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                 self.commands = {}
  19
  20                 node = impl
  21                 while True:
  22                         for name, value in node.attributes.itemsNS():
  23                                 if name[0] == XMLNS_NAMESPACE:
  24                                         xmltools.register_namespace(value, name[1])
  25                                 elif name not in self.attribs:
  26                                         self.attribs[name] = value
  27                         if node.nodeName == 'group':
  28                                 # We don't care about <requires> or <command> inside <implementation>;
  29                                 # they'll get copied over anyway
  30                                 for x in childNodes(node, XMLNS_IFACE, 'requires'):
  31                                         self.requires.append(x)
  32                                 for x in childNodes(node, XMLNS_IFACE, 'command'):
  33                                         self.commands[x.getAttribute('name')] = x
  34                         node = node.parentNode
  35                         if node.nodeName != 'group':
  36                                 break
  37
  38 def find_impls(parent):
  39         """Return all <implementation> children, including those inside groups."""
  40         for x in childNodes(parent, XMLNS_IFACE):
  41                 if x.localName == 'implementation':
  42                         yield x
  43                 elif x.localName == 'group':
  44                         for y in find_impls(x):
  45                                 yield y
  46
  47 def find_groups(parent):
  48         """Return all <group> children, including those inside other groups."""
  49         for x in childNodes(parent, XMLNS_IFACE, 'group'):
  50                 yield x
  51                 for y in find_groups(x):
  52                         yield y
  53
  54 def nodesEqual(a, b):
  55         assert a.nodeType == Node.ELEMENT_NODE
  56         assert b.nodeType == Node.ELEMENT_NODE
  57
  58         if a.namespaceURI != b.namespaceURI:
  59                 return False
  60
  61         if a.nodeName != b.nodeName:
  62                 return False
  63
  64         a_attrs = set(["%s %s" % (name, value) for name, value in a.attributes.itemsNS()])
  65         b_attrs = set(["%s %s" % (name, value) for name, value in b.attributes.itemsNS()])
  66
  67         if a_attrs != b_attrs:
  68                 #print "%s != %s" % (a_attrs, b_attrs)
  69                 return False
  70
  71         a_children = list(childNodes(a))
  72         b_children = list(childNodes(b))
  73
  74         if len(a_children) != len(b_children):
  75                 return False
  76
  77         for a_child, b_child in zip(a_children, b_children):
  78                 if not nodesEqual(a_child, b_child):
  79                         return False
  80
  81         return True
  82
  83 def score_subset(group, impl):
  84         """Returns (is_subset, goodness)"""
  85         for key in group.attribs:
  86                 if key not in impl.attribs.keys():
  87                         #print "BAD", key
  88                         return (0,)             # Group sets an attribute the impl doesn't want
  89         for name, g_command in group.commands.iteritems():
  90                 if name not in impl.commands:
  91                         return (0,)             # Group sets a command the impl doesn't want
  92         for g_req in group.requires:
  93                 for i_req in impl.requires:
  94                         if nodesEqual(g_req, i_req): break
  95                 else:
  96                         return (0,)             # Group adds a requires that the impl doesn't want
  97         # Score result so we get groups that have all the same requires/commands first, then ones with all the same attribs
  98         return (1, len(group.requires) + len(group.commands), len(group.attribs))
  99
 100 # Note: the namespace stuff isn't quite right yet.
 101 # Might get conflicts if both documents use the same prefix for different things.
 102 def merge(data, local):
 103         local_doc = minidom.parse(local)
 104         master_doc = minidom.parseString(data)
 105
 106         # Merge each implementation in the local feed in turn (normally there will only be one)
 107         for impl in find_impls(local_doc.documentElement):
 108                 # 1. Get the context of the implementation to add. This is:
 109                 #    - The set of its requirements
 110                 #    - The set of its commands
 111                 #    - Its attributes
 112                 new_impl_context = Context(impl)
 113
 114                 # 2. For each <group> in the master feed, see if it provides a compatible context:
 115                 #    - A subset of the new implementation's requirements
 116                 #    - A subset of the new implementation's command names
 117                 #    - A subset of the new implementation's attributes (names, not values)
 118                 #    Choose the most compatible <group> (the root counts as a minimally compatible group)
 119
 120                 best_group = ((1, 0, 0), master_doc.documentElement)    # (score, element)
 121
 122                 for group in find_groups(master_doc.documentElement):
 123                         group_context = Context(group)
 124                         score = score_subset(group_context, new_impl_context)
 125                         if score > best_group[0]:
 126                                 best_group = (score, group)
 127
 128                 group = best_group[1]
 129                 group_context = Context(group)
 130
 131                 new_commands = []
 132                 for name, new_command in new_impl_context.commands.iteritems():
 133                         old_command = group_context.commands.get(name, None)
 134                         if not (old_command and nodesEqual(old_command, new_command)):
 135                                 new_commands.append(master_doc.importNode(new_command, True))
 136
 137                 # If we have additional requirements, we'll need to create a subgroup and add them
 138                 if len(new_impl_context.requires) > len(group_context.requires) or new_commands:
 139                         subgroup = xmltools.create_element(group, 'group')
 140                         group = subgroup
 141                         #group_context = Context(group)
 142                         for x in new_impl_context.requires:
 143                                 for y in group_context.requires:
 144                                         if nodesEqual(x, y): break
 145                                 else:
 146                                         req = master_doc.importNode(x, True)
 147                                         #print "Add", req
 148                                         xmltools.insert_element(req, group)
 149                         for c in new_commands:
 150                                 xmltools.insert_element(c, group)
 151
 152                 new_impl = master_doc.importNode(impl, True)
 153
 154                 # Attributes might have been set on a parent group; move to the impl
 155                 for name in new_impl_context.attribs:
 156                         #print "Set", name, value
 157                         xmltools.add_attribute_ns(new_impl, name[0], name[1], new_impl_context.attribs[name])
 158
 159                 for name, value in new_impl.attributes.itemsNS():
 160                         if name[0] == XMLNS_NAMESPACE or \
 161                            (name in group_context.attribs and group_context.attribs[name] == value):
 162                                 #print "Deleting duplicate attribute", name, value
 163                                 new_impl.removeAttributeNS(name[0], name[1])
 164
 165                 xmltools.insert_element(new_impl, group)
 166
 167         return master_doc.toxml()