QGIS/python/ext-libs/owslib/util.py

# -*- coding: ISO-8859-15 -*-
# =============================================================================
# Copyright (c) 2008 Tom Kralidis
#
# Authors : Tom Kralidis <tomkralidis@gmail.com>
#
# Contact email: tomkralidis@gmail.com
# =============================================================================

import sys
from dateutil import parser
from datetime import datetime
import pytz
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
import cgi
from urllib import urlencode
import re


"""
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

# http://stackoverflow.com/questions/6256183/combine-two-dictionaries-of-dictionaries-python
dict_union = lambda d1,d2: dict((x,(dict_union(d1.get(x,{}),d2[x]) if
  isinstance(d2.get(x),dict) else d2.get(x,d1.get(x)))) for x in
  set(d1.keys()+d2.keys()))


# Infinite DateTimes for Python.  Used in SWE 2.0 and other OGC specs as "INF" and "-INF"
class InfiniteDateTime(object):
    def __lt__(self, other):
        return False
    def __gt__(self, other):
        return True
    def timetuple(self):
        return tuple()
class NegativeInfiniteDateTime(object):
    def __lt__(self, other):
        return True
    def __gt__(self, other):
        return False
    def timetuple(self):
        return tuple()


first_cap_re = re.compile('(.)([A-Z][a-z]+)')
all_cap_re = re.compile('([a-z0-9])([A-Z])')
def format_string(prop_string):
    """
        Formats a property string to remove spaces and go from CamelCase to pep8
        from: http://stackoverflow.com/questions/1175208/elegant-python-function-to-convert-camelcase-to-camel-case
    """
    if prop_string is None:
        return ''
    st_r = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', prop_string)
    st_r = st_r.replace(' ','')
    return re.sub('([a-z0-9])([A-Z])', r'\1_\2', st_r).lower()

def xml_to_dict(root, prefix=None, depth=1, diction=None):
    """
        Recursively iterates through an xml element to convert each element in the tree to a (key,val). Where key is the element
        tag and val is the inner-text of the element. Note that this recursively go through the tree until the depth specified.

        Parameters
        ===========
        :root - root xml element, starting point of iteration
        :prefix - a string to prepend to the resulting key (optional)
        :depth - the number of depths to process in the tree (optional)
        :diction - the dictionary to insert the (tag,text) pairs into (optional)

        Return
        =======
        Dictionary of (key,value); where key is the element tag stripped of namespace and cleaned up to be pep8 and
        value is the inner-text of the element. Note that duplicate elements will be replaced by the last element of the
        same tag in the tree.
    """
    ret = diction if diction is not None else dict()
    for child in root:
        val = testXMLValue(child)
        # skip values that are empty or None
        if val is None or val == '':
            if depth > 1:
                ret = xml_to_dict(child,prefix=prefix,depth=(depth-1),diction=ret)
            continue

        key = format_string(child.tag.split('}')[-1])

        if prefix is not None:
            key = prefix + key

        ret[key] = val
        if depth > 1:
            ret = xml_to_dict(child,prefix=prefix,depth=(depth-1),diction=ret)

    return ret

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:
        # NOTE: optionally set debuglevel>0 to debug HTTP connection
        #opener = urllib2.build_opener(urllib2.HTTPHandler(debuglevel=0))
        #openit = opener.open
        openit = urlopen

    try:
        if method == 'Post':
            req = Request(url_base, data)
            # set appropriate header if posting XML
            try:
                xml = etree.fromstring(data)
                req.add_header('Content-Type', "text/xml")
            except:
                pass
        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 nspath_eval(xpath, namespaces):
    ''' Return an etree friendly xpath '''
    out = []
    for chunks in xpath.split('/'):
        namespace, element = chunks.split(':')
        out.append('{%s}%s' % (namespaces[namespace], element))
    return '/'.join(out)

def cleanup_namespaces(element):
    """ Remove unused namespaces from an element """
    if etree.__name__ == 'lxml.etree':
        etree.cleanup_namespaces(element)
        return element
    else:
        return etree.fromstring(etree.tostring(element))

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:
            return val.strip()
        elif val.text:
            return val.text.strip()
        else:
            return None
    else:
        return None

def testXMLAttribute(element, attribute):
    """

    Test that the XML element and attribute exist, return attribute's value, else return None

