#ResponseFilter.py
#A Response Filter to Capture and Modify the Response
from javax import servlet
from javax.servlet import http
from java.lang import *
from java.io import *
import string , sys

#Buffer contains the stand-in stream response generated by the target servlet or HTML
buffer = None


#Class Wrapper Extends Standard HttpServletResponseWrapper
class Wrapper(http.HttpServletResponseWrapper):

    #Override the default toString method to capture the
    #target servlet or HTML Response
    def toString(self):

        global buffer
        return buffer.toString()

    #Override the Standard getWriter method
    #to have the response contents in a stand-in stream defined below
    def getWriter (self):

        global buffer
        buffer = StringWriter()
        return PrintWriter(buffer)



class ResponseFilter (servlet.Filter):
                
    def doFilter(self, req, res,chain):

        #Capture the Stream which writes response to the client
       
        toclient = res.getWriter()

        #Create the Wrapper object with its default constructor
        wrapper_stream = Wrapper(res)

        #Pass this Wrapper object to get the response from the target
        #Servlet or HTML by overriding the getWriter method
        chain.doFilter(req,wrapper_stream)

        #Get the Wrapped Response

        if (str(wrapper_stream.getContentType()) == "text/html"):

            #If response is HTML, set ContentType of Client Response to HTML
            res.setContentType("text/html")

            #Get the Response data in a string
            wrapped_response = str(wrapper_stream.toString())

            #Find the occurrence of end HTML tag in the response
            if wrapped_response.find("</HTML>") <> -1:

                #Append a message to this response
                
                wrapped_response = wrapped_response[:wrapped_response.rfind("</HTML>")] + """
                <div style="text-align: center;"><font style="font-weight: bold;"
                size="+2"><BR> This Response was Monitored by the Filter <BR></font>
                <span style="font-weight: bold;">
                """ + wrapped_response[wrapped_response.rfind("</HTML>"):]

                #Send the Modified response to the client
                toclient.println(wrapped_response)

            else:

                #If the end tag is </html> 
                wrapped_response = wrapped_response[:wrapped_response.rfind("</html>")] + """
                <div style="text-align: center;"><font style="font-weight: bold;"
                size="+2"><BR> This Response was Monitored by the Filter <BR></font>
                <span style="font-weight: bold;">
                """ + wrapped_response[wrapped_response.rfind("</html>"):]

                #write the modified response                
                toclient.println(wrapped_response)
               
        #Deallocate the buffer  
        buffer = None
        
    def init(self, config):

        print "Response Filter Initialized"

    def destroy(self):

        print "Response Filter Destroyed"
        sys.exit(0)