/*
  *
  *  *  Copyright 2014 Orient Technologies LTD (info(at)orientechnologies.com)
  *  *
  *  *  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.
  *  *
  *  * For more information: http://www.orientechnologies.com
  *
  */

package com.orientechnologies.orient.core.sql.functions.misc;

import com.orientechnologies.orient.core.command.OCommandContext;
import com.orientechnologies.orient.core.db.record.OIdentifiable;
import com.orientechnologies.orient.core.sql.functions.OSQLFunctionAbstract;

/**
 * Returns the first <code>field/value</code> not null parameter. if no <code>field/value</code> is <b>not</b> null, returns null.
 * 
 * <p>
 * Syntax: <blockquote>
 * 
 * <pre>
 * coalesce(<field|value>[,<field|value>]*)
 * </pre>
 * 
 * </blockquote>
 * 
 * <p>
 * Examples: <blockquote>
 * 
 * <pre>
 * SELECT <b>coalesce('a', 'b')</b> FROM ...
 *  -> 'a'
 * 
 * SELECT <b>coalesce(null, 'b')</b> FROM ...
 *  -> 'b'
 * 
 * SELECT <b>coalesce(null, null, 'c')</b> FROM ...
 *  -> 'c'
 * 
 * SELECT <b>coalesce(null, null)</b> FROM ...
 *  -> null
 * 
 * </pre>
 * 
 * </blockquote>
 * 
 * @author Claudio Tesoriero
 */

public class OSQLFunctionCoalesce extends OSQLFunctionAbstract {
  public static final String NAME = "coalesce";

  public OSQLFunctionCoalesce() {
    super(NAME, 1, 1000);
  }

  @Override
  public Object execute(Object iThis, OIdentifiable iCurrentRecord, Object iCurrentResult, final Object[] iParams, OCommandContext iContext) {
    int length = iParams.length;
    for (int i = 0; i < length; i++) {
      if (iParams[i] != null)
        return iParams[i];
    }
    return null;
  }

  @Override
  public String getSyntax() {
    return "Returns the first not-null parameter or null if all parameters are null. Syntax: coalesce(<field|value> [,<field|value>]*)";
  }
}