/*
 * Copyright 2015 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.trivial.impl;

import static org.apache.commons.lang3.concurrent.ConcurrentUtils.createIfAbsentUnchecked;
import static org.slf4j.LoggerFactory.getLogger;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Service;
import org.onlab.util.NewConcurrentHashMap;
import org.onosproject.core.DefaultGroupId;
import org.onosproject.core.GroupId;
import org.onosproject.net.DeviceId;
import org.onosproject.net.group.DefaultGroup;
import org.onosproject.net.group.DefaultGroupDescription;
import org.onosproject.net.group.Group;
import org.onosproject.net.group.Group.GroupState;
import org.onosproject.net.group.GroupBucket;
import org.onosproject.net.group.GroupBuckets;
import org.onosproject.net.group.GroupDescription;
import org.onosproject.net.group.GroupEvent;
import org.onosproject.net.group.GroupEvent.Type;
import org.onosproject.net.group.GroupKey;
import org.onosproject.net.group.GroupStore;
import org.onosproject.net.group.GroupStoreDelegate;
import org.onosproject.net.group.StoredGroupEntry;
import org.onosproject.store.AbstractStore;
import org.slf4j.Logger;

import com.google.common.base.Function;
import com.google.common.collect.FluentIterable;

/**
 * Manages inventory of group entries using trivial in-memory implementation.
 */
@Component(immediate = true)
@Service
public class SimpleGroupStore
        extends AbstractStore<GroupEvent, GroupStoreDelegate>
        implements GroupStore {

    private final Logger log = getLogger(getClass());

    // inner Map is per device group table
    private final ConcurrentMap<DeviceId, ConcurrentMap<GroupKey, StoredGroupEntry>>
            groupEntriesByKey = new ConcurrentHashMap<>();
    private final ConcurrentMap<DeviceId, ConcurrentMap<GroupId, StoredGroupEntry>>
            groupEntriesById = new ConcurrentHashMap<>();

    private final AtomicInteger groupIdGen = new AtomicInteger();

    @Activate
    public void activate() {
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        groupEntriesByKey.clear();
        groupEntriesById.clear();
        log.info("Stopped");
    }

    private static NewConcurrentHashMap<GroupKey, StoredGroupEntry> lazyEmptyGroupKeyTable() {
        return NewConcurrentHashMap.<GroupKey, StoredGroupEntry>ifNeeded();
    }

    private static NewConcurrentHashMap<GroupId, StoredGroupEntry> lazyEmptyGroupIdTable() {
        return NewConcurrentHashMap.<GroupId, StoredGroupEntry>ifNeeded();
    }

    /**
     * Returns the group key table for specified device.
     *
     * @param deviceId identifier of the device
     * @return Map representing group key table of given device.
     */
    private ConcurrentMap<GroupKey, StoredGroupEntry> getGroupKeyTable(DeviceId deviceId) {
        return createIfAbsentUnchecked(groupEntriesByKey,
                                       deviceId, lazyEmptyGroupKeyTable());
    }

    /**
     * Returns the group id table for specified device.
     *
     * @param deviceId identifier of the device
     * @return Map representing group key table of given device.
     */
    private ConcurrentMap<GroupId, StoredGroupEntry> getGroupIdTable(DeviceId deviceId) {
        return createIfAbsentUnchecked(groupEntriesById,
                                       deviceId, lazyEmptyGroupIdTable());
    }

    /**
     * Returns the number of groups for the specified device in the store.
     *
     * @return number of groups for the specified device
     */
    @Override
    public int getGroupCount(DeviceId deviceId) {
        return (groupEntriesByKey.get(deviceId) != null) ?
                 groupEntriesByKey.get(deviceId).size() : 0;
    }

