/*
 * Licensed 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 com.facebook.presto.accumulo.serializers;

import org.apache.accumulo.core.client.lexicoder.Lexicoder;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import static org.apache.accumulo.core.client.lexicoder.impl.ByteUtils.concat;
import static org.apache.accumulo.core.client.lexicoder.impl.ByteUtils.escape;
import static org.apache.accumulo.core.client.lexicoder.impl.ByteUtils.split;
import static org.apache.accumulo.core.client.lexicoder.impl.ByteUtils.unescape;

/**
 * Accumulo lexicoder for encoding a Java Map
 *
 * @param <K> Key data type
 * @param <V> Value data type
 */
public class MapLexicoder<K, V>
        implements Lexicoder<Map<K, V>>
{
    private final Lexicoder<K> keyLexicoder;
    private final Lexicoder<V> valueLexicoder;

    public MapLexicoder(
            Lexicoder<K> keyLexicoder,
            Lexicoder<V> valueLexicoder)
    {
        this.keyLexicoder = keyLexicoder;
        this.valueLexicoder = valueLexicoder;
    }

    @Override
    public byte[] encode(Map<K, V> v)
    {
        byte[][] elements = new byte[v.size() * 2][];
        int index = 0;
        for (Entry<K, V> entry : v.entrySet()) {
            elements[index++] = escape(keyLexicoder.encode(entry.getKey()));
            elements[index++] = escape(valueLexicoder.encode(entry.getValue()));
        }

        return concat(elements);
    }

    @Override
    public Map<K, V> decode(byte[] b)
    {
        byte[][] escapedElements = split(b);
        Map<K, V> decodedMap = new HashMap<>();
        for (int i = 0; i < escapedElements.length; i += 2) {
            K key = keyLexicoder.decode(unescape(escapedElements[i]));
            V value = valueLexicoder.decode(unescape(escapedElements[i + 1]));
            decodedMap.put(key, value);
        }

        return decodedMap;
    }
}