camera/docs/metadata_model.py

#!/usr/bin/python

#
# Copyright (C) 2012 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""
A set of classes (models) each closely representing an XML node in the
metadata_properties.xml file.

  Node: Base class for most nodes.
  Entry: A node corresponding to <entry> elements.
  Clone: A node corresponding to <clone> elements.
  MergedEntry: A node corresponding to either <entry> or <clone> elements.
  Kind: A node corresponding to <dynamic>, <static>, <controls> elements.
  InnerNamespace: A node corresponding to a <namespace> nested under a <kind>.
  OuterNamespace: A node corresponding to a <namespace> with <kind> children.
  Section: A node corresponding to a <section> element.
  Enum: A class corresponding an <enum> element within an <entry>
  EnumValue: A class corresponding to a <value> element within an Enum
  Metadata: Root node that also provides tree construction functionality.
  Tag: A node corresponding to a top level <tag> element.
"""

import sys
import itertools
from collections import OrderedDict

class Node(object):
  """
  Base class for most nodes that are part of the Metadata graph.

  Attributes (Read-Only):
    parent: An edge to a parent Node.
    name: A string describing the name, usually but not always the 'name'
          attribute of the corresponding XML node.
  """

  def __init__(self):
    self._parent = None
    self._name = None

  @property
  def parent(self):
    return self._parent

  @property
  def name(self):
    return self._name

  def find_all(self, pred):
    """
    Find all descendants that match the predicate.

    Args:
      pred: a predicate function that acts as a filter for a Node

    Yields:
      A sequence of all descendants for which pred(node) is true,
      in a pre-order visit order.
    """
    if pred(self):
      yield self

    if self._get_children() is None:
      return

    for i in self._get_children():
      for j in i.find_all(pred):
        yield j

  def find_first(self, pred):
    """
    Find the first descendant that matches the predicate.

    Args:
      pred: a predicate function that acts as a filter for a Node

    Returns:
      The first Node from find_all(pred), or None if there were no results.
    """
    for i in self.find_all(pred):
      return i

    return None

  def find_parent_first(self, pred):
    """
    Find the first ancestor that matches the predicate.

    Args:
      pred: A predicate function that acts as a filter for a Node

    Returns:
      The first ancestor closest to the node for which pred(node) is true.
    """
    for i in self.find_parents(pred):
      return i

    return None

  def find_parents(self, pred):
    """
    Find all ancestors that match the predicate.

    Args:
      pred: A predicate function that acts as a filter for a Node

    Yields:
      A sequence of all ancestors (closest to furthest) from the node,
      where pred(node) is true.
    """
    parent = self.parent

    while parent is not None:
      if pred(parent):
        yield parent
      parent = parent.parent

  def sort_children(self):
    """
    Sorts the immediate children in-place.
    """
    self._sort_by_name(self._children)

  def _sort_by_name(self, what):
    what.sort(key=lambda x: x.name)

  def _get_name(self):
    return lambda x: x.name

  # Iterate over all children nodes. None when node doesn't support children.
  def _get_children(self):
    return (i for i in self._children)

  def _children_name_map_matching(self, match=lambda x: True):
    d = {}
    for i in self._get_children():
      if match(i):
        d[i.name] = i
    return d

  @staticmethod
  def _dictionary_by_name(values):
    d = OrderedDict()
    for i in values:
      d[i.name] = i

    return d

  def validate_tree(self):
    """
    Sanity check the tree recursively, ensuring for a node n, all children's
    parents are also n.

    Returns:
      True if validation succeeds, False otherwise.
    """
    succ = True
    children = self._get_children()
    if children is None:
      return True

    for child in self._get_children():
      if child.parent != self:
        print >> sys.stderr, ("ERROR: Node '%s' doesn't match the parent" +    \
                             "(expected: %s, actual %s)")                      \
                             %(child, self, child.parent)
        succ = False

      succ = child.validate_tree() and succ

    return succ

  def __str__(self):
    return "<%s name='%s'>" %(self.__class__, self.name)

class Metadata(Node):
  """
  A node corresponding to a <metadata> entry.