    Parameters
    ----------

    - element: the element containing the attribute
    - attribute: the attribute name

    """
    if element is not None:
        return element.get(attribute)

    return None

def http_post(url=None, request=None, lang='en-US', timeout=10):
    """

    Invoke an HTTP POST request

    Parameters
    ----------

    - url: the URL of the server
    - request: the request message
    - lang: the language
    - timeout: timeout in seconds

    """

    if url is not None:
        u = urlparse.urlsplit(url)
        r = urllib2.Request(url, request)
        r.add_header('User-Agent', 'OWSLib (https://geopython.github.io/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)

        try:
            up = urllib2.urlopen(r,timeout=timeout);
        except TypeError:
            import socket
            socket.setdefaulttimeout(timeout)
            up = urllib2.urlopen(r)

        ui = up.info()  # headers
        response = up.read()
        up.close()

        # check if response is gzip compressed
        if ui.has_key('Content-Encoding'):
            if ui['Content-Encoding'] == 'gzip':  # uncompress response
                import gzip
                cds = StringIO(response)
                gz = gzip.GzipFile(fileobj=cds)
                response = gz.read()

        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(xml))
    return xsd2.validate(doc)

def xmltag_split(tag):
    ''' Return XML element bare tag name (without prefix) '''
    try:
        return tag.split('}')[1]
    except:
        return tag

def getNamespace(element):
    ''' Utility method to extract the namespace from an XML element tag encoded as {namespace}localname. '''
    if element.tag[0]=='{':
        return element.tag[1:].split("}")[0]
    else:
        return ""

def build_get_url(base_url, params):
    ''' Utility function to build a full HTTP GET URL from the service base URL and a dictionary of HTTP parameters. '''

    qs = []
    if base_url.find('?') != -1:
        qs = cgi.parse_qsl(base_url.split('?')[1])

    pars = [x[0] for x in qs]

    for key,value in params.iteritems():
        if key not in pars:
            qs.append( (key,value) )

    urlqs = urlencode(tuple(qs))
    return base_url.split('?')[0] + '?' + urlqs

def dump(obj, prefix=''):
    '''Utility function to print to standard output a generic object with all its attributes.'''

    print "%s %s : %s" % (prefix, obj.__class__, obj.__dict__)

def getTypedValue(type, value):
    ''' Utility function to cast a string value to the appropriate XSD type. '''

    if type=='boolean':
       return bool(value)
    elif type=='integer':
       return int(value)
    elif type=='float':
        return float(value)
    elif type=='string':
        return str(value)
    else:
        return value # no type casting


def extract_time(element):
    ''' return a datetime object based on a gml text string

ex:
<gml:beginPosition>2006-07-27T21:10:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="now"/>

If there happens to be a strange element with both attributes and text,
use the text.
ex: <gml:beginPosition indeterminatePosition="now">2006-07-27T21:10:00Z</gml:beginPosition>
Would be 2006-07-27T21:10:00Z, not 'now'

'''
    if element is None:
        return None

    try:
        dt = parser.parse(element.text)
    except Exception:
        att = testXMLValue(element.attrib.get('indeterminatePosition'), True)
        if att and att == 'now':
            dt = datetime.utcnow()
            dt.replace(tzinfo=pytz.utc)
        else:
            dt = None
    return dt


def extract_xml_list(elements):
    """
Some people don't have separate tags for their keywords and separate them with
a newline. This will extract out all of the keywords correctly.
"""
    keywords = [re.split(r'[\n\r]+',f.text) for f in elements if f.text]
    flattened = [item.strip() for sublist in keywords for item in sublist]
    remove_blank = filter(None, flattened)
    return remove_blank


def bind_url(url):
    """binds an HTTP GET query string endpiont"""
    if url.find('?') == -1: # like http://host/wms
        binder = '?'

    # if like http://host/wms?foo=bar& or http://host/wms?foo=bar
    if url.find('=') != -1:
        if url.find('&', -1) != -1: # like http://host/wms?foo=bar&
            binder = ''
        else: # like http://host/wms?foo=bar
            binder = '&'

    # if like http://host/wms?foo
    if url.find('?') != -1:
        if url.find('?', -1) != -1: # like http://host/wms?
            binder = ''
        elif url.find('&', -1) == -1: # like http://host/wms?foo=bar
            binder = '&'
    return '%s%s' % (url, binder)