appypod-rattail/shared/xml_parser.py

# ------------------------------------------------------------------------------
# Appy is a framework for building applications in the Python language.
# Copyright (C) 2007 Gaetan Delannay

# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,USA.

# ------------------------------------------------------------------------------
import xml.sax
from xml.sax.handler import ContentHandler, ErrorHandler
from xml.sax.xmlreader import InputSource
from StringIO import StringIO
from appy.shared.errors import AppyError

# Error-related constants ------------------------------------------------------
CONVERSION_ERROR = '"%s" value "%s" could not be converted by the XML ' \
    'unmarshaller.'
CUSTOM_CONVERSION_ERROR = 'Custom converter for "%s" values produced an ' \
    'error while converting value "%s". %s'

# ------------------------------------------------------------------------------
class XmlElement:
    '''Represents an XML tag.'''
    def __init__(self, elem, attrs=None, nsUri=None):
        '''An XmlElement instance may represent:
           - an already parsed tag (in this case, p_elem may be prefixed with a
             namespace);
           - the definition of an XML element (in this case, no namespace can be
             found in p_elem; but a namespace URI may be defined in p_nsUri).'''
        self.elem = elem
        self.attrs = attrs
        if elem.find(':') != -1:
            self.ns, self.name = elem.split(':')
        else:
            self.ns = ''
            self.name = elem
            self.nsUri = nsUri
    def equalsTo(self, other, namespaces=None):
        '''Does p_elem == p_other? If a p_namespaces dict is given, p_other must
           define a nsUri.'''
        res = None
        if namespaces:
            res = self.elem == ('%s:%s' % (namespaces[other.nsUri], other.name))
        else:
            res = self.elem == other.elem
        return res
    def __repr__(self):
        res = self.elem
        if self.attrs:
            res += '('
            for attrName, attrValue in self.attrs.items():
                res += '%s="%s"' % (attrName, attrValue)
            res += ')'
        return res
    def getFullName(self, namespaces=None):
        '''Gets the name of the element including the namespace prefix.'''
        if not namespaces:
            res = self.elem
        else:
            res = '%s:%s' % (namespaces[self.nsUri], self.name)
        return res

class XmlEnvironment:
    '''An XML environment remembers a series of elements during a SAX parsing.
       This class is an abstract class that gathers basic things like
       namespaces.'''
    def __init__(self):
        # This dict contains the xml namespace declarations encountered so far
        self.namespaces = {} # ~{s_namespaceUri:s_namespaceName}~
        self.currentElem = None # The currently parsed element
        self.parser = None
    def manageNamespaces(self, attrs):
        '''Manages namespaces definitions encountered in p_attrs.'''
        for attrName, attrValue in attrs.items():
            if attrName.startswith('xmlns:'):
                self.namespaces[attrValue] = attrName[6:]
    def ns(self, nsUri):
        '''Returns the namespace corresponding to o_nsUri.'''
        return self.namespaces[nsUri]

class XmlParser(ContentHandler, ErrorHandler):
    '''Basic XML content handler that does things like :
      - remembering the currently parsed element;
      - managing namespace declarations.'''
    def __init__(self, env=None, caller=None):
        '''p_env should be an instance of a class that inherits from
           XmlEnvironment: it specifies the environment to use for this SAX
           parser.'''
        ContentHandler.__init__(self)
        if not env: env = XmlEnvironment()
        self.env = env
        self.env.parser = self
        self.caller = caller # The class calling this parser
        self.parser = xml.sax.make_parser() # Fast, standard expat parser
        self.res = None # The result of parsing.
    def setDocumentLocator(self, locator):
        self.locator = locator
        return self.env
    def endDocument(self):
        return self.env
    def startElement(self, elem, attrs):
        self.env.manageNamespaces(attrs)
        if self.env.currentElem == None:
            self.env.currentElem = XmlElement(elem, attrs=attrs)
        else:
            # Reuse the exiting instance in order to avoid creating one instance
            # every time an elem is met in the XML file.
            self.env.currentElem.__init__(elem, attrs)
        return self.env
    def endElement(self, elem):
        self.env.currentElem.__init__(elem)
        return self.env
    def characters(self, content):
        return self.env
    def parse(self, xmlContent, source='string'):
        '''Parsers the XML file or string p_xmlContent.'''
        try:
            from cStringIO import StringIO
        except ImportError:
            from StringIO import StringIO
        self.parser.setContentHandler(self)
        self.parser.setErrorHandler(self)
        inputSource = InputSource()
        if source == 'string':
            inputSource.setByteStream(StringIO(xmlContent))
        else:
            inputSource.setByteStream(xmlContent)
        self.parser.parse(inputSource)
        return self.res