    /**
     * Returns the groups associated with a device.
     *
     * @param deviceId the device ID
     *
     * @return the group entries
     */
    @Override
    public Iterable<Group> getGroups(DeviceId deviceId) {
        // flatten and make iterator unmodifiable
        if (groupEntriesByKey.get(deviceId) != null) {
            return FluentIterable.from(groupEntriesByKey.get(deviceId).values())
                .transform(
                        new Function<StoredGroupEntry, Group>() {

                            @Override
                            public Group apply(
                                    StoredGroupEntry input) {
                                return input;
                            }
                        });
        } else {
            return null;
        }
    }

    /**
     * Returns the stored group entry.
     *
     * @param deviceId the device ID
     * @param appCookie the group key
     *
     * @return a group associated with the key
     */
    @Override
    public Group getGroup(DeviceId deviceId, GroupKey appCookie) {
        return (groupEntriesByKey.get(deviceId) != null) ?
                      groupEntriesByKey.get(deviceId).get(appCookie) :
                      null;
    }

    /**
     * Stores a new group entry using the information from group description.
     *
     * @param groupDesc group description to be used to create group entry
     */
    @Override
    public void storeGroupDescription(GroupDescription groupDesc) {
        /* Check if a group is existing with the same key */
        if (getGroup(groupDesc.deviceId(), groupDesc.appCookie()) != null) {
            return;
        }

        /* Get a new group identifier */
        GroupId id = new DefaultGroupId(groupIdGen.incrementAndGet());
        /* Create a group entry object */
        StoredGroupEntry group = new DefaultGroup(id, groupDesc);
        /* Insert the newly created group entry into concurrent key and id maps */
        ConcurrentMap<GroupKey, StoredGroupEntry> keyTable =
                getGroupKeyTable(groupDesc.deviceId());
        keyTable.put(groupDesc.appCookie(), group);
        ConcurrentMap<GroupId, StoredGroupEntry> idTable =
                getGroupIdTable(groupDesc.deviceId());
        idTable.put(id, group);
        notifyDelegate(new GroupEvent(GroupEvent.Type.GROUP_ADD_REQUESTED,
                                      group));
    }

    /**
     * Updates the existing group entry with the information
     * from group description.
     *
     * @param deviceId the device ID
     * @param oldAppCookie the current group key
     * @param type update type
     * @param newGroupDesc group description with updates
     */
    @Override
    public void updateGroupDescription(DeviceId deviceId,
                                GroupKey oldAppCookie,
                                UpdateType type,
                                GroupDescription newGroupDesc) {
        /* Check if a group is existing with the provided key */
        Group oldGroup = getGroup(deviceId, oldAppCookie);
        if (oldGroup == null) {
            return;
        }

        List<GroupBucket> newBucketList = getUpdatedBucketList(oldGroup,
                                                               type,
                                               newGroupDesc.buckets());
        if (newBucketList != null) {
            /* Create a new group object from the old group */
            GroupBuckets updatedBuckets = new GroupBuckets(newBucketList);
            GroupDescription updatedGroupDesc = new DefaultGroupDescription(
                                                        oldGroup.deviceId(),
                                                        oldGroup.type(),
                                                        updatedBuckets,
                                                        newGroupDesc.appCookie(),
                                                        oldGroup.appId());
            StoredGroupEntry newGroup = new DefaultGroup(oldGroup.id(),
                                                     updatedGroupDesc);
            newGroup.setState(GroupState.PENDING_UPDATE);
            newGroup.setLife(oldGroup.life());
            newGroup.setPackets(oldGroup.packets());
            newGroup.setBytes(oldGroup.bytes());
            /* Remove the old entry from maps and add new entry
             * using new key
             */
            ConcurrentMap<GroupKey, StoredGroupEntry> keyTable =
                    getGroupKeyTable(oldGroup.deviceId());
            ConcurrentMap<GroupId, StoredGroupEntry> idTable =
                    getGroupIdTable(oldGroup.deviceId());
            keyTable.remove(oldGroup.appCookie());
            idTable.remove(oldGroup.id());
            keyTable.put(newGroup.appCookie(), newGroup);
            idTable.put(newGroup.id(), newGroup);
            notifyDelegate(new GroupEvent(Type.GROUP_UPDATE_REQUESTED, newGroup));
        }
    }

