package org.opendaylight.yangtools.triemap;

import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Mimic immutable ListMap in Scala
 *  
 * @author Roman Levenstein <romixlev@gmail.com>
 *
 * @param <V>
 */
abstract class ListMap<K,V> {

    ListMap<K,V> next;
    
    static <K,V> ListMap<K, V> map(K k, V v, ListMap<K, V> tail){
        return new Node<K, V> (k, v, tail);
    }

    static <K,V> ListMap<K, V> map(K k, V v){
        return new Node<K, V> (k, v, null);
    }

    static <K,V> ListMap<K, V> map(K k1, V v1, K k2, V v2){
        return new Node<K, V> (k1, v1, new Node<K,V>(k2,v2, null));
    }
    
    public abstract int size ();

    public abstract boolean isEmpty() ;
    
    abstract public boolean contains(K k, V v);

    abstract public boolean contains(K key);

    abstract public Option<V> get (K key);

    abstract public ListMap<K, V> add (K key, V value);

    abstract public ListMap<K, V> remove (K key);
    
    abstract public Iterator<Map.Entry<K, V>> iterator();

    
    static class EmptyListMap<K,V> extends ListMap<K, V> {
        public ListMap<K,V> add (K key, V value) {
            return ListMap.map(key, value, null);
        }
        
        public boolean contains(K k, V v) {
            return false;
        }
        
        public boolean contains(K k) {
            return false;
        }
        
        public ListMap<K,V> remove(K key) {
            return this;
        }

        @Override
        public int size () {
            return 0;
        }

        @Override
        public boolean isEmpty () {
            return true;
        }

        @Override
        public Option<V> get (K key) {
            return Option.makeOption (null);
        }

        @Override
        public Iterator<Entry<K, V>> iterator () {
            return new EmptyListMapIterator<K, V> ();
        } 
        
        static class EmptyListMapIterator<K,V> implements Iterator<Entry<K, V>> {

            @Override
            public boolean hasNext () {
                return false;
            }

            @Override
            public Entry<K, V> next () {
                return null;
            }

            @Override
            public void remove () {
                throw new RuntimeException("Operation not supported");
            }
            
        }
    }
    
    static class Node<K,V> extends ListMap<K, V> {
        final K k;
        final V v;
        
        Node(K k, V v, ListMap<K,V> next) {
            this.k = k;
            this.v = v;
            this.next = next;
        }
        
        public ListMap<K,V> add (K key, V value) {
            return ListMap.map(key, value, remove (key));
        }
                
        public boolean contains(K k, V v) {
            if(k.equals (this.k) && v.equals (this.v))
                return true;
            else if(next != null) 
                return next.contains (k, v);
            return false;
        }
        
        public boolean contains(K k) {
            if(k.equals (this.k))
                return true;
            else if(next != null) 
                return next.contains (k);
            return false;
        }
        
        public ListMap<K,V> remove(K key) {
            if(!contains(key))
                return this;
            else
                return remove0(key);
        }
        
        private ListMap<K, V> remove0 (K key) {
            ListMap<K, V> n = this;
            ListMap<K, V> newN = null;
            ListMap<K, V> lastN = null;
            while (n != null) {
                if(n instanceof EmptyListMap) {
                    newN.next = n;
                    break;
                }
                Node<K, V> nn = (Node<K, V>)n;
                if (key.equals (nn.k)) {
                    n = n.next;
                    continue;
                } else {
                    if (newN != null) {
                        lastN.next = ListMap.map (nn.k, nn.v, null);
                        lastN = lastN.next;
                    } else {
                        newN = ListMap.map (nn.k, nn.v, null);
                        lastN = newN;
                    }
                }
                n = n.next;
            }
            return newN;
        }

        @Override
        public int size () {
            if(next == null)
                return 1;
            else
                return 1+next.size ();
        }

        @Override
        public boolean isEmpty () {
            return false;
        }

        @Override
        public Option<V> get (K key) {
            if(key.equals (k))
                return Option.makeOption (v);
            if(next != null)
                return next.get (key);
            return Option.makeOption (null);
        }


        @Override
        public Iterator<Entry<K, V>> iterator () {
            return new NodeIterator<K, V> (this);
        }

        static class NodeIterator<K,V> implements Iterator<Entry<K, V>> {
            ListMap<K, V> n;

            public NodeIterator (Node<K, V> n) {
                this.n = n;
            }

            @Override
            public boolean hasNext () {
//                return n!= null && n.next != null && !(n.next instanceof EmptyListMap);
                return n!= null && !(n instanceof EmptyListMap);
            }

            @Override
            public Entry<K, V> next () {
                if (n instanceof Node) {
                    Node<K, V> nn = (Node<K, V>) n;
                    Pair<K, V> res = new Pair<K, V> (nn.k, nn.v);
                    n = n.next;
                    return res;
                } else {
                    return null;
                }
            }

            @Override
            public void remove () {
                throw new RuntimeException("Operation not supported");
            }
            
        }
    }
}