package graph;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.TreeMap;

import feature.StreetSegment;

/**
 * Permanent label manager backed by exact-value ordered buckets.
 */
public class PermanentLabelBuckets extends AbstractLabelManager implements PermanentLabelManager
{
  private TreeMap<Double, Deque<Integer>> buckets;

  /**
   * @param networkSize network size
   */
  public PermanentLabelBuckets(final int networkSize)
  {
    super(networkSize);
    this.buckets = new TreeMap<Double, Deque<Integer>>();
  }

  @Override
  public void adjustHeadValue(final StreetSegment segment)
  {
    if (segment == null)
    {
      return;
    }

    int headID = segment.getHead();
    Label head = getLabel(headID);
    if (head == null || head.isPermanent())
    {
      return;
    }

    double previous = head.getValue();
    super.adjustHeadValue(segment);
    if (head.getValue() < previous)
    {
      addToBucket(headID, head.getValue());
    }
  }

  @Override
  public Label getSmallestLabel()
  {
    while (!buckets.isEmpty())
    {
      Double smallestKey = buckets.firstKey();
      Deque<Integer> ids = buckets.get(smallestKey);
      while (ids != null && !ids.isEmpty())
      {
        int id = ids.removeFirst();
        Label label = getLabel(id);
        if (label == null || label.isPermanent())
        {
          continue;
        }

        if (Double.compare(label.getValue(), smallestKey.doubleValue()) == 0)
        {
          if (ids.isEmpty())
          {
            buckets.remove(smallestKey);
          }
          return label;
        }
      }

      buckets.remove(smallestKey);
    }

    Label smallest = null;
    for (Label label : labels)
    {
      if (label == null || label.isPermanent())
      {
        continue;
      }
      if (smallest == null || label.getValue() < smallest.getValue())
      {
        smallest = label;
      }
    }
    return smallest;
  }

  @Override
  public void makePermanent(final int intersectionID)
  {
    Label label = getLabel(intersectionID);
    if (label != null)
    {
      label.makePermanent();
    }
  }

  private void addToBucket(final int intersectionID, final double value)
  {
    Deque<Integer> ids = buckets.get(value);
    if (ids == null)
    {
      ids = new ArrayDeque<Integer>();
      buckets.put(value, ids);
    }
    ids.addLast(intersectionID);
  }
}