package com.telegraph.online.timmy.rest;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.dom4j.Document;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

import com.telegraph.online.exception.ImporterException;
import com.telegraph.online.exception.InputException;
import com.telegraph.online.exception.ProgrammingException;
import com.telegraph.online.exception.ResourceException;
import com.telegraph.online.timmy.action.EscenicMessages;
import com.telegraph.online.timmy.action.ImportAction;
import com.telegraph.online.timmy.xml.ResponseXmlWriter;

public class ImportServlet extends HttpServlet {
	
    private static final String RETURN_CONTENT_TYPE = "text/xml;charset=utf-8";
	private static final String MESSAGE_OK          = "OK";    
    private static final String ENCODING_SCHEME     = "UTF-8";	
	private static final long serialVersionUID      = 7780962167339325634L;

	
    private static Logger LOGGER = Logger.getLogger(ImportServlet.class);

	public void init() throws ServletException{
        super.init();
    }      
     
    public void doDelete(HttpServletRequest request, HttpServletResponse response){
    	createNotSupportedResponse(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "DELETE is not supported for this resource", response);
    }
    
    public void doGet(HttpServletRequest request, HttpServletResponse response){
    	createNotSupportedResponse(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "GET is not supported for this resource", response);
    }
    
    public void doPost(HttpServletRequest request, HttpServletResponse response){        
    	createNotSupportedResponse(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "POST is not supported for this resource", response);
    }
    
    //TODO Add XML Schema validation for returned xml
    //TODO Pass parameter for articletype (news, sports, etc.) to importer? (ImportAction.XML_IMPORT_SERVICE)
    public void doPut(HttpServletRequest request, HttpServletResponse response){
    	try {
    		EscenicMessages escenicMessages;
			try {
				
				//Call the business process we are exposing 
				escenicMessages = (new ImportAction()).doImport(request.getInputStream());
			} catch (IOException e) {
				throw new ImporterException(new InputException("Unable to read the XML"), new EscenicMessages());
			}
			
			//Everything went well
			createOkResponse(escenicMessages, response);
			
			
    	} catch (ImporterException e){
    		if (e.getCause() instanceof InputException){
    			createErrorResponse(e, HttpServletResponse.SC_BAD_REQUEST, "Unble to parse the XML", response);
    		}
    		if (e.getCause() instanceof ProgrammingException){
    			LOGGER.error("Programmers error", e);
    			createErrorResponse(e, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Unexpected error", response);
    		}
    		if (e.getCause() instanceof ResourceException){
    			LOGGER.error("Resource not available", e);
    			createErrorResponse(e, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Problem accessing resources", response);
    		}
    		if (e.getCause() == null){
    			createErrorResponse(e, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Undetermined error encountered", response);
    		}
        }catch (Throwable t){
        	LOGGER.error("Unexpected exception. All exceptions need to be wrapped in an ImporterException before being " +
        			"thrown back to ImportServlet. Check your code and make sure you've handled and wrapped this exception appropriatly", t);
        	createSimpleErrorResponse(t, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Undetermined error encountered", response);
        }
    }
    
    private void createOkResponse(EscenicMessages escenicMessages, HttpServletResponse response){
		Document doc = createOkReturnBody(escenicMessages);
    	try {
			XMLWriter xmlWriter = initResponse(response, HttpServletResponse.SC_OK);
			xmlWriter.write(doc);
			xmlWriter.flush();
		} catch (Exception e) {
			LOGGER.error("Programmer error: Unable to return XML: " + e.getMessage(), e);
		} 
    }    
    
    private void createErrorResponse(ImporterException importerException, int httpReturnCode, String message, HttpServletResponse response) {
		Document doc = createErrorReturnBody(importerException, message);
    	try {
			XMLWriter xmlWriter = initResponse(response, httpReturnCode);
			xmlWriter.write(doc);
			xmlWriter.flush();
		} catch (Exception e) {
			LOGGER.error("Programmer error: Unable to return XML: " + e.getMessage(), e);
		} 
    }
    
    private void createSimpleErrorResponse(Throwable t, int httpReturnCode, String message, HttpServletResponse response) {
    	Document doc = ResponseXmlWriter.createCommonBody(message);
    	try {
			XMLWriter xmlWriter = initResponse(response, httpReturnCode);
			xmlWriter.write(doc);
			xmlWriter.flush();
		} catch (Exception e) {
			LOGGER.error("Programmer error: Unable to return XML: " + e.getMessage(), e);
		} 
    }    
    

    private void createNotSupportedResponse(int httpReturnCode, String message, HttpServletResponse response) {
		try {
			XMLWriter xmlWriter = initResponse(response, httpReturnCode);
			Document doc = ResponseXmlWriter.createCommonBody(message);
			xmlWriter.write(doc);
			xmlWriter.flush();
		} catch (Exception e) {
			LOGGER.error("Programmer error: Unable to return XML: " + e.getMessage(), e);
		} 
    } 
    
    private static Document createOkReturnBody(EscenicMessages escenicMessages) {
    	Document doc = ResponseXmlWriter.createCommonBody(MESSAGE_OK);
    	ResponseXmlWriter.createInfoAndWarnings(doc.getRootElement(), escenicMessages);		
		return doc;
    }
       
    private static Document createErrorReturnBody(ImporterException importerException, String errorMessage) {
    	Document doc = ResponseXmlWriter.createCommonBody(errorMessage);
    	ResponseXmlWriter.createInfoAndWarnings(doc.getRootElement(), importerException.getEscenicMessages());
    	ResponseXmlWriter.createErrors(doc.getRootElement(), importerException);
		return doc;
    }
    
    private XMLWriter initResponse(HttpServletResponse response, int httpReturnCode) throws Exception{
    	response.setStatus(httpReturnCode);
        response.setContentType(RETURN_CONTENT_TYPE);
        
        ServletOutputStream os = response.getOutputStream();
        OutputFormat outformat = OutputFormat.createPrettyPrint();            
        outformat.setEncoding(ENCODING_SCHEME);	 
        XMLWriter writer = new XMLWriter(os, outformat);
        return writer;
    }
}