package Presenter.Algorithms;

import Model.Line;
import Model.Slab;
import Presenter.InversionCounter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Implementierung verschiedener Algorithmen zur Berechnung von Ausgleichsgeraden.
 *
 * @Author: Armin Wolf
 * @Email: a_wolf28@uni-muenster.de
 * @Date: 28.05.2017.
 */
public class RepeatedMedianEstimator implements Algorithm {

  private LinkedList<Line> set;
  private HashMap<Line, ArrayList<Line>> linePairs;
  private HashMap<Line, Double> medianIntersections = new HashMap<>();
  private HashMap<Line, ArrayList<Double>> intersectionAbscissas = new HashMap<>();
  private Slab interval;

  //in der Literatur als L_i, C_i, und R_i bekannt
  private ArrayList<Integer> countLeftSlab;
  private ArrayList<Integer> countCenterSlab;
  private ArrayList<Integer> countRightSlab;

  //die Mengen L,C und R
  private ArrayList<Line> linesInLeftSlab;
  private ArrayList<Line> linesInCenterSlab;
  private ArrayList<Line> linesInRightSlab;

  private Double r;
  private Integer n;
  private Double k;
  private Double kLow;
  private Double kHigh;
  private Double beta;

  private Double thetaLow;
  private Double thetaHigh;


  public RepeatedMedianEstimator(LinkedList<Line> set) {
    this.set = set;
    interval = new Slab(-10000, 10000);
    n = set.size();
    beta = 0.5;
    countLeftSlab = new ArrayList<>();
    countCenterSlab = new ArrayList<>();
    countRightSlab = new ArrayList<>();

    for (int i = 0; i < n; i++) {
      countLeftSlab.add(0);
      countRightSlab.add(0);
      countCenterSlab.add(n - 1);
      intersectionAbscissas.put(set.get(i), new ArrayList<>());
    }

    linesInLeftSlab = new ArrayList<>();
    linesInCenterSlab = new ArrayList<>(set);
    linesInRightSlab = new ArrayList<>();
    linePairs = new HashMap<>();
  }

  /**
   *
   */
  public void run() {

    while (linesInCenterSlab.size() != 1) {
      r = Math.ceil(Math.pow(n, beta));
      ArrayList<Line> lines = sampleLines(linesInCenterSlab, r);

      InversionCounter invCounter = new InversionCounter();
      //int intersectionCount = invCounter.run(lines, interval);

      //For each Sampled Line, compute its median intersection abscissa
      ArrayList<Double> medianIntersectionAbscissas = new ArrayList<>();
      for (Line l : lines) {
        Double abscissa = estimateMedianIntersectionAbscissas(l);
        medianIntersections.put(l, abscissa);
        medianIntersectionAbscissas.add(abscissa);
      }

      //rank of the repeated median in C
      k = (Math.floor(n * 0.5) - linesInLeftSlab.size());

      //compute k_lo and k_hi
      computeSlabBorders();

      //Employ fast selection algorithm to determine the Elements Theta_lo and Theta_hi
      thetaLow = randomizedSelect(medianIntersectionAbscissas, 0,
          medianIntersectionAbscissas.size() - 1, kLow);
      thetaHigh = randomizedSelect(medianIntersectionAbscissas, 0,
          medianIntersectionAbscissas.size() - 1, kHigh);

      //For each dual Line in C count the number of intersection abscissas that lie
      //in each of the intervals.
      countNumberOfIntersectionsAbscissas();

      //Based on this 3 counts, determine which of the subintervals contains the repeated median
      //and contract to this subiinterval.
      contractIntervals();

    }

    System.out.println(
        "Ergebnis: " + thetaLow * (-1) + " * x + " + (
            (linesInCenterSlab.get(0).getM() * (thetaLow * (-1))) + linesInCenterSlab.get(0)
                .getB()));
  }

  /**
   *
   * @param set
   * @param r
   * @return
   */
  public ArrayList<Line> sampleLines(ArrayList<Line> set, Double r) {

    ArrayList<Line> sampledLines = new ArrayList<>();

    for (int i = 0; i < r; i++) {
      sampledLines.add(set.get(ThreadLocalRandom.current().nextInt(0, linesInCenterSlab.size())));
    }

    return sampledLines;
  }

  /**
   *
   * @param sampledLine
   * @return
   */
  public Double estimateMedianIntersectionAbscissas(Line sampledLine) {

    Integer index = Integer.parseInt(sampledLine.getId());
    ArrayList<Double> intersections = new ArrayList<>();
    double intersection;

    for (Line line : linesInCenterSlab) {
      if (line != sampledLine) {
        intersection = (line.getB() - sampledLine.getB()) / (sampledLine.getM() - line.getM());

        if (!intersectionAbscissas.get(line).contains(intersection))
          intersectionAbscissas.get(line).add(intersection);
        if (!intersectionAbscissas.get(sampledLine).contains(intersection))
          intersectionAbscissas.get(sampledLine).add(intersection);

        intersections.add(intersection);
      }
    }

    Collections.sort(intersections);
    double ki = Math.ceil((n - 1) / 2) - countLeftSlab.get(index);
    double i = (Math.ceil((Math.sqrt(n) * ki) / countCenterSlab.get(index)));
    int accessIndex;
    if (i < 0)
      accessIndex = 0;
    else if (i >= intersections.size())
      accessIndex = intersections.size()-1;
    else
      accessIndex = (int) i;

