list: a data source

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The list object would almost appear to be a superfluity given the fact that the repmgr API really treats a list name and key as nearly equivalent coordinates of an entry -- but lists are indeed somewhat privileged, and a useful function for the list object to fulfill is that it can act as an iterator along a list or query. I'm probably going to end up conflating the list and query notions into a single list object -- this is because a list storage in the repository needn't necessarily be the only kind of list we think of as a "list". In short, a list should be thought of as any collection of entries, even if it's not strictly a storage-oriented list defined by the repository.

In fact, a list could even be constructed dynamically and simply contain a bunch of otherwise unrelated entries or something. We'll see what makes the most sense later. This is fun.
  
class list(xml):
   """Implements a repository manager list.
   """
   def __init__ (self, repository, id=None):
      self._repository = repository
      self._listid = id
      self.reset()

   def reset (self):
      self._keys = []
      self._recs = []
      self._lookup = {}
      if self._listid != None:
         self._list = self._repository.defn (self._listid).new_copy()
      else:
         self._list = xml.create ('list')

   def query (self, where=''):
      self.reset()
      self._list.set ('where', where)
      self._keys = repmgr.list (self._repository.repos, self._list._xml)
      self._recs = self._list.elements()
      for r in self._recs:
         self._lookup[r.attrval('id')] = r

   def keys (self):
      return self._keys

   def __str__ (self):
      return self._list.__str__()
   def __repr__ (self):
      return self._list.__repr__()
   def __getitem__ (self, key):
      return self._lookup[key]

   #def setquery
   #def rewind
   #def advance
   #def current
   #def prev
   #def next
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