# ------------------------------------------------------------------------------
from appy.shared import UnmarshalledObject, UnmarshalledFile
try:
    from DateTime import DateTime
except ImportError:
    DateTime = 'unicode'

class XmlUnmarshaller(XmlParser):
    '''This class allows to parse a XML file and recreate the corresponding web
       of Python objects. This parser assumes that the XML file respects this
       convention: any tag may define in attribute "type" storing the type of
       its content, which may be:
       
       bool * int * float * long * DateTime * tuple * list * object

       If "object" is specified, it means that the tag contains sub-tags, each
       one corresponding to the value of an attribute for this object.
       if "tuple" is specified, it will be converted to a list.'''
    def __init__(self, klass=None, tagTypes={}, conversionFunctions={}):
        XmlParser.__init__(self)
        self.klass = klass # If a klass is given here, instead of creating
        # a root UnmarshalledObject instance, we will create an instance of this
        # class (only if the root object is an object; this does not apply if
        # it is a list or tuple; yes, technically the root tag can be a list or
        # tuple even if it is silly because only one root tag can exist). But be
        # careful: we will not call the constructor of this class. We will
        # simply create an instance of UnmarshalledObject and dynamically change
        # the class of the created instance to this class.
        self.tagTypes = tagTypes
        # We expect that the parsed XML file will follow some conventions
        # (ie, a tag that corresponds to a list has attribute type="list" or a
        # tag that corresponds to an object has attribute type="object".). If
        # it is not the case of p_xmlContent, you can provide the missing type
        # information in p_tagTypes. Here is an example of p_tagTypes:
        # {"information": "list", "days": "list", "person": "object"}.
        self.conversionFunctions = conversionFunctions
        # The parser assumes that data is represented in some standard way. If
        # it is not the case, you may provide, in this dict, custom functions
        # allowing to convert values of basic types (long, float, DateTime...).
        # Every such function must take a single arg which is the value to
        # convert and return the converted value. Dict keys are strings
        # representing types ('bool', 'int', 'unicode', etc) and dict values are
        # conversion functions. Here is an example:
        # {'int': convertInteger, 'DateTime': convertDate}
        # NOTE: you can even invent a new basic type, put it in self.tagTypes,
        # and create a specific conversionFunction for it. This way, you can
        # for example convert strings that have specific values (in this case,
        # knowing that the value is a 'string' is not sufficient).

    def startDocument(self):
        self.res = None # The resulting web of Python objects
        # (UnmarshalledObject instances).
        self.env.containerStack = [] # The stack of current "containers" where
        # to store the next parsed element. A container can be a list, a tuple,
        # an object (the root object of the whole web or a sub-object).
        self.env.currentBasicType = None # Will hold the name of the currently
        # parsed basic type (unicode, float...)
        self.env.currentContent = '' # We store here the content of tags.

    containerTags = ('tuple', 'list', 'object', 'file')
    numericTypes = ('bool', 'int', 'float', 'long')
    def startElement(self, elem, attrs):
        e = XmlParser.startElement(self, elem, attrs)
        # Determine the type of the element.
        elemType = 'unicode' # Default value
        if attrs.has_key('type'):
            elemType = attrs['type']
        elif self.tagTypes.has_key(elem):
            elemType = self.tagTypes[elem]
        if elemType in self.containerTags:
            # I must create a new container object.
            if elemType == 'object': newObject = UnmarshalledObject()
            elif elemType == 'tuple': newObject = [] # Tuples become lists
            elif elemType == 'list': newObject = []
            elif elemType == 'file':
                newObject = UnmarshalledFile()
                if attrs.has_key('name'):
                    newObject.name = attrs['name']
                if attrs.has_key('mimeType'):
                    newObject.mimeType = attrs['mimeType']
            else: newObject = UnmarshalledObject()
            # Store the value on the last container, or on the root object.
            self.storeValue(elem, newObject)
            # Push the new object on the container stack
            e.containerStack.append(newObject)
        else:
            e.currentBasicType = elemType

    def storeValue(self, name, value):
        '''Stores the newly parsed p_value (contained in tag p_name) on the
           current container in environment p_e.'''
        e = self.env
        # Where must I store this value?
        if not e.containerStack:
            # I store the object at the root of the web.
            self.res = value
            if self.klass and isinstance(value, UnmarshalledObject):
                self.res.__class__ = self.klass
        else:
            currentContainer = e.containerStack[-1]
            if isinstance(currentContainer, list):
                currentContainer.append(value)
            elif isinstance(currentContainer, UnmarshalledFile):
                currentContainer.content += value
            else:
                # Current container is an object
                if hasattr(currentContainer, name):
                    # We have already encountered a sub-object with this name.
                    # Having several sub-objects with the same name, we will
                    # create a list.
                    attrValue = getattr(currentContainer, name)
                    if not isinstance(attrValue, list):
                        attrValue = [attrValue, value]
                    else:
                        attrValue.append(value)
                else:
                    attrValue = value
                setattr(currentContainer, name, attrValue)

