/*
 * 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.wicket.resource.loader;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import org.apache.wicket.Application;
import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.Page;
import org.apache.wicket.core.util.resource.locator.IResourceNameIterator;
import org.apache.wicket.core.util.resource.locator.IResourceStreamLocator;
import org.apache.wicket.markup.html.WebComponent;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.markup.html.WebPage;
import org.apache.wicket.markup.repeater.AbstractRepeater;
import org.apache.wicket.resource.IPropertiesFactory;
import org.apache.wicket.resource.Properties;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.string.Strings;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * This is one of Wicket's default string resource loaders.
 * <p>
 * The component based string resource loader attempts to find the resource from a bundle that
 * corresponds to the supplied component object or one of its parent containers.
 * <p>
 * The search order for resources is built around the containers that hold the component (if it is
 * not a page). Consider a Page that contains a Panel that contains a Label. If we pass the Label as
 * the component then resource loading will first look for the resource against the page, then
 * against the panel and finally against the label.
 * <p>
 * The above search order may seem slightly odd at first, but can be explained thus: Team A writes a
 * new component X and packages it as a reusable Wicket component along with all required resources.
 * Team B then creates a new container component Y that holds a instance of an X. However, Team B
 * wishes the text to be different to that which was provided with X so rather than needing to
 * change X, they include override values in the resources for Y. Finally, Team C makes use of
 * component Y in a page they are writing. Initially they are happy with the text for Y so they do
 * not include any override values in the resources for the page. However, after demonstrating to
 * the customer, the customer requests the text for Y to be different. Team C need only provide
 * override values against their page and thus do not need to change Y.
 * <p>
 * This implementation is fully aware of both locale and style values when trying to obtain the
 * appropriate resources.
 * <p>
 * In addition to the above search order, each key will be pre-pended with the relative path of the
 * current component related to the component that is being searched. E.g. assume a component
 * hierarchy like page1.form1.input1 and your are requesting a key named 'Required'. Wicket will
 * search the property in the following order:
 * 
 * <pre>
 *        page1.properties =&gt; form1.input1.Required
 *        page1.properties =&gt; Required
 *        form1.properties =&gt; input1.Required
 *        form1.properties =&gt; Required
 *        input1.properties =&gt; Required
 *        myApplication.properties =&gt; form1.input1.Required
 *        myApplication.properties =&gt; Required
 * </pre>
 * 
 * Note that the latter two property files are only checked if the ClassStringResourceLoader has
 * been registered with Application as well, which is the default.
 * <p>
 * In addition to the above search order, each component that is being searched for a resource also
 * includes the resources from any parent classes that it inherits from. For example, PageA extends
 * CommonBasePage which in turn extends WebPage When a resource lookup is requested on PageA, the
 * resource bundle for PageA is first checked. If the resource is not found in this bundle then the
 * resource bundle for CommonBasePage is checked. This allows designers of base pages and components
 * to define default sets of string resources and then developers implementing subclasses to either
 * override or extend these in their own resource bundle.
 * <p>
 * This implementation can be subclassed to implement modified behavior. The new implementation must
 * be registered with the Application (ResourceSettings) though.
 * <p>
 * You may enable log debug messages for this class to fully understand the search order.
 * 
 * @author Chris Turner
 * @author Juergen Donnerstag
 */
public class ComponentStringResourceLoader implements IStringResourceLoader
{
        /** Log. */
        private static final Logger log = LoggerFactory.getLogger(ComponentStringResourceLoader.class);

        /**
         * Create and initialize the resource loader.
         */
        public ComponentStringResourceLoader()
        {
        }

        @Override
        public String loadStringResource(Class<?> clazz, final String key, final Locale locale,
                final String style, final String variation)
        {
                if (clazz == null)
                {
                        return null;
                }

                if (log.isDebugEnabled())
                {
                        log.debug("key: '" + key + "'; class: '" + clazz.getName() + "'; locale: '" + locale +
                                "'; Style: '" + style + "'; Variation: '" + variation + '\'');
                }

                // Load the properties associated with the path
                IPropertiesFactory propertiesFactory = getPropertiesFactory();
                while (true)
                {
                        // Create the base path
                        String path = clazz.getName().replace('.', '/');

                        // Iterator over all the combinations
                        IResourceNameIterator iter = newResourceNameIterator(path, locale, style, variation);
                        while (iter.hasNext())
                        {
                                String newPath = iter.next();

                                Properties props = propertiesFactory.load(clazz, newPath);
                                if (props != null)
                                {
                                        // Lookup the value
                                        String value = props.getString(key);
                                        if (value != null)
                                        {
                                                return value;
                                        }
                                }
                        }

                        // Didn't find the key yet, continue searching if possible
                        if (isStopResourceSearch(clazz))
                        {
                                break;
                        }

