text: import copy
  import types
  
  from .util import six, Lexicon
  
  from .config import merge_dicts, copy_dict
  from .parser import Context as ParserContext
  from .tasks import Task
  
  
  class Collection(object):
      """
      A collection of executable tasks.
      """
      def __init__(self, *args, **kwargs):
          """
          Create a new task collection/namespace.
  
          `.Collection` offers a set of methods for building a collection of
          tasks from scratch, plus a convenient constructor wrapping said API.
  
          In either case:
  
          * The first positional argument may be a string, which (if given) is
            used as the collection's default name when performing namespace
            lookups;
          * A ``loaded_from`` keyword argument may be given, which sets metadata
            indicating the filesystem path the collection was loaded from. This
            is used as a guide when loading per-project :ref:`configuration files
            <config-hierarchy>`.
          * An ``auto_dash_names`` kwarg may be given, controlling whether task
            and collection names have underscores turned to dashes in most cases;
            it defaults to ``True`` but may be set to ``False`` to disable.
  
            The CLI machinery will pass in the value of the
            ``tasks.auto_dash_names`` config value to this kwarg.
  
          **The method approach**
  
          May initialize with no arguments and use methods (e.g.
          `.add_task`/`.add_collection`) to insert objects::
  
              c = Collection()
              c.add_task(some_task)
  
          If an initial string argument is given, it is used as the default name
          for this collection, should it be inserted into another collection as a
          sub-namespace::
  
              docs = Collection('docs')
              docs.add_task(doc_task)
              ns = Collection()
              ns.add_task(top_level_task)
              ns.add_collection(docs)
              # Valid identifiers are now 'top_level_task' and 'docs.doc_task'
              # (assuming the task objects were actually named the same as the
              # variables we're using :))
  
          For details, see the API docs for the rest of the class.
  
          **The constructor approach**
  
          All ``*args`` given to `.Collection` (besides the abovementioned
          optional positional 'name' argument and ``loaded_from`` kwarg) are
          expected to be `.Task` or `.Collection` instances which will be passed
          to `.add_task`/`.add_collection` as appropriate. Module objects are
          also valid (as they are for `.add_collection`). For example, the below
          snippet results in the same two task identifiers as the one above::
  
              ns = Collection(top_level_task, Collection('docs', doc_task))
  
          If any ``**kwargs`` are given, the keywords are used as the initial
          name arguments for the respective values::
  
              ns = Collection(
                  top_level_task=some_other_task,
                  docs=Collection(doc_task)
              )
  
          That's exactly equivalent to::
  
              docs = Collection(doc_task)
              ns = Collection()
              ns.add_task(some_other_task, 'top_level_task')
              ns.add_collection(docs, 'docs')
  
          See individual methods' API docs for details.
          """
          # Initialize
          self.tasks = Lexicon()
          self.collections = Lexicon()
          self.default = None
          self.name = None
          self._configuration = {}
          # Specific kwargs if applicable
          self.loaded_from = kwargs.pop('loaded_from', None)
          self.auto_dash_names = kwargs.pop('auto_dash_names', None)
          # splat-kwargs version of default value (auto_dash_names=True)
          if self.auto_dash_names is None:
              self.auto_dash_names = True
          # Name if applicable
          args = list(args)
          if args and isinstance(args[0], six.string_types):
              self.name = self.transform(args.pop(0))
          # Dispatch args/kwargs
          for arg in args:
              self._add_object(arg)
          # Dispatch kwargs
          for name, obj in six.iteritems(kwargs):
              self._add_object(obj, name)
  
      def _add_object(self, obj, name=None):
          if isinstance(obj, Task):
              method = self.add_task
          elif isinstance(obj, (Collection, types.ModuleType)):
              method = self.add_collection
          else:
              raise TypeError("No idea how to insert {!r}!".format(type(obj)))
          return method(obj, name=name)
  
      def __repr__(self):
          return "<Collection {!r}: {}>".format(
              self.name,
              ", ".join(sorted(self.tasks.keys())),
          )
  
      def __eq__(self, other):
          return self.name == other.name and self.tasks == other.tasks
  
      @classmethod
      def from_module(
          cls,
          module,
          name=None,
          config=None,
          loaded_from=None,
          auto_dash_names=None,
      ):
          """
          Return a new `.Collection` created from ``module``.
  
