package org.eclipse.nebula.widgets.nattable.core.painter;

/**
 * Instances of this class represent rectangular areas in an
 * (x, y) coordinate system. The top left corner of the rectangle
 * is specified by its x and y values, and the extent of the
 * rectangle is specified by its width and height.
 * <p>
 * The coordinate space for rectangles and points is considered
 * to have increasing values downward and to the right from its
 * origin making this the normal, computer graphics oriented notion
 * of (x, y) coordinates rather than the strict mathematical one.
 * </p>
 * <p>
 * The hashCode() method in this class uses the values of the public
 * fields to compute the hash value. When storing instances of the
 * class in hashed collections, do not modify these fields after the
 * object has been inserted.  
 * </p>
 * <p>
 * Application code does <em>not</em> need to explicitly release the
 * resources managed by each instance when those instances are no longer
 * required, and thus no <code>dispose()</code> method is provided.
 * </p>
 * <p>
 * There might be an implementation for this in every UI toolkit, like
 * org.eclipse.swt.graphics.Rectangle or java.awt.Rectangle, but they are 
 * dependent to the UI toolkit because of their package and inheritance. 
 * That's why we reimplemented it again to make use of it in NatTable core
 * without any further dependencies.
 * </p>
 * <p>
 * This implementation is based on org.eclipse.swt.graphics.Rectangle.
 * </p>
 */
public class Rectangle {
	
	/**
	 * the x coordinate of the rectangle
	 */
	public int x;
	
	/**
	 * the y coordinate of the rectangle
	 */
	public int y;
	
	/**
	 * the width of the rectangle
	 */
	public int width;
	
	/**
	 * the height of the rectangle
	 */
	public int height;
	
	/**
	 * Construct a new instance of this class given the 
	 * x, y, width and height values.
	 *
	 * @param x the x coordinate of the origin of the rectangle
	 * @param y the y coordinate of the origin of the rectangle
	 * @param width the width of the rectangle
	 * @param height the height of the rectangle
	 */
	public Rectangle (int x, int y, int width, int height) {
		this.x = x;
		this.y = y;
		this.width = width;
		this.height = height;
	}

	/**
	 * Destructively replaces the x, y, width and height values
	 * in the receiver with ones which represent the union of the
	 * rectangles specified by the receiver and the given rectangle.
	 * <p>
	 * The union of two rectangles is the smallest single rectangle
	 * that completely covers both of the areas covered by the two
	 * given rectangles.
	 * </p>
	 *
	 * @param rect the rectangle to merge with the receiver
	 *
	 * @throws IllegalArgumentException if the specified rectangle is <code>null</code>
	 */
	public void add (Rectangle rect) {
		if (rect == null) throw new IllegalArgumentException("rectangle can not be null"); //$NON-NLS-1$
		int left = x < rect.x ? x : rect.x;
		int top = y < rect.y ? y : rect.y;
		int lhs = x + width;
		int rhs = rect.x + rect.width;
		int right = lhs > rhs ? lhs : rhs;
		lhs = y + height;
		rhs = rect.y + rect.height;
		int bottom = lhs > rhs ? lhs : rhs;
		x = left;  y = top;  width = right - left;  height = bottom - top;
	}

	/**
	 * Returns <code>true</code> if the point specified by the
	 * arguments is inside the area specified by the receiver,
	 * and <code>false</code> otherwise.
	 *
	 * @param x the x coordinate of the point to test for containment
	 * @param y the y coordinate of the point to test for containment
	 * @return <code>true</code> if the rectangle contains the point and <code>false</code> otherwise
	 */
	public boolean contains (int x, int y) {
		return (x >= this.x) && (y >= this.y) && x < (this.x + width) && y < (this.y + height);
	}
	
	/**
	 * Returns <code>true</code> if the given point is inside the
	 * area specified by the receiver, and <code>false</code>
	 * otherwise.
	 *
	 * @param pt the point to test for containment
	 * @return <code>true</code> if the rectangle contains the point and <code>false</code> otherwise
	 *
	 * @throws IllegalArgumentException if the specified point is <code>null</code>
	 */
	public boolean contains (Point pt) {
		if (pt == null) throw new IllegalArgumentException("point can not be null"); //$NON-NLS-1$
		return contains(pt.x, pt.y);
	}
	
	/**
	* Returns <code>true</code> if the receiver does not cover any
	* area in the (x, y) coordinate plane, and <code>false</code> if
	* the receiver does cover some area in the plane.
	* <p>
	* A rectangle is considered to <em>cover area</em> in the 
	* (x, y) coordinate plane if both its width and height are 
	* non-zero.
	* </p>
	*
	* @return <code>true</code> if the receiver is empty, and <code>false</code> otherwise
	*/
	public boolean isEmpty () {
		return (width <= 0) || (height <= 0);
	}

	/**
	 * Destructively replaces the x, y, width and height values
	 * in the receiver with ones which represent the intersection of the
	 * rectangles specified by the receiver and the given rectangle.
	 *
	 * @param rect the rectangle to intersect with the receiver
	 *
	 * @throws IllegalArgumentException if the specified rectangle is <code>null</code>
	 */
	public void intersect (Rectangle rect) {
		if (rect == null) throw new IllegalArgumentException("rectangle can not be null"); //$NON-NLS-1$
		if (this == rect) return;
		int left = x > rect.x ? x : rect.x;
		int top = y > rect.y ? y : rect.y;
		int lhs = x + width;
		int rhs = rect.x + rect.width;
		int right = lhs < rhs ? lhs : rhs;
		lhs = y + height;
		rhs = rect.y + rect.height;
		int bottom = lhs < rhs ? lhs : rhs;
		x = right < left ? 0 : left;
		y = bottom < top ? 0 : top;
		width = right < left ? 0 : right - left;
		height = bottom < top ? 0 : bottom - top;
	}

