game_entry.py

"""**Code Fragment 5.7**: Python code for a simple ``GameEntry`` class.
We include methods for returning the name and score for a game entry object, 
as well as a method for returning a string representation of this entry.\n

**Code Fragment 5.8**: Python code for a ``Scoreboard`` class that maintains
an ordered series of scores as GameEntry objects.
"""
from typing import List, Union


class GameEntry:
	"""Represents one entry of a list of high scores."""
	def __init__(self, name, score):
		self._name = name
		self._score = score

	def get_name(self):
		return self._name

	def get_score(self):
		return self._score

	def __str__(self):
		return "({0}, {1:2d})".format(self._name, self._score)


class Scoreboard:
	"""Fixed-length sequence of high scores in nondecreasing order."""

	def __init__(self, capacity=10):
		""" All enteries are initially ``None``.\n
		- ``self._board``: A collection of ``GameEntry`` objects (reserved space for future scores).
		- ``self._n``: Number of actual entries.
		"""
		self._board: Union[List[GameEntry], List[None]] = [None] * capacity
		self._n: int = 0

	def __getitem__(self, k):
		"""Return ``GameEntry`` at index ``k``."""
		return self._board[k]

	def __str__(self):
		"""Return string representation of the high score list (``_board``)."""
		return "\n".join(str(self._board[j]) for j in range(self._n))

	def add(self, entry: GameEntry):
		"""Consider adding ``entry`` to high scores.\n
		- ``score``: Proposed high score which is verified by boolean expression ``good``.
		- ``good``: Evaluates as ``True`` if ``_board`` not full or ``score`` is higher than last entry.
		"""
		score = entry.get_score()
		good = self._n < len(self._board) or score > self._board[-1].get_score()
		if good:
			if self._n < len(self._board):			# No score drops from list.
				self._n += 1						# So overall number increases.
			j = self._n - 1							# Shift lower scores rightward to make room.
			while j > 0 and self._board[j-1].get_score() < score:
				self._board[j] = self._board[j-1] 	# Shift entry from j-1 to j.
				j -= 1								# And decrement j.
			self._board[j] = entry					# When done, add new entry.