  Attributes (Read-Only):
    parent: An edge to the parent Node. This is always None for Metadata.
    outer_namespaces: A sequence of immediate OuterNamespace children.
    tags: A sequence of all Tag instances available in the graph.
  """

  def __init__(self):
    """
    Initialize with no children. Use insert_* functions and then
    construct_graph() to build up the Metadata from some source.
    """

# Private
    self._entries = []
    # kind => { name => entry }
    self._entry_map = { 'static': {}, 'dynamic': {}, 'controls': {} }
    self._entries_ordered = [] # list of ordered Entry/Clone instances
    self._clones = []

# Public (Read Only)
    self._parent = None
    self._outer_namespaces = None
    self._tags = []

  @property
  def outer_namespaces(self):
    if self._outer_namespaces is None:
      return None
    else:
      return (i for i in self._outer_namespaces)

  @property
  def tags(self):
    return (i for i in self._tags)

  def _get_properties(self):

    for i in self._entries:
      yield i

    for i in self._clones:
      yield i

  def insert_tag(self, tag, description=""):
    """
    Insert a tag into the metadata.

    Args:
      tag: A string identifier for a tag.
      description: A string description for a tag.

    Example:
      metadata.insert_tag("BC", "Backwards Compatibility for old API")

    Remarks:
      Subsequent calls to insert_tag with the same tag are safe (they will
      be ignored).
    """
    tag_ids = [tg.name for tg in self.tags if tg.name == tag]
    if not tag_ids:
      self._tags.append(Tag(tag, self, description))

  def insert_entry(self, entry):
    """
    Insert an entry into the metadata.

    Args:
      entry: A key-value dictionary describing an entry. Refer to
             Entry#__init__ for the keys required/optional.

    Remarks:
      Subsequent calls to insert_entry with the same entry+kind name are safe
      (they will be ignored).
    """
    e = Entry(**entry)
    self._entries.append(e)
    self._entry_map[e.kind][e.name] = e
    self._entries_ordered.append(e)

  def insert_clone(self, clone):
    """
    Insert a clone into the metadata.

    Args:
      clone: A key-value dictionary describing a clone. Refer to
            Clone#__init__ for the keys required/optional.

    Remarks:
      Subsequent calls to insert_clone with the same clone+kind name are safe
      (they will be ignored). Also the target entry need not be inserted
      ahead of the clone entry.
    """
    # figure out corresponding entry later. allow clone insert, entry insert
    entry = None
    c = Clone(entry, **clone)
    self._entry_map[c.kind][c.name] = c
    self._clones.append(c)
    self._entries_ordered.append(c)

  def prune_clones(self):
    """
    Remove all clones that don't point to an existing entry.

    Remarks:
      This should be called after all insert_entry/insert_clone calls have
      finished.
    """
    remove_list = []
    for p in self._clones:
      if p.entry is None:
        remove_list.append(p)

    for p in remove_list:

      # remove from parent's entries list
      if p.parent is not None:
        p.parent._entries.remove(p)
      # remove from parents' _leafs list
      for ancestor in p.find_parents(lambda x: not isinstance(x, Metadata)):
        ancestor._leafs.remove(p)

      # remove from global list
      self._clones.remove(p)
      self._entry_map[p.kind].pop(p.name)
      self._entries_ordered.remove(p)


  # After all entries/clones are inserted,
  # invoke this to generate the parent/child node graph all these objects
  def construct_graph(self):
    """
    Generate the graph recursively, after which all Entry nodes will be
    accessible recursively by crawling through the outer_namespaces sequence.

    Remarks:
      This is safe to be called multiple times at any time. It should be done at
      least once or there will be no graph.
    """
    self.validate_tree()
    self._construct_tags()
    self.validate_tree()
    self._construct_clones()
    self.validate_tree()
    self._construct_outer_namespaces()
    self.validate_tree()

  def _construct_tags(self):
    tag_dict = self._dictionary_by_name(self.tags)
    for p in self._get_properties():
      p._tags = []
      for tag_id in p._tag_ids:
        tag = tag_dict.get(tag_id)

        if tag not in p._tags:
          p._tags.append(tag)

        if p not in tag.entries:
          tag._entries.append(p)

  def _construct_clones(self):
    for p in self._clones:
      target_kind = p.target_kind
      target_entry = self._entry_map[target_kind].get(p.name)
      p._entry = target_entry