    private List<GroupBucket> getUpdatedBucketList(Group oldGroup,
                                   UpdateType type,
                                   GroupBuckets buckets) {
        GroupBuckets oldBuckets = oldGroup.buckets();
        List<GroupBucket> newBucketList = new ArrayList<GroupBucket>(
                oldBuckets.buckets());
        boolean groupDescUpdated = false;

        if (type == UpdateType.ADD) {
            /* Check if the any of the new buckets are part of the
             * old bucket list
             */
            for (GroupBucket addBucket:buckets.buckets()) {
                if (!newBucketList.contains(addBucket)) {
                    newBucketList.add(addBucket);
                    groupDescUpdated = true;
                }
            }
        } else if (type == UpdateType.REMOVE) {
            /* Check if the to be removed buckets are part of the
             * old bucket list
             */
            for (GroupBucket removeBucket:buckets.buckets()) {
                if (newBucketList.contains(removeBucket)) {
                    newBucketList.remove(removeBucket);
                    groupDescUpdated = true;
                }
            }
        }

        if (groupDescUpdated) {
            return newBucketList;
        } else {
            return null;
        }
    }

    /**
     * Triggers deleting the existing group entry.
     *
     * @param deviceId the device ID
     * @param appCookie the group key
     */
    @Override
    public void deleteGroupDescription(DeviceId deviceId,
                                GroupKey appCookie) {
        /* Check if a group is existing with the provided key */
        StoredGroupEntry existing = (groupEntriesByKey.get(deviceId) != null) ?
                           groupEntriesByKey.get(deviceId).get(appCookie) :
                           null;
        if (existing == null) {
            return;
        }

        synchronized (existing) {
            existing.setState(GroupState.PENDING_DELETE);
        }
        notifyDelegate(new GroupEvent(Type.GROUP_REMOVE_REQUESTED, existing));
    }

    /**
     * Stores a new group entry, or updates an existing entry.
     *
     * @param group group entry
     */
    @Override
    public void addOrUpdateGroupEntry(Group group) {
        // check if this new entry is an update to an existing entry
        StoredGroupEntry existing = (groupEntriesById.get(
                      group.deviceId()) != null) ?
                      groupEntriesById.get(group.deviceId()).get(group.id()) :
                      null;
        GroupEvent event = null;

        if (existing != null) {
            synchronized (existing) {
                existing.setLife(group.life());
                existing.setPackets(group.packets());
                existing.setBytes(group.bytes());
                if (existing.state() == GroupState.PENDING_ADD) {
                    existing.setState(GroupState.ADDED);
                    event = new GroupEvent(Type.GROUP_ADDED, existing);
                } else {
                    if (existing.state() == GroupState.PENDING_UPDATE) {
                        existing.setState(GroupState.PENDING_UPDATE);
                    }
                    event = new GroupEvent(Type.GROUP_UPDATED, existing);
                }
            }
        }

        if (event != null) {
            notifyDelegate(event);
        }
    }

    /**
     * Removes the group entry from store.
     *
     * @param group group entry
     */
    @Override
    public void removeGroupEntry(Group group) {
        StoredGroupEntry existing = (groupEntriesById.get(
                         group.deviceId()) != null) ?
                         groupEntriesById.get(group.deviceId()).get(group.id()) :
                         null;

        if (existing != null) {
            ConcurrentMap<GroupKey, StoredGroupEntry> keyTable =
                    getGroupKeyTable(existing.deviceId());
            ConcurrentMap<GroupId, StoredGroupEntry> idTable =
                    getGroupIdTable(existing.deviceId());
            idTable.remove(existing.id());
            keyTable.remove(existing.appCookie());
            notifyDelegate(new GroupEvent(Type.GROUP_REMOVED, existing));
        }
    }
}