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The main purpose of this libraryis to modernize and maintain the slick2D library.
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package com.github.mathiewz.slick.util.pathfinding;

import java.io.Serializable;
import java.util.ArrayList;

/**
 * A path determined by some path finding algorithm. A series of steps from
 * the starting location to the target location. This includes a step for the
 * initial location.
 *
 * @author Kevin Glass
 */
public class Path implements Serializable {
    /** The serial identifier for this class */
    private static final long serialVersionUID = 1L;
    
    /** The list of steps building up this path */
    private final ArrayList steps = new ArrayList<>();
    
    /**
     * Create an empty path
     */
    public Path() {
        
    }
    
    /**
     * Get the length of the path, i.e. the number of steps
     *
     * @return The number of steps in this path
     */
    public int getLength() {
        return steps.size();
    }
    
    /**
     * Get the step at a given index in the path
     *
     * @param index
     *            The index of the step to retrieve. Note this should
     *            be between 0 and getLength();
     * @return The step information, the position on the map.
     */
    public Step getStep(int index) {
        return steps.get(index);
    }
    
    /**
     * Get the x coordinate for the step at the given index
     *
     * @param index
     *            The index of the step whose x coordinate should be retrieved
     * @return The x coordinate at the step
     */
    public int getX(int index) {
        return getStep(index).x;
    }
    
    /**
     * Get the y coordinate for the step at the given index
     *
     * @param index
     *            The index of the step whose y coordinate should be retrieved
     * @return The y coordinate at the step
     */
    public int getY(int index) {
        return getStep(index).y;
    }
    
    /**
     * Append a step to the path.
     *
     * @param x
     *            The x coordinate of the new step
     * @param y
     *            The y coordinate of the new step
     */
    public void appendStep(int x, int y) {
        steps.add(new Step(x, y));
    }
    
    /**
     * Prepend a step to the path.
     *
     * @param x
     *            The x coordinate of the new step
     * @param y
     *            The y coordinate of the new step
     */
    public void prependStep(int x, int y) {
        steps.add(0, new Step(x, y));
    }
    
    /**
     * Check if this path contains the given step
     *
     * @param x
     *            The x coordinate of the step to check for
     * @param y
     *            The y coordinate of the step to check for
     * @return True if the path contains the given step
     */
    public boolean contains(int x, int y) {
        return steps.contains(new Step(x, y));
    }
    
    /**
     * A single step within the path
     *
     * @author Kevin Glass
     */
    public class Step implements Serializable {
        /** The x coordinate at the given step */
        private final int x;
        /** The y coordinate at the given step */
        private final int y;
        
        /**
         * Create a new step
         *
         * @param x
         *            The x coordinate of the new step
         * @param y
         *            The y coordinate of the new step
         */
        public Step(int x, int y) {
            this.x = x;
            this.y = y;
        }
        
        /**
         * Get the x coordinate of the new step
         *
         * @return The x coodindate of the new step
         */
        public int getX() {
            return x;
        }
        
        /**
         * Get the y coordinate of the new step
         *
         * @return The y coodindate of the new step
         */
        public int getY() {
            return y;
        }
        
        /**
         * @see Object#hashCode()
         */
        @Override
        public int hashCode() {
            return x * y;
        }
        
        /**
         * @see Object#equals(Object)
         */
        @Override
        public boolean equals(Object other) {
            if (other instanceof Step) {
                Step o = (Step) other;
                
                return o.x == x && o.y == y;
            }
            
            return false;
        }
    }
}