#!/usr/bin/env python  """ Reference abstractions.  Copyright (C) 2016 Paul Boddie <paul@boddie.org.uk>  This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.  You should have received a copy of the GNU General Public License along with this program.  If not, see <http://www.gnu.org/licenses/>. """  class Reference:      "A reference abstraction."      def __init__(self, kind, origin=None, name=None):          """         Initialise a reference using 'kind' to indicate the kind of object,         'origin' to indicate the actual origin of a referenced object, and a         'name' indicating an alias for the object in the program structure.         """          if isinstance(kind, Reference):             raise ValueError, (kind, origin)         self.kind = kind         self.origin = origin         self.name = name      def __repr__(self):         return "Reference(%r, %r, %r)" % (self.kind, self.origin, self.name)      def __str__(self):          """         Serialise the reference as '<var>' or a description incorporating the         kind and origin.         """          if self.kind == "<var>":             alias = self.name and ";%s" % self.name or ""             return "%s%s" % (self.kind, alias)         else:             alias = self.name and self.name != self.origin and ";%s" % self.name or ""             return "%s:%s%s" % (self.kind, self.origin, alias)      def __hash__(self):          "Hash instances using the kind and origin only."          return hash((self.kind, self.get_origin()))      def __cmp__(self, other):          "Compare with 'other' using the kind and origin only."          if isinstance(other, Reference):             return cmp((self.kind, self.get_origin()), (other.kind, other.get_origin()))         else:             return cmp(str(self), other)      def get_name(self):          "Return the name used for this reference."          return self.name      def get_origin(self):          "Return the origin of the reference."          return self.kind != "<var>" and self.origin or None      def get_kind(self):          "Return the kind of object referenced."          return self.kind      def has_kind(self, kinds):          """         Return whether the reference describes an object from the given 'kinds',         where such kinds may be "<class>", "<function>", "<instance>",         "<module>" or "<var>". Unresolved references may also have kinds of         "<depends>" and "<invoke>".         """          if not isinstance(kinds, (list, tuple)):             kinds = [kinds]         return self.get_kind() in kinds      def get_path(self):          "Return the attribute names comprising the path to the origin."          return self.get_origin().split(".")      def unresolved(self):          "Return whether this reference is unresolved."          return self.has_kind(["<depends>", "<invoke>", "<var>"])      def static(self):          "Return this reference if it refers to a static object, None otherwise."          return self.has_kind(["<class>", "<function>", "<module>"]) and self or None      def final(self):          "Return a reference to either a static object or None."          static = self.static()         return static and static.origin or None      def instance_of(self, alias=None):          """         Return a reference to an instance of the referenced class, indicating an         'alias' for the instance if specified.         """          return self.has_kind("<class>") and Reference("<instance>", self.origin, alias) or None      def as_var(self):          """         Return a variable version of this reference. Any origin information is         discarded since variable references are deliberately ambiguous.         """          return Reference("<var>", None, self.name)      def alias(self, name):          "Alias this reference employing 'name'."          return Reference(self.get_kind(), self.get_origin(), name)      def unaliased(self):          "Return this reference without any alias."          return Reference(self.get_kind(), self.get_origin())      def mutate(self, ref):          "Mutate this reference to have the same details as 'ref'."          self.kind = ref.kind         self.origin = ref.origin         self.name = ref.name      def parent(self):          "Return the parent of this reference's origin."          if not self.get_origin():             return None          return self.get_origin().rsplit(".", 1)[0]      def name_parent(self):          "Return the parent of this reference's aliased name."          if not self.get_name():             return None          return self.get_name().rsplit(".", 1)[0]      def ancestors(self):          """         Return ancestors of this reference's origin in order of decreasing         depth.         """          if not self.get_origin():             return None          parts = self.get_origin().split(".")         ancestors = []          for i in range(len(parts) - 1, 0, -1):             ancestors.append(".".join(parts[:i]))          return ancestors      def is_constant_alias(self):          "Return whether this reference is an alias for a constant."          name = self.get_name()         return name and name.rsplit(".")[-1].startswith("$c")      def get_types(self):          "Return class, instance-only and module types for this reference."          class_types = self.has_kind("<class>") and [self.get_origin()] or []         instance_types = []         module_types = self.has_kind("<module>") and [self.get_origin()] or []         return class_types, instance_types, module_types  def decode_reference(s, name=None):      "Decode 's', making a reference."      if isinstance(s, Reference):         return s.alias(name)      # Null value.      elif not s:         return Reference("<var>", None, name)      # Kind and origin.      elif ":" in s:         kind, origin = s.split(":")         if ";" in origin:             origin, name = origin.split(";")         return Reference(kind, origin, name)      # Kind and name.      elif ";" in s:         kind, name = s.split(";")         return Reference(kind, None, name)      # Kind-only, origin is indicated name.      elif s[0] == "<":         return Reference(s, name, name)      # Module-only.      else:         return Reference("<module>", s, name)    # Type/reference collection functions.  def is_single_class_type(all_types):      """     Return whether 'all_types' is a mixture of class and instance kinds for     a single class type.     """      kinds = set()     types = set()      for type in all_types:         kinds.add(type.get_kind())         types.add(type.get_origin())      return len(types) == 1 and kinds == set(["<class>", "<instance>"])  def combine_types(class_types, instance_types, module_types):      """     Combine 'class_types', 'instance_types', 'module_types' into a single     list of references.     """      all_types = []     for kind, l in [("<class>", class_types), ("<instance>", instance_types), ("<module>", module_types)]:         for t in l:             all_types.append(Reference(kind, t))     return all_types  def separate_types(refs):      """     Separate 'refs' into type-specific lists, returning a tuple containing     lists of class types, instance types, module types, function types and     unknown "var" types.     """      class_types = []     instance_types = []     module_types = []     function_types = []     var_types = []      for kind, l in [         ("<class>", class_types), ("<instance>", instance_types), ("<module>", module_types),         ("<function>", function_types), ("<var>", var_types)         ]:          for ref in refs:             if ref.get_kind() == kind:                 l.append(ref.get_origin())      return class_types, instance_types, module_types, function_types, var_types  # vim: tabstop=4 expandtab shiftwidth=4