# Copyright (c) 2013 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.

import os
import sys

BASE_PATH = os.path.dirname(os.path.abspath(__file__))
BINTREES_PATH = os.path.join(
    BASE_PATH, os.pardir, os.pardir, 'third_party', 'bintrees')
sys.path.insert(0, BINTREES_PATH)

from bintrees import FastRBTree  # pylint: disable=F0401


class ExclusiveRangeDict(object):
  """A class like dict whose key is a range [begin, end) of integers.

  It has an attribute for each range of integers, for example:
  [10, 20) => Attribute(0),
  [20, 40) => Attribute(1),
  [40, 50) => Attribute(2),
  ...

  An instance of this class is accessed only via iter_range(begin, end).
  The instance is accessed as follows:

  1) If the given range [begin, end) is not covered by the instance,
  the range is newly created and iterated.

  2) If the given range [begin, end) exactly covers ranges in the instance,
  the ranges are iterated.
  (See test_set() in tests/range_dict_tests.py.)

  3) If the given range [begin, end) starts at and/or ends at a mid-point of
  an existing range, the existing range is split by the given range, and
  ranges in the given range are iterated.  For example, consider a case that
  [25, 45) is given to an instance of [20, 30), [30, 40), [40, 50).  In this
  case, [20, 30) is split into [20, 25) and [25, 30), and [40, 50) into
  [40, 45) and [45, 50).  Then, [25, 30), [30, 40), [40, 45) are iterated.
  (See test_split() in tests/range_dict_tests.py.)

  4) If the given range [begin, end) includes non-existing ranges in an
  instance, the gaps are filled with new ranges, and all ranges are iterated.
  For example, consider a case that [25, 50) is given to an instance of
  [30, 35) and [40, 45).  In this case, [25, 30), [35, 40) and [45, 50) are
  created in the instance, and then [25, 30), [30, 35), [35, 40), [40, 45)
  and [45, 50) are iterated.
  (See test_fill() in tests/range_dict_tests.py.)
  """
  class RangeAttribute(object):
    def __init__(self):
      pass

    def __str__(self):
      return '<RangeAttribute>'

    def __repr__(self):
      return '<RangeAttribute>'

    def copy(self):  # pylint: disable=R0201
      return ExclusiveRangeDict.RangeAttribute()

  def __init__(self, attr=RangeAttribute):
    self._tree = FastRBTree()
    self._attr = attr

  def iter_range(self, begin=None, end=None):
    if not begin:
      begin = self._tree.min_key()
    if not end:
      end = self._tree.max_item()[1][0]

    # Assume that self._tree has at least one element.
    if self._tree.is_empty():
      self._tree[begin] = (end, self._attr())

    # Create a beginning range (border)
    try:
      bound_begin, bound_value = self._tree.floor_item(begin)
      bound_end = bound_value[0]
      if begin >= bound_end:
        # Create a blank range.
        try:
          new_end, _ = self._tree.succ_item(bound_begin)
        except KeyError:
          new_end = end
        self._tree[begin] = (min(end, new_end), self._attr())
      elif bound_begin < begin and begin < bound_end:
        # Split the existing range.
        new_end = bound_value[0]
        new_value = bound_value[1]
        self._tree[bound_begin] = (begin, new_value.copy())
        self._tree[begin] = (new_end, new_value.copy())
      else:  # bound_begin == begin
        # Do nothing (just saying it clearly since this part is confusing)
        pass
    except KeyError:  # begin is less than the smallest element.
      # Create a blank range.
      # Note that we can assume self._tree has at least one element.
      self._tree[begin] = (min(end, self._tree.min_key()), self._attr())

    # Create an ending range (border)
    try:
      bound_begin, bound_value = self._tree.floor_item(end)
      bound_end = bound_value[0]
      if end > bound_end:
        # Create a blank range.
        new_begin = bound_end
        self._tree[new_begin] = (end, self._attr())
      elif bound_begin < end and end < bound_end:
        # Split the existing range.
        new_end = bound_value[0]
        new_value = bound_value[1]
        self._tree[bound_begin] = (end, new_value.copy())
        self._tree[end] = (new_end, new_value.copy())
      else:  # bound_begin == begin
        # Do nothing (just saying it clearly since this part is confusing)
        pass
    except KeyError:  # end is less than the smallest element.
      # It must not happen.  A blank range [begin,end) has already been created
      # even if [begin,end) is less than the smallest range.
      # Do nothing (just saying it clearly since this part is confusing)
      raise

    missing_ranges = []

    prev_end = None
    for range_begin, range_value in self._tree.itemslice(begin, end):
      range_end = range_value[0]
      # Note that we can assume that we have a range beginning with |begin|
      # and a range ending with |end| (they may be the same range).
      if prev_end and prev_end != range_begin:
        missing_ranges.append((prev_end, range_begin))
      prev_end = range_end

    for missing_begin, missing_end in missing_ranges:
      self._tree[missing_begin] = (missing_end, self._attr())

    for range_begin, range_value in self._tree.itemslice(begin, end):
      yield range_begin, range_value[0], range_value[1]

  def __str__(self):
    return str(self._tree)