# Copyright (c) 2002, Daniel Krech, http://eikeon.com/
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#   * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#
#   * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials provided
# with the distribution.
#
#   * Neither the name of Daniel Krech nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

"""
"""
from xml.sax import make_parser
from xml.sax.handler import ErrorHandler
from xml.sax.saxutils import handler, quoteattr, escape
from urlparse import urljoin, urldefrag

from rdflib.namespace import RDF, is_ncname
from rdflib.term import URIRef
from rdflib.term import BNode
from rdflib.term import Literal
from rdflib.exceptions import ParserError, Error
from rdflib.parser import Parser

__all__ = ['create_parser', 'BagID', 'ElementHandler', 'RDFXMLHandler', 'RDFXMLParser']

RDFNS = RDF

# http://www.w3.org/TR/rdf-syntax-grammar/#eventterm-attribute-URI
# A mapping from unqualified terms to there qualified version.
UNQUALIFIED = {"about" : RDF.about,
               "ID" : RDF.ID,
               "type" : RDF.type,
               "resource": RDF.resource,
               "parseType": RDF.parseType}

# http://www.w3.org/TR/rdf-syntax-grammar/#coreSyntaxTerms
CORE_SYNTAX_TERMS = [RDF.RDF, RDF.ID, RDF.about, RDF.parseType, RDF.resource, RDF.nodeID, RDF.datatype]

# http://www.w3.org/TR/rdf-syntax-grammar/#syntaxTerms
SYNTAX_TERMS = CORE_SYNTAX_TERMS + [RDF.Description, RDF.li]

# http://www.w3.org/TR/rdf-syntax-grammar/#oldTerms
OLD_TERMS = [
    URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#aboutEach"), 
    URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#aboutEachPrefix"), 
    URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#bagID")]

NODE_ELEMENT_EXCEPTIONS = CORE_SYNTAX_TERMS + [RDF.li,] + OLD_TERMS
NODE_ELEMENT_ATTRIBUTES = [RDF.ID, RDF.nodeID, RDF.about]

PROPERTY_ELEMENT_EXCEPTIONS = CORE_SYNTAX_TERMS + [RDF.Description,] + OLD_TERMS
PROPERTY_ATTRIBUTE_EXCEPTIONS = CORE_SYNTAX_TERMS + [RDF.Description, RDF.li] + OLD_TERMS
PROPERTY_ELEMENT_ATTRIBUTES = [RDF.ID, RDF.resource, RDF.nodeID]

XMLNS = "http://www.w3.org/XML/1998/namespace"
BASE = (XMLNS, "base")
LANG = (XMLNS, "lang")


class BagID(URIRef):
    __slots__ = ['li']
    def __init__(self, val):
        super(URIRef, self).__init__(val)
        self.li = 0

    def next_li(self):
        self.li += 1
        return RDFNS[self.li]


class ElementHandler(object):
    __slots__ = ['start', 'char', 'end', 'li', 'id',
                 'base', 'subject', 'predicate', 'object',
                 'list', 'language', 'datatype', 'declared', 'data']
    def __init__(self):
        self.start = None
        self.char = None
        self.end = None
        self.li = 0
        self.id = None
        self.base = None
        self.subject = None
        self.object = None
        self.list = None
        self.language = None
        self.datatype = None
        self.declared = None
        self.data = None

    def next_li(self):
        self.li += 1
        return RDFNS[self.li]


class RDFXMLHandler(handler.ContentHandler):

    def __init__(self, store):
        self.store = store
        self.preserve_bnode_ids = False
        self.reset()

    def reset(self):
        document_element = ElementHandler()
        document_element.start = self.document_element_start
        document_element.end = lambda name, qname: None
        self.stack = [None, document_element,]
        self.ids = {} # remember IDs we have already seen
        self.bnode = {}
        self._ns_contexts = [{}] # contains uri -> prefix dicts
        self._current_context = self._ns_contexts[-1]

