/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.felix.resolver.util;

import java.util.*;

public class ArrayMap<K, V> extends AbstractMap<K, V> {

    private Object[] table;
    private int size;
    protected transient Collection<V> values;

    public ArrayMap() {
        this(32);
    }

    public ArrayMap(int capacity) {
        table = new Object[capacity * 2];
        size = 0;
    }

    @Override
    @SuppressWarnings("unchecked")
    public V get(Object key) {
        for (int i = 0, l = size << 1; i < l; i += 2) {
            if (key.equals(table[i])) {
                return (V) table[i + 1];
            }
        }
        return null;
    }

    @Override
    @SuppressWarnings("unchecked")
    public V put(K key, V value) {
        for (int i = 0, l = size << 1; i < l; i += 2) {
            if (key.equals(table[i])) {
                V old = (V) table[i + 1];
                table[i + 1] = value;
                return old;
            }
        }
        if (size * 2 == table.length) {
            Object[] n = new Object[table.length * 2];
            System.arraycopy(table, 0, n, 0, table.length);
            table = n;
        }
        int i = size++ << 1;
        table[i++] = key;
        table[i] = value;
        return null;
    }

    @SuppressWarnings("unchecked")
    public V getOrCompute(K key) {
        for (int i = 0, l = size << 1; i < l; i += 2) {
            if (key.equals(table[i])) {
                return (V) table[i + 1];
            }
        }
        V v = compute(key);
        if (size << 1 == table.length) {
            Object[] n = new Object[table.length << 1];
            System.arraycopy(table, 0, n, 0, table.length);
            table = n;
        }
        int i = size++ << 1;
        table[i++] = key;
        table[i] = v;
        return v;
    }

    protected V compute(K key) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Collection<V> values() {
        if (values == null) {
            values = new AbstractCollection<V>() {
                @Override
                public Iterator<V> iterator() {
                    return new Iterator<V>() {
                        int index = 0;

                        public boolean hasNext() {
                            return index < size;
                        }

                        @SuppressWarnings("unchecked")
                        public V next() {
                            if (index >= size) {
                                throw new NoSuchElementException();
                            }
                            return (V) table[(index++ << 1) + 1];
                        }
                        
                        public void remove() {
                            throw new UnsupportedOperationException();
                        }
                    };
                }

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

    @Override
    public Set<Entry<K, V>> entrySet() {
        return new AbstractSet<Entry<K, V>>() {
            @Override
            public Iterator<Entry<K, V>> iterator() {
                return new Iterator<Entry<K, V>>() {
                    FastEntry<K, V> entry = new FastEntry<K, V>();
                    int index = 0;

                    public boolean hasNext() {
                        return index < size;
                    }

                    @SuppressWarnings("unchecked")
                    public FastEntry<K, V> next() {
                        if (index >= size) {
                            throw new NoSuchElementException();
                        }
                        int i = index << 1;
                        entry.key = (K) table[i];
                        entry.value = (V) table[i + 1];
                        index++;
                        return entry;
                    }

                    public void remove() {
                        throw new UnsupportedOperationException();
                    }
                };
            }

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

    static class FastEntry<K, V> implements Entry<K, V> {
        K key;
        V value;

        public K getKey() {
            return key;
        }


        public V getValue() {
            return value;
        }

        public V setValue(V value) {
            throw new UnsupportedOperationException();
        }
    }
}