      # should not throw if we pass validation
      # but can happen when importing obsolete CSV entries
      if target_entry is None:
        print >> sys.stderr, ("WARNING: Clone entry '%s' target kind '%s'" +   \
                              " has no corresponding entry")                   \
                             %(p.name, p.target_kind)

  def _construct_outer_namespaces(self):

    if self._outer_namespaces is None: #the first time this runs
      self._outer_namespaces = []

    root = self._dictionary_by_name(self._outer_namespaces)
    for ons_name, ons in root.iteritems():
      ons._leafs = []

    for p in self._entries_ordered:
      ons_name = p.get_outer_namespace()
      ons = root.get(ons_name, OuterNamespace(ons_name, self))
      root[ons_name] = ons

      if p not in ons._leafs:
        ons._leafs.append(p)

    for ons_name, ons in root.iteritems():

      ons.validate_tree()

      self._construct_sections(ons)

      if ons not in self._outer_namespaces:
        self._outer_namespaces.append(ons)

      ons.validate_tree()

  def _construct_sections(self, outer_namespace):

    sections_dict = self._dictionary_by_name(outer_namespace.sections)
    for sec_name, sec in sections_dict.iteritems():
      sec._leafs = []
      sec.validate_tree()

    for p in outer_namespace._leafs:
      does_exist = sections_dict.get(p.get_section())

      sec = sections_dict.get(p.get_section(), \
          Section(p.get_section(), outer_namespace))
      sections_dict[p.get_section()] = sec

      sec.validate_tree()

      if p not in sec._leafs:
        sec._leafs.append(p)

    for sec_name, sec in sections_dict.iteritems():

      if not sec.validate_tree():
        print >> sys.stderr, ("ERROR: Failed to validate tree in " +           \
                             "construct_sections (start), with section = '%s'")\
                             %(sec)

      self._construct_kinds(sec)

      if sec not in outer_namespace.sections:
        outer_namespace._sections.append(sec)

      if not sec.validate_tree():
        print >> sys.stderr, ("ERROR: Failed to validate tree in " +           \
                              "construct_sections (end), with section = '%s'") \
                             %(sec)

  # 'controls', 'static' 'dynamic'. etc
  def _construct_kinds(self, section):
    for kind in section.kinds:
      kind._leafs = []
      section.validate_tree()

    group_entry_by_kind = itertools.groupby(section._leafs, lambda x: x.kind)
    leaf_it = ((k, g) for k, g in group_entry_by_kind)

    # allow multiple kinds with the same name. merge if adjacent
    # e.g. dynamic,dynamic,static,static,dynamic -> dynamic,static,dynamic
    # this helps maintain ABI compatibility when adding an entry in a new kind
    for idx, (kind_name, entry_it) in enumerate(leaf_it):
      if idx >= len(section._kinds):
        kind = Kind(kind_name, section)
        section._kinds.append(kind)
        section.validate_tree()

      kind = section._kinds[idx]

      for p in entry_it:
        if p not in kind._leafs:
          kind._leafs.append(p)

    for kind in section._kinds:
      kind.validate_tree()
      self._construct_inner_namespaces(kind)
      kind.validate_tree()
      self._construct_entries(kind)
      kind.validate_tree()

      if not section.validate_tree():
        print >> sys.stderr, ("ERROR: Failed to validate tree in " +           \
                             "construct_kinds, with kind = '%s'") %(kind)

      if not kind.validate_tree():
        print >> sys.stderr, ("ERROR: Failed to validate tree in " +           \
                              "construct_kinds, with kind = '%s'") %(kind)

  def _construct_inner_namespaces(self, parent, depth=0):
    #parent is InnerNamespace or Kind
    ins_dict = self._dictionary_by_name(parent.namespaces)
    for name, ins in ins_dict.iteritems():
      ins._leafs = []

    for p in parent._leafs:
      ins_list = p.get_inner_namespace_list()

      if len(ins_list) > depth:
        ins_str = ins_list[depth]
        ins = ins_dict.get(ins_str, InnerNamespace(ins_str, parent))
        ins_dict[ins_str] = ins

        if p not in ins._leafs:
          ins._leafs.append(p)

    for name, ins in ins_dict.iteritems():
      ins.validate_tree()
      # construct children INS
      self._construct_inner_namespaces(ins, depth + 1)
      ins.validate_tree()
      # construct children entries
      self._construct_entries(ins, depth + 1)

      if ins not in parent.namespaces:
        parent._namespaces.append(ins)

      if not ins.validate_tree():
        print >> sys.stderr, ("ERROR: Failed to validate tree in " +           \
                              "construct_inner_namespaces, with ins = '%s'")   \
                             %(ins)

