[Findit] Reorganizing findit_for_*.py

appengine/findit/crash/classifier.py

-# Copyright 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-
-class Occurrence(list):
-  """A list of indices where something occurs in a list.
-
-  The list of indices can be accessed directly, since this class is a
-  subclass of |list|. In addition to this list, we also have a |name|
-  property which specifies what thing is occurring in those positions. For
-  our uses here, the name is a string denoting either a project name
-  (e.g., 'chromium' or 'chromium-skia') or a component name (e.g.,
-  'Blink>API' or 'Blink>DOM').
-  """
-  def __init__(self, name, indices=None):
-    super(Occurrence, self).__init__(indices or [])
-    self.name = name
-
-
-# TODO(wrengr): why not return the dict itself? Or if we're going to
-# return a list, why not take in the ranking function so we can perform
-# the sorting ourselves?
-def GetOccurrences(names):
-  """Return a concordance of elements in a list.
-
-  Args:
-    names (list): a list of "names". Typically names are strings, but
-      they're actually allowed to be anything which can serve as a key
-      in a dict.
-
-  Returns:
-    A list of Occurrence objects. For each name in |names| we produce
-    an Occurrence object, which in turn contains a list of the indices
-    where that name occurs in |names|.
-  """
-  occurrences = {}
-  for index, name in enumerate(names or []):
-    if name not in occurrences:
-      occurrences[name] = Occurrence(name, [index])
-    else:
-      occurrences[name].append(index)
-
-  return occurrences.values()
-
-
-def DefaultRankFunction(class_occurrence):
-  """Default function for ranking classes.
-
-  Note: The default behavior works for component classifier and for
-  project classifier, it works for cpp callstack class ranking.
-
-  Returns:
-    A pair of the weight/priority for this |class_occurrence|, and the
-    index of the first occurrence of this class's name in the list the
-    |class_occurrence| came from.
-  """
-  # If the top 2 frames are in this class, then give it highest priority.
-  if 0 in class_occurrence and 1 in class_occurrence:
-    return -float('inf'), class_occurrence[0]
-
-  return -len(class_occurrence), class_occurrence[0]
-
-
-# TODO(http://crbug.com/644476): this class needs a better name.
-class Classifier(object):
-  """Classifies results or crash stack into a class or a list of classes."""
-
-  def GetClassFromStackFrame(self, frame):  # pragma: no cover.
-    raise NotImplementedError()
-
-  def GetClassFromResult(self, result):  # pragma: no cover.
-    raise NotImplementedError()
-
-  def _Classify(self, results, crash_stack, top_n, max_classes,
-                rank_function=DefaultRankFunction):
-    """Classifies a crash to a list of classes, ranked by rank_function.
-
-    Extracts a list of classes from results or crash_stack, rank the classes and
-    returns max_classes number of classes on the top.
-
-    Args:
-      results (list of Result): Culprit results.
-      crash_stack (CallStack): The callstack that caused the crash.
-      top_n (int): Number of top frames to be considered when classifying.
-      max_classes (int): Maximal number of classes to return.
-      rank_function (function): Used to rank classes based on Occurrence.
-
-    Returns:
-      A list of classes for this crash, ordered by the |rank_function|.
-    """
-    # Extracts the class list from culprit results if possible since it's more
-    # reliable.
-    if results:
-      classes = map(self.GetClassFromResult, results[:top_n])
-    else:
-      classes = map(self.GetClassFromStackFrame, crash_stack[:top_n])
-
-    occurrences = sorted(GetOccurrences(classes), key=rank_function)
-
-    # Filter out unnamed classes.
-    classes = [occurrence.name for occurrence in occurrences if occurrence.name]
-
-    return classes[:max_classes]
-
-  def Classify(self, results, crash_stack):  # pragma: no cover.
-    raise NotImplementedError()