/*
    * 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.shiro.web.filter.mgt;
  
  import org.apache.shiro.config.ConfigurationException;
  import org.apache.shiro.util.CollectionUtils;
  import org.apache.shiro.util.Nameable;
  import org.apache.shiro.util.StringUtils;
  import org.apache.shiro.web.filter.PathConfigProcessor;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Default {@link FilterChainManager} implementation maintaining a map of {@link Filter Filter} instances
   * (key: filter name, value: Filter) as well as a map of {@link NamedFilterList NamedFilterList}s created from these
   * {@code Filter}s (key: filter chain name, value: NamedFilterList).  The {@code NamedFilterList} is essentially a
   * {@link FilterChain} that also has a name property by which it can be looked up.
   *
   * @see NamedFilterList
   * @since 1.0
   */
  public class DefaultFilterChainManager implements FilterChainManager {
  
      private static transient final Logger log = LoggerFactory.getLogger(DefaultFilterChainManager.class);
  
      private FilterConfig filterConfig;
  
      private Map<String, Filter> filters; //pool of filters available for creating chains
  
      private Map<String, NamedFilterList> filterChains; //key: chain name, value: chain
  
      public DefaultFilterChainManager() {
          this.filters = new LinkedHashMap<String, Filter>();
          this.filterChains = new LinkedHashMap<String, NamedFilterList>();
          addDefaultFilters(false);
      }
  
      public DefaultFilterChainManager(FilterConfig filterConfig) {
          this.filters = new LinkedHashMap<String, Filter>();
          this.filterChains = new LinkedHashMap<String, NamedFilterList>();
          setFilterConfig(filterConfig);
          addDefaultFilters(true);
      }
  
      /**
       * Returns the {@code FilterConfig} provided by the Servlet container at webapp startup.
       *
       * @return the {@code FilterConfig} provided by the Servlet container at webapp startup.
       */
      public FilterConfig getFilterConfig() {
          return filterConfig;
      }
  
      /**
       * Sets the {@code FilterConfig} provided by the Servlet container at webapp startup.
       *
       * @param filterConfig the {@code FilterConfig} provided by the Servlet container at webapp startup.
       */
      public void setFilterConfig(FilterConfig filterConfig) {
          this.filterConfig = filterConfig;
      }
  
      public Map<String, Filter> getFilters() {
          return filters;
      }
  
      @SuppressWarnings({"UnusedDeclaration"})
      public void setFilters(Map<String, Filter> filters) {
          this.filters = filters;
      }
  
      public Map<String, NamedFilterList> getFilterChains() {
          return filterChains;
      }
 
     @SuppressWarnings({"UnusedDeclaration"})
     public void setFilterChains(Map<String, NamedFilterList> filterChains) {
         this.filterChains = filterChains;
     }
 
     public Filter getFilter(String name) {
         return this.filters.get(name);
     }
 
     public void addFilter(String name, Filter filter) {
         addFilter(name, filter, false);
     }
 
     public void addFilter(String name, Filter filter, boolean init) {
         addFilter(name, filter, init, true);
     }
 
     public void createChain(String chainName, String chainDefinition) {
         if (!StringUtils.hasText(chainName)) {
             throw new NullPointerException("chainName cannot be null or empty.");
         }
         if (!StringUtils.hasText(chainDefinition)) {
             throw new NullPointerException("chainDefinition cannot be null or empty.");
         }
 
         if (log.isDebugEnabled()) {
             log.debug("Creating chain [" + chainName + "] from String definition [" + chainDefinition + "]");
         }
 
         //parse the value by tokenizing it to get the resulting filter-specific config entries
         //
         //e.g. for a value of
         //
         //     "authc, roles[admin,user], perms[file:edit]"
         //
         // the resulting token array would equal
         //
         //     { "authc", "roles[admin,user]", "perms[file:edit]" }
         //
         String[] filterTokens = splitChainDefinition(chainDefinition);
 
