// 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

// 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.utils.db;

import java.lang.reflect.Field;

import javax.persistence.Column;

import com.cloud.utils.Pair;

import com.cloud.utils.ReflectUtil;

/**

* Try to use static initialization to help you in finding incorrect

* field names being passed in early.

*

* Something like the following:

* protected static final Filter s_NameFilter = new Filter(VMInstanceVO, name, true, null, null);

*

* Filter nameFilter = new Filter(s_nameFilter);

*

*/

public class Filter {

Long _offset;

Long _limit;

String _orderBy;

/**

* @param clazz the VO object type

* @param field name of the field

* @param offset

* @param limit

*/

public Filter(Class<?> clazz, String field, boolean ascending, Long offset, Long limit) {

_offset = offset;

_limit = limit;

addOrderBy(clazz, field, ascending);

}

public Filter(long limit) {

_orderBy = " ORDER BY RAND() LIMIT " + limit;

}

/**

* Note that this copy constructor does not copy offset and limit.

* @param that filter

*/

public Filter(Filter that) {

this._orderBy = that._orderBy;

this._limit = null;

that._limit = null;

}

public void addOrderBy(Class<?> clazz, String field, boolean ascending) {

if (field == null) {

return;

}

Field f;

Pair<Class<?>, Field> pair = ReflectUtil.getAnyField(clazz, field);

assert (pair != null) : "Can't find field " + field + " in " + clazz.getName();

clazz = pair.first();

f = pair.second();

Column column = f.getAnnotation(Column.class);

String name = column != null ? column.name() : field;

StringBuilder order = new StringBuilder();

if (column.table() == null || column.table().length() == 0) {

order.append(DbUtil.getTableName(clazz));

} else {

order.append(column.table());

}

order.append(".").append(name).append(ascending ? " ASC " : " DESC ");

if (_orderBy == null) {

_orderBy = order.insert(0, " ORDER BY ").toString();

} else {

_orderBy = order.insert(0, _orderBy).toString();

}

}

public String getOrderBy() {

return _orderBy;

}

public void setOffset(Long offset) {

_offset = offset;

}

public Long getOffset() {

return _offset;

}

public Long getLimit() {

return _limit;

}

public void setLimit(Long limit) {

_limit = limit;

}

}