w, 0
      ),
      context.occlusionBox.copy(),
      context.hasRegisteredGuiArea,
      context.horizontal
    );
    pad();
  }

  protected void groupEnd() {
    padEnd();
    Drawing.setLayer(getPreviousLayer());
    float h = context.box.h;
    Assets.uiFrame.draw(context.box);
    context = contextStack.pop();
    adjustBox(context.box.w, h);
  }

  protected void pad() {
    contextStack.push(context);
    if(context.fixedSize) {
      context = new StackingContext(true,
        new Box(
          context.box.x + 8, context.box.y + 8, context.box.w - 16, context.box.h - 16
        ),
        context.occlusionBox.copy(),
        context.hasRegisteredGuiArea,
        context.horizontal
      );
    } else {
      context = new StackingContext(false,
        new Box(
          context.box.x + 8, context.box.y + 8, context.box.w - 16, 0
        ),
        context.occlusionBox.copy(),
        context.hasRegisteredGuiArea,
        context.horizontal
      );
    }
  }

  protected void padEnd() {
    float h = context.box.h + 16;
    context = contextStack.pop();
    adjustBox(context.box.w + 16, h);
  }

  protected void horizontal(RenderCallback cb) {
    contextStack.push(context);
    context = new StackingContext(
      false,
      new Box(context.box.x, context.box.y, 0, 0),
      context.occlusionBox,
      context.hasRegisteredGuiArea,
      true
    );
    cb.apply();
    float w = context.box.w;
    float h = context.box.h;
    context = contextStack.pop();
    adjustBox(w, h);
  }

  protected void space(int space) {
    if(context.horizontal)
      adjustBox(space, 1);
    else
      adjustBox(1, space);
  }

  protected void end() {

    List<String> buttonIdsToRemove = new ArrayList<String>();

    for(String id : this.buttons.keySet()) {
      if(usedButtonId.contains(id)) continue;
      buttonIdsToRemove.add(id);
    }

    for(String id : buttonIdsToRemove) {
      Button btn = buttons.get(id);
      remove(btn);
      buttons.remove(id);
      if(clicks.containsKey(btn)) {
        clicks.remove(btn);
      }
    }
  }

  protected void text(String text) {
    text(text, Assets.font);
  }

  protected void header(String text) {
    text(text, Assets.bigFont);
  }

  protected void text(String text, Font font) {
    Vector4i measured = font.measure(text);
    Drawing.setLayer(getCurrentLayer());

    int x = (int) context.box.x;
    int y = (int) context.box.y;

    if(!context.fixedSize) {
      if(context.vertical()) {
        y += (int) context.box.h;
      } else {
        x += (int) context.box.w;
      }
    }

    font.drawString(text, x, y);

    adjustBox(measured.x, measured.y);
  }
}