    # ContentHandler methods

    def setDocumentLocator(self, locator):
        self.locator = locator

    def startDocument(self):
        pass

    def startPrefixMapping(self, prefix, namespace):
        self._ns_contexts.append(self._current_context.copy())
        self._current_context[namespace] = prefix
        self.store.bind(prefix, URIRef(namespace), override=False)

    def endPrefixMapping(self, prefix):
        self._current_context = self._ns_contexts[-1]
        del self._ns_contexts[-1]

    def startElementNS(self, name, qname, attrs):
        stack = self.stack
        stack.append(ElementHandler())
        current = self.current
        parent = self.parent
        base = attrs.get(BASE, None)
        if base is not None:
            base, frag = urldefrag(base)
            if parent and parent.base:
                base = urljoin(parent.base, base)
            else:
                systemId = self.locator.getPublicId() or self.locator.getSystemId()
                if systemId:
                    base = urljoin(systemId, base)
        else:
            if parent:
                base = parent.base
            if base is None:
                systemId = self.locator.getPublicId() or self.locator.getSystemId()
                if systemId:
                    base, frag = urldefrag(systemId)
        current.base = base
        language = attrs.get(LANG, None)
        if language is None:
            if parent:
                language = parent.language
        current.language = language
        current.start(name, qname, attrs)

    def endElementNS(self, name, qname):
        self.current.end(name, qname)
        self.stack.pop()

    def characters(self, content):
        char = self.current.char
        if char:
            char(content)

    def ignorableWhitespace(self, content):
        pass

    def processingInstruction(self, target, data):
        pass

    def add_reified(self, sid, (s, p, o)):
        self.store.add((sid, RDF.type, RDF.Statement))
        self.store.add((sid, RDF.subject, s))
        self.store.add((sid, RDF.predicate, p))
        self.store.add((sid, RDF.object, o))

    def error(self, message):
        locator = self.locator
        info = "%s:%s:%s: " % (locator.getSystemId(),
                            locator.getLineNumber(), locator.getColumnNumber())
        raise ParserError(info + message)

    def get_current(self):
        return self.stack[-2]
    # Create a read only property called current so that self.current
    # give the current element handler.
    current = property(get_current)

    def get_next(self):
        return self.stack[-1]
    # Create a read only property that gives the element handler to be
    # used for the next element.
    next = property(get_next)

    def get_parent(self):
        return self.stack[-3]
    # Create a read only property that gives the current parent
    # element handler
    parent = property(get_parent)

    def absolutize(self, uri):
        result = urljoin(self.current.base, uri, allow_fragments=1)
        if uri and uri[-1]=="#" and result[-1]!="#":
            result = "%s#" % result
        return URIRef(result)

    def convert(self, name, qname, attrs):
        if name[0] is None:
            name = URIRef(name[1])
        else:
            name = URIRef("".join(name))
        atts = {}
        for (n, v) in attrs.items(): #attrs._attrs.iteritems(): #
            if n[0] is None:
                att = URIRef(n[1])
            else:
                att = URIRef("".join(n))
            if att.startswith(XMLNS) or att[0:3].lower()=="xml":
                pass
            elif att in UNQUALIFIED:
                #if not RDFNS[att] in atts:
                atts[RDFNS[att]] = v
            else:
                atts[URIRef(att)] = v
        return name, atts

    def document_element_start(self, name, qname, attrs):
        if name[0] and URIRef("".join(name)) == RDF.RDF:
            # Cheap hack so 2to3 doesn't turn it into __next__
            next = getattr(self, 'next')
            next.start = self.node_element_start
            next.end = self.node_element_end
        else:
            self.node_element_start(name, qname, attrs)
            #self.current.end = self.node_element_end
            # TODO... set end to something that sets start such that
            # another element will cause error


    def node_element_start(self, name, qname, attrs):
        name, atts = self.convert(name, qname, attrs)
        current = self.current
        absolutize = self.absolutize
        
        # Cheap hack so 2to3 doesn't turn it into __next__
        next = getattr(self, 'next')
        next.start = self.property_element_start
        next.end = self.property_element_end

        if name in NODE_ELEMENT_EXCEPTIONS:
            self.error("Invalid node element URI: %s" % name)

        if RDF.ID in atts:
            if RDF.about in atts or RDF.nodeID in atts:
                self.error("Can have at most one of rdf:ID, rdf:about, and rdf:nodeID")

            id = atts[RDF.ID]
            if not is_ncname(id):
                self.error("rdf:ID value is not a valid NCName: %s" % id)
            subject = absolutize("#%s" % id)
            if subject in self.ids:
                self.error("two elements cannot use the same ID: '%s'" % subject)
            self.ids[subject] = 1 # IDs can only appear once within a document
        elif RDF.nodeID in atts:
            if RDF.ID in atts or RDF.about in atts:
                self.error("Can have at most one of rdf:ID, rdf:about, and rdf:nodeID")
            nodeID = atts[RDF.nodeID]
            if not is_ncname(nodeID):
                self.error("rdf:nodeID value is not a valid NCName: %s" % nodeID)
            if self.preserve_bnode_ids is False:
                if nodeID in self.bnode:
                    subject = self.bnode[nodeID]
                else:
                    subject = BNode()
                    self.bnode[nodeID] = subject
            else:
                subject = BNode(nodeID)
        elif RDF.about in atts:
            if RDF.ID in atts or RDF.nodeID in atts:
                self.error("Can have at most one of rdf:ID, rdf:about, and rdf:nodeID")
            subject = absolutize(atts[RDF.about])
        else:
            subject = BNode()

