/*
 *    ServiceRack.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3.service;

// greenstone classes
import org.greenstone.gsdl3.util.*;
import org.greenstone.gsdl3.core.*;

// xml classes
import org.w3c.dom.Node; 
import org.w3c.dom.NodeList; 
import org.w3c.dom.Element; 
import org.w3c.dom.Document; 
import org.xml.sax.InputSource;
import javax.xml.parsers.*;
import org.apache.xpath.XPathAPI;

// general java classes
import java.io.Reader;
import java.io.StringReader;
import java.io.File;
import java.util.HashMap;
import java.util.ResourceBundle;
import java.util.Locale;
import java.lang.reflect.Method;

/**
 * ServiceRack - abstract base class for services
 *
 * A ServiceRack provides one or more Services. 
 * This base class implements the process method.
 *Each service is invoked
 * by a method called process<service name> which takes one parameter - the xml request Element, and returns an XML response Element. 
 * for example, the TextQuery service would be invoked by 
 * processTextQuery(Element request)
 *
 * @author <a href="mailto:kjdon@cs.waikato.ac.nz">Katherine Don</a>
 * @version $Revision: 9874 $
 */
public abstract class ServiceRack
    implements ModuleInterface
{

    /** the absolute address of the site home */
    protected String site_home =null;
    /** the http address of the site home */
    protected String site_http_address =null;

    /** the name of the cluster (or collection) that this service 
	belongs to - if any */ 
    protected String cluster_name = null;

    /** some services can talk back to the message router */
    protected ModuleInterface router = null;

    /** a converter class to create Documents etc */
    protected XMLConverter converter = null;

    /** the original config info - if need to store it */
    protected Element config_info = null;

    /** XML element for describe requests - the container doc */
    protected Document doc = null;

    /** XML element for describe requests - list of supported services
	- this is static     */
    protected Element short_service_info = null;

    /** XML element for stylesheet requests - map of service name to format 
	elem */
    protected HashMap format_info_map = null;

    /** sets the cluster name */
    public void setClusterName(String cluster_name) {
	this.cluster_name = cluster_name;
    }
    /** sets the collect name */
    public void setCollectionName(String coll_name) {
	setClusterName(coll_name);
    }

    public void cleanUp() {}
    
    /** sets the site home */
    public void setSiteHome(String site_home) {
	this.site_home = site_home;
    }
    /** sets the site http address */
    public void setSiteAddress(String site_address) {
	this.site_http_address = site_address;
    }

    /** sets the message router */
    public void setMessageRouter(ModuleInterface m) {
       this.router = m;
    }

    /** the no-args constructor */
    public ServiceRack() {
	this.converter = new XMLConverter();
	this.doc = this.converter.newDOM();
	this.short_service_info = this.doc.createElement(GSXML.SERVICE_ELEM+GSXML.LIST_MODIFIER);
	this.format_info_map = new HashMap();
    }
    

    /** configure the service module
     *
     * @param info the XML node <serviceRack name="XXX"/> with name equal
     * to the class name (of the subclass)
     *
     * must configure short_service_info_ and service_info_map_
     * @return true if configured ok
     * must be implemented in subclasses
     */
    public boolean configure(Element info) {
	return configure(info, null);
    }
    
    abstract public boolean configure(Element info, Element extra_info);

    /**
     * Process an XML document - convenience method that uses Strings rather than Elements. just calls process(Element).
     *
     * @param xml_in the Document to process - a string
     * @return the resultant document as a string - contains any error messages
     * @see String
     */
    public String process(String xml_in) {
	
	Document doc = this.converter.getDOM(xml_in);
	if (doc == null) {
	    System.err.println("ServiceRack.process(String) Error: Couldn't parse request");
	    System.err.println(xml_in);
	    return null;
	}
	Element res = process(doc.getDocumentElement());
	return this.converter.getString(res);
	
    }

    /** process an XML request in DOM form
     *
     * @param xml_in the Element node containing the request
     * should be <message> 
     * @return an Element with the result XML
     * @see Element
     */
    public Element process(Element message) {

