Application: gvSIG desktop

/**

 * gvSIG. Desktop Geographic Information System.

 *

 * Copyright (C) 2007-2020 gvSIG Association.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 3

 * of the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

 * MA  02110-1301, USA.

 *

 * For any additional information, do not hesitate to contact us

 * at info AT gvsig.com, or visit our website www.gvsig.com.

 */

package org.gvsig.expressionevaluator.impl.function.dataaccess;

import java.util.List;

import org.apache.commons.lang3.Range;

import org.gvsig.expressionevaluator.Codes;

import org.gvsig.expressionevaluator.ExpressionRuntimeException;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.impl.DALFunctions;

import org.gvsig.expressionevaluator.spi.AbstractFunction;

import static org.gvsig.fmap.dal.DataManager.FUNCTION_EXISTS;

import org.gvsig.tools.util.UnmodifiableBasicCollection;

import org.gvsig.tools.util.UnmodifiableBasicCollection64;

/**

 *

 * @author jjdelcerro

 */

public class ExistsFunction extends AbstractFunction {

  public static final String NAME = "EXISTS";

  public ExistsFunction() {

    //

    // https://www.postgresql.org/docs/current/functions-subquery.html

    //

    // Nota:

    // En H2 no existe la funcion EXISTS, pero muy probablemente se pueda

    // trasladar a:

    //   NVL2(COALESCE(lista-subselect),FALSE,TRUE)

    //

    super(DALFunctions.SYMBOLTABLE_NAME,

            FUNCTION_EXISTS,

            Range.between(1, 2),

            "Receive a list as an argument. Returns true if the list has some value and false if the list is empty.",

            FUNCTION_EXISTS + "({{list}})",

            new String[]{

              "list - a list of values or null"

            },

            "Boolean",

            true

    );

  }

  @Override

  public boolean allowConstantFolding() {

    return false;

  }

  @Override

  public boolean useArgumentsInsteadObjects() {

    return true;

  }

  @Override

  public Object call(Interpreter interpreter, Object[] args) throws Exception {

    throw new UnsupportedOperationException("Not supported yet.");

  }

  @Override

  public Object call(Interpreter interpreter, Codes args) throws Exception {

    if (args.size() == 2) {

      Object id = this.getObject(interpreter, args, 1);

      if (id instanceof CharSequence) {

        if (interpreter.getSymbolTable().exists(id.toString())) {

          Object value = interpreter.getSymbolTable().value(id.toString());

          if (value == null) {

            return false;

          }

          if (value instanceof Boolean) {

            return value;

          }

        }

      }

    }

    Object list = this.getObject(interpreter, args, 0);

    if (list == null) {

      return false;

    }

    boolean isEmpty = true;

    if (list instanceof Object[]) {

      isEmpty = (((Object[]) list).length==0);

    } else if (list instanceof List) {

      isEmpty = ((List) list).isEmpty();

    } else if (list instanceof UnmodifiableBasicCollection) {

      isEmpty = ((UnmodifiableBasicCollection) list).isEmpty();

    } else if (list instanceof UnmodifiableBasicCollection64) {

      isEmpty = ((UnmodifiableBasicCollection64) list).isEmpty();

    } else {

      throw new ExpressionRuntimeException("Invalid argument. List or null expected.");

    }

//    System.out.println("EXISTS: "+ interpreter.getSymbolTable().value("NAME")+", "+isEmpty);

    return !isEmpty;

  }

}