/*
 * $Id: ModuleUtils.java 54929 2004-10-16 16:38:42Z germuska $ 
 *
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * Licensed 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.struts.util;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.Globals;
import org.apache.struts.action.RequestProcessor;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.config.MessageResourcesConfig;

/**
 * General purpose utility methods related to module processing.
 * 
 * @version $Rev: 54929 $
 * @since Struts 1.2
 */
public class ModuleUtils {

    /**
     * The Singleton instance.
     */
    private static final ModuleUtils instance = new ModuleUtils();

    /**
     * Commons logging instance.
     */
    private static final Log log = LogFactory.getLog(ModuleUtils.class);

    /**
     * Returns the Singleton instance of TagUtils.
     */
    public static ModuleUtils getInstance() {
        return instance;
    }

    /**
     * Constructor for ModuleUtils.
     */
    protected ModuleUtils() {
        super();
    }
    
	/**
	 * Return the current ModuleConfig object stored in request, if it exists,
	 * null otherwise.
	 * This method can be used by plugin to retrieve the current module config
	 * object. If no moduleConfig is found, this means that the request haven't
	 * hit the server throught the struts servlet. The appropriate module config
	 * can be set and found with
	 * <code>{@link RequestUtils#selectModule(HttpServletRequest, ServletContext)} </code>.
	 * @param request The servlet request we are processing
	 * @return the ModuleConfig object from request, or null if none is set in
	 * the request.
	 */
	public ModuleConfig getModuleConfig(HttpServletRequest request) {
		return (ModuleConfig) request.getAttribute(Globals.MODULE_KEY);
	}
    
	/**
	 * Return the desired ModuleConfig object stored in context, if it exists,
	 * null otherwise.
	 * 
     * @param prefix The module prefix of the desired module
     * @param context The ServletContext for this web application
	 * @return the ModuleConfig object specified, or null if not found in
	 * the context.
	 */
	public ModuleConfig getModuleConfig(String prefix, ServletContext context) {
		return (ModuleConfig) context.getAttribute(Globals.MODULE_KEY + prefix);
	}
    
	/**
	 * Return the desired ModuleConfig object stored in context, if it exists,
	 * otherwise return the current ModuleConfig
	 * 
	 * @param prefix The module prefix of the desired module
	 * @param request The servlet request we are processing
	 * @param context The ServletContext for this web application
	 * @return the ModuleConfig object specified, or null if not found in
	 * the context.
	 */
	public ModuleConfig getModuleConfig(String prefix, HttpServletRequest request, ServletContext context) {
		ModuleConfig moduleConfig = null;
		
		
		if(prefix != null) {
			//lookup module stored with the given prefix.
			moduleConfig = this.getModuleConfig(prefix, context);
		}
		else {
			//return the current module if no prefix was supplied.
			moduleConfig = this.getModuleConfig(request, context);
		}
		return moduleConfig;
	}

    /**
     * Return the ModuleConfig object is it exists, null otherwise.
     * @param request The servlet request we are processing
     * @param context The ServletContext for this web application
     * @return the ModuleConfig object
     */
    public ModuleConfig getModuleConfig(
        HttpServletRequest request,
        ServletContext context) {

		ModuleConfig moduleConfig = this.getModuleConfig(request);

		if (moduleConfig == null) {
			moduleConfig = this.getModuleConfig("", context);
			request.setAttribute(Globals.MODULE_KEY, moduleConfig);
		}

		return moduleConfig;
    }


    /**
     * Get the module name to which the specified request belong.
     * @param request The servlet request we are processing
     * @param context The ServletContext for this web application
     * @return The module prefix or ""
     */
    public String getModuleName(
        HttpServletRequest request,
        ServletContext context) {

        // Acquire the path used to compute the module
        String matchPath =
            (String) request.getAttribute(RequestProcessor.INCLUDE_SERVLET_PATH);

        if (matchPath == null) {
            matchPath = request.getServletPath();
        }

        return this.getModuleName(matchPath, context);
    }

    /**
     * Get the module name to which the specified uri belong.
     * @param matchPath The uri from which we want the module name.
     * @param context The ServletContext for this web application
     * @return The module prefix or ""
     */
    public String getModuleName(String matchPath, ServletContext context) {
        if (log.isDebugEnabled()) {
            log.debug("Get module name for path " + matchPath);
        }

        String prefix = ""; // Initialize prefix before we try lookup
        String prefixes[] = getModulePrefixes(context);
        // Get all other possible prefixes
        int lastSlash = 0; // Initialize before loop

        while (prefix.equals("")
            && ((lastSlash = matchPath.lastIndexOf("/")) > 0)) {

            // We may be in a non-default module.  Try to get it's prefix.
            matchPath = matchPath.substring(0, lastSlash);

            // Match against the list of module prefixes
            for (int i = 0; i < prefixes.length; i++) {
                if (matchPath.equals(prefixes[i])) {
                    prefix = prefixes[i];
                    break;
                }
            }
        }

        if (log.isDebugEnabled()) {
            log.debug(
                "Module name found: " + (prefix.equals("") ? "default" : prefix));
        }

        return prefix;
    }

    /**
     * Return the list of module prefixes that are defined for
     * this web application.  <strong>NOTE</strong> -
     * the "" prefix for the default module is not included in this list.
     *
     * @param context The ServletContext for this web application.
     * @return An array of module prefixes.
     */
    public String[] getModulePrefixes(ServletContext context) {
        return (String[]) context.getAttribute(Globals.MODULE_PREFIXES_KEY);
    }

    /**
     * Select the module to which the specified request belongs, and
     * add corresponding request attributes to this request.
     *
     * @param request The servlet request we are processing
     * @param context The ServletContext for this web application
     */
    public void selectModule(HttpServletRequest request, ServletContext context) {
        // Compute module name
        String prefix = getModuleName(request, context);

        // Expose the resources for this module
        this.selectModule(prefix, request, context);

    }

    /**
     * Select the module to which the specified request belongs, and
     * add corresponding request attributes to this request.
     *
     * @param prefix The module prefix of the desired module
     * @param request The servlet request we are processing
     * @param context The ServletContext for this web application
     */
    public void selectModule(
        String prefix,
        HttpServletRequest request,
        ServletContext context) {

        // Expose the resources for this module
        ModuleConfig config = getModuleConfig(prefix, context);

        if (config != null) {
            request.setAttribute(Globals.MODULE_KEY, config);
        } else {
            request.removeAttribute(Globals.MODULE_KEY);
        }

        MessageResourcesConfig[] mrConfig = config.findMessageResourcesConfigs();
        for(int i = 0; i < mrConfig.length; i++) {
          String key = mrConfig[i].getKey();
          MessageResources resources =
            (MessageResources) context.getAttribute(key + prefix);
          if (resources != null) {
              request.setAttribute(key, resources);
          } else {
              request.removeAttribute(key);
          }
        }
    }
}