package kademlia

import (
  "container/list";
  "container/vector";
  "exp/iterable";
  "sort";
)

const BucketSize = 20;

type RoutingTable struct {
  node Contact;
  buckets [IdLength*8]*list.List;
}

type ContactRecord struct {
  node *Contact;
  sortKey NodeID;
}

func (rec *ContactRecord) Less(other interface{}) bool {
  return rec.sortKey.Less(other.(*ContactRecord).sortKey);
}

func NewRoutingTable(node *Contact) (ret *RoutingTable) {
  ret = new(RoutingTable);
  for i := 0; i < IdLength * 8; i++ {
    ret.buckets[i] = list.New();
  }
  ret.node = *node;
  return;
}

func (table *RoutingTable) Update(contact *Contact) {
  prefix_length := contact.id.Xor(table.node.id).PrefixLen();
  bucket := table.buckets[prefix_length];
  element := iterable.Find(bucket, func(x interface{}) bool {
    return x.(*Contact).id.Equals(table.node.id);
  });
  if element == nil {
    if bucket.Len() <= BucketSize {
      bucket.PushFront(contact);
    }
    // TODO: Handle insertion when the list is full by evicting old elements if
    // they don't respond to a ping.
  } else {
    bucket.MoveToFront(element.(*list.Element));
  }
}

func copyToVector(start, end *list.Element, vec *vector.Vector, target NodeID) {
  for elt := start; elt != end; elt = elt.Next() {
    contact := elt.Value.(*Contact);
    vec.Push(&ContactRecord{contact, contact.id.Xor(target)});
  }
}

func (table *RoutingTable) FindClosest(target NodeID, count int) (ret *vector.Vector) {
  ret = new(vector.Vector).Resize(0, count);

  bucket_num := target.Xor(table.node.id).PrefixLen();
  bucket := table.buckets[bucket_num];
  copyToVector(bucket.Front(), nil, ret, target);

  for i := 1; (bucket_num-i >= 0 || bucket_num+i < IdLength*8) && ret.Len() < count; i++ {
    if bucket_num - i >= 0 {
      bucket = table.buckets[bucket_num - i];
      copyToVector(bucket.Front(), nil, ret, target);
    }
    if bucket_num + i < IdLength * 8 {
      bucket = table.buckets[bucket_num + i];
      copyToVector(bucket.Front(), nil, ret, target);
    }
  }
  
  sort.Sort(ret);
  if ret.Len() > count {
    ret.Cut(count, ret.Len());
  }
  return;
}