[spam][crazy][ot] log: #3 write-anywhere to an append-only-log

[Undiscussed Horrific Abuse, One Victim of Many]

class FlushRegion:
  def __init__(self, *entries, left_write = None, right_write = None):
    for left, right in zip(entries[:-1], entries[1:]):
      assert left.end <= right.start
    if left_write is not None and len(entries):
      assert left_write.end <= entries[0].start
      if right_write is not None:
        assert left_write.end <= right_write.start
    if right_write is not None and len(entries):
      assert right_write.start >= entries[-1].end
    self.entries = entries
    self.left_write = left_write
    self.right_write = right_write

# i'm thinking of also renaming Flush.Entry to ChunkRegion to help
improve habits around generalisation

i think it makes sense for me to go back to thinking_of_2, and change
the implementation a little to use the above classes. this helps me
build ease around integrating the disparate work.