	NodeList requests = message.getElementsByTagName(GSXML.REQUEST_ELEM);
	Document mess_doc = message.getOwnerDocument();
	Element mainResult = this.doc.createElement(GSXML.MESSAGE_ELEM);
	if (requests.getLength()==0) {
	    // no requests
	    return mainResult; // empty message for now
	}

	for (int i=0; i<requests.getLength(); i++) {
	    Element request = (Element)requests.item(i);
	
	    String type = request.getAttribute(GSXML.TYPE_ATT);
	    if (type.equals(GSXML.REQUEST_TYPE_DESCRIBE)) {
		Element response = processDescribe(request);
		if (response !=null) {
		    mainResult.appendChild(this.doc.importNode(response, true));
		}
		
	    } else if (type.equals(GSXML.REQUEST_TYPE_FORMAT)) {
		Element response = processFormat(request);
		    mainResult.appendChild(this.doc.importNode(response, true));
		
	       
	    } else {
		// other type of request, must be processed by the subclass - 
		// send to the service method
		StringBuffer error_string = new StringBuffer();
		String to = GSPath.getFirstLink(request.getAttribute(GSXML.TO_ATT));		
		Element response = null;
		try {
		    Class c = this.getClass();
		    Class []params = {Class.forName("org.w3c.dom.Element")};
		    
		    String method_name = "process"+to;
		    Method m = null;
		    while (c != null) {
			
			try {
			    m = c.getDeclaredMethod(method_name, params);
			    // if this has worked, break
			    break;
			} catch (NoSuchMethodException e) {
			    c = c.getSuperclass();
			} catch (SecurityException e) {
			    System.err.println("ServiceRack.process: security exception for finding method "+method_name);
			    error_string.append("ServiceRack.process: security exception for finding method "+method_name);
			}
		    } // while
		    if (m != null) {
			Object []args = {request};
			try {
			    response = (Element)m.invoke(this, args);
			    
			} catch (Exception e) {
			    System.err.println("ServiceRack.process: Trying to call a processService type method (process"+to+") on a subclass("+this.getClass().getName()+"), but an exception happened:"+e.toString());
			    error_string.append("ServiceRack.process: Trying to call a processService type method (process"+to+") on a subclass("+this.getClass().getName()+"), but an exception happened:"+e.toString());
			}
		    } else {
			System.err.println("ServiceRack.process: method "+method_name+" not found for class "+this.getClass().getName());
			error_string.append("ServiceRack.process: method "+method_name+" not found for class "+this.getClass().getName());
		    }
		    
		} catch (ClassNotFoundException e) {
		    System.err.println("ServiceRack error: Element class not found");
		    error_string.append("ServiceRack error: Element class not found");
		}
		if (response !=null) {
		    mainResult.appendChild(this.doc.importNode(response, true));
		} else {
		    // add in a dummy response
		    System.err.println("adding in an error element\n");
		    response = this.doc.createElement(GSXML.RESPONSE_ELEM);
		    GSXML.addError(this.doc, response, error_string.toString());
		    mainResult.appendChild(response);
		    
		}
 
	    } // else process request
	} // for each request
	
	return mainResult;
		
    }

 

    /** process method for describe requests 
     */
    protected Element processDescribe(Element request) {
	
	Element response = this.doc.createElement(GSXML.RESPONSE_ELEM);
	response.setAttribute(GSXML.TYPE_ATT, GSXML.REQUEST_TYPE_DESCRIBE);
	
	String lang = request.getAttribute(GSXML.LANG_ATT);
	String to = GSPath.getFirstLink(request.getAttribute(GSXML.TO_ATT));
	if (to.equals("")) { // return the service list
	    response.appendChild(getServiceList(lang));
	    return response;
	} 
	response.setAttribute(GSXML.FROM_ATT, to);
	Element param_list = (Element)GSXML.getChildByTagName(request, GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
	Element description = null;
	if (param_list == null) {
	    description = getServiceDescription(to, lang, null);
	} else {
	    NodeList params = param_list.getElementsByTagName(GSXML.PARAM_ELEM);
	    for (int i=0; i<params.getLength(); i++) {
		
