cmlenz@1: # -*- coding: utf-8 -*-
cmlenz@1: #
cmlenz@1: # Copyright (C) 2006 Edgewall Software
cmlenz@1: # All rights reserved.
cmlenz@1: #
cmlenz@1: # This software is licensed as described in the file COPYING, which
cmlenz@1: # you should have received as part of this distribution. The terms
cmlenz@1: # are also available at http://trac.edgewall.com/license.html.
cmlenz@1: #
cmlenz@1: # This software consists of voluntary contributions made by many
cmlenz@1: # individuals. For the exact contribution history, see the revision
cmlenz@1: # history and logs, available at http://projects.edgewall.com/trac/.
cmlenz@1: 
cmlenz@1: """Basic support for evaluating XPath expressions against streams."""
cmlenz@1: 
cmlenz@1: import re
cmlenz@1: 
cmlenz@1: from markup.core import QName, Stream
cmlenz@1: 
cmlenz@1: __all__ = ['Path']
cmlenz@1: 
cmlenz@1: _QUOTES = (("'", "'"), ('"', '"'))
cmlenz@1: 
cmlenz@1: class Path(object):
cmlenz@1:     """Basic XPath support on markup event streams.
cmlenz@1:     
cmlenz@1:     >>> from markup.input import XML
cmlenz@1:     
cmlenz@1:     Selecting specific tags:
cmlenz@1:     
cmlenz@1:     >>> Path('root').select(XML('<root/>')).render()
cmlenz@1:     '<root/>'
cmlenz@1:     >>> Path('//root').select(XML('<root/>')).render()
cmlenz@1:     '<root/>'
cmlenz@1:     
cmlenz@1:     Using wildcards for tag names:
cmlenz@1:     
cmlenz@1:     >>> Path('*').select(XML('<root/>')).render()
cmlenz@1:     '<root/>'
cmlenz@1:     >>> Path('//*').select(XML('<root/>')).render()
cmlenz@1:     '<root/>'
cmlenz@1:     
cmlenz@1:     Selecting attribute values:
cmlenz@1:     
cmlenz@1:     >>> Path('@foo').select(XML('<root/>')).render()
cmlenz@1:     ''
cmlenz@1:     >>> Path('@foo').select(XML('<root foo="bar"/>')).render()
cmlenz@1:     'bar'
cmlenz@1:     
cmlenz@1:     Selecting descendants:
cmlenz@1:     
cmlenz@1:     >>> Path("root/*").select(XML('<root><foo/><bar/></root>')).render()
cmlenz@1:     '<foo/><bar/>'
cmlenz@1:     >>> Path("root/bar").select(XML('<root><foo/><bar/></root>')).render()
cmlenz@1:     '<bar/>'
cmlenz@1:     >>> Path("root/baz").select(XML('<root><foo/><bar/></root>')).render()
cmlenz@1:     ''
cmlenz@1:     >>> Path("root/foo/*").select(XML('<root><foo><bar/></foo></root>')).render()
cmlenz@1:     '<bar/>'
cmlenz@1:     
cmlenz@1:     Selecting text nodes:
cmlenz@1:     >>> Path("item/text()").select(XML('<root><item>Foo</item></root>')).render()
cmlenz@1:     'Foo'
cmlenz@1:     >>> Path("item/text()").select(XML('<root><item>Foo</item><item>Bar</item></root>')).render()
cmlenz@1:     'FooBar'
cmlenz@1:     
cmlenz@1:     Skipping ancestors:
cmlenz@1:     
cmlenz@1:     >>> Path("foo/bar").select(XML('<root><foo><bar/></foo></root>')).render()
cmlenz@1:     '<bar/>'
cmlenz@1:     >>> Path("foo/*").select(XML('<root><foo><bar/></foo></root>')).render()
cmlenz@1:     '<bar/>'
cmlenz@1:     >>> Path("root/bar").select(XML('<root><foo><bar/></foo></root>')).render()
cmlenz@1:     ''
cmlenz@1:     >>> Path("root/bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
cmlenz@1:     '<bar id="2"/>'
cmlenz@1:     >>> Path("root/*/bar").select(XML('<root><foo><bar/></foo></root>')).render()
cmlenz@1:     '<bar/>'
cmlenz@1:     >>> Path("root//bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
cmlenz@1:     '<bar id="1"/><bar id="2"/>'
cmlenz@1:     >>> Path("root//bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
cmlenz@1:     '<bar id="1"/><bar id="2"/>'
cmlenz@1:     
cmlenz@1:     Using simple attribute predicates:
cmlenz@1:     >>> Path("root/item[@important]").select(XML('<root><item/><item important="very"/></root>')).render()
cmlenz@1:     '<item important="very"/>'
cmlenz@1:     >>> Path('root/item[@important="very"]').select(XML('<root><item/><item important="very"/></root>')).render()
cmlenz@1:     '<item important="very"/>'
cmlenz@1:     >>> Path("root/item[@important='very']").select(XML('<root><item/><item important="notso"/></root>')).render()
cmlenz@1:     ''
cmlenz@1:     >>> Path("root/item[@important!='very']").select(
cmlenz@1:     ...     XML('<root><item/><item important="notso"/></root>')).render()
cmlenz@1:     '<item/><item important="notso"/>'
cmlenz@1:     """
cmlenz@1: 
cmlenz@1:     _TOKEN_RE = re.compile('(::|\.\.|\(\)|[/.:\[\]\(\)@=!])|'
cmlenz@1:                            '([^/:\[\]\(\)@=!\s]+)|'
cmlenz@1:                            '\s+')
cmlenz@1: 
cmlenz@1:     def __init__(self, text):
cmlenz@1:         self.source = text
cmlenz@1: 
cmlenz@1:         steps = []
cmlenz@1:         cur_op = ''
cmlenz@1:         cur_tag = ''
cmlenz@1:         in_predicate = False
cmlenz@1:         for op, tag in self._TOKEN_RE.findall(text):
