Tech Erudition

""" A basic implementation of (xmllint --shell)
Author: Prasad.A
"""

import sys
from xml.dom import minidom
from readline import *

class xmlsh(object):
   """The base class which holds the xml document."""

   def __init__(self,xmlfile):
       self.filename=xmlfile
       self.__loadFile()

   def __loadFile(self):
       self.xmlDoc = minidom.parse(self.filename)

   # Get the element from the dom (currentElement)
   def __getElement(self,elemname,currentElement,index=0):
       if(elemname==""): return (currentElement,1)
       elementList = currentElement.getElementsByTagName(elemname)
       return (elementList[index],len(elementList))

   # Handler for cat command
   def __catHandler(self,path,currentElement):
       if(path[0]=="/"): #absolute path is used
           element=self.xmlDoc
           path=path[1:]
       else: # relative path is used
           element=currentElement

       parentElement = None
       count=-1
       pathSplit = path.split("/")
       if(len(pathSplit)>1):
           for elemname in pathSplit[:len(pathSplit)]:
               parentElement = element
               (element,count) = self.__getElement(elemname,element)
       else:
           (element,count) = self.__getElement(pathSplit[-1],element)

       if(count != -1 and count > 1):
           for index in range(count):
               (element,count) = self.__getElement(pathSplit[-1],parentElement,index)

       print element.toxml()

   # Display the help
   def __printHelp(self):
       print """
The following commands are supported:
  cd [xpath]: Change to the given node.
 cat [xpath]: See the content.
 pwd        : Current position in the document.
help        : Displays this help.
This implementation will support only very basic xpath.
"""
   # Wrapper for displaying help
   def help(self):
       self.__printHelp()

   # Main loop to run the program
   def run(self):
       print "Type bye or quit to terminate."
       stop = False
       prompt = "/"
       self.currentElement = self.xmlDoc

       while(stop!=True):
           try:
               # Accept the input
               inputLine = raw_input("%s%s " % (prompt,">"))
               # If the input is empty or newline do nothing
               if(inputLine == "" or inputLine == "\n"): continue
               # Split the input
               inputSplit = inputLine.split()

               # Assume the first element of split is command
               command = inputSplit[0]
               # Adjust the arguments passed
               arguments=None
               if(len(inputSplit) > 1): arguments = "".join(inputSplit[1:])

               # Command is not still handled
               commandHandled =False

               # Handle "bye" or "quit" command
               if(command=="bye" or command=="quit"):
                   commandHandled=True
                   stop=True
                   continue

               # Handle "cd" command
               if(command=="cd"):
                   commandHandled=True
                   inputArg=arguments

                   if(arguments[0]=="/"):
                       arguments=arguments[1:]
                       self.currentElement=self.xmlDoc

                   element=self.currentElement
                   parentElement=None
                   count = -1
                   pathSplit=arguments.split("/")
                   if(len(pathSplit) > 1):
                       for elemname in pathSplit[:len(pathSplit)-1]:
                           parentElement=element
                           (element,count)=self.__getElement(elemname,element)
                   parentElement=element
                   (element,count)=self.__getElement(pathSplit[-1],element)
                   whichOne=-1
                   if(count!=-1 and count>1):
                       print count, " elements of ", pathSplit[-1]," is present."
                       whichOne = raw_input("Specify the index to select: ")

                       if whichOne != " ":
                           whichOne = int(whichOne)
                           (element,count) = self.__getElement(pathSplit[-1],parentElement,whichOne-1)
                       else:
                           element=parentElement

                   self.currentElement=element

                   separator="/"
                   if(inputArg[0]=="/"):
                       prompt=""
                       separator=""
                   elif(prompt=="/"):
                       prompt=""
                       separator="/"

                   if(whichOne==-1): prompt="%s%s%s" % (prompt,separator,inputArg)
                   else: prompt="%s%s%s[%d]" % (prompt,separator,inputArg,whichOne)

                   if(self.currentElement==None):
                       stop=True
                       continue

               # Handle "cat" command
               if(command=="cat"):
                   commandHandled = True
                   if(arguments != None): self.__catHandler(arguments,self.currentElement)
                   else: print self.currentElement.toxml()

               # Handle "pwd" command
               if(command=="pwd"):
                   commandHandled = True
                   print prompt

               # Handle "help" command
               if(command=="help"):
                   commandHandled = True
                   self.__printHelp()

               if(commandHandled==False):
                   print "Unknown Command:"
                   print self.__printHelp()

           except Exception, ex:
               print "Exception: ",ex

# Start the shell
if(len(sys.argv)>1):
   ob=xmlsh(sys.argv[1])
   print "Object created...function run() will be invoked..."
   ob.help()
   ob.run()
else:
   print "Usage: python", sys.argv[0], "xmlfilename"

XML File: xmlsh.xml 
<?xml version="1.0"?>
<root>
    <element>
        <item>
            <title>Title of item1</title>
            <description>Description of item1</description>
        </item>
        <item>
            <title>Title of item2</title>
            <description>Description of item2</description>
        </item>
        <item>
            <title>Title of item3</title>
            <description>Description of item3</description>
        </item>
        <item>
            <title>Title of item4</title>
            <description>Description of item4</description>
        </item>
    </element>
</root>
Usage: python xmlsh.py xmlsh.xml
/> cat
/> cd root
/root> cd /root/element
/root/element> cat
/root/element> cd item
[Specify the index: 1]
/root/element/item[1]> cat
/root/element/item[1]> cd /root/element
/root/element> pwd
/root/element> cd item
[Specify the index: 2]
/root/element/item[2]> cd /
/> bye