          Inspects ``module`` for any `.Task` instances and adds them to a new
          `.Collection`, returning it. If any explicit namespace collections
          exist (named ``ns`` or ``namespace``) a copy of that collection object
          is preferentially loaded instead.
  
          When the implicit/default collection is generated, it will be named
          after the module's ``__name__`` attribute, or its last dotted section
          if it's a submodule. (I.e. it should usually map to the actual ``.py``
          filename.)
  
          Explicitly given collections will only be given that module-derived
          name if they don't already have a valid ``.name`` attribute.
  
          :param str name:
              A string, which if given will override any automatically derived
              collection name (or name set on the module's root namespace, if it
              has one.)
  
          :param dict config:
              Used to set config options on the newly created `.Collection`
              before returning it (saving you a call to `.configure`.)
  
              If the imported module had a root namespace object, ``config`` is
              merged on top of it (i.e. overriding any conflicts.)
  
          :param str loaded_from:
              Identical to the same-named kwarg from the regular class
              constructor - should be the path where the module was
              found.
  
          :param bool auto_dash_names:
              Identical to the same-named kwarg from the regular class
              constructor - determines whether emitted names are auto-dashed.
          """
          module_name = module.__name__.split('.')[-1]
          def instantiate(obj_name=None):
              # Explicitly given name wins over root ns name (if applicable),
              # which wins over actual module name.
              args = [name or obj_name or module_name]
              kwargs = dict(
                  loaded_from=loaded_from,
                  auto_dash_names=auto_dash_names,
              )
              return cls(*args, **kwargs)
          # See if the module provides a default NS to use in lieu of creating
          # our own collection.
          for candidate in ('ns', 'namespace'):
              obj = getattr(module, candidate, None)
              if obj and isinstance(obj, Collection):
                  # TODO: make this into Collection.clone() or similar?
                  ret = instantiate(obj_name=obj.name)
                  ret.tasks = ret.transform_lexicon(obj.tasks)
                  ret.collections = ret.transform_lexicon(obj.collections)
                  ret.default = ret.transform(obj.default)
                  # Explicitly given config wins over root ns config
                  obj_config = copy_dict(obj._configuration)
                  if config:
                      merge_dicts(obj_config, config)
                  ret._configuration = obj_config
                  return ret
          # Failing that, make our own collection from the module's tasks.
          tasks = filter(
              lambda x: isinstance(x, Task),
              vars(module).values()
          )
          # Again, explicit name wins over implicit one from module path
          collection = instantiate()
          for task in tasks:
              collection.add_task(task)
          if config:
              collection.configure(config)
          return collection
  
      def add_task(self, task, name=None, aliases=None, default=None):
          """
          Add `.Task` ``task`` to this collection.
  
          :param task: The `.Task` object to add to this collection.
  
          :param name:
              Optional string name to bind to (overrides the task's own
              self-defined ``name`` attribute and/or any Python identifier (i.e.
              ``.func_name``.)
  
          :param aliases:
              Optional iterable of additional names to bind the task as, on top
              of the primary name. These will be used in addition to any aliases
              the task itself declares internally.
  