cmlenz@1:             if op:
cmlenz@1:                 if op == '[':
cmlenz@1:                     in_predicate = True
cmlenz@1:                 elif op == ']':
cmlenz@1:                     in_predicate = False
cmlenz@1:                 elif op.startswith('('):
cmlenz@1:                     if cur_tag == 'text':
cmlenz@1:                         steps[-1] = (False, self.fn_text(), [])
cmlenz@1:                     else:
cmlenz@1:                         raise NotImplementedError('XPath function "%s" not '
cmlenz@1:                                                   'supported' % cur_tag)
cmlenz@1:                 else:
cmlenz@1:                     cur_op += op
cmlenz@1:                 cur_tag = ''
cmlenz@1:             else:
cmlenz@1:                 closure = cur_op in ('', '//')
cmlenz@1:                 if cur_op == '@':
cmlenz@1:                     if tag == '*':
cmlenz@1:                         node_test = self.any_attribute()
cmlenz@1:                     else:
cmlenz@1:                         node_test = self.attribute_by_name(tag)
cmlenz@1:                 else:
cmlenz@1:                     if tag == '*':
cmlenz@1:                         node_test = self.any_element()
cmlenz@1:                     elif in_predicate:
cmlenz@1:                         if len(tag) > 1 and (tag[0], tag[-1]) in _QUOTES:
cmlenz@1:                             node_test = self.literal_string(tag[1:-1])
cmlenz@1:                         if cur_op == '=':
cmlenz@1:                             node_test = self.op_eq(steps[-1][2][-1], node_test)
cmlenz@1:                             steps[-1][2].pop()
cmlenz@1:                         elif cur_op == '!=':
cmlenz@1:                             node_test = self.op_neq(steps[-1][2][-1], node_test)
cmlenz@1:                             steps[-1][2].pop()
cmlenz@1:                     else:
cmlenz@1:                         node_test = self.element_by_name(tag)
cmlenz@1:                 if in_predicate:
cmlenz@1:                     steps[-1][2].append(node_test)
cmlenz@1:                 else:
cmlenz@1:                     steps.append([closure, node_test, []])
cmlenz@1:                 cur_op = ''
cmlenz@1:                 cur_tag = tag
cmlenz@1:         self.steps = steps
cmlenz@1: 
cmlenz@1:     def __repr__(self):
cmlenz@1:         return '<%s "%s">' % (self.__class__.__name__, self.source)
cmlenz@1: 
cmlenz@1:     def select(self, stream):
cmlenz@1:         stream = iter(stream)
cmlenz@1:         def _generate(tests):
cmlenz@1:             test = self.test()
cmlenz@1:             for kind, data, pos in stream:
cmlenz@1:                 result = test(kind, data, pos)
cmlenz@1:                 if result is True:
cmlenz@1:                     yield kind, data, pos
cmlenz@1:                     depth = 1
cmlenz@1:                     while depth > 0:
cmlenz@1:                         ev = stream.next()
cmlenz@1:                         if ev[0] is Stream.START:
cmlenz@1:                             depth += 1
cmlenz@1:                         elif ev[0] is Stream.END:
cmlenz@1:                             depth -= 1
cmlenz@1:                         yield ev
cmlenz@1:                         test(*ev)
cmlenz@1:                 elif result:
cmlenz@1:                     yield result
cmlenz@1:         return Stream(_generate(self.steps))
cmlenz@1: 
cmlenz@1:     def test(self):
cmlenz@1:         stack = [0] # stack of cursors into the location path
cmlenz@1: 
cmlenz@1:         def _test(kind, data, pos):
cmlenz@1:             #print '\nTracker %r test [%s] %r' % (self, kind, data)
cmlenz@1: 
cmlenz@1:             if not stack:
cmlenz@1:                 return False
cmlenz@1: 
cmlenz@1:             if kind is Stream.END:
cmlenz@1:                 stack.pop()
cmlenz@1:                 return None
cmlenz@1: 
cmlenz@1:             if kind is Stream.START:
cmlenz@1:                 stack.append(stack[-1])
cmlenz@1: 
cmlenz@1:             matched = False
cmlenz@1:             closure, node_test, predicates = self.steps[stack[-1]]
cmlenz@1: 
cmlenz@1:             #print '  Testing against %r' % node_test
cmlenz@1:             matched = node_test(kind, data, pos)
cmlenz@1:             if matched and predicates:
cmlenz@1:                 for predicate in predicates:
cmlenz@1:                     if not predicate(kind, data, pos):
cmlenz@1:                         matched = None
cmlenz@1:                         break
cmlenz@1: 
cmlenz@1:             if matched:
cmlenz@1:                 if stack[-1] == len(self.steps) - 1:
cmlenz@1:                     #print '  Last step %r... returned %r' % (node_test, matched)
cmlenz@1:                     return matched
cmlenz@1: 
