/*
 * The MIT License (MIT)
 * 
 * Copyright (c) 2015 Camil Staps <info@camilstaps.nl>
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package com.camilstaps.mandelbrot;

import java.util.HashMap;
import java.util.Map;

/**
 * Class for calculating Mandelbrot numbers
 * By remembering seen numbers, we can significantly decrease calculation time
 * 
 * @author Camil Staps
 */
public class MandelbrotFractal {
    
    /**
     * Storage for previously calculated numbers
     */
    private static final Map<Point,Result> mandelNumbers = new HashMap<>();
    
    /**
     * Calculate the Mandelbrot number for a specific point up to some maximum
     * @param x the x coordinate of the point
     * @param y the y coordinate of the point
     * @param repetitions the maximum
     * @return the mandelbrot number
     */
    public synchronized static int mandelNumber(double x, double y, int repetitions) {
        Point p = new Point(x, y);
        return mandelNumber(p, repetitions);
    }
    
    /**
     * Calculate the Mandelbrot number for a specific point up to some maximum
     * @param p the point
     * @param repetitions the maximum
     * @return the mandelbrot number
     */
    public synchronized static int mandelNumber(Point p, int repetitions) {
        if (mandelNumbers.containsKey(p)) {
            Result result = mandelNumbers.get(p);
            if (repetitions < result.repetitions ||
                    result.mandelNumber < result.repetitions) {
                return result.mandelNumber;
            } else {
                calculateMandelNumber(p, repetitions, result);
                return result.mandelNumber;
            }
        } else {
            Result result = calculateMandelNumber(p, repetitions);
            mandelNumbers.put(p, result);
            return result.mandelNumber;
        }
    }
    
    /**
     * Calculate the Mandelbrot number for a specifc point up to some maximum
     * @param p the point
     * @param repetitions the maximum
     * @return the result
     */
    protected synchronized static Result calculateMandelNumber(Point p, int repetitions) {
        Result start = new Result();
        start.x = p.x;
        start.y = p.y;
        calculateMandelNumber(p, repetitions, start);
        return start;
    }
    
    /**
     * Calculate the Mandelbrot number for a specific point up to some maximum,
     * starting from an earlier result
     * @param p the point
     * @param repetitions the maximum
     * @param start the earlier result; will be updated with the new result
     */
    protected synchronized static void calculateMandelNumber(Point p, int repetitions, Result start) {
        int n = start.repetitions;
        
        while (start.x * start.x + start.y * start.y <= 4 && n < repetitions) {
            double new_x = start.x * start.x - start.y * start.y + p.x;
            start.y = 2 * start.x * start.y + p.y;
            start.x = new_x;
            n++;
        }
        
        start.mandelNumber = n;
    }
    
    /**
     * A point on a coordinate system
     */
    public static class Point {
        double x, y;
        
        public Point(double x, double y) {
            this.x = x;
            this.y = y;
        }
        
        @Override
        public boolean equals(Object another) {
            if (another == null || another.getClass() != Point.class) {
                return false;
            }
            Point that = (Point) another;
            return that.x == x && that.y == y;
        }

        @Override
        public int hashCode() {
            int hash = 7;
            hash = 97 * hash + (int) (Double.doubleToLongBits(this.x) ^ (Double.doubleToLongBits(this.x) >>> 32));
            hash = 97 * hash + (int) (Double.doubleToLongBits(this.y) ^ (Double.doubleToLongBits(this.y) >>> 32));
            return hash;
        }
        
        @Override
        public String toString() {
            return String.format("(%f,%f)", x, y);
        }
    }
    
    /**
     * A Mandelbrot result consists of a point, the mandelbrot number and the 
     * maximum with which we calculated that result.
     */
    protected static class Result {
        int mandelNumber = -1, repetitions = 0;
        double x, y;
    }
    
}