| gvSIG desktop 1

/* gvSIG. Geographic Information System of the Valencian Government

 *

 * Copyright (C) 2007-2008 Infrastructures and Transports Department

 * of the Valencian Government (CIT)

 *

 * 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 2

 * 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.

 *

 */

/*

 * AUTHORS (In addition to CIT):

 * 2008 {DiSiD Technologies}  {Create a JTable TableModel for a FeatureCollection}

 */

package org.gvsig.fmap.dal.feature.paging;

import org.gvsig.fmap.dal.exception.DataException;

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

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

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

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

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

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

import org.gvsig.tools.dispose.impl.AbstractDisposable;

import org.gvsig.tools.dynobject.DynObject;

import org.gvsig.tools.dynobject.DynObjectSet;

import org.gvsig.tools.exception.BaseException;

import org.gvsig.tools.visitor.VisitCanceledException;

import org.gvsig.tools.visitor.Visitor;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

/**

 * Helper class to access the values of a FeatureCollection by position. Handles

 * pagination automatically to avoid filling the memory in case of big

 * collections.

 * 

 * TODO: evaluate if its more convenient to read values in the background when

 * the returned value is near the end of the page, instead of loading a page on

 * demand.

 * 

 * @author <a href="mailto:cordin@disid.com">C?sar Ordi?ana</a>

 */

public class FeaturePagingHelperImpl extends AbstractDisposable implements

                FeaturePagingHelper {

        private static final Logger LOG =

                        LoggerFactory.getLogger(FeaturePagingHelperImpl.class);

        private FeatureQuery query;

        private FeatureSet featureSet;

        private FeatureStore featureStore;

        private int maxPageSize;

        private long numPages;

        private long currentPage = -1;

        private Feature[] values;

        /**

         * Constructs a FeaturePagingHelperImpl from data of a FeatureStore.

         * 

         * @param featureStore

         *            to extract data from

         * @throws DataException

         *             if there is an error initializing the helper

         */

        public FeaturePagingHelperImpl(FeatureStore featureStore)

                        throws DataException {

                this(featureStore, DEFAULT_PAGE_SIZE);

        }

        /**

         * Constructs a FeaturePagingHelperImpl from data of a FeatureStore.

         * 

         * @param featureStore

         *            to extract data from

         * @param pageSize

         *            the number of elements per page data

         * @throws DataException

         *             if there is an error initializing the helper

         */

        public FeaturePagingHelperImpl(FeatureStore featureStore, int pageSize)

                        throws DataException {

                this(featureStore, null, pageSize);

        }

        /**

         * Constructs a FeaturePagingHelperImpl from data of a FeatureStore.

         * 

         * @param featureStore

         *            to extract data from

         * @throws DataException

         *             if there is an error initializing the helper

         */

        public FeaturePagingHelperImpl(FeatureStore featureStore,

                        FeatureQuery featureQuery) throws DataException {

                this(featureStore, featureQuery, DEFAULT_PAGE_SIZE);

        }

        /**

         * Constructs a FeaturePagingHelperImpl from data of a FeatureStore.

         * 

         * @param featureSet

         *            to extract data from

         * @param pageSize

         *            the number of elements per page data

         * @throws DataException

         *             if there is an error initializing the helper

         */

        public FeaturePagingHelperImpl(FeatureStore featureStore,

                        FeatureQuery featureQuery, int pageSize) throws DataException {

                if (featureQuery == null) {

                        featureQuery = featureStore.createFeatureQuery();

                        featureQuery.setFeatureType(featureStore.getDefaultFeatureType());

                }

                this.maxPageSize = pageSize;

                this.featureStore = featureStore;

                this.query = featureQuery;

                this.query.setPageSize(getMaxPageSize());

                loadFeatureSet();

                setNumPages(calculateNumPages());

                if (LOG.isDebugEnabled()) {

                        LOG.debug("FeaturePagingHelperImpl created with {} pages, "

                                        + "and a page size of {}", new Long(numPages), new Integer(

                                        pageSize));

                }

        }

        public int getMaxPageSize() {

                return maxPageSize;

        }

        public void setMaxPageSize(int pageSize) throws DataException {

                this.maxPageSize = pageSize;

                reloadCurrentPage();

        }

        public long getNumPages() {

                return numPages;

        }

        /**

         * Sets the number of pages.