                        // Move to the next superclass
                        clazz = clazz.getSuperclass();

                        if (clazz == null)
                        {
                                // nothing more to search, done
                                break;
                        }
                }

                // not found
                return null;
        }

        /**
         * @see IResourceStreamLocator#newResourceNameIterator(String, Locale, String, String, String,
         *      boolean)
         * 
         * @param path
         * @param locale
         * @param style
         * @param variation
         * @return resource name iterator
         */
        protected IResourceNameIterator newResourceNameIterator(final String path, final Locale locale,
                final String style, final String variation)
        {
                return Application.get()
                        .getResourceSettings()
                        .getResourceStreamLocator()
                        .newResourceNameIterator(path, locale, style, variation, null, false);
        }

        /**
         * Get the properties file factory which loads the properties based on locale and style from
         * *.properties and *.xml files
         * 
         * @return properties factory
         */
        protected IPropertiesFactory getPropertiesFactory()
        {
                return Application.get().getResourceSettings().getPropertiesFactory();
        }

        /**
         * @see org.apache.wicket.resource.loader.IStringResourceLoader#loadStringResource(org.apache.wicket.Component,
         *      java.lang.String, java.util.Locale, java.lang.String, java.lang.String)
         */
        @Override
        public String loadStringResource(final Component component, final String key,
                final Locale locale, final String style, final String variation)
        {
                if (component == null)
                {
                        return null;
                }

                if (log.isDebugEnabled())
                {
                        log.debug("component: '" + component.toString(false) + "'; key: '" + key + '\'');
                }

                // The return value
                String string = null;

                // The key prefix is equal to the component path relative to the
                // current component on the top of the stack.
                String prefix = getResourcePath(component);

                // walk downwards starting with page going down to component
                for (Component current : getComponentTrail(component))
                {
                        // get current component class
                        final Class<?> clazz = current.getClass();

                        // first, try the fully qualified resource name relative to the
                        // component on the path from page down.
                        if (Strings.isEmpty(prefix) == false)
                        {
                                // lookup fully qualified path
                                string = loadStringResource(clazz, prefix + '.' + key, locale, style, variation);

                                // return string if we found it
                                if (string != null)
                                {
                                        return string;
                                }

                                // shorten resource key prefix when going downwards (skip for repeaters)
                                if ((current instanceof AbstractRepeater) == false)
                                {
                                        prefix = Strings.afterFirst(prefix, '.');
                                }
                        }
                        // If not found, than check if a property with the 'key' provided by
                        // the user can be found.
                        string = loadStringResource(clazz, key, locale, style, variation);

                        // return string if we found it
                        if (string != null)
                        {
                                return string;
                        }
                }

                return string;
        }

        /**
         * get path for resource lookup
         * 
         * @param component
         * @return path
         */
        protected String getResourcePath(final Component component)
        {
                Component current = Args.notNull(component, "component");

                final StringBuilder buffer = new StringBuilder();

                while (current.getParent() != null)
                {
                        final boolean skip = current.getParent() instanceof AbstractRepeater;

                        if (skip == false)
                        {
                                if (buffer.length() > 0)
                                {
                                        buffer.insert(0, '.');
                                }
                                buffer.insert(0, current.getId());
                        }
                        current = current.getParent();
                }
                return buffer.toString();
        }

        /**
         * return the trail of components from page to specified component
         * 
         * @param component
         *            The component to retrieve path for
         * @return The list of components starting from top going down to component
         */
        private List<Component> getComponentTrail(Component component)
        {
                final List<Component> path = new ArrayList<Component>();

                while (component != null)
                {
                        path.add(0, component);
                        if (isStopResourceSearch(component))
                        {
                                break;
                        }
                        component = component.getParent();
                }
                return path;
        }

        /**
         * Check the supplied component to see if it is one that we shouldn't bother further searches up
         * the component hierarchy for properties.
         * 
         * @param component
         *            The component to check
         * @return Whether to stop the search
         */
        protected boolean isStopResourceSearch(Component component)
        {
                return false;
        }

        /**
         * Check the supplied class to see if it is one that we shouldn't bother further searches up the
         * class hierarchy for properties.
         * 
         * @param clazz
         *            The class to check
         * @return Whether to stop the search
         */
        protected boolean isStopResourceSearch(final Class<?> clazz)
        {
                if ((clazz == null) || clazz.equals(Object.class) || clazz.equals(Application.class))
                {
                        return true;
                }

                // Stop at all html markup base classes
                if (clazz.equals(WebPage.class) || clazz.equals(WebMarkupContainer.class) ||
                        clazz.equals(WebComponent.class))
                {
                        return true;
                }

                // Stop at all wicket base classes
                return clazz.equals(Page.class) || clazz.equals(MarkupContainer.class) ||
                        clazz.equals(Component.class);
        }
}