merge.py

   1 import os
   2 from xml.dom import minidom, XMLNS_NAMESPACE, Node
   3 from zeroinstall.injector.namespaces import XMLNS_IFACE
   4 from zeroinstall.injector import model, reader
   5 from logging import info
   6
   7 def childNodes(parent, namespaceURI, localName = None):
   8         for x in parent.childNodes:
   9                 if x.nodeType != Node.ELEMENT_NODE: continue
  10                 if x.namespaceURI != namespaceURI: continue
  11
  12                 if localName is None or x.localName == localName:
  13                         yield x
  14
  15 class Context:
  16         def __init__(self, impl):
  17                 doc = impl.ownerDocument
  18                 self.attribs = {}
  19                 self.requires = []
  20
  21                 node = impl
  22                 while True:
  23                         for name, value in node.attributes.itemsNS():
  24                                 if 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 is_subset(group, impl):
  51         for key in group.attribs:
  52                 if key not in impl.attribs.keys():
  53                         print "BAD", key
  54                         return False            # Group sets an attribute the impl doesn't want
  55         for g_req in group.requires:
  56                 for i_req in impl.requires:
  57                         if nodesEqual(g_req, i_req): break
  58                 else:
  59                         return False            # Group adds a requires that the impl doesn't want
  60         return True
  61
  62 def merge(data, local):
  63         local_doc = minidom.parse(local)
  64         master_doc = minidom.parseString(data)
  65
  66         # Merge each implementation in the local feed in turn (normally there will only be one)
  67         for impl in find_impls(local_doc.documentElement):
  68                 # 1. Get the context of the implementation to add. This is:
  69                 #    - The set of its requirements
  70                 #    - Its attributes
  71                 new_impl_context = Context(impl)
  72
  73                 # 2. For each <group> in the master feed, see if it provides a compatible context:
  74                 #    - A subset of the new implementation's requirements
  75                 #    - A subset of the new implementation's attributes (names, not values)
  76                 #    Choose the most compatible <group> (the root counts as a minimally compatible group)
  77
  78                 best_group = (0, master_doc.documentElement)
  79
  80                 for group in find_groups(master_doc.documentElement):
  81                         group_context = Context(group)
  82                         if is_subset(group_context, new_impl_context):
  83                                 best_group = (0, group)
  84
  85                 group = best_group[1]
  86                 group_context = Context(group)
  87
  88                 # If we have additional requirements, we'll need to create a subgroup and add them
  89                 if len(new_impl_context.requires) > len(group_context.requires):
  90                         subgroup = master_doc.createElementNS(XMLNS_IFACE, 'group')
  91                         group.appendChild(subgroup)
  92                         group = subgroup
  93                         group_context = Context(group)
  94                         for x in new_impl_context.requires:
  95                                 for y in group_context.requires:
  96                                         if nodesEqual(x, y): break
  97                                 else:
  98                                         req = master_doc.importNode(x, True)
  99                                         #print "Add", req
 100                                         group.appendChild(req)
 101
 102                 new_impl = master_doc.importNode(impl, True)
 103                 for name, value in new_impl.attributes.itemsNS():
 104                         if name in group_context.attribs and group_context.attribs[name] == value:
 105                                 #print "Deleting duplicate attribute", name, value
 106                                 new_impl.removeAttributeNS(name[0], name[1])
 107                         else:
 108                                 # Might have been on a parent group; move to the impl
 109                                 #print "Set", name, value
 110                                 new_impl.setAttributeNS(name[0], name[1], value)
 111
 112                 group.appendChild(master_doc.createTextNode('  '))
 113                 group.appendChild(new_impl)
 114                 group.appendChild(master_doc.createTextNode('\n'))
 115
 116         return master_doc.toxml()