         //each token is specific to each filter.
         //strip the name and extract any filter-specific config between brackets [ ]
         for (String token : filterTokens) {
             String[] nameConfigPair = toNameConfigPair(token);
 
             //now we have the filter name, path and (possibly null) path-specific config.  Let's apply them:
             addToChain(chainName, nameConfigPair[0], nameConfigPair[1]);
         }
     }
 
     /**
      * Splits the comma-delimited filter chain definition line into individual filter definition tokens.
      * <p/>
      * Example Input:
      * <pre>
      *     foo, bar[baz], blah[x, y]
      * </pre>
      * Resulting Output:
      * <pre>
      *     output[0] == foo
      *     output[1] == bar[baz]
      *     output[2] == blah[x, y]
      * </pre>
      * @param chainDefinition the comma-delimited filter chain definition.
      * @return an array of filter definition tokens
      * @since 1.2
      * @see <a href="https://issues.apache.org/jira/browse/SHIRO-205">SHIRO-205</a>
      */
     protected String[] splitChainDefinition(String chainDefinition) {
         return StringUtils.split(chainDefinition, StringUtils.DEFAULT_DELIMITER_CHAR, '[', ']', true, true);
     }
 
     /**
      * Based on the given filter chain definition token (e.g. 'foo' or 'foo[bar, baz]'), this will return the token
      * as a name/value pair, removing any brackets as necessary.  Examples:
      * <table>
      *     <tr>
      *         <th>Input</th>
      *         <th>Result</th>
      *     </tr>
      *     <tr>
      *         <td>{@code foo}</td>
      *         <td>returned[0] == {@code foo}<br/>returned[1] == {@code null}</td>
      *     </tr>
      *     <tr>
      *         <td>{@code foo[bar, baz]}</td>
      *         <td>returned[0] == {@code foo}<br/>returned[1] == {@code bar, baz}</td>
      *     </tr>
      * </table>
      * @param token the filter chain definition token
      * @return A name/value pair representing the filter name and a (possibly null) config value.
      * @throws ConfigurationException if the token cannot be parsed
      * @since 1.2
      * @see <a href="https://issues.apache.org/jira/browse/SHIRO-205">SHIRO-205</a>
      */
     protected String[] toNameConfigPair(String token) throws ConfigurationException {
 
         try {
             String[] pair = token.split("\\[", 2);
             String name = StringUtils.clean(pair[0]);
 
             if (name == null) {
                 throw new IllegalArgumentException("Filter name not found for filter chain definition token: " + token);
             }
             String config = null;
 
             if (pair.length == 2) {
                 config = StringUtils.clean(pair[1]);
                 //if there was an open bracket, it assumed there is a closing bracket, so strip it too:
                 config = config.substring(0, config.length() - 1);
                 config = StringUtils.clean(config);
 
                 //backwards compatibility prior to implementing SHIRO-205:
                 //prior to SHIRO-205 being implemented, it was common for end-users to quote the config inside brackets
                 //if that config required commas.  We need to strip those quotes to get to the interior quoted definition
                 //to ensure any existing quoted definitions still function for end users:
                 if (config != null && config.startsWith("\"") && config.endsWith("\"")) {
                     String stripped = config.substring(1, config.length() - 1);
                     stripped = StringUtils.clean(stripped);
 
                     //if the stripped value does not have any internal quotes, we can assume that the entire config was
                     //quoted and we can use the stripped value.
                     if (stripped != null && stripped.indexOf('"') == -1) {
                         config = stripped;
                     }
                     //else:
                     //the remaining config does have internal quotes, so we need to assume that each comma delimited
                     //pair might be quoted, in which case we need the leading and trailing quotes that we stripped
                     //So we ignore the stripped value.
                 }
             }
             
             return new String[]{name, config};
 
