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.function.Predicate;

import org.apache.commons.lang3.Range;

import org.gvsig.expressionevaluator.Code;

import org.gvsig.expressionevaluator.Codes;

import org.gvsig.expressionevaluator.ExpressionRuntimeException;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.Optimizer;

import org.gvsig.expressionevaluator.impl.DALFunctions;

import org.gvsig.fmap.dal.feature.FeatureStore;

import org.gvsig.fmap.dal.impl.expressionevaluator.DefaultFeatureExpressionEvaluator;

import org.gvsig.expressionevaluator.Code.Callable;

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

import org.gvsig.fmap.dal.feature.FeatureSet;

import org.gvsig.tools.evaluator.EvaluatorData;

import org.gvsig.tools.evaluator.EvaluatorException;

import org.gvsig.tools.util.FilteredIterator;

import org.gvsig.tools.util.LimitIterator;

/**

 *

 * @author jjdelcerro

 */

@SuppressWarnings("UseSpecificCatch")

public class SelectFromSelectionFunction

        extends AbstractSelectFunction

        implements Optimizer.FunctionOptimizer {

    public SelectFromSelectionFunction() {

        super(DALFunctions.GROUP_DATA_ACCESS,

                FUNCTION_SELECT_FROM_SELECTION,

                Range.is(5),

                "Returns a list of features of the table by applying the filter, order and limit indicated.\n"

                + "The syntax is:\n\n"

                + "SELECT * FROM SELECTION [IF NOT EMPTY] OF table_name WHERE boolean_expression ;\n\n"

                + "Indicate a filter expression with WHERE.\n"

                + "You can use an asterisk or enter the column names you want to retrieve separated by commas.\n"

                + "The SELECT statement must always end with a semicolon.",

                "SELECT * FROM SELECTION OF table_name WHERE boolean_expression ;",

                new String[]{

                    "column_names/asterisk - Names of the columns table to retrieve.",

                    "table_name - Name of the table",

                    "filter - Optional, boolean expression to apply as filter",

                },

                "Iterable",

                false

        );

    }

    @Override

    public boolean isHidden() {

        return false;

    }

    @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();

    }

    private static final int COLUMNS = 0;

    private static final int TABLE = 1;

    private static final int WHERE = 2;

    private static final int LIMIT = 3;

    private static final int SELECCTION_IF_NOT_EMPTY = 4;

    @Override

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

        Code columns = getTupleOrNull(args, COLUMNS);

        String storeName = this.getTableName(args, TABLE);

        Code where = this.getWhereCode(args, WHERE);

        Number limit = (Number) getObject(interpreter, args, LIMIT);

        Object selection_if_not_empty = getObject(interpreter, args, SELECCTION_IF_NOT_EMPTY);

        FeatureStore featureStore;

        try {

            featureStore = this.getFeatureStore(storeName);

            if (featureStore == null) {

                throw new ExpressionRuntimeException("Cant locate the feature store '" + storeName + "' in function '" + this.name() + "'.");

            }

            Iterable features = featureStore.getFeatureSelection();

            if( ((FeatureSet)features).isEmpty() ) {

                if( selection_if_not_empty != null ) {

                    features = featureStore.getFeatureSet();

                    // En este caso habria que optimizar el where, pero de 

                    // momento asi va, aunque lento.

                }                

            }

            if (where != null) {

                final Iterable baseSelection = features;

                final DefaultFeatureExpressionEvaluator evaluator = new DefaultFeatureExpressionEvaluator(where.toString());

                evaluator.toSymbolTable().addSymbolTable(interpreter.getSymbolTable());

                final Predicate filter = (Predicate) (Object t) -> {

                    try {

                        return (boolean) evaluator.evaluate((EvaluatorData) t);

                    } catch (EvaluatorException ex1) {

                        throw new ExpressionRuntimeException("Can't evaluate expression for row.", ex1);

                    }

                };

                features = (Iterable) () -> new FilteredIterator(baseSelection.iterator(), filter);

            }

            if( limit!=null ) {

                final Iterable baseSelection = features;

                features = (Iterable) () -> new LimitIterator(baseSelection.iterator(), limit.longValue());

            }

            return features;

        } catch (ExpressionRuntimeException ex) {

            throw ex;

        } catch (Exception ex) {

            throw new ExpressionRuntimeException("Problems calling '" + this.name() + "' function", ex);

        }

    }

    @Override

    public Code optimize(Optimizer optimizer, Callable caller) {

        return caller; // Don't optimize SELECT

    }

}