    def characters(self, content):
        e = XmlParser.characters(self, content)
        if e.currentBasicType:
            e.currentContent += content

    def endElement(self, elem):
        e = XmlParser.endElement(self, elem)
        if e.currentBasicType:
            value = e.currentContent.strip()
            if not value: value = None
            else:
                # If we have a custom converter for values of this type, use it.
                if self.conversionFunctions.has_key(e.currentBasicType):
                    try:
                        value = self.conversionFunctions[e.currentBasicType](
                            value)
                    except Exception, err:
                        raise AppyError(CUSTOM_CONVERSION_ERROR % (
                            e.currentBasicType, value, str(err)))
                # If not, try a standard conversion
                elif e.currentBasicType in self.numericTypes:
                    try:
                        exec 'value = %s' % value
                    except SyntaxError:
                        raise AppyError(CONVERSION_ERROR % (
                            e.currentBasicType, value))
                    except NameError:
                        raise AppyError(CONVERSION_ERROR % (
                            e.currentBasicType, value))
                    # Check that the value is of the correct type. For instance,
                    # a float value with a comma in it could have been converted
                    # to a tuple instead of a float.
                    if not isinstance(value, eval(e.currentBasicType)):
                        raise AppyError(CONVERSION_ERROR % (
                            e.currentBasicType, value))
                elif e.currentBasicType == 'DateTime':
                    value = DateTime(value)
                elif e.currentBasicType == 'base64':
                    value = e.currentContent.decode('base64')
            # Store the value on the last container
            self.storeValue(elem, value)
            # Clean the environment
            e.currentBasicType = None
            e.currentContent = ''
        else:
            e.containerStack.pop()

    # Alias: "unmarshall" -> "parse"
    unmarshall = XmlParser.parse

class CssParser(XmlUnmarshaller):
    cssTags = {'rss': 'object', 'channel': 'object', 'item': 'object'}
    def startDocument(self):
        XmlUnmarshaller.startDocument(self)
        self.tagTypes.update(self.cssTags)

# ------------------------------------------------------------------------------
class XmlMarshaller:
    '''This class allows to produce a XML version of a Python object, which
       respects some conventions as described in the doc of the corresponding
       Unmarshaller (see above).'''
    xmlPrologue = '<?xml version="1.0" encoding="utf-8"?>'
    xmlEntities = {'<': '&lt;', '>': '&gt;', '&': '&amp;', '"': '&quot;',
                   "'": '&apos;'}
    trueFalse = {True: 'True', False: 'False'}
    sequenceTypes = (tuple, list)
    rootElementName = 'xmlPythonData'
    fieldsToMarshall = 'all'
    fieldsToExclude = []
    atFiles = ('image', 'file') # Types of archetypes fields that contain files.

    def dumpString(self, res, s):
        '''Dumps a string into the result.'''
        # Replace special chars by XML entities
        for c in s:
            if self.xmlEntities.has_key(c):
                res.write(self.xmlEntities[c])
            else:
                res.write(c)

    def dumpFile(self, res, v):
        '''Dumps a file into the result.'''
        # p_value contains the (possibly binary) content of a file. We will
        # encode it in Base64, in one or several parts.
        res.write('<part type="base64" number="1">')
        if hasattr(v, 'data'):
            # The file is an Archetypes file.
            valueType = v.data.__class__.__name__
            if valueType == 'Pdata':
                # There will be several parts.
                res.write(v.data.data.encode('base64'))
                # Write subsequent parts
                nextPart = v.data.next
                nextPartNumber = 2
                while nextPart:
                    res.write('</part>') # Close the previous part
                    res.write('<part type="base64" number="%d">'%nextPartNumber)
                    res.write(nextPart.data.encode('base64'))
                    nextPart = nextPart.next
                    nextPartNumber += 1
            else:
                res.write(v.data.encode('base64'))
        else:
            res.write(v.encode('base64'))
        res.write('</part>')

