/*
 * Copyright 2016 Open Networking Laboratory
 *
 * 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 org.onosproject.store.primitives.impl;

import java.util.Collection;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import org.onosproject.store.service.AsyncConsistentMap;
import org.onosproject.store.service.MapEvent;
import org.onosproject.store.service.MapEventListener;
import org.onosproject.store.service.Versioned;

import com.google.common.collect.Maps;

/**
 * An {@code AsyncConsistentMap} that maps its operations to operations on a
 * differently typed {@code AsyncConsistentMap} by transcoding operation inputs and outputs.
 *
 * @param <K2> key type of other map
 * @param <V2> value type of other map
 * @param <K1> key type of this map
 * @param <V1> value type of this map
 */
public class TranscodingAsyncConsistentMap<K1, V1, K2, V2> implements AsyncConsistentMap<K1, V1> {

    private final AsyncConsistentMap<K2, V2> backingMap;
    private final Function<K1, K2> keyEncoder;
    private final Function<K2, K1> keyDecoder;
    private final Function<V2, V1> valueDecoder;
    private final Function<V1, V2> valueEncoder;
    private final Function<Versioned<V2>, Versioned<V1>> versionedValueTransform;
    private final Map<MapEventListener<K1, V1>, InternalBackingMapEventListener> listeners =
            Maps.newIdentityHashMap();

    public TranscodingAsyncConsistentMap(AsyncConsistentMap<K2, V2> backingMap,
                                   Function<K1, K2> keyEncoder,
                                   Function<K2, K1> keyDecoder,
                                   Function<V1, V2> valueEncoder,
                                   Function<V2, V1> valueDecoder) {
        this.backingMap = backingMap;
        this.keyEncoder = k -> k == null ? null : keyEncoder.apply(k);
        this.keyDecoder = k -> k == null ? null : keyDecoder.apply(k);
        this.valueEncoder = v -> v == null ? null : valueEncoder.apply(v);
        this.valueDecoder = v -> v == null ? null : valueDecoder.apply(v);
        this.versionedValueTransform = v -> v == null ? null : v.map(valueDecoder);
    }

    @Override
    public String name() {
        return backingMap.name();
    }

    @Override
    public CompletableFuture<Integer> size() {
        return backingMap.size();
    }

    @Override
    public CompletableFuture<Boolean> containsKey(K1 key) {
        return backingMap.containsKey(keyEncoder.apply(key));
    }

    @Override
    public CompletableFuture<Boolean> containsValue(V1 value) {
        return backingMap.containsValue(valueEncoder.apply(value));
    }

    @Override
    public CompletableFuture<Versioned<V1>> get(K1 key) {
        return backingMap.get(keyEncoder.apply(key)).thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Versioned<V1>> computeIf(K1 key,
            Predicate<? super V1> condition,
            BiFunction<? super K1, ? super V1, ? extends V1> remappingFunction) {
        return backingMap.computeIf(keyEncoder.apply(key),
                                    v -> condition.test(valueDecoder.apply(v)),
                                    (k, v) -> valueEncoder.apply(remappingFunction.apply(keyDecoder.apply(k),
                                                                                         valueDecoder.apply(v))))
                         .thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Versioned<V1>> put(K1 key, V1 value) {
        return backingMap.put(keyEncoder.apply(key), valueEncoder.apply(value))
                         .thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Versioned<V1>> putAndGet(K1 key, V1 value) {
        return backingMap.putAndGet(keyEncoder.apply(key), valueEncoder.apply(value))
                         .thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Versioned<V1>> remove(K1 key) {
        return backingMap.remove(keyEncoder.apply(key)).thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Void> clear() {
        return backingMap.clear();
    }

    @Override
    public CompletableFuture<Set<K1>> keySet() {
        return backingMap.keySet()
                         .thenApply(s -> s.stream().map(keyDecoder).collect(Collectors.toSet()));
    }

    @Override
    public CompletableFuture<Collection<Versioned<V1>>> values() {
        return backingMap.values()
                .thenApply(c -> c.stream().map(versionedValueTransform).collect(Collectors.toList()));
    }

    @Override
    public CompletableFuture<Set<Entry<K1, Versioned<V1>>>> entrySet() {
        return backingMap.entrySet()
                         .thenApply(s -> s.stream()
                                          .map(e -> Maps.immutableEntry(keyDecoder.apply(e.getKey()),
                                                                        versionedValueTransform.apply(e.getValue())))
                                          .collect(Collectors.toSet()));
    }

    @Override
    public CompletableFuture<Versioned<V1>> putIfAbsent(K1 key, V1 value) {
        return backingMap.putIfAbsent(keyEncoder.apply(key), valueEncoder.apply(value))
                         .thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Boolean> remove(K1 key, V1 value) {
        return backingMap.remove(keyEncoder.apply(key), valueEncoder.apply(value));
    }

    @Override
    public CompletableFuture<Boolean> remove(K1 key, long version) {
        return backingMap.remove(keyEncoder.apply(key), version);
    }

    @Override
    public CompletableFuture<Versioned<V1>> replace(K1 key, V1 value) {
        return backingMap.replace(keyEncoder.apply(key), valueEncoder.apply(value))
                .thenApply(versionedValueTransform);
    }

    @Override
    public CompletableFuture<Boolean> replace(K1 key, V1 oldValue, V1 newValue) {
        return backingMap.replace(keyEncoder.apply(key), valueEncoder.apply(oldValue), valueEncoder.apply(newValue));
    }

    @Override
    public CompletableFuture<Boolean> replace(K1 key, long oldVersion, V1 newValue) {
        return backingMap.replace(keyEncoder.apply(key), oldVersion, valueEncoder.apply(newValue));
    }

    @Override
    public CompletableFuture<Void> addListener(MapEventListener<K1, V1> listener) {
        synchronized (listeners) {
            InternalBackingMapEventListener backingMapListener =
                    listeners.computeIfAbsent(listener, k -> new InternalBackingMapEventListener(listener));
            return backingMap.addListener(backingMapListener);
        }
    }

    @Override
    public CompletableFuture<Void> removeListener(MapEventListener<K1, V1> listener) {
        InternalBackingMapEventListener backingMapListener = listeners.remove(listener);
        if (backingMapListener != null) {
            return backingMap.removeListener(backingMapListener);
        } else {
            return CompletableFuture.completedFuture(null);
        }
    }

    private class InternalBackingMapEventListener implements MapEventListener<K2, V2> {

        private final MapEventListener<K1, V1> listener;

        InternalBackingMapEventListener(MapEventListener<K1, V1> listener) {
            this.listener = listener;
        }

        @Override
        public void event(MapEvent<K2, V2> event) {
            listener.event(new MapEvent<K1, V1>(event.name(),
                    keyDecoder.apply(event.key()),
                    event.newValue().map(valueDecoder),
                    event.oldValue().map(valueDecoder)));
        }
    }
}