package ie.dcu.swt;

import ie.dcu.swt.event.*;

import java.util.*;

import org.eclipse.swt.graphics.*;

public class ObservableImage {
	private final List<ImageListener> listeners;
	private Image image;
	private ImageData data;
	private Rectangle modified;
	private GC gc;
	private int refCount;
	private boolean suspendNotifications;

	
	public ObservableImage(Image image) {
		this.listeners = new ArrayList<ImageListener>(2);
		this.image = image;
	}
	
	
	public GC beginPaint() {
		if (refCount > 0) {
			refCount++;
			return gc;		
		} else {
			modified = null;
			refCount = 1;
			return (gc = new GC(image));
		}	
	}

	
	public void endPaint() {
		endPaint(null);
	}
	
	
	public void endPaint(Rectangle modified) {
		refCount--;
		if (refCount < 0) {
			throw new IllegalStateException();
		}

		updateModified(modified);

		if (refCount == 0) {
			data = null;
			gc.dispose();
			gc = null;		
			fireImageChanged();
		}
	}
	
	
	public Image getImage() {
		return image;
	}
	
	
	public ImageData getImageData() {
		if (data == null) {
			data = image.getImageData();
		}
		return data;
	}
	
	
	public void setImage(Image image, boolean disposeOld) {
		if (gc != null) {
			throw new IllegalStateException();
		}
		
		if (image == null) {
			throw new NullPointerException();
		}
		
		boolean dimensionsChanged = false;
		if (this.image != null && !this.image.isDisposed()) {
			Rectangle oldBounds = this.image.getBounds();
			Rectangle newBounds = image.getBounds();
			
			dimensionsChanged = !oldBounds.equals(newBounds);
		} else {
			dimensionsChanged = true;
		}
		
		if (disposeOld) {
			dispose();
		}
		
		this.image = image;
		
		// Invalidate cached image data
		this.data = null;
		fireImageChanged(dimensionsChanged);
	}
	


	public void setSuspendNotifications(boolean suspend) {
		this.suspendNotifications = suspend;
	}


	public boolean isDisposed() {
		if (image != null) {
			return image.isDisposed();
		}
		return false;
	}
	
	
	public void dispose() {
		if (image != null && !image.isDisposed()) {
			image.dispose();
		}
		data = null;
	}
	

	public Rectangle getBounds() {
		return image.getBounds();	
	}
	
	
	public Rectangle getModifiedArea() {
		return modified;
	}
	
	
	public void addImageListener(ImageListener listener) {
		listeners.add(listener);
	}
	
	
	public void removeImageListener(ImageListener listener) {
		listeners.remove(listener);
	}
	
	
	public void fireImageChanged() {
		fireImageChanged(getModifiedArea(), false);
	}
	
	
	public void fireImageChanged(Rectangle modified) {
		fireImageChanged(modified, false);
	}
	
	
	private void fireImageChanged(boolean dimensionsChanged) {
		fireImageChanged(getModifiedArea(), dimensionsChanged);
	}
		

	private void fireImageChanged(Rectangle modified, boolean dimensionsChanged) {
		if (suspendNotifications) {
			return;
		}
		
		ImageEvent e = null;
		for (ImageListener i : listeners) {
			if (e == null) {
				e = new ImageEvent(this, modified, dimensionsChanged);
			}
			i.imageChanged(e);
		}
	}


	private void updateModified(Rectangle m) {
		if (m == null) {
			this.modified = image.getBounds();
		} else {
			if (this.modified != null) {
				this.modified = this.modified.union(m);
			} else {
				this.modified = SwtUtils.clone(m);
			}
		}
	}
}