/*
 * $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package org.apache.tiles.definition.dao;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.tiles.Definition;
import org.apache.tiles.Initializable;
import org.apache.tiles.TilesApplicationContext;
import org.apache.tiles.awareness.TilesApplicationContextAware;
import org.apache.tiles.definition.DefinitionsFactory;
import org.apache.tiles.definition.DefinitionsFactoryException;
import org.apache.tiles.definition.DefinitionsReader;
import org.apache.tiles.definition.RefreshMonitor;
import org.apache.tiles.definition.digester.DigesterDefinitionsReader;
import org.apache.tiles.impl.BasicTilesContainer;
import org.apache.tiles.reflect.ClassUtil;

/**
 * Base abstract class for a DAO that is based on URLs and locale as a
 * customization key.
 *
 * @version $Rev$ $Date$
 * @since 2.1.0
 */
public abstract class BaseLocaleUrlDefinitionDAO implements
        DefinitionDAO<Locale>, Initializable, TilesApplicationContextAware,
        RefreshMonitor, URLReader {

    /**
     * The logging object.
     */
    private static final Log LOG = LogFactory
            .getLog(BaseLocaleUrlDefinitionDAO.class);

    /**
     * Compatibility constant.
     *
     * @deprecated use {@link DEFINITIONS_CONFIG} to avoid namespace collisions.
     */
    private static final String LEGACY_DEFINITIONS_CONFIG = "definitions-config";

    /**
     * Contains the URL objects identifying where configuration data is found.
     *
     * @since 2.1.0
     */
    protected List<URL> sourceURLs;

    /**
     * Contains the dates that the URL sources were last modified.
     *
     * @since 2.1.0
     */
    protected Map<String, Long> lastModifiedDates;

    /**
     * The application context.
     *
     * @since 2.1.0
     */
    protected TilesApplicationContext applicationContext;

    /**
     * Reader used to get definitions from the sources.
     *
     * @since 2.1.0
     */
    protected DefinitionsReader reader;

    /**
     * Constructor.
     */
    public BaseLocaleUrlDefinitionDAO() {
        sourceURLs = new ArrayList<URL>();
        lastModifiedDates = new HashMap<String, Long>();
    }

    /**  {@inheritDoc}*/
    public void setSourceURLs(List<URL> sourceURLs) {
        this.sourceURLs = sourceURLs;
    }

    /**  {@inheritDoc}*/
    public void setReader(DefinitionsReader reader) {
        this.reader = reader;
    }

    /**  {@inheritDoc}*/
    public void addSourceURL(URL sourceURL) {
        if (sourceURLs == null) {
            sourceURLs = new ArrayList<URL>();
        }
        sourceURLs.add(sourceURL);
    }

    /** {@inheritDoc} */
    public void setApplicationContext(TilesApplicationContext applicationContext) {
        this.applicationContext = applicationContext;
    }

    /** {@inheritDoc} */
    public void init(Map<String, String> params) {
        identifySources(params);
        String readerClassName = params
                .get(DefinitionsFactory.READER_IMPL_PROPERTY);

        if (readerClassName != null) {
            reader = (DefinitionsReader) ClassUtil.instantiate(readerClassName);
        } else {
            reader = new DigesterDefinitionsReader();
        }
        reader.init(params);
    }

    /** {@inheritDoc} */
    public boolean refreshRequired() {
        boolean status = false;

        Set<String> urls = lastModifiedDates.keySet();

        try {
            for (String urlPath : urls) {
                Long lastModifiedDate = lastModifiedDates.get(urlPath);
                URL url = new URL(urlPath);
                URLConnection connection = url.openConnection();
                connection.connect();
                long newModDate = connection.getLastModified();
                if (newModDate != lastModifiedDate) {
                    status = true;
                    break;
                }
            }
        } catch (Exception e) {
            LOG.warn("Exception while monitoring update times.", e);
            return true;
        }
        return status;
    }