        if name!=RDF.Description: # S1
            self.store.add((subject, RDF.type, absolutize(name)))

        language = current.language
        for att in atts:
            if not att.startswith(str(RDFNS)):
                predicate = absolutize(att)
                try:
                    object = Literal(atts[att], language)
                except Error, e:
                    self.error(e.msg)
            elif att==RDF.type: #S2
                predicate = RDF.type
                object = absolutize(atts[RDF.type])
            elif att in NODE_ELEMENT_ATTRIBUTES:
                continue
            elif att in PROPERTY_ATTRIBUTE_EXCEPTIONS: #S3
                self.error("Invalid property attribute URI: %s" % att)
                continue # for when error does not throw an exception
            else:
                predicate = absolutize(att)
                try:
                    object = Literal(atts[att], language)
                except Error, e:
                    self.error(e.msg)
            self.store.add((subject, predicate, object))

        current.subject = subject


    def node_element_end(self, name, qname):
        self.parent.object = self.current.subject

    def property_element_start(self, name, qname, attrs):
        name, atts = self.convert(name, qname, attrs)
        current = self.current
        absolutize = self.absolutize
        
        # Cheap hack so 2to3 doesn't turn it into __next__
        next = getattr(self, 'next')
        object = None
        current.data = None
        current.list = None

        if not name.startswith(str(RDFNS)):
            current.predicate = absolutize(name)
        elif name==RDF.li:
            current.predicate = current.next_li()
        elif name in PROPERTY_ELEMENT_EXCEPTIONS:
            self.error("Invalid property element URI: %s" % name)
        else:
            current.predicate = absolutize(name)

        id = atts.get(RDF.ID, None)
        if id is not None:
            if not is_ncname(id):
                self.error("rdf:ID value is not a value NCName: %s" % id)
            current.id = absolutize("#%s" % id)
        else:
            current.id = None

        resource = atts.get(RDF.resource, None)
        nodeID = atts.get(RDF.nodeID, None)
        parse_type = atts.get(RDF.parseType, None)
        if resource is not None and nodeID is not None:
            self.error("Property element cannot have both rdf:nodeID and rdf:resource")
        if resource is not None:
            object = absolutize(resource)
            next.start = self.node_element_start
            next.end = self.node_element_end
        elif nodeID is not None:
            if not is_ncname(nodeID):
                self.error("rdf:nodeID value is not a valid NCName: %s" % nodeID)
            if self.preserve_bnode_ids is False:
                if nodeID in self.bnode:
                    object = self.bnode[nodeID]
                else:
                    subject = BNode()
                    self.bnode[nodeID] = subject
                    object = subject
            else:
                object = subject = BNode(nodeID)
            next.start = self.node_element_start
            next.end = self.node_element_end
        else:
            if parse_type is not None:
                for att in atts:
                    if att!=RDF.parseType and att!=RDF.ID:
                        self.error("Property attr '%s' now allowed here" % att)
                if parse_type=="Resource":
                    current.subject = object = BNode()
                    current.char = self.property_element_char
                    next.start = self.property_element_start
                    next.end = self.property_element_end
                elif parse_type=="Collection":
                    current.char = None
                    object = current.list = RDF.nil #BNode()#self.parent.subject
                    next.start = self.node_element_start
                    next.end = self.list_node_element_end
                else: #if parse_type=="Literal":
                     # All other values are treated as Literal
                     # See: http://www.w3.org/TR/rdf-syntax-grammar/#parseTypeOtherPropertyElt
                    object = Literal("", datatype=RDF.XMLLiteral)
                    current.char = self.literal_element_char
                    current.declared = {}
                    next.start = self.literal_element_start
                    next.char = self.literal_element_char
                    next.end = self.literal_element_end
                current.object = object
                return
            else:
                object = None
                current.char = self.property_element_char
                next.start = self.node_element_start
                next.end = self.node_element_end

        datatype = current.datatype = atts.get(RDF.datatype, None)
        language = current.language
        if datatype is not None:
            # TODO: check that there are no atts other than datatype and id
            datatype = absolutize(datatype)
        else:
            for att in atts:
                if not att.startswith(str(RDFNS)):
                    predicate = absolutize(att)
                elif att in PROPERTY_ELEMENT_ATTRIBUTES:
                    continue
                elif att in PROPERTY_ATTRIBUTE_EXCEPTIONS:
                    self.error("""Invalid property attribute URI: %s""" % att)
                else:
                    predicate = absolutize(att)

