merge.py

   1 from xml.dom import minidom, XMLNS_NAMESPACE, Node
   2 from zeroinstall.injector.namespaces import XMLNS_IFACE
   3 import xmltools
   4
   5 def childNodes(parent, namespaceURI = None, localName = None):
   6         for x in parent.childNodes:
   7                 if x.nodeType != Node.ELEMENT_NODE: continue
   8                 if namespaceURI is not None and x.namespaceURI != namespaceURI: continue
   9
  10                 if localName is None or x.localName == localName:
  11                         yield x
  12
  13 class Context:
  14         def __init__(self, impl):
  15                 doc = impl.ownerDocument
  16                 self.attribs = {}
  17                 self.requires = []
  18
  19                 node = impl
  20                 while True:
  21                         for name, value in node.attributes.itemsNS():
  22                                 if name[0] == XMLNS_NAMESPACE:
  23                                         xmltools.register_namespace(value, name[1])
  24                                 elif name not in self.attribs:
  25                                         self.attribs[name] = value
  26                         if node.nodeName == 'group':
  27                                 # We don't care about <requires> inside <implementation>; they'll get copied over anyway
  28                                 for x in childNodes(node, XMLNS_IFACE, 'requires'):
  29                                         self.requires.append(x)
  30                         node = node.parentNode
  31                         if node.nodeName != 'group':
  32                                 break
  33
  34 def find_impls(parent):
  35         """Return all <implementation> children, including those inside groups."""
  36         for x in childNodes(parent, XMLNS_IFACE):
  37                 if x.localName == 'implementation':
  38                         yield x
  39                 elif x.localName == 'group':
  40                         for y in find_impls(x):
  41                                 yield y
  42
  43 def find_groups(parent):
  44         """Return all <group> children, including those inside other groups."""
  45         for x in childNodes(parent, XMLNS_IFACE, 'group'):
  46                 yield x
  47                 for y in find_groups(x):
  48                         yield y
  49
  50 def nodesEqual(a, b):
  51         assert a.nodeType == Node.ELEMENT_NODE
  52         assert b.nodeType == Node.ELEMENT_NODE
  53
  54         if a.namespaceURI != b.namespaceURI:
  55                 return False
  56
  57         if a.nodeName != b.nodeName:
  58                 return False
  59
  60         a_attrs = set(["%s %s" % (name, value) for name, value in a.attributes.itemsNS()])
  61         b_attrs = set(["%s %s" % (name, value) for name, value in b.attributes.itemsNS()])
  62
  63         if a_attrs != b_attrs:
  64                 #print "%s != %s" % (a_attrs, b_attrs)
  65                 return False
  66
  67         a_children = list(childNodes(a))
  68         b_children = list(childNodes(b))
  69
  70         if len(a_children) != len(b_children):
  71                 return False
  72
  73         for a_child, b_child in zip(a_children, b_children):
  74                 if not nodesEqual(a_child, b_child):
  75                         return False
  76
  77         return True
  78
  79 def score_subset(group, impl):
  80         """Returns (is_subset, goodness)"""
  81         for key in group.attribs:
  82                 if key not in impl.attribs.keys():
  83                         #print "BAD", key
  84                         return (0,)             # Group sets an attribute the impl doesn't want
  85         for g_req in group.requires:
  86                 for i_req in impl.requires:
  87                         if nodesEqual(g_req, i_req): break
  88                 else:
  89                         return (0,)             # Group adds a requires that the impl doesn't want
  90         # Score result so we get groups that have all the same requires first, then ones with all the same attribs
  91         return (1, len(group.requires), len(group.attribs))
  92
  93 # Note: the namespace stuff isn't quite right yet.
  94 # Might get conflicts if both documents use the same prefix for different things.
  95 def merge(data, local):
  96         local_doc = minidom.parse(local)
  97         master_doc = minidom.parseString(data)
  98
  99         # Merge each implementation in the local feed in turn (normally there will only be one)
 100         for impl in find_impls(local_doc.documentElement):
 101                 # 1. Get the context of the implementation to add. This is:
 102                 #    - The set of its requirements
 103                 #    - Its attributes
 104                 new_impl_context = Context(impl)
 105
 106                 # 2. For each <group> in the master feed, see if it provides a compatible context:
 107                 #    - A subset of the new implementation's requirements
 108                 #    - A subset of the new implementation's attributes (names, not values)
 109                 #    Choose the most compatible <group> (the root counts as a minimally compatible group)
 110
 111                 best_group = ((1, 0, 0), master_doc.documentElement)    # (score, element)
 112
 113                 for group in find_groups(master_doc.documentElement):
 114                         group_context = Context(group)
 115                         score = score_subset(group_context, new_impl_context)
 116                         if score > best_group[0]:
 117                                 best_group = (score, group)
 118
 119                 group = best_group[1]
 120                 group_context = Context(group)
 121
 122                 # If we have additional requirements, we'll need to create a subgroup and add them
 123                 if len(new_impl_context.requires) > len(group_context.requires):
 124                         subgroup = xmltools.create_element(group, 'group')
 125                         group = subgroup
 126                         group_context = Context(group)
 127                         for x in new_impl_context.requires:
 128                                 for y in group_context.requires:
 129                                         if nodesEqual(x, y): break
 130                                 else:
 131                                         req = master_doc.importNode(x, True)
 132                                         #print "Add", req
 133                                         xmltools.insert_element(req, group)
 134
 135                 new_impl = master_doc.importNode(impl, True)
 136
 137                 # Attributes might have been set on a parent group; move to the impl
 138                 for name in new_impl_context.attribs:
 139                         #print "Set", name, value
 140                         xmltools.add_attribute_ns(new_impl, name[0], name[1], new_impl_context.attribs[name])
 141
 142                 for name, value in new_impl.attributes.itemsNS():
 143                         if name[0] == XMLNS_NAMESPACE or \
 144                            (name in group_context.attribs and group_context.attribs[name] == value):
 145                                 #print "Deleting duplicate attribute", name, value
 146                                 new_impl.removeAttributeNS(name[0], name[1])
 147
 148                 xmltools.insert_element(new_impl, group)
 149
 150         return master_doc.toxml()