/*
  *
  *  *  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.geo;

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

/**
 * Haversine formula to compute the distance between 2 gro points.
 * 
 * @author Luca Garulli (l.garulli--at--orientechnologies.com)
 * 
 */
public class OSQLFunctionDistance extends OSQLFunctionAbstract {
  public static final String  NAME         = "distance";

  private final static double EARTH_RADIUS = 6371;

  public OSQLFunctionDistance() {
    super(NAME, 4, 5);
  }

  public Object execute(Object iThis, final OIdentifiable iCurrentRecord, Object iCurrentResult, final Object[] iParams,
      OCommandContext iContext) {
    try {
      double distance;

      final double[] values = new double[4];

      for (int i = 0; i < iParams.length && i < 4; ++i) {
        if (iParams[i] == null)
          return null;

        values[i] = ((Double) OType.convert(iParams[i], Double.class)).doubleValue();
      }

      final double deltaLat = Math.toRadians(values[2] - values[0]);
      final double deltaLon = Math.toRadians(values[3] - values[1]);

      final double a = Math.pow(Math.sin(deltaLat / 2), 2) + Math.cos(Math.toRadians(values[0]))
          * Math.cos(Math.toRadians(values[2])) * Math.pow(Math.sin(deltaLon / 2), 2);
      distance = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)) * EARTH_RADIUS;

      if (iParams.length > 4) {
        final String unit = iParams[4].toString();
        if (unit.equalsIgnoreCase("km"))
          // ALREADY IN KM
          ;
        else if (unit.equalsIgnoreCase("mi"))
          // MILES
          distance *= 0.621371192;
        else if (unit.equalsIgnoreCase("nmi"))
          // NAUTICAL MILES
          distance *= 0.539956803;
        else
          throw new IllegalArgumentException("Unsupported unit '" + unit + "'. Use km, mi and nmi. Default is km.");
      }

      return distance;
    } catch (IllegalArgumentException e) {
      throw e;
    } catch (Exception e) {
      return null;
    }
  }

  public String getSyntax() {
    return "distance(<field-x>,<field-y>,<x-value>,<y-value>[,<unit>])";
  }
}