          :param default: Whether this task should be the collection default.
          """
          if name is None:
              if task.name:
                  name = task.name
              elif hasattr(task.body, 'func_name'):
                  name = task.body.func_name
              elif hasattr(task.body, '__name__'):
                  name = task.__name__
              else:
                  raise ValueError("Could not obtain a name for this task!")
          name = self.transform(name)
          if name in self.collections:
              raise ValueError("Name conflict: this collection has a sub-collection named {!r} already".format(name)) # noqa
          self.tasks[name] = task
          for alias in list(task.aliases) + list(aliases or []):
              self.tasks.alias(self.transform(alias), to=name)
          if default is True or (default is None and task.is_default):
              if self.default:
                  msg = "'{}' cannot be the default because '{}' already is!"
                  raise ValueError(msg.format(name, self.default))
              self.default = name
  
      def add_collection(self, coll, name=None):
          """
          Add `.Collection` ``coll`` as a sub-collection of this one.
  
          :param coll: The `.Collection` to add.
  
          :param str name:
              The name to attach the collection as. Defaults to the collection's
              own internal name.
          """
          # Handle module-as-collection
          if isinstance(coll, types.ModuleType):
              coll = Collection.from_module(coll)
          # Ensure we have a name, or die trying
          name = name or coll.name
          if not name:
              raise ValueError("Non-root collections must have a name!")
          name = self.transform(name)
          # Test for conflict
          if name in self.tasks:
              raise ValueError("Name conflict: this collection has a task named {!r} already".format(name)) # noqa
          # Insert
          self.collections[name] = coll
  
      def split_path(self, path):
          """
          Obtain first collection + remainder, of a task path.
  
          E.g. for ``"subcollection.taskname"``, return ``("subcollection",
          "taskname")``; for ``"subcollection.nested.taskname"`` return
          ``("subcollection", "nested.taskname")``, etc.
  
          An empty path becomes simply ``('', '')``.
          """
          parts = path.split('.')
          coll = parts.pop(0)
          rest = '.'.join(parts)
          return coll, rest
  
      def __getitem__(self, name=None):
          """
          Returns task named ``name``. Honors aliases and subcollections.
  
          If this collection has a default task, it is returned when ``name`` is
          empty or ``None``. If empty input is given and no task has been
          selected as the default, ValueError will be raised.
  
          Tasks within subcollections should be given in dotted form, e.g.
          'foo.bar'. Subcollection default tasks will be returned on the
          subcollection's name.
          """
          return self.task_with_config(name)[0]
  
      def _task_with_merged_config(self, coll, rest, ours):
          task, config = self.collections[coll].task_with_config(rest)
          return task, dict(config, **ours)
  
      def task_with_config(self, name):
          """
          Return task named ``name`` plus its configuration dict.
  
          E.g. in a deeply nested tree, this method returns the `.Task`, and a
          configuration dict created by merging that of this `.Collection` and
          any nested `Collections <.Collection>`, up through the one actually
          holding the `.Task`.
  
          See `~.Collection.__getitem__` for semantics of the ``name`` argument.
  
          :returns: Two-tuple of (`.Task`, `dict`).
          """
          # Our top level configuration
          ours = self.configuration()
          # Default task for this collection itself
          if not name:
              if self.default:
                  return self[self.default], ours
              else:
                  raise ValueError("This collection has no default task.")
          # Normalize name to the format we're expecting
          name = self.transform(name)
          # Non-default tasks within subcollections -> recurse (sorta)
          if '.' in name:
              coll, rest = self.split_path(name)
              return self._task_with_merged_config(coll, rest, ours)
          # Default task for subcollections (via empty-name lookup)
          if name in self.collections:
              return self._task_with_merged_config(name, '', ours)
          # Regular task lookup
          return self.tasks[name], ours
  
      def __contains__(self, name):
          try:
              self[name]
              return True
          except KeyError:
              return False
  
      def to_contexts(self):
          """
          Returns all contained tasks and subtasks as a list of parser contexts.
          """
          result = []
          for primary, aliases in six.iteritems(self.task_names):
              task = self[primary]
              result.append(ParserContext(
                  name=primary, aliases=aliases, args=task.get_arguments()
              ))
          return result
  
      def subtask_name(self, collection_name, task_name):
          return '.'.join([
              self.transform(collection_name), self.transform(task_name)
          ])
  
      def transform(self, name):
          """
          Transform ``name`` with the configured auto-dashes behavior.
  