    def dumpValue(self, res, value, fieldType):
        '''Dumps the XML version of p_value to p_res.'''
        if fieldType == 'file':
            self.dumpFile(res, value)
        elif fieldType == 'ref':
            if value:
                if type(value) in self.sequenceTypes:
                    for elem in value:
                        self.dumpField(res, 'url', elem.absolute_url())
                else:
                    self.dumpField(res, 'url', value.absolute_url())
        elif type(value) in self.sequenceTypes:
            # The previous condition must be checked before this one because
            # Referred objects may be stored in lists or tuples, too.
            for elem in value:
                self.dumpField(res, 'e', elem)
        elif isinstance(value, basestring):
            self.dumpString(res, value)
        elif isinstance(value, bool):
            res.write(self.trueFalse[value])
        else:
            res.write(value)

    def dumpField(self, res, fieldName, fieldValue, fieldType='basic'):
        '''Dumps in p_res, the value of the p_field for p_instance.'''
        res.write('<'); res.write(fieldName);
        # Dump the type of the field as an XML attribute
        fType = None # No type will mean "unicode".
        if fieldType == 'file': fType ='file'
        elif fieldType == 'ref': fType = 'list'
        elif isinstance(fieldValue, bool): fType = 'bool'
        elif isinstance(fieldValue, int): fType = 'int'
        elif isinstance(fieldValue, float): fType = 'float'
        elif isinstance(fieldValue, long): fType = 'long'
        elif isinstance(fieldValue, tuple): fType = 'tuple'
        elif isinstance(fieldValue, list): fType = 'list'
        elif fieldValue.__class__.__name__ == 'DateTime': fType = 'DateTime'
        if fType: res.write(' type="%s"' % fType)
        # Dump other attributes if needed
        if type(fieldValue) in self.sequenceTypes:
            res.write(' count="%d"' % len(fieldValue))
        if fieldType == 'file':
            if hasattr(fieldValue, 'content_type'):
                res.write(' mimeType="%s"' % fieldValue.content_type)
            if hasattr(fieldValue, 'filename'):
                res.write(' name="')
                self.dumpString(res, fieldValue.filename)
                res.write('"')
        res.write('>')
        # Dump the field value
        self.dumpValue(res, fieldValue, fieldType)
        res.write('</'); res.write(fieldName); res.write('>')

    def marshall(self, instance, objectType='popo'):
        '''Returns in a StringIO the XML version of p_instance. If p_instance
           corresponds to a Plain Old Python Object, specify 'popo' for
           p_objectType. If p_instance corresponds to an Archetypes object
           (Zope/Plone), specify 'archetype' for p_objectType.'''
        res = StringIO()
        # Dump the XML prologue and root element
        res.write(self.xmlPrologue)
        res.write('<'); res.write(self.rootElementName)
        res.write(' type="object">')
        # Dump the value of the fields that must be dumped
        if objectType == 'popo':
            for fieldName, fieldValue in instance.__dict__.iteritems():
                mustDump = False
                if fieldName in self.fieldsToExclude:
                    mustDump = False
                elif self.fieldsToMarshall == 'all':
                    mustDump = True
                else:
                    if (type(self.fieldsToMarshall) in self.sequenceTypes) and \
                       (fieldName in self.fieldsToMarshall):
                        mustDump = True
                if mustDump:
                    self.dumpField(res, fieldName, fieldValue)
        elif objectType == 'archetype':
            fields = instance.schema.fields()
            for field in instance.schema.fields():
                # Dump only needed fields
                mustDump = False
                if field.getName() in self.fieldsToExclude:
                    mustDump = False
                elif (self.fieldsToMarshall == 'all') and \
                   (field.schemata != 'metadata'):
                    mustDump = True
                elif self.fieldsToMarshall == 'all_with_metadata':
                    mustDump = True
                else:
                    if (type(self.fieldsToMarshall) in self.sequenceTypes) and \
                       (field.getName() in self.fieldsToMarshall):
                        mustDump = True
                if mustDump:
                    fieldType = 'basic'
                    if field.type in self.atFiles:
                        fieldType = 'file'
                    elif field.type == 'reference':
                        fieldType = 'ref'
                    self.dumpField(res, field.getName(), field.get(instance),
                        fieldType=fieldType)
        self.marshallSpecificElements(instance, res)
        # Return the result
        res.write('</'); res.write(self.rootElementName); res.write('>')
        data = res.getvalue()
        res.close()
        return data

    def marshallSpecificElements(self, instance, res):
        '''You can use this marshaller as a base class for creating your own.
           In this case, this method will be called by the marshall method
           for allowing your concrete marshaller to insert more things in the
           result. p_res is the StringIO buffer where the result of the
           marshalling process is currently dumped; p_instance is the instance
           currently marshalled.'''
# ------------------------------------------------------------------------------