		Element param = (Element)params.item(i);
		// Identify the structure information desired
		if (param.getAttribute(GSXML.NAME_ATT).equals(GSXML.SUBSET_PARAM )) {
		    String info = param.getAttribute(GSXML.VALUE_ATT);
		    if (description == null) {
			 description = getServiceDescription(to, lang, info);
		    } else {
			Element temp = getServiceDescription(to, lang, info);
			GSXML.mergeElements(description, temp);
		    }
		}
	    }
	}
	if (description != null) { // may be null if non-existant service
	    response.appendChild(description);
	}
	return response;
    
    }

    /** process method for stylesheet requests
     */
    protected Element processFormat(Element request) {
	Element response = this.doc.createElement(GSXML.RESPONSE_ELEM);
	response.setAttribute(GSXML.TYPE_ATT, GSXML.REQUEST_TYPE_FORMAT);
	
	String to = GSPath.getFirstLink(request.getAttribute(GSXML.TO_ATT));
	
	if (to.equals("")) { // serviceRack query - is this appropriate??
	    return response;
	} 
	
	
	// describe a particular service	
	if (this.format_info_map.containsKey(to)) {
	    response.appendChild(getServiceFormat(to));
	    response.setAttribute(GSXML.FROM_ATT, to);
	    return response;
	}
	// else no format info
	System.err.println("ServiceRack describe request: no format info for "+to+".");
	return response;
    }	
    
    /** returns the service list for the subclass */
    protected Element getServiceList(String lang) {
	// for now, it is static and has no language stuff
	return (Element) this.short_service_info.cloneNode(true);
    }
    
    /** returns a specific service description */
    abstract protected Element getServiceDescription(String service, String lang, String subset);

    protected Element getServiceFormat(String service) {
	Element format = (Element)((Element)this.format_info_map.get(service)).cloneNode(true);
	return format;
    }

    /** overloaded version for no args case */
    protected String getTextString(String key, String lang) {
	return getTextString(key, lang, null, null);
    }

    protected String getTextString(String key, String lang, String dictionary) {
	return getTextString(key, lang, dictionary, null);
    }
    protected String getTextString(String key, String lang, String [] args) {
	return getTextString(key, lang, null, args);
    }
	
    /** getTextString - retrieves a language specific text string for the given
key and locale, from the specified resource_bundle (dictionary)
    */
    protected String getTextString(String key, String lang, String dictionary, String[] args) {

	// we want to use the collection class loader in case there are coll specific files
	CollectionClassLoader class_loader = new CollectionClassLoader(this.site_home, this.cluster_name);
	
	if (dictionary != null) {
	    // just try the one specified dictionary
	    Dictionary dict = new Dictionary(dictionary, lang, class_loader);
	    String result = dict.get(key, args);
	    if (result == null) { // not found
		return "_"+key+"_";
	    }
	    return result;
	}

	// now we try class names for dictionary names
	String class_name = this.getClass().getName();
	class_name = class_name.substring(class_name.lastIndexOf('.')+1);
	Dictionary dict = new Dictionary(class_name, lang, class_loader);
	String result = dict.get(key, args);
	if (result != null) {
	    return result;
	}

	// we have to try super classes
	Class c = this.getClass().getSuperclass();
	while (result == null && c != null) {
	    class_name = c.getName();
	    class_name = class_name.substring(class_name.lastIndexOf('.')+1);
	    if (class_name.equals("ServiceRack")) {
		// this is as far as we go
		break;
	    }
	    dict = new Dictionary(class_name, lang, class_loader);
	    result = dict.get(key, args);
	    c = c.getSuperclass();
	}
	if (result == null) {
	    return "_"+key+"_";
	}
	return result;
	
    }

    protected String getMetadataNameText(String key, String lang) {

	String properties_name = "metadata_names";
	Dictionary dict = new Dictionary(properties_name, lang);
	
	String result = dict.get(key);
	if (result == null) { // not found
	    return null;
	} 
	return result;
    }
}