    System.out.println(accessIndex);

    return intersections.get(accessIndex);
  }

  /**
   *
   */
  public void computeSlabBorders() {
    kLow = Math
        .max(1, Math.floor(((r * k) / (linesInCenterSlab.size())) - ((3 * Math.sqrt(r)) / (2))));
    kHigh = Math
        .min(r, Math.floor(((r * k) / (linesInCenterSlab.size())) + ((3 * Math.sqrt(r)) / (2))));
  }

  /**
   *
   * @param a
   * @param start
   * @param end
   * @param i
   * @return
   */
  public Double randomizedSelect(ArrayList<Double> a, int start, int end, double i) {
    if (start == end) {
      return a.get(start);
    }
    int q = randomizedPartition(a, start, end);
    int tmpPivot = q - start + 1;

    if (i == tmpPivot) {
      return a.get(q);
    } else if (i < tmpPivot) {
      return randomizedSelect(a, start, q - 1, i);
    } else {
      return randomizedSelect(a, q + 1, end, i - tmpPivot);
    }
  }

  /**
   *
   * @param a
   * @param start
   * @param end
   * @return
   */
  public int randomizedPartition(ArrayList<Double> a, int start, int end) {
    int delta = Math.abs(end - start);
    int i = start + ThreadLocalRandom.current().nextInt(0, delta);
    Collections.swap(a, end, i);
    return partition(a, start, end);
  }

  /**
   *
   * @param a
   * @param start
   * @param end
   * @return
   */
  public int partition(ArrayList<Double> a, int start, int end) {
    Double x = a.get(end);
    int i = start - 1;
    for (int j = start; j < end; j++) {
      if (a.get(j) <= x) {
        i++;
        Collections.swap(a, i, j);
      }
    }
    Collections.swap(a, i + 1, end);
    return i + 1;
  }

  /**
   *
   */
  public void countNumberOfIntersectionsAbscissas() {

    for (Line line : linesInCenterSlab) {
      ArrayList<Double> intersections = intersectionAbscissas.get(line);
      Integer index = Integer.parseInt(line.getId());
      int left = 0;
      int center = 0;
      int right = 0;

      for (Double intersection : intersections) {
        if (intersection <= thetaLow) {
          left++;
        } else if (intersection > thetaLow && intersection <= thetaHigh) {
          center++;
        } else if (intersection > thetaHigh){
          right++;
        }
      }

      System.out.println("Linie: "+line.getId()+"\tLeft: "+left+"\t Center: "+center+"\t Right: "+right);
      countLeftSlab.set(index, left);
      countCenterSlab.set(index, center);
      countRightSlab.set(index, right);
    }

  }

  /**
   *
   */
  public void contractIntervals() {
    //if (linesInLeftSlab.size() < Math.floor(n / 2) && Math.floor(n / 2) <= (linesInLeftSlab.size()
    //    + linesInCenterSlab.size())) {
       for (int i = 0; i < linesInCenterSlab.size(); i++) {

         int left = countLeftSlab.get(i);
         int center = countCenterSlab.get(i);
         int right = countRightSlab.get(i);

         int max = Math.max(left, Math.max(center, right));

         if (left == max){
           linesInLeftSlab.add(linesInCenterSlab.get(i));
           linesInCenterSlab.remove(i);
         } else if (right == max) {
           linesInRightSlab.add(linesInCenterSlab.get(i));
           linesInCenterSlab.remove(i);
         }
    //      if (medianIntersections.get(linesInCenterSlab.get(i)) != null) {
    //        if (medianIntersections.get(linesInCenterSlab.get(i)) <= thetaLow) {
    //          linesInLeftSlab.add(linesInCenterSlab.get(i));
    //          linesInCenterSlab.remove(i);
    //          countLeftSlab.set(i, countLeftSlab.get(i) + 1);
    //          countCenterSlab.set(i, countCenterSlab.get(i) - 1);
    //        } else if (medianIntersections.get(linesInCenterSlab.get(i)) > thetaHigh) {
    //          linesInRightSlab.add(linesInCenterSlab.get(i));
    //          linesInCenterSlab.remove(i);
    //          countRightSlab.set(i, countRightSlab.get(i) + 1);
    //          countCenterSlab.set(i, countCenterSlab.get(i) - 1);
    //        }
    //      }
    //    }
    //
      }

    //wähle C als C
    if (linesInLeftSlab.size() < Math.ceil(n/2)  && Math.ceil(n/2) <= linesInLeftSlab.size()+linesInCenterSlab.size()){
      interval.setLower(thetaLow + 0.1);
      interval.setUpper(thetaHigh);
    }
    // wähle L als C
    else if (Math.ceil(n/2) <= linesInLeftSlab.size()){
      interval.setUpper(thetaLow);
    }
    //wähle R als C
    else if (linesInLeftSlab.size()+linesInCenterSlab.size() < Math.ceil(n/2) && Math.ceil(n/2) <= (linesInLeftSlab.size()+linesInCenterSlab.size()+linesInRightSlab.size()) ){
      interval.setLower(thetaHigh - 0.1);
    }
  }
}