// 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 com.cloud.dao;

import java.io.Serializable;
import java.util.List;

import com.cloud.utils.db.GenericSearchBuilder;
import com.cloud.utils.db.SearchBuilder;
import com.cloud.utils.db.SearchCriteria;

/**
 * Generic Entity Manager to retrieve database objects.
 *
 */
public interface EntityManager {
    /**
     * Finds an entity by its id.
     * @param <T> class of the entity you're trying to find.
     * @param <K> class of the id that the entity uses.
     * @param entityType Type of the entity.
     * @param id id value
     * @return T if found; null if not.
     */
    public <T, K extends Serializable> T findById(Class<T> entityType, K id);
    
    /**
     * Finds an entity by external id which is always String
     * @param <T> entity class
     * @param entityType type of entity you're looking for.
     * @param xid external id
     * @return T if found, null if not.
     */
    public <T> T findByXid(Class<T> entityType, String xid);
    
    /**
     * Lists all entities.  Use this method at your own risk.
     * @param <T> entity class
     * @param entityType type of entity you're looking for.
     * @return List<T>
     */
    public <T> List<? extends T> list(Class<T> entityType);
    
    /**
     * Persists the entity.
     * @param <T> entity class
     * @param t entity
     * @return persisted entity.  Only use this after persisting.
     */
    public <T> T persist(T t);
    
    public <T> SearchBuilder<T> createSearchBuilder(Class<T> entityType);
    
    public <T, K> GenericSearchBuilder<T, K> createGenericSearchBuilder(Class<T> entityType, Class<K> resultType);
    
    public <T, K> List<K> search(Class<T> entityType, SearchCriteria<K> sc);
    
    public <T, K extends Serializable> void remove(Class<T> entityType, K id);
}