/**
 *  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.
 */
package org.apache.felix.useradmin.mongodb;

import java.util.ArrayList;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.List;

import org.apache.felix.useradmin.RoleFactory;
import org.osgi.service.useradmin.Group;
import org.osgi.service.useradmin.Role;
import org.osgi.service.useradmin.User;

import com.mongodb.BasicDBList;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.MongoException;

/**
 * Provides a helper class for (de)serializing data to/from MongoDB.
 */
final class MongoSerializerHelper
{

    static final String TYPE = "type";
    static final String NAME = "name";

    static final String PROPERTIES = "properties";
    static final String CREDENTIALS = "credentials";
    static final String MEMBERS = "members";
    static final String REQUIRED_MEMBERS = "requiredMembers";

    static final String SET = "$set";

    private final RoleProvider m_roleProvider;

    /**
     * Creates a new {@link MongoSerializerHelper} instance.
     * 
     * @param roleProvider the role provider to use, cannot be <code>null</code>.
     */
    public MongoSerializerHelper(RoleProvider roleProvider)
    {
        m_roleProvider = roleProvider;
    }

    /**
     * Converts a given {@link DBObject} to a {@link Role} instance.
     * 
     * @param object the {@link DBObject} to convert, cannot be <code>null</code>.
     * @return a {@link Role} instance, never <code>null</code>.
     */
    public Role deserialize(DBObject object)
    {
        int type = ((Integer) object.get(TYPE)).intValue();
        String name = (String) object.get(NAME);

        Role result = RoleFactory.createRole(type, name);
        // Read the generic properties of the role...
        deserializeDictionary(result.getProperties(), (DBObject) object.get(PROPERTIES));

        if ((Role.GROUP == type) || (Role.USER == type))
        {
            // This is safe, as Group extends from User...
            deserializeDictionary(((User) result).getCredentials(), (DBObject) object.get(CREDENTIALS));

            if (Role.GROUP == type)
            {
                for (Role member : getRoles((BasicDBList) object.get(MEMBERS)))
                {
                    ((Group) result).addMember(member);
                }

                for (Role member : getRoles((BasicDBList) object.get(REQUIRED_MEMBERS)))
                {
                    ((Group) result).addRequiredMember(member);
                }
            }
        }

        return result;
    }

    /**
     * Serializes the given {@link Role} to a {@link DBObject} instance.
     * 
     * @param role the {@link Role} to serialize, cannot be <code>null</code> (unchecked!).
     * @return a {@link DBObject} representing the given {@link Role}, never <code>null</code>.
     */
    public DBObject serialize(Role role)
    {
        BasicDBObject data = new BasicDBObject();

        int type = role.getType();

        data.put(TYPE, type);
        data.put(NAME, role.getName());

        data.put(PROPERTIES, serializeDictionary(role.getProperties()));
        if ((Role.GROUP == type) || (Role.USER == type))
        {
            data.put(CREDENTIALS, serializeDictionary(((User) role).getCredentials()));

            if (Role.GROUP == type)
            {
                data.put(MEMBERS, getRoleNames(((Group) role).getMembers()));
                data.put(REQUIRED_MEMBERS, getRoleNames(((Group) role).getRequiredMembers()));
            }
        }

        return data;
    }

    /**
     * Creates a {@link DBObject} with the given role and name. 
     * 
     * @param roleName the name of the role to serialize, cannot be <code>null</code> or empty (unchecked!);
     * @param type the type of the role to serialize.
     * @return a {@link DBObject} representing the role with the given name and type, never <code>null</code>.
     */
    public DBObject serialize(String roleName, int type)
    {
        BasicDBObject data = new BasicDBObject();

        data.put(TYPE, type);
        data.put(NAME, roleName);

        return data;
    }

    /**
     * Creates a serialized version of the given {@link Role} to be used in an update statement.
     * 
     * @param role the {@link Role} to update, cannot be <code>null</code>.
     * @return a {@link DBObject} representing an update statement for the given {@link Role}.
     */
    public DBObject serializeUpdate(Role role)
    {
        int type = role.getType();

        BasicDBObject changeSet = new BasicDBObject();

        changeSet.put(PROPERTIES, serializeDictionary(role.getProperties()));
        if ((Role.GROUP == type) || (Role.USER == type))
        {
            changeSet.put(CREDENTIALS, serializeDictionary(((User) role).getCredentials()));

            if (Role.GROUP == type)
            {
                changeSet.put(MEMBERS, getRoleNames(((Group) role).getMembers()));
                changeSet.put(REQUIRED_MEMBERS, getRoleNames(((Group) role).getRequiredMembers()));
            }
        }

        return new BasicDBObject(SET, changeSet);
    }

    /**
     * Finds an existing member by its name.
     * 
     * @param name the name of the member to return, cannot be <code>null</code>.
     * @return a member instance, never <code>null</code>.
     * @throws MongoException in case the requested member was not found (or any other MongoDB exception).
     */
    final Role findExistingMember(String name)
    {
        Role result = m_roleProvider.getRole(name);
        if (result == null)
        {
            throw new MongoException("No such role: " + name);
        }
        return result;
    }

    /**
     * Deserializes the given {@link DBObject} into the given {@link Dictionary}.
     * 
     * @param dictionary the dictionary to fill, cannot be <code>null</code>;
     * @param object the {@link DBObject} to deserialize, can be <code>null</code>.
     */
    private void deserializeDictionary(Dictionary dictionary, DBObject object)
    {
        // FELIX-4399: MongoDB does return null for empty properties...
        if (object != null)
        {
            for (String key : object.keySet())
            {
                dictionary.put(KeyCodec.decode(key), object.get(key));
            }
        }
    }

    /**
     * Serializes a given array of {@link Role}s to an list for storing in a {@link DBObject}.
     * 
     * @param members the {@link Role}s to serialize, cannot be <code>null</code>.
     * @return the "serialized" array, never <code>null</code>.
     */
    private List<String> getRoleNames(Role[] members)
    {
        List<String> result = new ArrayList<String>();
        if (members != null)
        {
            for (Role member : members)
            {
                result.add(member.getName());
            }
        }
        return result;
    }

    /**
     * Returns all roles mentioned in the given list.
     * 
     * @param list the list with role names to convert, can be <code>null</code>.
     * @return a list with {@link Role}s, never <code>null</code>.
     */
    private List<Role> getRoles(BasicDBList list)
    {
        List<Role> result = new ArrayList<Role>();
        // FELIX-4399: MongoDB does return null for empty properties...
        int size = (list == null) ? 0 : list.size();
        for (int i = 0; i < size; i++)
        {
            final String memberName = (String) list.get(i);
            result.add(findExistingMember(memberName));
        }
        return result;
    }

    /**
     * Serializes a given {@link Dictionary} into a {@link DBObject}.
     * 
     * @param properties the {@link Dictionary} to serialize, cannot be <code>null</code>.
     * @return the serialized dictionary, never <code>null</code>. 
     */
    private DBObject serializeDictionary(Dictionary properties)
    {
        BasicDBObject result = new BasicDBObject();

        Enumeration<String> keysEnum = properties.keys();
        while (keysEnum.hasMoreElements())
        {
            String key = keysEnum.nextElement();
            Object value = properties.get(key);

            result.append(KeyCodec.encode(key), value);
        }

        return result;
    }
}