Triangle.java

import java.awt.Graphics;
import java.awt.Color;

/**
 * A triangle that can be manipulated and that draws itself on a canvas.
 * 
 * @author  Michael Kölling and David J. Barnes and Brian Dahlem
 * @version 2018.11.26
 */

public class Triangle
{
    private int height;
    private int width;
    private int xPosition;
    private int yPosition;
    private Color color;
    private boolean isVisible;

    /**
     * Create a new triangle at default position with default color.
     */
    public Triangle()
    {
        height = 60;
        width = 70;
        xPosition = 210;
        yPosition = 140;
        color = Canvas.getColor("green");
        isVisible = false;
    }
    
    /**
     * Make this triangle visible. If it was already visible, do nothing.
     */
    public void makeVisible()
    {
        if (!isVisible)
        {
            isVisible = true;
            add();
        }
    }

    /**
     * Make this triangle invisible. If it was already invisible, do nothing.
     */
    public void makeInvisible()
    {
        if (isVisible) 
        {
            remove();
            isVisible = false;
        }
    }

    /**
     * Move the triangle a few pixels to the right.
     */
    public void moveRight()
    {
        moveHorizontal(20);
    }

    /**
     * Move the triangle a few pixels to the left.
     */
    public void moveLeft()
    {
        moveHorizontal(-20);
    }

    /**
     * Move the triangle a few pixels up.
     */
    public void moveUp()
    {
        moveVertical(-20);
    }

    /**
     * Move the triangle a few pixels down.
     */
    public void moveDown()
    {
        moveVertical(20);
    }

    /**
     * Move the triangle horizontally by 'distance' pixels.
     * @param distance the distance to move the triangle along the x axis, 
     *                  positive to the right
     */
    public void moveHorizontal(int distance)
    {
        xPosition += distance;
    }

    /**
     * Move the triangle vertically by 'distance' pixels.
     * @param distance the distance to move the triangle along the y axis,
     *                  positive down
     */
    public void moveVertical(int distance)
    {
        yPosition += distance;
    }

    /**
     * Change the size of the triangle (in pixels).
     * @param newHeight the new height of the triangle, positive points up, negative points down
     * @param newWidth the new width of the triangle, must be > 0
     */
    public void changeSize(int newHeight, int newWidth)
    {
        height = newHeight;
        width = newWidth;
    }

    /**
     * Change the color. Valid colors are "red", "yellow", "blue", "green",
     * "magenta", "cyan", "brown", "white", and "black", or rgb hex strings
     * "#rrggbb" where rr, gg, bb are 2-hexit values for red, green, and
     * blue levels.
     * @param newColor a string naming the new color for the triangle
     */
    public void changeColor(String newColor)
    {
        color = Canvas.getColor(newColor);
    }

    /**
     * Draw a triangle with current specifications on the screen.
     */
    private void add()
    {
        if(isVisible) {
            Canvas canvas = Canvas.getCanvas();
            canvas.add(this, (g) -> {int[] xpoints = {xPosition, 
                                                      xPosition + (width/2),
                                                      xPosition - (width/2)};
                                     int[] ypoints = {yPosition,
                                                      yPosition + height,
                                                      yPosition + height};
                                     g.setColor(color);
                                     g.fillPolygon(xpoints, ypoints, 3);});                                             
        }
    }

    /**
     * Remove the triangle from the screen.
     */
    private void remove()
    {
        if(isVisible) {
            Canvas canvas = Canvas.getCanvas();
            canvas.remove(this);
        }
    }

    
    /**
     * Get a text description of the triangle.
     */
    public String toString() {
        String visibility;
        if (isVisible) {
            visibility = "Visible";
        }
        else {
            visibility = "Invisible";
        }

        return visibility + " Triangle" +
            " with width " + this.width + 
            " height  " + this.height +
            " at (" + this.xPosition + ", " + this.yPosition + ")" +
            " with color " + this.color;
    }
}