KinderMalen/src/main/java/de/ph87/kindermalen/drawing/DrawingPanel.java

package de.ph87.kindermalen.drawing;

import de.ph87.kindermalen.ComponentListener;
import de.ph87.kindermalen.Environment;
import de.ph87.kindermalen.MyComponent;
import de.ph87.kindermalen.toolbox.tool.Tool;
import de.ph87.kindermalen.util.Subscription;
import de.ph87.kindermalen.util.Vector;
import lombok.extern.slf4j.Slf4j;

import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.geom.Point2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

@Slf4j
public class DrawingPanel extends MyComponent {

  private static final File SAVE_DIR = new File("./data/images");

  private final Environment environment;

  private Subscription<Tool> toolChangeSubscription = null;

  private Vector lastPoint = null;

  private Vector cursor = null;

  private AffineTransform transform;

  private AffineTransform inverseTransform;

  public DrawingPanel(final Environment environment) {
    this.environment = environment;
    subscribe(environment.getToolbox().getOnSelect(), this::onToolSelect);
    subscribe(environment.getOnDrawingChange(), drawing -> repaint());
    ComponentListener.on(this)
      .componentResized(this::calculateTransform)
      .componentMoved(this::calculateTransform)
      .componentShown(this::calculateTransform)
      .mousePressed(this::mousePressed)
      .mouseReleased(this::mouseReleased)
      .mouseDragged(this::mouseDragged)
      .mouseMoved(this::mouseMoved);

  }

  private void onToolSelect(final Tool tool) {
    repaint();
    if (toolChangeSubscription != null) {
      unsubscribe(toolChangeSubscription);
    }
    toolChangeSubscription = subscribe(tool.getOnChange(), ignore -> repaint());
  }

  public void mousePressed(final MouseEvent mouseEvent) {
    if (mouseEvent.getButton() == 3) {
      environment.getDrawing().undo();
      return;
    }
    environment.getDrawing().newRevision();
    lastPoint = environment.getToolbox().getTool().apply(null, environment.getDrawing(), transform(mouseEvent.getPoint()));
    repaint();
  }

  public void mouseReleased(final MouseEvent mouseEvent) {
    try {
      environment.getDrawing().save(SAVE_DIR);
    } catch (IOException ex) {
      log.error(ex.toString());
    }
  }

  public void mouseDragged(final MouseEvent mouseEvent) {
    cursor = transform(mouseEvent.getPoint());
    lastPoint = environment.getToolbox().getTool().apply(lastPoint, environment.getDrawing(), transform(mouseEvent.getPoint()));
    repaint();
  }

  public void mouseMoved(final MouseEvent mouseEvent) {
    cursor = transform(mouseEvent.getPoint());
    repaint();
  }

  private void calculateTransform() {
    final Drawing drawing = environment.getDrawing();
    final Rectangle box = fitInside(drawing.width, drawing.height, getWidth(), getHeight(), false);
    final double scale = (double) box.width / drawing.width;
    transform = new AffineTransform();
    transform.translate(box.x, box.y);
    transform.scale(scale, scale);
    try {
      inverseTransform = transform.createInverse();
    } catch (NoninvertibleTransformException ex) {
      log.error(ex.toString());
    }
  }

  private Vector transform(final Point point) {
    final Point2D transformed = inverseTransform.transform(new Point2D.Double(point.x, point.y), null);
    return new Vector(transformed);
  }

  @Override
  public void paint(final Graphics graphics) {
    final Graphics2D g = (Graphics2D) graphics;
    g.setColor(Color.gray);
    g.fillRect(0, 0, getWidth(), getHeight());

    if (transform == null || environment == null || environment.getDrawing() == null) {
      return;
    }

    g.setTransform(transform);
    draw(g, environment.getDrawing());
  }

  private void draw(final Graphics2D g, final Drawing drawing) {
    g.setColor(Color.white);
    g.fillRect(0, 0, drawing.width, drawing.height);
    g.drawImage(drawing.getImage(), 0, 0, drawing.width, drawing.height, null);

    final BufferedImage preview = environment.getToolbox().getTool().getPreview();
    if (cursor != null && preview != null) {
      g.drawImage(preview, cursor.intX() - preview.getWidth() / 2, cursor.intY() - preview.getHeight() / 2, null);
    }
  }

  private Rectangle fitInside(int w, int h, final int width, final int height, final boolean grow) {
    final double r = (double) w / h;
    if (grow && h < height) {
      h = height;
      w = (int) Math.round(h * r);
    }
    if (w > width || (grow && w < width)) {
      w = width;
      h = (int) Math.round(w / r);
    }
    if (h > height) {
      h = height;
      w = (int) Math.round(h * r);
    }
    final int x = (int) Math.round((width - w) / 2.0);
    final int y = (int) Math.round((height - h) / 2.0);
    return new Rectangle(x, y, w, h);
  }

}