  # doesnt construct the entries, so much as links them
  def _construct_entries(self, parent, depth=0):
    #parent is InnerNamespace or Kind
    entry_dict = self._dictionary_by_name(parent.entries)
    for p in parent._leafs:
      ins_list = p.get_inner_namespace_list()

      if len(ins_list) == depth:
        entry = entry_dict.get(p.name, p)
        entry_dict[p.name] = entry

    for name, entry in entry_dict.iteritems():

      old_parent = entry.parent
      entry._parent = parent

      if entry not in parent.entries:
        parent._entries.append(entry)

      if old_parent is not None and old_parent != parent:
        print >> sys.stderr, ("ERROR: Parent changed from '%s' to '%s' for " + \
                              "entry '%s'")                                    \
                             %(old_parent.name, parent.name, entry.name)

  def _get_children(self):
    if self.outer_namespaces is not None:
      for i in self.outer_namespaces:
        yield i

    if self.tags is not None:
      for i in self.tags:
        yield i

class Tag(Node):
  """
  A tag Node corresponding to a top-level <tag> element.

  Attributes (Read-Only):
    name: alias for id
    id: The name of the tag, e.g. for <tag id="BC"/> id = 'BC'
    description: The description of the tag, the contents of the <tag> element.
    parent: An edge to the parent, which is always the Metadata root node.
    entries: A sequence of edges to entries/clones that are using this Tag.
  """
  def __init__(self, name, parent, description=""):
    self._name        = name  # 'id' attribute in XML
    self._id          = name
    self._description = description
    self._parent      = parent

    # all entries that have this tag, including clones
    self._entries     = []  # filled in by Metadata#construct_tags

  @property
  def id(self):
    return self._id

  @property
  def description(self):
    return self._description

  @property
  def entries(self):
    return (i for i in self._entries)

  def _get_children(self):
    return None

class OuterNamespace(Node):
  """
  A node corresponding to a <namespace> element under <metadata>

  Attributes (Read-Only):
    name: The name attribute of the <namespace name="foo"> element.
    parent: An edge to the parent, which is always the Metadata root node.
    sections: A sequence of Section children.
  """
  def __init__(self, name, parent, sections=[]):
    self._name = name
    self._parent = parent # MetadataSet
    self._sections = sections[:]
    self._leafs = []

    self._children = self._sections

  @property
  def sections(self):
    return (i for i in self._sections)

class Section(Node):
  """
  A node corresponding to a <section> element under <namespace>

  Attributes (Read-Only):
    name: The name attribute of the <section name="foo"> element.
    parent: An edge to the parent, which is always an OuterNamespace instance.
    description: A string description of the section, or None.
    kinds: A sequence of Kind children.
    merged_kinds: A sequence of virtual Kind children,
                  with each Kind's children merged by the kind.name
  """
  def __init__(self, name, parent, description=None, kinds=[]):
    self._name = name
    self._parent = parent
    self._description = description
    self._kinds = kinds[:]

    self._leafs = []


  @property
  def description(self):
    return self._description

  @property
  def kinds(self):
    return (i for i in self._kinds)

  def sort_children(self):
    self.validate_tree()
    # order is always controls,static,dynamic
    find_child = lambda x: [i for i in self._get_children() if i.name == x]
    new_lst = find_child('controls') \
            + find_child('static')   \
            + find_child('dynamic')
    self._kinds = new_lst
    self.validate_tree()

  def _get_children(self):
    return (i for i in self.kinds)

  @property
  def merged_kinds(self):

    def aggregate_by_name(acc, el):
      existing = [i for i in acc if i.name == el.name]
      if existing:
        k = existing[0]
      else:
        k = Kind(el.name, el.parent)
        acc.append(k)

      k._namespaces.extend(el._namespaces)
      k._entries.extend(el._entries)

      return acc

    new_kinds_lst = reduce(aggregate_by_name, self.kinds, [])

    for k in new_kinds_lst:
      yield k

  def combine_kinds_into_single_node(self):
    r"""
    Combines the section's Kinds into a single node.