         } catch (Exception e) {
             String msg = "Unable to parse filter chain definition token: " + token;
             throw new ConfigurationException(msg, e);
         }
     }
 
     protected void addFilter(String name, Filter filter, boolean init, boolean overwrite) {
         Filter existing = getFilter(name);
         if (existing == null || overwrite) {
             if (filter instanceof Nameable) {
                 ((Nameable) filter).setName(name);
             }
             if (init) {
                 initFilter(filter);
             }
             this.filters.put(name, filter);
         }
     }
 
     public void addToChain(String chainName, String filterName) {
         addToChain(chainName, filterName, null);
     }
 
     public void addToChain(String chainName, String filterName, String chainSpecificFilterConfig) {
         if (!StringUtils.hasText(chainName)) {
             throw new IllegalArgumentException("chainName cannot be null or empty.");
         }
         Filter filter = getFilter(filterName);
         if (filter == null) {
             throw new IllegalArgumentException("There is no filter with name '" + filterName +
                     "' to apply to chain [" + chainName + "] in the pool of available Filters.  Ensure a " +
                     "filter with that name/path has first been registered with the addFilter method(s).");
         }
 
         applyChainConfig(chainName, filter, chainSpecificFilterConfig);
 
         NamedFilterList chain = ensureChain(chainName);
         chain.add(filter);
     }
 
     protected void applyChainConfig(String chainName, Filter filter, String chainSpecificFilterConfig) {
         if (log.isDebugEnabled()) {
             log.debug("Attempting to apply path [" + chainName + "] to filter [" + filter + "] " +
                     "with config [" + chainSpecificFilterConfig + "]");
         }
         if (filter instanceof PathConfigProcessor) {
             ((PathConfigProcessor) filter).processPathConfig(chainName, chainSpecificFilterConfig);
         } else {
             if (StringUtils.hasText(chainSpecificFilterConfig)) {
                 //they specified a filter configuration, but the Filter doesn't implement PathConfigProcessor
                 //this is an erroneous config:
                 String msg = "chainSpecificFilterConfig was specified, but the underlying " +
                         "Filter instance is not an 'instanceof' " +
                         PathConfigProcessor.class.getName() + ".  This is required if the filter is to accept " +
                         "chain-specific configuration.";
                 throw new ConfigurationException(msg);
             }
         }
     }
 
     protected NamedFilterList ensureChain(String chainName) {
         NamedFilterList chain = getChain(chainName);
         if (chain == null) {
             chain = new SimpleNamedFilterList(chainName);
             this.filterChains.put(chainName, chain);
         }
         return chain;
     }
 
     public NamedFilterList getChain(String chainName) {
         return this.filterChains.get(chainName);
     }
 
     public boolean hasChains() {
         return !CollectionUtils.isEmpty(this.filterChains);
     }
 
     public Set<String> getChainNames() {
         //noinspection unchecked
         return this.filterChains != null ? this.filterChains.keySet() : Collections.EMPTY_SET;
     }
 
     public FilterChain proxy(FilterChain original, String chainName) {
         NamedFilterList configured = getChain(chainName);
         if (configured == null) {
             String msg = "There is no configured chain under the name/key [" + chainName + "].";
             throw new IllegalArgumentException(msg);
         }
         return configured.proxy(original);
     }
 
     /**
      * Initializes the filter by calling <code>filter.init( {@link #getFilterConfig() getFilterConfig()} );</code>.
      *
      * @param filter the filter to initialize with the {@code FilterConfig}.
      */
     protected void initFilter(Filter filter) {
         FilterConfig filterConfig = getFilterConfig();
         if (filterConfig == null) {
             throw new IllegalStateException("FilterConfig attribute has not been set.  This must occur before filter " +
                     "initialization can occur.");
         }
         try {
             filter.init(filterConfig);
         } catch (ServletException e) {
             throw new ConfigurationException(e);
         }
     }
 
     protected void addDefaultFilters(boolean init) {
         for (DefaultFilter defaultFilter : DefaultFilter.values()) {
             addFilter(defaultFilter.name(), defaultFilter.newInstance(), init, false);
         }
     }
 }