// A FigureStack is an ordered collection of figures, drawn from the bottom up.

// This file contains an implementation of a FigureStack where a stack
// of n figures is represented as an array of n figures ordered from 
// bottom (low index) to top (high index). 

import java.awt.*; // Allows us to use AWT classes. 

public class FigureStackArray extends FigureStack {
	
	//----------------------------------------------------------------------
	// INSTANCE VARIABLES
	
	private Figure [] figs; // Array of figures, ordered from bottom to top. 
	
	//----------------------------------------------------------------------
	// CONSTRUCTOR METHOD 

	public FigureStackArray () {
		figs = new Figure[0];
	}
	
	//----------------------------------------------------------------------
	// INSTANCE METHODS

	// Draws figures in this FigureStack from bottom up
	public void draw (Graphics g) {
		for (int i = 0; i < figs.length; i++) {// Must traverse bottom up!
			figs[i].draw(g);
		}
	}
	
	// Returns the topmost figure in this FigureStack whose bounding box
	// contains the point (x,y). If there is no such figure returns null. 
	public Figure find (int x, int y) {
		for (int i = figs.length - 1; i >= 0; i--) {// Must traverse top down!
			if (figs[i].contains(x,y)) {
				return figs[i];
			}
		}
		return null;
	}
	
	// Adds the given figure to the top of this FigureStack.
	public void add (Figure f) {
		Figure [] newFigs = new Figure [figs.length + 1];
		for (int i = 0; i < figs.length; i++) {
			newFigs[i] = figs[i];
		}
		newFigs[figs.length] = f;
		figs = newFigs;
	}
	
	// Inserts the given figure to the bottom of this FigureStack.
	public void insertAtBottom (Figure f) {
		Figure [] newFigs = new Figure [figs.length + 1];
		newFigs[0] = f;
		for (int i = 1; i <= figs.length; i++) {
			newFigs[i] = figs[i-1];
		}
		figs = newFigs;
	}
	
	// Removes the given figure from this FigureStack.
	// Assume the given figure occurs at most once in FigureStack.
	public void remove (Figure f) {
		int index = indexOf(f, figs);
		if (index >= 0) { // Only make smaller array if figure was found.
			Figure [] newFigs = new Figure [figs.length - 1];
			// Copy all elements at indices less than index to newFigs.
			for (int i = 0; i < index; i++) {
				newFigs[i] = figs[i];
			}
			// Copy all elements at indices greater than index to newFigs.
			for (int i = index + 1; i < figs.length; i++) {
				newFigs[i - 1] = figs[i];
			}
			figs = newFigs;
		}
	}
	
	
	//----------------------------------------------------------------------
	// CLASS METHODS

	// Auxiliary method that returns the index of a given figure in an array of figures.
	// Assume that any figure occurs at most once in the array.  
	// It returns -1 if the figure is not found.
	protected static int indexOf (Figure fig, Figure [] figures) {
		for (int i = 0; i < figures.length; i++) {
			if (figures[i] == fig) {
				return i;
			}
		}
		// Only reach this point if f not in figs. 
		return -1;
	}

}