    Combines all the children (kinds) of this section into a single
    virtual Kind node.

    Returns:
      A new Kind node that collapses all Kind siblings into one, combining
      all their children together.

      For example, given self.kinds == [ x, y ]

        x  y               z
      / |  | \    -->   / | | \
      a b  c d          a b c d

      a new instance z is returned in this example.

    Remarks:
      The children of the kinds are the same references as before, that is
      their parents will point to the old parents and not to the new parent.
    """
    combined = Kind(name="combined", parent=self)

    for k in self._get_children():
      combined._namespaces.extend(k.namespaces)
      combined._entries.extend(k.entries)

    return combined

class Kind(Node):
  """
  A node corresponding to one of: <static>,<dynamic>,<controls> under a
  <section> element.

  Attributes (Read-Only):
    name: A string which is one of 'static', 'dynamic, or 'controls'.
    parent: An edge to the parent, which is always a Section  instance.
    namespaces: A sequence of InnerNamespace children.
    entries: A sequence of Entry/Clone children.
    merged_entries: A sequence of MergedEntry virtual nodes from entries
  """
  def __init__(self, name, parent):
    self._name = name
    self._parent = parent
    self._namespaces = []
    self._entries = []

    self._leafs = []

  @property
  def namespaces(self):
    return self._namespaces

  @property
  def entries(self):
    return self._entries

  @property
  def merged_entries(self):
    for i in self.entries:
      yield i.merge()

  def sort_children(self):
    self._namespaces.sort(key=self._get_name())
    self._entries.sort(key=self._get_name())

  def _get_children(self):
    for i in self.namespaces:
      yield i
    for i in self.entries:
      yield i

  def combine_children_by_name(self):
    r"""
    Combine multiple children with the same name into a single node.

    Returns:
      A new Kind where all of the children with the same name were combined.

      For example:

      Given a Kind k:

              k
            / | \
            a b c
            | | |
            d e f

      a.name == "foo"
      b.name == "foo"
      c.name == "bar"

      The returned Kind will look like this:

             k'
            /  \
            a' c'
          / |  |
          d e  f

    Remarks:
      This operation is not recursive. To combine the grandchildren and other
      ancestors, call this method on the ancestor nodes.
    """
    return Kind._combine_children_by_name(self, new_type=type(self))

  # new_type is either Kind or InnerNamespace
  @staticmethod
  def _combine_children_by_name(self, new_type):
    new_ins_dict = OrderedDict()
    new_ent_dict = OrderedDict()

    for ins in self.namespaces:
      new_ins = new_ins_dict.setdefault(ins.name,
                                        InnerNamespace(ins.name, parent=self))
      new_ins._namespaces.extend(ins.namespaces)
      new_ins._entries.extend(ins.entries)

    for ent in self.entries:
      new_ent = new_ent_dict.setdefault(ent.name,
                                        ent.merge())

    kind = new_type(self.name, self.parent)
    kind._namespaces = new_ins_dict.values()
    kind._entries = new_ent_dict.values()

    return kind

class InnerNamespace(Node):
  """
  A node corresponding to a <namespace> which is an ancestor of a Kind.
  These namespaces may have other namespaces recursively, or entries as leafs.

  Attributes (Read-Only):
    name: Name attribute from the element, e.g. <namespace name="foo"> -> 'foo'
    parent: An edge to the parent, which is an InnerNamespace or a Kind.
    namespaces: A sequence of InnerNamespace children.
    entries: A sequence of Entry/Clone children.
    merged_entries: A sequence of MergedEntry virtual nodes from entries
  """
  def __init__(self, name, parent):
    self._name        = name
    self._parent      = parent
    self._namespaces  = []
    self._entries     = []
    self._leafs       = []

  @property
  def namespaces(self):
    return self._namespaces

  @property
  def entries(self):
    return self._entries

  @property
  def merged_entries(self):
    for i in self.entries:
      yield i.merge()

  def sort_children(self):
    self._namespaces.sort(key=self._get_name())
    self._entries.sort(key=self._get_name())

  def _get_children(self):
    for i in self.namespaces:
      yield i
    for i in self.entries:
      yield i

  def combine_children_by_name(self):
    r"""
    Combine multiple children with the same name into a single node.