    /**
     * Detects the sources to load.
     *
     * @param initParameters The initialization parameters.
     * @since 2.1.0
     */
    protected void identifySources(Map<String, String> initParameters) {
        if (applicationContext == null) {
            throw new IllegalStateException(
                    "The TilesApplicationContext cannot be null");
        }

        String resourceString = getResourceString(initParameters);
        String[] resources = getResourceNames(resourceString);

        try {
            for (int i = 0; i < resources.length; i++) {
                Set<URL> urls = applicationContext.getResources(resources[i]);
                if (urls != null && !urls.isEmpty()) {
                    for (URL resourceUrl : urls) {
                        if (resourceUrl != null) {
                            if (LOG.isDebugEnabled()) {
                                LOG.debug("Adding resource '" + resourceUrl
                                        + "' to definitions factory.");
                            }
                            String externalForm = resourceUrl.toExternalForm();
                            if (externalForm.indexOf('_', externalForm
                                    .lastIndexOf("/")) < 0) {
                                sourceURLs.add(resourceUrl);
                            } else if (LOG.isDebugEnabled()) {
                                LOG.debug("Not adding resource '" + resourceUrl
                                        + "' to definitions factory because it is "
                                        + "supposed to be an internationalization.");
                            }

                        } else {
                            LOG.warn("Unable to find configured definition '"
                                    + resources[i] + "'");
                        }
                    }
                } else {
                    LOG.warn("Unable to find resources under the name '"
                            + resources[i] + "'");
                }
            }
        } catch (IOException e) {
            throw new DefinitionsFactoryException(
                    "Unable to parse definitions from " + resourceString, e);
        }
    }

    /**
     * Derive the resource string from the initialization parameters. If no
     * parameter {@link DefinitionsFactory#DEFINITIONS_CONFIG} is available,
     * attempts to retrieve {@link BasicTilesContainer#DEFINITIONS_CONFIG} and
     * {@link #LEGACY_DEFINITIONS_CONFIG}. If neither are available, returns
     * "/WEB-INF/tiles.xml".
     *
     * @param parms The initialization parameters.
     * @return resource string to be parsed.
     */
    @SuppressWarnings("deprecation")
    protected String getResourceString(Map<String, String> parms) {
        String resourceStr = parms.get(DefinitionsFactory.DEFINITIONS_CONFIG);
        if (resourceStr == null) {
            resourceStr = parms.get(BasicTilesContainer.DEFINITIONS_CONFIG);
        }
        if (resourceStr == null) {
            resourceStr = parms.get(LEGACY_DEFINITIONS_CONFIG);
        }
        if (resourceStr == null) {
            resourceStr = "/WEB-INF/tiles.xml";
        }
        return resourceStr;
    }

    /**
     * Parse the resourceString into a list of resource paths which can be
     * loaded by the application context.
     *
     * @param resourceString comma separated resources
     * @return parsed resources
     */
    protected String[] getResourceNames(String resourceString) {
        return resourceString.split(",");
    }

    /**
     * Loads definitions from an URL without loading from "parent" URLs.
     *
     * @param url The URL to read.
     * @return The definition map that has been read.
     */
    protected Map<String, Definition> loadDefinitionsFromURL(URL url) {
        Map<String, Definition> defsMap = null;
        try {
            URLConnection connection = url.openConnection();
            connection.connect();
            lastModifiedDates.put(url.toExternalForm(), connection
                    .getLastModified());

            // Definition must be collected, starting from the base
            // source up to the last localized file.
            defsMap = reader.read(connection.getInputStream());
        } catch (FileNotFoundException e) {
            // File not found. continue.
            if (LOG.isDebugEnabled()) {
                LOG.debug("File " + null + " not found, continue");
            }
        } catch (IOException e) {
            throw new DefinitionsFactoryException(
                    "I/O error processing configuration.", e);
        }

        return defsMap;
    }
}