	/**
	 * Returns a new rectangle which represents the intersection
	 * of the receiver and the given rectangle. 
	 * <p>
	 * The intersection of two rectangles is the rectangle that
	 * covers the area which is contained within both rectangles.
	 * </p>
	 *
	 * @param rect the rectangle to intersect with the receiver
	 * @return the intersection of the receiver and the argument
	 *
	 * @throws IllegalArgumentException if the specified rectangle is <code>null</code>
	 */
	public Rectangle intersection (Rectangle rect) {
		if (rect == null) throw new IllegalArgumentException("rectangle can not be null"); //$NON-NLS-1$
		if (this == rect) return new Rectangle (x, y, width, height);
		int left = x > rect.x ? x : rect.x;
		int top = y > rect.y ? y : rect.y;
		int lhs = x + width;
		int rhs = rect.x + rect.width;
		int right = lhs < rhs ? lhs : rhs;
		lhs = y + height;
		rhs = rect.y + rect.height;
		int bottom = lhs < rhs ? lhs : rhs;
		return new Rectangle (
			right < left ? 0 : left,
			bottom < top ? 0 : top,
			right < left ? 0 : right - left,
			bottom < top ? 0 : bottom - top);
	}

	/**
	 * Returns <code>true</code> if the rectangle described by the
	 * arguments intersects with the receiver and <code>false</code>
	 * otherwise.
	 * <p>
	 * Two rectangles intersect if the area of the rectangle
	 * representing their intersection is not empty.
	 * </p>
	 *
	 * @param x the x coordinate of the origin of the rectangle
	 * @param y the y coordinate of the origin of the rectangle
	 * @param width the width of the rectangle
	 * @param height the height of the rectangle
	 * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise
	 *
	 * @see #intersection(Rectangle)
	 * @see #isEmpty()
	 */
	public boolean intersects (int x, int y, int width, int height) {
		return (x < this.x + this.width) && (y < this.y + this.height) &&
			(x + width > this.x) && (y + height > this.y);
	}
	
	/**
	 * Returns <code>true</code> if the given rectangle intersects
	 * with the receiver and <code>false</code> otherwise.
	 * <p>
	 * Two rectangles intersect if the area of the rectangle
	 * representing their intersection is not empty.
	 * </p>
	 *
	 * @param rect the rectangle to test for intersection
	 * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise
	 *
	 * @throws IllegalArgumentException if the specified rectangle is <code>null</code>
	 *
	 * @see #intersection(Rectangle)
	 * @see #isEmpty()
	 */
	public boolean intersects (Rectangle rect) {
		if (rect == null) throw new IllegalArgumentException("rectangle can not be null"); //$NON-NLS-1$
		return rect == this || intersects (rect.x, rect.y, rect.width, rect.height);
	}

	/**
	 * Returns a new rectangle which represents the union of
	 * the receiver and the given rectangle.
	 * <p>
	 * The union of two rectangles is the smallest single rectangle
	 * that completely covers both of the areas covered by the two
	 * given rectangles.
	 * </p>
	 *
	 * @param rect the rectangle to perform union with
	 * @return the union of the receiver and the argument
	 *
	 * @throws IllegalArgumentException if the specified rectangle is <code>null</code>
	 *
	 * @see #add(Rectangle)
	 */
	public Rectangle union (Rectangle rect) {
		if (rect == null) throw new IllegalArgumentException("rectangle can not be null"); //$NON-NLS-1$
		int left = x < rect.x ? x : rect.x;
		int top = y < rect.y ? y : rect.y;
		int lhs = x + width;
		int rhs = rect.x + rect.width;
		int right = lhs > rhs ? lhs : rhs;
		lhs = y + height;
		rhs = rect.y + rect.height;
		int bottom = lhs > rhs ? lhs : rhs;
		return new Rectangle (left, top, right - left, bottom - top);
	}

	/**
	 * Compares the argument to the receiver, and returns true
	 * if they represent the <em>same</em> object using a class
	 * specific comparison.
	 *
	 * @param object the object to compare with this object
	 * @return <code>true</code> if the object is the same as this object and <code>false</code> otherwise
	 *
	 * @see #hashCode()
	 */
	public boolean equals (Object object) {
		if (object == this) return true;
		if (!(object instanceof Rectangle)) return false;
		Rectangle r = (Rectangle)object;
		return (r.x == this.x) && (r.y == this.y) && (r.width == this.width) && (r.height == this.height);
	}
	
	/**
	 * Returns an integer hash code for the receiver. Any two 
	 * objects that return <code>true</code> when passed to 
	 * <code>equals</code> must return the same value for this
	 * method.
	 *
	 * @return the receiver's hash
	 *
	 * @see #equals(Object)
	 */
	public int hashCode () {
		return x ^ y ^ width ^ height;
	}
	
	/**
	 * Returns a string containing a concise, human-readable
	 * description of the receiver.
	 *
	 * @return a string representation of the rectangle
	 */
	public String toString () {
		return "Rectangle {" + x + ", " + y + ", " + width + ", " + height + "}"; //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$
	}

}