    Returns:
      A new InnerNamespace where all of the children with the same name were
      combined.

      For example:

      Given an InnerNamespace i:

              i
            / | \
            a b c
            | | |
            d e f

      a.name == "foo"
      b.name == "foo"
      c.name == "bar"

      The returned InnerNamespace will look like this:

             i'
            /  \
            a' c'
          / |  |
          d e  f

    Remarks:
      This operation is not recursive. To combine the grandchildren and other
      ancestors, call this method on the ancestor nodes.
    """
    return Kind._combine_children_by_name(self, new_type=type(self))

class EnumValue(Node):
  """
  A class corresponding to a <value> element within an <enum> within an <entry>.

  Attributes (Read-Only):
    name: A string,                 e.g. 'ON' or 'OFF'
    id: An optional numeric string, e.g. '0' or '0xFF'
    optional: A boolean
    notes: A string describing the notes, or None.
    parent: An edge to the parent, always an Enum instance.
  """
  def __init__(self, name, parent, id=None, optional=False, notes=None):
    self._name = name                    # str, e.g. 'ON' or 'OFF'
    self._id = id                        # int, e.g. '0'
    self._optional = optional            # bool
    self._notes = notes                  # None or str
    self._parent = parent

  @property
  def id(self):
    return self._id

  @property
  def optional(self):
    return self._optional

  @property
  def notes(self):
    return self._notes

  def _get_children(self):
    return None

class Enum(Node):
  """
  A class corresponding to an <enum> element within an <entry>.

  Attributes (Read-Only):
    parent: An edge to the parent, always an Entry instance.
    values: A sequence of EnumValue children.
    has_values_with_id: A boolean representing if any of the children have a
        non-empty id property.
  """
  def __init__(self, parent, values, ids={}, optionals=[], notes={}):
    self._values =                                                             \
      [ EnumValue(val, self, ids.get(val), val in optionals, notes.get(val))   \
        for val in values ]

    self._parent = parent
    self._name = None

  @property
  def values(self):
    return (i for i in self._values)

  @property
  def has_values_with_id(self):
    return bool(any(i for i in self.values if i.id))

  def _get_children(self):
    return (i for i in self._values)

class Entry(Node):
  """
  A node corresponding to an <entry> element.

  Attributes (Read-Only):
    parent: An edge to the parent node, which is an InnerNamespace or Kind.
    name: The fully qualified name string, e.g. 'android.shading.mode'
    name_short: The name attribute from <entry name="mode">, e.g. mode
    type: The type attribute from <entry type="bar">
    kind: A string ('static', 'dynamic', 'controls') corresponding to the
          ancestor Kind#name
    container: The container attribute from <entry container="array">, or None.
    container_sizes: A sequence of size strings or None if container is None.
    enum: An Enum instance if the enum attribute is true, None otherwise.
    tuple_values: A sequence of strings describing the tuple values,
                  None if container is not 'tuple'.
    description: A string description, or None.
    range: A string range, or None.
    units: A string units, or None.
    tags: A sequence of Tag nodes associated with this Entry.
    type_notes: A string describing notes for the type, or None.

  Remarks:
    Subclass Clone can be used interchangeable with an Entry,
    for when we don't care about the underlying type.

    parent and tags edges are invalid until after Metadata#construct_graph
    has been invoked.
  """
  def __init__(self, **kwargs):
    """
    Instantiate a new Entry node.

    Args:
      name: A string with the fully qualified name, e.g. 'android.shading.mode'
      type: A string describing the type, e.g. 'int32'
      kind: A string describing the kind, e.g. 'static'

    Args (if container):
      container: A string describing the container, e.g. 'array' or 'tuple'
      container_sizes: A list of string sizes if a container, or None otherwise

    Args (if container is 'tuple'):
      tuple_values: A list of tuple values, e.g. ['width', 'height']

    Args (if the 'enum' attribute is true):
      enum: A boolean, True if this is an enum, False otherwise
      enum_values: A list of value strings, e.g. ['ON', 'OFF']
      enum_optionals: A list of optional enum values, e.g. ['OFF']
      enum_notes: A dictionary of value->notes strings.
      enum_ids: A dictionary of value->id strings.