         */

        private void setNumPages(long numPages) {

                this.numPages = numPages;

        }

        public long getCurrentPage() {

                return currentPage;

        }

        public void setCurrentPage(long page) throws DataException {

                if (LOG.isDebugEnabled()) {

                        LOG.debug("Current page: {}", Long.toString(page));

                }

                if (page < 0) {

                        throw new IndexOutOfBoundsException(

                                        "Error, unable to set helper current page to a "

                                                        + "negative value: " + page);

                }

                if (page >= getNumPages()) {

                        throw new IndexOutOfBoundsException(

                                        "Error, unable to set helper current page to the page num. "

                                                        + page + ", as the Collection only has "

                                                        + getNumPages() + " pages of Features");

                }

                currentPage = page;

                loadCurrentPageData();

        }

        public long getTotalSize() throws DataException {

                return getFeatureSet().getSize();

        }

        public Feature getFeatureAt(long index) throws DataException {

                // Check if we have currently loaded the viewed page data,

                // or we need to load a new one

                long pageForIndex = (long) Math.floor(index / getMaxPageSize());

                if (pageForIndex != getCurrentPage()) {

                        setCurrentPage(pageForIndex);

                }

                long positionForIndex = index - (getCurrentPage() * getMaxPageSize());

                return values[(int) positionForIndex];

        }

        public Feature[] getCurrentPageFeatures() {

                return values;

        }

        public FeatureSet getFeatureSet() {

                return featureSet;

        }

        public void reloadCurrentPage() throws DataException {

                setNumPages(calculateNumPages());

                if (currentPage > -1) {

                        loadCurrentPageData();

                }

        }

        public void reload() throws DataException {

                loadFeatureSet();

                reloadCurrentPage();

        }

        public FeatureStore getFeatureStore() {

                return featureStore;

        }

        public FeatureQuery getFeatureQuery() {

                return query;

        }

        /**

         * Calculates the number of pages.

         */

        private long calculateNumPages() throws DataException {

                double num = getTotalSize();

                double pageSize = getMaxPageSize();

                return (long) Math.ceil(num / pageSize);

        }

        /**

         * Loads all the Features of the current page.

         */

        private void loadCurrentPageData() throws DataException {

                long t1 = 0;

                long currentPage = getCurrentPage();

                final int currentPageSize;

                if (currentPage < (numPages - 1)) {

                        currentPageSize = getMaxPageSize();

                } else {

                        currentPageSize =

                                        (int) (getTotalSize() - (currentPage * getMaxPageSize()));

                }

                values = new Feature[currentPageSize];

                long firstPosition = currentPage * getMaxPageSize();

                if (LOG.isDebugEnabled()) {

                        LOG.debug("Loading {} Features starting at position {}",

                                        new Integer(currentPageSize), new Long(firstPosition));

                }

                if (LOG.isTraceEnabled()) {

                        t1 = System.currentTimeMillis();

                }

                try {

                        getFeatureSet().accept(new Visitor() {

                                private int i = 0;

                                public void visit(Object obj) throws VisitCanceledException,

                                                BaseException {

                                        if (i >= currentPageSize) {

                                                throw new VisitCanceledException();

                                        }

                                        values[i] = (Feature) obj;

                                        i++;

                                }

                        }, firstPosition);

                } catch (BaseException e) {

                        if (e instanceof DataException) {

                                throw ((DataException) e);

                        }

                        else {

                                LOG.error("Error loading the data starting at position {}",

                                                new Long(firstPosition), e);

                        }

                }

                if (LOG.isTraceEnabled()) {

                        long t2 = System.currentTimeMillis();

                        LOG.trace("Time to load {} features: {} ms", new Integer(

                                        currentPageSize), new Long(t2 - t1));

                }

        }

        private void loadFeatureSet() throws DataException {

                if (featureSet != null) {

                        featureSet.dispose();

                }

                featureSet = getFeatureStore().getFeatureSet(getFeatureQuery());

        }

        public void delete(Feature feature) throws DataException {

                if (featureSet == null) {

                        // FIXME change to RuntimeDalException

                        throw new IllegalStateException();

                }

                featureSet.delete(feature);

                reloadCurrentPage();

        }

        public void insert(EditableFeature feature) throws DataException {

                if (featureSet == null) {

                        // FIXME change to RuntimeDalException

                        throw new IllegalStateException();

                }

                featureSet.insert(feature);

                reloadCurrentPage();

        }

        public void update(EditableFeature feature) throws DataException {

                if (featureSet == null) {

                        // FIXME change to RuntimeDalException

                        throw new IllegalStateException();

                }

                featureSet.update(feature);

                reloadCurrentPage();

        }

        public FeatureType getFeatureType() {

                return featureSet.getDefaultFeatureType();

        }

        protected void doDispose() throws BaseException {

                featureSet.dispose();

        }

        public DynObject[] getCurrentPageDynObjects() {

                return getCurrentPageFeatures();

        }

        public DynObject getDynObjectAt(long index) throws BaseException {

                return getFeatureAt(index);

        }

        public DynObjectSet getDynObjectSet() {

                return getFeatureSet();

        }

}