/**
 * 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.jena.fuseki.webapp;

import java.io.IOException ;
import java.io.InputStream ;
import java.nio.file.Path ;
import java.nio.file.Paths ;

import javax.servlet.ServletContext ;
import javax.servlet.ServletContextEvent ;
import javax.servlet.ServletContextListener ;

import org.apache.jena.fuseki.Fuseki ;
import org.apache.jena.util.FileUtils ;
import org.apache.shiro.config.ConfigurationException ;
import org.apache.shiro.io.ResourceUtils ;
import org.apache.shiro.web.env.EnvironmentLoader ;
import org.apache.shiro.web.env.ResourceBasedWebEnvironment ;
import org.apache.shiro.web.env.WebEnvironment ;

/** A place to perform Fuseki-specific initialization of Apache Shiro.
 *  Runs after listener {@link FusekiServerEnvironmentInit} and before {@link FusekiServerListener}.
 *  This means finding shiro.ini in multiple possible places, based on
 *  different deployment setups.
 */
public class ShiroEnvironmentLoader extends EnvironmentLoader implements ServletContextListener {
    private ServletContext servletContext ; 
    
    public ShiroEnvironmentLoader() {}
    
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        FusekiWebapp.formatBaseArea() ; 
        this.servletContext = sce.getServletContext() ;
        try { 
            // Shiro.
            initEnvironment(servletContext);
        } catch (ConfigurationException  ex) {
            Fuseki.configLog.error("Shiro initialization failed: "+ex.getMessage());
            // Exit?
            throw ex ;
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        destroyEnvironment(sce.getServletContext());
    }

    /** 
     * Normal Shiro initialization only supports one location for an INI file.
     *  
     * When given multiple locations for the shiro.ini file, and 
     * if a {@link ResourceBasedWebEnvironment}, check the list of configuration
     * locations, testing whether the name identified an existing resource.  
     * For the first resource name found to exist, reset the {@link ResourceBasedWebEnvironment}
     * to name that resource alone so the normal Shiro initialization  
     */
    @Override
    protected void customizeEnvironment(WebEnvironment environment) {
        if ( environment instanceof ResourceBasedWebEnvironment ) {
            ResourceBasedWebEnvironment env = (ResourceBasedWebEnvironment)environment ;
            String[] locations = env.getConfigLocations() ;
            String loc = huntForShiroIni(locations) ;
            Fuseki.configLog.info("Shiro file: "+loc);
            if (loc != null )
                locations = new String[] {loc} ;
            env.setConfigLocations(locations);
        }
    }
    
    private static final String FILE = "file" ;
    
    /** Look for a Shiro ini file, or return null */
    private static String huntForShiroIni(String[] locations) {
        FusekiEnv.setEnvironment() ;
        Fuseki.init();
        for ( String loc : locations ) {
            // If file:, look for that file.
            // If a relative name without scheme, look in FUSEKI_BASE, FUSEKI_HOME, webapp. 
            String scheme = FileUtils.getScheme(loc) ;
            
            // Covers C:\\ as a "scheme name"
            if ( scheme != null ) {
                if ( scheme.equalsIgnoreCase(FILE)) {
                    // Test file: for exists
                    Path p = Paths.get(loc.substring(FILE.length()+1)) ;
                    if ( ! p.toFile().exists() )
                        continue ;
                    // Fall through.
                }
                // Can't test - try 
                return loc ;
            }
            // No scheme .
            Path p = Paths.get(loc) ;
            
            String fn = resolve(FusekiEnv.FUSEKI_BASE, p) ;
            if ( fn != null )
                return "file://"+fn ;
            fn = resolve(FusekiEnv.FUSEKI_HOME, p) ;
            if ( fn != null )
                return "file://"+fn ;
            
            // Try in webapp.
            
            try ( InputStream is = ResourceUtils.getInputStreamForPath(loc); ) {
                boolean exists = (is != null ) ;
                return loc ;
            } catch (IOException e) { }
        }
        return null ;
    }
    
    /** Directory + name -> filename if it exists */ 
    private static String resolve(Path dir, Path file) {
        Path p = dir.resolve(file) ;
        if ( p.toFile().exists() )
            return p.normalize().toString() ;
        return null ;
    }

//    /** 
//     * Test whether a name identified an existing resource
//     * @param resource    A String in Shiro-resource name format (e.g. URL scheme names) 
//     * @return True/false as to whether the resource can be found or not. 
//     */
//    
//    private boolean resourceExists(String resource) {
//        try {
//            // See IniWebEnvironment.convertPathToIni
//            if (!ResourceUtils.hasResourcePrefix(resource)) {
//                //Sort out "path" and open as a webapp resource.
//                resource = WebUtils.normalize(resource);
//                URL url = servletContext.getResource(resource) ;
//                return ( url == null ) ;
//            } else {
//                // Treat as a plain name. 
//                InputStream is = ResourceUtils.getInputStreamForPath(resource);
//                boolean exists = (is != null ) ;
//                is.close() ;
//                return exists ;
//            }
//        } catch (IOException e) { return false ; }
//    }
}