    Args (optional):
      description: A string with a description of the entry.
      range: A string with the range of the values of the entry, e.g. '>= 0'
      units: A string with the units of the values, e.g. 'inches'
      notes: A string with the notes for the entry
      tag_ids: A list of tag ID strings, e.g. ['BC', 'V1']
      type_notes: A string with the notes for the type
    """

    if kwargs.get('type') is None:
      print >> sys.stderr, "ERROR: Missing type for entry '%s' kind  '%s'"     \
      %(kwargs.get('name'), kwargs.get('kind'))

    # Attributes are Read-Only, but edges may be mutated by
    # Metadata, particularly during construct_graph

    self._name = kwargs['name']
    self._type = kwargs['type']
    self._kind = kwargs['kind'] # static, dynamic, or controls

    self._init_common(**kwargs)

  @property
  def type(self):
    return self._type

  @property
  def kind(self):
    return self._kind

  @property
  def name_short(self):
    return self.get_name_minimal()

  @property
  def container(self):
    return self._container

  @property
  def container_sizes(self):
    if self._container_sizes is None:
      return None
    else:
      return (i for i in self._container_sizes)

  @property
  def tuple_values(self):
    if self._tuple_values is None:
      return None
    else:
      return (i for i in self._tuple_values)

  @property
  def description(self):
    return self._description

  @property
  def range(self):
    return self._range

  @property
  def units(self):
    return self._units

  @property
  def notes(self):
    return self._notes

  @property
  def tags(self):
    if self._tags is None:
      return None
    else:
      return (i for i in self._tags)

  @property
  def type_notes(self):
    return self._type_notes

  @property
  def enum(self):
    return self._enum

  def _get_children(self):
    if self.enum:
      yield self.enum

  def sort_children(self):
    return None

  def is_clone(self):
    """
    Whether or not this is a Clone instance.

    Returns:
      False
    """
    return False

  def _init_common(self, **kwargs):

    self._parent = None # filled in by MetadataSet::_construct_entries

    self._container = kwargs.get('container')
    self._container_sizes = kwargs.get('container_sizes')

    # access these via the 'enum' prop
    enum_values = kwargs.get('enum_values')
    enum_optionals = kwargs.get('enum_optionals')
    enum_notes = kwargs.get('enum_notes')  # { value => notes }
    enum_ids = kwargs.get('enum_ids')  # { value => notes }
    self._tuple_values = kwargs.get('tuple_values')

    self._description = kwargs.get('description')
    self._range = kwargs.get('range')
    self._units = kwargs.get('units')
    self._notes = kwargs.get('notes')

    self._tag_ids = kwargs.get('tag_ids', [])
    self._tags = None  # Filled in by MetadataSet::_construct_tags

    self._type_notes = kwargs.get('type_notes')

    if kwargs.get('enum', False):
      self._enum = Enum(self, enum_values, enum_ids, enum_optionals, enum_notes)
    else:
      self._enum = None

    self._property_keys = kwargs

  def merge(self):
    """
    Copy the attributes into a new entry, merging it with the target entry
    if it's a clone.
    """
    return MergedEntry(self)

  # Helpers for accessing less than the fully qualified name

  def get_name_as_list(self):
    """
    Returns the name as a list split by a period.

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_name_as_list() == ['android', 'lens', 'info', 'shading']
    """
    return self.name.split(".")

  def get_inner_namespace_list(self):
    """
    Returns the inner namespace part of the name as a list

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_inner_namespace_list() == ['info']
    """
    return self.get_name_as_list()[2:-1]

  def get_outer_namespace(self):
    """
    Returns the outer namespace as a string.

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_outer_namespace() == 'android'

    Remarks:
      Since outer namespaces are non-recursive,
      and each entry has one, this does not need to be a list.
    """
    return self.get_name_as_list()[0]

  def get_section(self):
    """
    Returns the section as a string.