                if att==RDF.type:
                    o = URIRef(atts[att])
                else:
                    if datatype is not None:
                        language = None
                    o = Literal(atts[att], language, datatype)

                if object is None:
                    object = BNode()
                self.store.add((object, predicate, o))
        if object is None:
            current.data = ""
            current.object = None
        else:
            current.data = None
            current.object = object

    def property_element_char(self, data):
        current = self.current
        if current.data is not None:
            current.data += data

    def property_element_end(self, name, qname):
        current = self.current
        if current.data is not None and current.object is None:
            literalLang = current.language
            if current.datatype is not None:
                literalLang = None
            current.object = Literal(current.data, literalLang, current.datatype)
            current.data = None
        if self.next.end==self.list_node_element_end:
            if current.object!=RDF.nil:
                self.store.add((current.list, RDF.rest, RDF.nil))
        if current.object is not None:
            self.store.add((self.parent.subject, current.predicate, current.object))
            if current.id is not None:
                self.add_reified(current.id, (self.parent.subject,
                                 current.predicate, current.object))
        current.subject = None

    def list_node_element_end(self, name, qname):
        current = self.current
        if self.parent.list==RDF.nil:
            list = BNode()
            # Removed between 20030123 and 20030905
            #self.store.add((list, RDF.type, LIST))
            self.parent.list = list
            self.store.add((self.parent.list, RDF.first, current.subject))
            self.parent.object = list
            self.parent.char = None
        else:
            list = BNode()
            # Removed between 20030123 and 20030905
            #self.store.add((list, RDF.type, LIST))
            self.store.add((self.parent.list, RDF.rest, list))
            self.store.add((list, RDF.first, current.subject))
            self.parent.list = list

    def literal_element_start(self, name, qname, attrs):
        current = self.current
        self.next.start = self.literal_element_start
        self.next.char = self.literal_element_char
        self.next.end = self.literal_element_end
        current.declared = self.parent.declared.copy()
        if name[0]:
            prefix = self._current_context[name[0]]
            if prefix:
                current.object = "<%s:%s" % (prefix, name[1])
            else:
                current.object = "<%s" % name[1]
            if not name[0] in current.declared:
                current.declared[name[0]] = prefix
                if prefix:
                    current.object += (' xmlns:%s="%s"' % (prefix, name[0]))
                else:
                    current.object += (' xmlns="%s"' % name[0])
        else:
            current.object = "<%s" % name[1]

        for (name, value) in attrs.items():
            if name[0]:
                if not name[0] in current.declared:
                    current.declared[name[0]] = self._current_context[name[0]]
                name = current.declared[name[0]] + ":" + name[1]
            else:
                name = name[1]
            current.object += (' %s=%s' % (name, quoteattr(value)))
        current.object += ">"

    def literal_element_char(self, data):
        self.current.object += escape(data)

    def literal_element_end(self, name, qname):
        if name[0]:
            prefix = self._current_context[name[0]]
            if prefix:
                end = u"</%s:%s>" % (prefix, name[1])
            else:
                end = u"</%s>" % name[1]
        else:
            end = u"</%s>" % name[1]
        self.parent.object += self.current.object + end


def create_parser(target, store):
    parser = make_parser()
    try:
        # Workaround for bug in expatreader.py. Needed when
        # expatreader is trying to guess a prefix.
        parser.start_namespace_decl("xml", "http://www.w3.org/XML/1998/namespace")
    except AttributeError:
        pass # Not present in Jython (at least)
    parser.setFeature(handler.feature_namespaces, 1)
    rdfxml = RDFXMLHandler(store)
    rdfxml.setDocumentLocator(target)
    #rdfxml.setDocumentLocator(_Locator(self.url, self.parser))
    parser.setContentHandler(rdfxml)
    parser.setErrorHandler(ErrorHandler())
    return parser


class RDFXMLParser(Parser):

    def __init__(self):
        pass

    def parse(self, source, sink, **args):
        self._parser = create_parser(source, sink)
        content_handler = self._parser.getContentHandler()
        preserve_bnode_ids = args.get("preserve_bnode_ids", None)
        if preserve_bnode_ids is not None:
            content_handler.preserve_bnode_ids = preserve_bnode_ids
        # We're only using it once now
        #content_handler.reset()
        #self._parser.reset()
        self._parser.parse(source)



