/********************************************************************
 * 2014 -
 * open source under Apache License Version 2.0
 ********************************************************************/
/**
 * 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.
 */
#ifndef _HDFS_LIBHDFS3_COMMON_LRUMAP_H_
#define _HDFS_LIBHDFS3_COMMON_LRUMAP_H_

#include "Unordered.h"
#include "Thread.h"

#include <list>

namespace Hdfs {
namespace Internal {

template <typename K, typename V>
class LruMap {
public:
    typedef K KeyType;
    typedef V ValueType;
    typedef std::pair<K, V> ItmeType;
    typedef std::list<ItmeType> ListType;
    typedef unordered_map<K, typename ListType::iterator> MapType;

public:
    LruMap() : count(0), maxSize(1000) {
    }

    LruMap(size_t size) : count(0), maxSize(size) {
    }

    ~LruMap() {
        lock_guard<mutex> lock(mut);
        map.clear();
        list.clear();
    }

    void setMaxSize(size_t s) {
        lock_guard<mutex> lock(mut);
        maxSize = s;

        for (size_t i = count; i > s; --i) {
            map.erase(list.back().first);
            list.pop_back();
            --count;
        }
    }

    void insert(const KeyType& key, const ValueType& value) {
        lock_guard<mutex> lock(mut);
        typename MapType::iterator it = map.find(key);

        if (it != map.end()) {
            --count;
            list.erase(it->second);
        }

        list.push_front(std::make_pair(key, value));
        map[key] = list.begin();
        ++count;

        if (count > maxSize) {
            map.erase(list.back().first);
            list.pop_back();
            --count;
        }
    }

    void erase(const KeyType& key) {
        lock_guard<mutex> lock(mut);
        typename MapType::iterator it = map.find(key);

        if (it != map.end()) {
            list.erase(it->second);
            map.erase(it);
            --count;
        }
    }

    bool find(const KeyType& key, ValueType* value) {
        lock_guard<mutex> lock(mut);
        return findAndEraseInternal(key, value, false);
    }

    bool findAndErase(const KeyType& key, ValueType* value) {
        lock_guard<mutex> lock(mut);
        return findAndEraseInternal(key, value, true);
    }

    size_t size() {
        lock_guard<mutex> lock(mut);
        return count;
    }

private:
    bool findAndEraseInternal(const KeyType& key, ValueType* value,
                              bool erase) {
        typename MapType::iterator it = map.find(key);

        if (it != map.end()) {
            *value = it->second->second;
            list.erase(it->second);

            if (erase) {
                map.erase(it);
                --count;
            } else {
                list.push_front(std::make_pair(key, *value));
                map[key] = list.begin();
            }

            return true;
        }

        return false;
    }

private:
    size_t count;
    size_t maxSize;
    ListType list;
    MapType map;
    mutex mut;
};
}
}
#endif /* _HDFS_LIBHDFS3_COMMON_LRU_H_ */