from __future__ import generators

import os
from urlparse import urlparse        

from rdflib.syntax.parser import Parser
from rdflib.syntax.nt_parser import NTParser
from rdflib.syntax.serializer import Serializer
from rdflib import URIRef
from rdflib.URLInputSource import URLInputSource

from threading import Lock

from xml.sax.xmlreader import InputSource
from urlparse import urljoin
from os import getcwd


class LoadSave(NTParser, Parser, Serializer, object):
    """LoadSave

    Mixed-in with a store that implements add and visit and provides
    I/O for that class. Also, needs to be mixed in with something that
    provides parse_URI and output methods.
    """
    
    def __init__(self):
        super(LoadSave, self).__init__()
        self.location = None
        self.__lock = Lock()

    def load(self, location):
        if isinstance(location, InputSource):
            self.parse(location)
        else:
            location = urljoin("file://%s/" % getcwd(), location)
            scheme, netloc, path, params, query, fragment = urlparse(location)
            if netloc=="":
                # If local and it does not exist then create one.
                if not os.access(path, os.F_OK): # TODO: is this equiv to os.path.exists?
                    self.save(path)
            if location[-3:]==".nt":
                self.parse_nt_URI(location, None)
            else:
                source = URLInputSource(location)                    
                self.parse(source)

            if not self.location:
                self.location = location        
            

    def save(self, location=None):
        try:
            self.__lock.acquire()
            location = location or self.location
            if not location:
                print "WARNING: not saving as no location has been set"
                return
            scheme, netloc, path, params, query, fragment = urlparse(location)
            if netloc!="":
                print "WARNING: not saving as location is not a local file reference"
                return

            import tempfile, shutil, os
            name = tempfile.mktemp()            
            stream = open(name, 'wb')
            self.output(stream)            
            stream.close()

            if os.path.isfile(path):
                os.remove(path)
            shutil.copy(name, path)
            os.unlink(name)

        finally:
            self.__lock.release()