cmlenz@1:                 #print '  Matched intermediate step %r... proceed to next step %r' % (node_test, self.steps[stack[-1] + 1])
cmlenz@1:                 stack[-1] += 1
cmlenz@1: 
cmlenz@1:             elif kind is Stream.START and not closure:
cmlenz@1:                 # FIXME: If this step is not a closure, it cannot be matched
cmlenz@1:                 #        until the current element is closed... so we need to
cmlenz@1:                 #        move the cursor back to the last closure and retest
cmlenz@1:                 #        that against the current element
cmlenz@1:                 closures = [step for step in self.steps[:stack[-1]] if step[0]]
cmlenz@1:                 closures.reverse()
cmlenz@1:                 for closure, node_test, predicates in closures:
cmlenz@1:                     stack[-1] -= 1
cmlenz@1:                     if closure:
cmlenz@1:                         matched = node_test(kind, data, pos)
cmlenz@1:                         if matched:
cmlenz@1:                             stack[-1] += 1
cmlenz@1:                         break
cmlenz@1: 
cmlenz@1:             return None
cmlenz@1: 
cmlenz@1:         return _test
cmlenz@1: 
cmlenz@1:     class any_element(object):
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             if kind is Stream.START:
cmlenz@1:                 return True
cmlenz@1:             return None
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s>' % self.__class__.__name__
cmlenz@1: 
cmlenz@1:     class element_by_name(object):
cmlenz@1:         def __init__(self, name):
cmlenz@1:             self.name = QName(name)
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             if kind is Stream.START:
cmlenz@1:                 return data[0].localname == self.name
cmlenz@1:             return None
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s "%s">' % (self.__class__.__name__, self.name)
cmlenz@1: 
cmlenz@1:     class any_attribute(object):
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             if kind is Stream.START:
cmlenz@1:                 text = ''.join([val for name, val in data[1]])
cmlenz@1:                 if text:
cmlenz@1:                     return Stream.TEXT, text, pos
cmlenz@1:                 return None
cmlenz@1:             return None
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s>' % (self.__class__.__name__)
cmlenz@1: 
cmlenz@1:     class attribute_by_name(object):
cmlenz@1:         def __init__(self, name):
cmlenz@1:             self.name = QName(name)
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             if kind is Stream.START:
cmlenz@1:                 if self.name in data[1]:
cmlenz@1:                     return Stream.TEXT, data[1].get(self.name), pos
cmlenz@1:                 return None
cmlenz@1:             return None
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s "%s">' % (self.__class__.__name__, self.name)
cmlenz@1: 
cmlenz@1:     class fn_text(object):
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             if kind is Stream.TEXT:
cmlenz@1:                 return kind, data, pos
cmlenz@1:             return None
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s>' % (self.__class__.__name__)
cmlenz@1: 
cmlenz@1:     class literal_string(object):
cmlenz@1:         def __init__(self, value):
cmlenz@1:             self.value = value
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             return Stream.TEXT, self.value, (-1, -1)
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s>' % (self.__class__.__name__)
cmlenz@1: 
cmlenz@1:     class op_eq(object):
cmlenz@1:         def __init__(self, lval, rval):
cmlenz@1:             self.lval = lval
cmlenz@1:             self.rval = rval
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             lval = self.lval(kind, data, pos)
cmlenz@1:             rval = self.rval(kind, data, pos)
cmlenz@1:             return (lval and lval[1]) == (rval and rval[1])
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s %r = %r>' % (self.__class__.__name__, self.lval,
cmlenz@1:                                      self.rval)
cmlenz@1: 
cmlenz@1:     class op_neq(object):
cmlenz@1:         def __init__(self, lval, rval):
cmlenz@1:             self.lval = lval
cmlenz@1:             self.rval = rval
cmlenz@1:         def __call__(self, kind, data, pos):
cmlenz@1:             lval = self.lval(kind, data, pos)
cmlenz@1:             rval = self.rval(kind, data, pos)
cmlenz@1:             return (lval and lval[1]) != (rval and rval[1])
cmlenz@1:         def __repr__(self):
cmlenz@1:             return '<%s %r != %r>' % (self.__class__.__name__, self.lval,
cmlenz@1:                                       self.rval)