/*
 * Copyright 2016-present 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.Map;
import java.util.concurrent.CompletableFuture;

import org.onosproject.store.service.AsyncDocumentTree;
import org.onosproject.store.service.DocumentPath;
import org.onosproject.store.service.DocumentTreeEvent;
import org.onosproject.store.service.DocumentTreeListener;
import org.onosproject.store.service.Serializer;
import org.onosproject.store.service.Versioned;

import com.google.common.collect.Maps;

/**
 * Default implementation of {@link AsyncDocumentTree}.
 * <p>
 * This implementation delegates execution to a backing tree implemented on top of Atomix framework.
 *
 * @See AtomixDocumentTree
 *
 * @param <V> tree node value type.
 */
public class DefaultDistributedDocumentTree<V> implements AsyncDocumentTree<V> {

    private final String name;
    private final AsyncDocumentTree<byte[]> backingTree;
    private final Serializer serializer;
    private final Map<DocumentTreeListener<V>, InternalBackingDocumentTreeListener> listeners =
            Maps.newIdentityHashMap();

    DefaultDistributedDocumentTree(String name, AsyncDocumentTree<byte[]> backingTree, Serializer serializer) {
        this.name = name;
        this.backingTree = backingTree;
        this.serializer = serializer;
    }

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

    @Override
    public Type primitiveType() {
        return backingTree.primitiveType();
    }

    @Override
    public DocumentPath root() {
        return backingTree.root();
    }

    @Override
    public CompletableFuture<Map<String, Versioned<V>>> getChildren(DocumentPath path) {
        return backingTree.getChildren(path)
                          .thenApply(map -> Maps.transformValues(map, v -> v.map(serializer::decode)));
    }

    @Override
    public CompletableFuture<Versioned<V>> get(DocumentPath path) {
        return backingTree.get(path)
                          .thenApply(v -> v == null ? null : v.map(serializer::decode));
    }

    @Override
    public CompletableFuture<Versioned<V>> set(DocumentPath path, V value) {
        return backingTree.set(path, serializer.encode(value))
                          .thenApply(v -> v == null ? null : v.map(serializer::decode));
    }

    @Override
    public CompletableFuture<Boolean> create(DocumentPath path, V value) {
        return backingTree.create(path, serializer.encode(value));
    }

    @Override
    public CompletableFuture<Boolean> replace(DocumentPath path, V newValue, long version) {
        return backingTree.replace(path, serializer.encode(newValue), version);
    }

    @Override
    public CompletableFuture<Boolean> replace(DocumentPath path, V newValue, V currentValue) {
        return backingTree.replace(path, serializer.encode(newValue), serializer.encode(currentValue));
    }

    @Override
    public CompletableFuture<Versioned<V>> removeNode(DocumentPath path) {
        return backingTree.removeNode(path)
                          .thenApply(v -> v == null ? null : v.map(serializer::decode));
    }

    @Override
    public CompletableFuture<Void> addListener(DocumentPath path, DocumentTreeListener<V> listener) {
        synchronized (listeners) {
            InternalBackingDocumentTreeListener backingListener =
                    listeners.computeIfAbsent(listener, k -> new InternalBackingDocumentTreeListener(listener));
            return backingTree.addListener(path, backingListener);
        }
    }

    @Override
    public CompletableFuture<Void> removeListener(DocumentTreeListener<V> listener) {
        synchronized (listeners) {
            InternalBackingDocumentTreeListener backingListener = listeners.remove(listener);
            if (backingListener != null) {
                return backingTree.removeListener(backingListener);
            } else {
                return CompletableFuture.completedFuture(null);
            }
        }
    }

    private class InternalBackingDocumentTreeListener implements DocumentTreeListener<byte[]> {

        private final DocumentTreeListener<V> listener;

        InternalBackingDocumentTreeListener(DocumentTreeListener<V> listener) {
            this.listener = listener;
        }

        @Override
        public void event(DocumentTreeEvent<byte[]> event) {
            listener.event(new DocumentTreeEvent<V>(event.path(),
                    event.type(),
                    event.newValue().map(v -> v.map(serializer::decode)),
                    event.oldValue().map(v -> v.map(serializer::decode))));
        }
    }
}