#!/usr/bin/python
# -*- coding: ISO-8859-15 -*-
# =============================================================================
# Copyright (c) 2008 Tom Kralidis
#
# Authors : Tom Kralidis <tomkralidis@hotmail.com>
#
# Contact email: tomkralidis@hotmail.com
# =============================================================================

from owslib.etree import etree
import urlparse, urllib2
from urllib2 import urlopen, HTTPError, Request
from urllib2 import HTTPPasswordMgrWithDefaultRealm
from urllib2 import HTTPBasicAuthHandler
from StringIO import StringIO

"""
Utility functions and classes
"""

class RereadableURL(StringIO,object):
    """ Class that acts like a combination of StringIO and url - has seek method and url headers etc """
    def __init__(self, u):
        #get url headers etc from url
        self.headers = u.headers                
        #get file like seek, read methods from StringIO
        content=u.read()
        super(RereadableURL, self).__init__(content)


class ServiceException(Exception):
    #TODO: this should go in ows common module when refactored.  
    pass

def openURL(url_base, data, method='Get', cookies=None, username=None, password=None):
    ''' function to open urls - wrapper around urllib2.urlopen but with additional checks for OGC service exceptions and url formatting, also handles cookies and simple user password authentication'''
    url_base.strip() 
    lastchar = url_base[-1]
    if lastchar not in ['?', '&']:
        if url_base.find('?') == -1:
            url_base = url_base + '?'
        else:
            url_base = url_base + '&'
            
    if username and password:
        # Provide login information in order to use the WMS server
        # Create an OpenerDirector with support for Basic HTTP 
        # Authentication...
        passman = HTTPPasswordMgrWithDefaultRealm()
        passman.add_password(None, url_base, username, password)
        auth_handler = HTTPBasicAuthHandler(passman)
        opener = urllib2.build_opener(auth_handler)
        openit = opener.open
    else:
        openit = urlopen
   
    try:
        if method == 'Post':
            req = Request(url_base, data)
        else:
            req=Request(url_base + data)
        if cookies is not None:
            req.add_header('Cookie', cookies)
        u = openit(req)
    except HTTPError, e: #Some servers may set the http header to 400 if returning an OGC service exception or 401 if unauthorised.
        if e.code in [400, 401]:
            raise ServiceException, e.read()
        else:
            raise e
    # check for service exceptions without the http header set
    if u.info()['Content-Type'] in ['text/xml', 'application/xml']:          
        #just in case 400 headers were not set, going to have to read the xml to see if it's an exception report.
        #wrap the url stram in a extended StringIO object so it's re-readable
        u=RereadableURL(u)      
        se_xml= u.read()
        se_tree = etree.fromstring(se_xml)
        serviceException=se_tree.find('{http://www.opengis.net/ows}Exception')
        if serviceException is None:
            serviceException=se_tree.find('ServiceException')
        if serviceException is not None:
            raise ServiceException, \
            str(serviceException.text).strip()
        u.seek(0) #return cursor to start of u      
    return u

#default namespace for nspath is OWS common
OWS_NAMESPACE = 'http://www.opengis.net/ows/1.1'
def nspath(path, ns=OWS_NAMESPACE):

    """

    Prefix the given path with the given namespace identifier.
    
    Parameters
    ----------

    - path: ElementTree API Compatible path expression
    - ns: the XML namespace URI.

    """

    if ns is None or path is None:
        return -1

    components = []
    for component in path.split('/'):
        if component != '*':
            component = '{%s}%s' % (ns, component)
        components.append(component)
    return '/'.join(components)

def testXMLValue(val, attrib=False):
    """

    Test that the XML value exists, return val.text, else return None

    Parameters
    ----------

    - val: the value to be tested

    """

    if val is not None:
        if attrib == True:
            return val
        else:
            return val.text
    else:
        return None


def http_post(url=None, request=None, lang='en-US'):
    """

    Invoke an HTTP POST request 

    Parameters
    ----------

    - url: the URL of the server
    - request: the request message
    - lang: the language

    """

    if url is not None:
        u = urlparse.urlsplit(url)
        r = urllib2.Request(url, request)
        r.add_header('User-Agent', 'OWSLib (http://trac.gispython.org/lab/wiki/OwsLib)')
        r.add_header('Content-type', 'text/xml')
        r.add_header('Content-length', '%d' % len(request))
        r.add_header('Accept', 'text/xml')
        r.add_header('Accept-Language', lang)
        r.add_header('Accept-Encoding', 'gzip,deflate')
        r.add_header('Host', u.netloc)
        up = urllib2.urlopen(r)
        response = up.read()
        up.close()
        return response
       
        
def xml2string(xml):
    """

    Return a string of XML object

    Parameters
    ----------

    - xml: xml string

    """
    return '<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>\n' + xml

def xmlvalid(xml, xsd):
    """

    Test whether an XML document is valid

    Parameters
    ----------

    - xml: XML content
    - xsd: pointer to XML Schema (local file path or URL)

    """

    xsd1 = etree.parse(xsd)
    xsd2 = etree.XMLSchema(xsd1)

    doc = etree.parse(StringIO.StringIO(xml))
    return xsd2.validate(doc)