          If ``auto_dash_names`` is ``True`` (default), all non leading/trailing
          underscores are turned into dashes. (Leading/trailing underscores tend
          to get stripped elsewhere in the stack.)
  
          If it is ``False``, the inverse is applied - all dashes are turned into
          underscores.
          """
          # Short-circuit on anything non-applicable, e.g. empty strings, bools,
          # None, etc.
          if not name:
              return name
          from_, to = '_', '-'
          if not self.auto_dash_names:
              from_, to = '-', '_'
          replaced = []
          end = len(name) - 1
          for i, char in enumerate(name):
              # Don't replace leading or trailing underscores (+ taking dotted
              # names into account)
              # TODO: not 100% convinced of this / it may be exposing a
              # discrepancy between this level & higher levels which tend to
              # strip out leading/trailing underscores entirely.
              if (
                  i not in (0, end) and
                  char == from_ and
                  name[i - 1] != '.' and
                  name[i + 1] != '.'
              ):
                  char = to
              replaced.append(char)
          return ''.join(replaced)
  
      def transform_lexicon(self, old):
          """
          Take a Lexicon and apply `.transform` to its keys and aliases.
  
          :returns: A new Lexicon.
          """
          new_ = Lexicon()
          # Lexicons exhibit only their real keys in most places, so this will
          # only grab those, not aliases.
          for key, value in six.iteritems(old):
              # Deepcopy the value so we're not just copying a reference
              new_[self.transform(key)] = copy.deepcopy(value)
          # Also copy all aliases, which are string-to-string key mappings
          for key, value in six.iteritems(old.aliases):
              new_.alias(from_=self.transform(key), to=self.transform(value))
          return new_
  
      @property
      def task_names(self):
          """
          Return all task identifiers for this collection as a dict.
  
          Specifically, a dict with the primary/"real" task names as the key, and
          any aliases as a list value.
          """
          ret = {}
          # Our own tasks get no prefix, just go in as-is: {name: [aliases]}
          for name, task in six.iteritems(self.tasks):
              ret[name] = list(map(self.transform, task.aliases))
          # Subcollection tasks get both name + aliases prefixed
          for coll_name, coll in six.iteritems(self.collections):
              for task_name, aliases in six.iteritems(coll.task_names):
                  # Cast to list to handle Py3 map() 'map' return value,
                  # so we can add to it down below if necessary.
                  aliases = list(map(
                      lambda x: self.subtask_name(coll_name, x),
                      aliases
                  ))
                  # Tack on collection name to alias list if this task is the
                  # collection's default.
                  if coll.default and coll.default == task_name:
                      aliases += (coll_name,)
                  ret[self.subtask_name(coll_name, task_name)] = aliases
          return ret
  
      def configuration(self, taskpath=None):
          """
          Obtain merged configuration values from collection & children.
  
          :param taskpath:
              (Optional) Task name/path, identical to that used for
              `~.Collection.__getitem__` (e.g. may be dotted for nested tasks,
              etc.) Used to decide which path to follow in the collection tree
              when merging config values.
  
          :returns: A `dict` containing configuration values.
          """
          if taskpath is None:
              return copy_dict(self._configuration)
          return self.task_with_config(taskpath)[1]
  
      def configure(self, options):
          """
          (Recursively) merge ``options`` into the current `.configuration`.
  
          Options configured this way will be available to all tasks. It is
          recommended to use unique keys to avoid potential clashes with other
          config options
  
          For example, if you were configuring a Sphinx docs build target
          directory, it's better to use a key like ``'sphinx.target'`` than
          simply ``'target'``.
  
          :param options: An object implementing the dictionary protocol.
          :returns: ``None``.
          """
          merge_dicts(self._configuration, options)
  