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_section() == ''

    Remarks:
      Since outer namespaces are non-recursive,
      and each entry has one, this does not need to be a list.
    """
    return self.get_name_as_list()[1]

  def get_name_minimal(self):
    """
    Returns only the last component of the fully qualified name as a string.

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_name_minimal() == 'shading'

    Remarks:
      entry.name_short it an alias for this
    """
    return self.get_name_as_list()[-1]

  def get_path_without_name(self):
    """
    Returns a string path to the entry, with the name component excluded.

    For example:
      entry.name is 'android.lens.info.shading'
      entry.get_path_without_name() == 'android.lens.info'
    """
    return ".".join(self.get_name_as_list()[0:-1])


class Clone(Entry):
  """
  A Node corresponding to a <clone> element. It has all the attributes of an
  <entry> element (Entry) plus the additions specified below.

  Attributes (Read-Only):
    entry: an edge to an Entry object that this targets
    target_kind: A string describing the kind of the target entry.
    name: a string of the name, same as entry.name
    kind: a string of the Kind ancestor, one of 'static', 'controls', 'dynamic'
          for the <clone> element.
    type: always None, since a clone cannot override the type.
  """
  def __init__(self, entry=None, **kwargs):
    """
    Instantiate a new Clone node.

    Args:
      name: A string with the fully qualified name, e.g. 'android.shading.mode'
      type: A string describing the type, e.g. 'int32'
      kind: A string describing the kind, e.g. 'static'
      target_kind: A string for the kind of the target entry, e.g. 'dynamic'

    Args (if container):
      container: A string describing the container, e.g. 'array' or 'tuple'
      container_sizes: A list of string sizes if a container, or None otherwise

    Args (if container is 'tuple'):
      tuple_values: A list of tuple values, e.g. ['width', 'height']

    Args (if the 'enum' attribute is true):
      enum: A boolean, True if this is an enum, False otherwise
      enum_values: A list of value strings, e.g. ['ON', 'OFF']
      enum_optionals: A list of optional enum values, e.g. ['OFF']
      enum_notes: A dictionary of value->notes strings.
      enum_ids: A dictionary of value->id strings.

    Args (optional):
      entry: An edge to the corresponding target Entry.
      description: A string with a description of the entry.
      range: A string with the range of the values of the entry, e.g. '>= 0'
      units: A string with the units of the values, e.g. 'inches'
      notes: A string with the notes for the entry
      tag_ids: A list of tag ID strings, e.g. ['BC', 'V1']
      type_notes: A string with the notes for the type

    Remarks:
      Note that type is not specified since it has to be the same as the
      entry.type.
    """
    self._entry = entry  # Entry object
    self._target_kind = kwargs['target_kind']
    self._name = kwargs['name']  # same as entry.name
    self._kind = kwargs['kind']

    # illegal to override the type, it should be the same as the entry
    self._type = None
    # the rest of the kwargs are optional
    # can be used to override the regular entry data
    self._init_common(**kwargs)

  @property
  def entry(self):
    return self._entry

  @property
  def target_kind(self):
    return self._target_kind

  def is_clone(self):
    """
    Whether or not this is a Clone instance.

    Returns:
      True
    """
    return True

class MergedEntry(Entry):
  """
  A MergedEntry has all the attributes of a Clone and its target Entry merged
  together.

  Remarks:
    Useful when we want to 'unfold' a clone into a real entry by copying out
    the target entry data. In this case we don't care about distinguishing
    a clone vs an entry.
  """
  def __init__(self, entry):
    """
    Create a new instance of MergedEntry.

    Args:
      entry: An Entry or Clone instance
    """
    props_distinct = ['description', 'units', 'range', 'notes', 'tags', 'kind']

    for p in props_distinct:
      p = '_' + p
      if entry.is_clone():
        setattr(self, p, getattr(entry, p) or getattr(entry.entry, p))
      else:
        setattr(self, p, getattr(entry, p))

    props_common = ['parent', 'name', 'container',
                    'container_sizes', 'enum',
                    'tuple_values',
                    'type',
                    'type_notes',
                   ]

    for p in props_common:
      p = '_' + p
      if entry.is_clone():
        setattr(self, p, getattr(entry.entry, p))
      else:
        setattr(self, p, getattr(entry, p))