Add up/down arrow command history to game input
Replace bare input() with a custom terminal reader that supports arrow-key history navigation, cursor movement, and line editing. History buffer grows dynamically with no fixed limit. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
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"""Terminal input with up/down arrow command history."""
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from __future__ import annotations
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import sys
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import tty
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import termios
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class InputHistory:
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"""Reads a line of input with up/down arrow history navigation.
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History buffer grows dynamically with no fixed limit.
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"""
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def __init__(self) -> None:
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self._history: list[str] = []
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def input(self, prompt: str = "> ") -> str:
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"""Read a line with history support. Raises EOFError on Ctrl-D."""
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sys.stdout.write(prompt)
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sys.stdout.flush()
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fd = sys.stdin.fileno()
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old_settings = termios.tcgetattr(fd)
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try:
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tty.setraw(fd)
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line = self._read_line(fd, prompt)
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finally:
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termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
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sys.stdout.write("\n")
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sys.stdout.flush()
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if line:
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self._history.append(line)
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return line
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def _read_line(self, fd: int, prompt: str) -> str:
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buf: list[str] = []
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cursor = 0
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# Index into history; len(history) means "current new line"
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hist_idx = len(self._history)
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saved_line = "" # what the user typed before browsing history
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while True:
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ch = self._read_char(fd)
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if ch == "\r" or ch == "\n":
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return "".join(buf)
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if ch == "\x04": # Ctrl-D
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if not buf:
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raise EOFError
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continue
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if ch == "\x03": # Ctrl-C
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raise KeyboardInterrupt
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if ch == "\x7f" or ch == "\x08": # Backspace
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if cursor > 0:
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buf.pop(cursor - 1)
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cursor -= 1
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self._redraw(buf, cursor, prompt)
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continue
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if ch == "\x1b": # Escape sequence
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seq1 = self._read_char(fd)
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if seq1 == "[":
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seq2 = self._read_char(fd)
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if seq2 == "A": # Up arrow
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if hist_idx > 0:
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if hist_idx == len(self._history):
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saved_line = "".join(buf)
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hist_idx -= 1
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buf = list(self._history[hist_idx])
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cursor = len(buf)
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self._redraw(buf, cursor, prompt)
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continue
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if seq2 == "B": # Down arrow
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if hist_idx < len(self._history):
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hist_idx += 1
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if hist_idx == len(self._history):
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buf = list(saved_line)
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else:
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buf = list(self._history[hist_idx])
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cursor = len(buf)
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self._redraw(buf, cursor, prompt)
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continue
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if seq2 == "C": # Right arrow
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if cursor < len(buf):
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cursor += 1
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sys.stdout.write("\x1b[C")
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sys.stdout.flush()
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continue
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if seq2 == "D": # Left arrow
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if cursor > 0:
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cursor -= 1
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sys.stdout.write("\x1b[D")
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sys.stdout.flush()
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continue
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if seq2 == "3": # Possible Delete key
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seq3 = self._read_char(fd)
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if seq3 == "~" and cursor < len(buf):
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buf.pop(cursor)
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self._redraw(buf, cursor, prompt)
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continue
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if seq2 == "H": # Home
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cursor = 0
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self._redraw(buf, cursor, prompt)
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continue
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if seq2 == "F": # End
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cursor = len(buf)
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self._redraw(buf, cursor, prompt)
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continue
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continue
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# Regular printable character
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if ch.isprintable():
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buf.insert(cursor, ch)
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cursor += 1
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if cursor == len(buf):
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sys.stdout.write(ch)
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sys.stdout.flush()
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else:
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self._redraw(buf, cursor, prompt)
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return "".join(buf) # unreachable, keeps type-checker happy
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def _read_char(self, fd: int) -> str:
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return sys.stdin.read(1)
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@staticmethod
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def _redraw(buf: list[str], cursor: int, prompt: str) -> None:
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"""Clear the line and redraw the prompt + buffer with cursor positioned."""
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line = "".join(buf)
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# Move to start of line, clear it, rewrite
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sys.stdout.write(f"\r\x1b[K{prompt}{line}")
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# Position cursor
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back = len(line) - cursor
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if back > 0:
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sys.stdout.write(f"\x1b[{back}D")
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sys.stdout.flush()
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+3
-1
@@ -8,6 +8,7 @@ from h2g2.engine.game_object import (
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GameObject, Room, Flag, Direction,
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DirectExit, ConditionalExit, GatedExit, BlockedExit,
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)
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from h2g2.engine.input_history import InputHistory
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from h2g2.engine.parser import Parser, ParseResult
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from h2g2.engine.state import GameState
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from h2g2.engine.output import Output
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@@ -47,6 +48,7 @@ class GameLoop:
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def __init__(self, state: GameState, parser: Parser) -> None:
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self.state = state
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self.parser = parser
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self._input = InputHistory()
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def run(self) -> None:
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"""Run the main game loop until the game ends."""
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@@ -59,7 +61,7 @@ class GameLoop:
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while state.running:
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try:
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raw = input("\n> ")
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raw = self._input.input("\n> ")
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except (EOFError, KeyboardInterrupt):
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print("\nGoodbye!")
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break
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@@ -0,0 +1,212 @@
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"""Tests for InputHistory — command history buffer and line editing."""
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from __future__ import annotations
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import io
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from collections import deque
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import pytest
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from h2g2.engine.input_history import InputHistory
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# Escape sequences for arrow keys
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UP = "\x1b[A"
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DOWN = "\x1b[B"
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RIGHT = "\x1b[C"
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LEFT = "\x1b[D"
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HOME = "\x1b[H"
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END = "\x1b[F"
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DELETE = "\x1b[3~"
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BACKSPACE = "\x7f"
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ENTER = "\r"
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CTRL_D = "\x04"
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CTRL_C = "\x03"
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class FakeInputHistory(InputHistory):
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"""InputHistory subclass that reads from a character queue
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and captures terminal output instead of touching the real terminal."""
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def __init__(self, chars: str = "") -> None:
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super().__init__()
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self._chars: deque[str] = deque(chars)
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self.output = io.StringIO()
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def feed(self, chars: str) -> None:
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self._chars.extend(chars)
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def _read_char(self, fd: int) -> str:
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return self._chars.popleft()
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def input(self, prompt: str = "> ") -> str:
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"""Bypass terminal raw-mode setup; drive _read_line directly."""
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self.output.write(prompt)
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line = self._read_line(0, prompt)
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if line:
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self._history.append(line)
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return line
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@staticmethod
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def _redraw(buf: list[str], cursor: int, prompt: str) -> None:
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# Suppress terminal escape codes during tests
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pass
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# ---------------------------------------------------------------------------
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# History buffer basics
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# ---------------------------------------------------------------------------
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class TestHistoryGrowsDynamically:
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def test_single_entry(self):
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h = FakeInputHistory("hello" + ENTER)
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assert h.input() == "hello"
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assert h._history == ["hello"]
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def test_multiple_entries(self):
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h = FakeInputHistory()
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for cmd in ["north", "take lamp", "inventory"]:
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h.feed(cmd + ENTER)
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h.input()
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assert h._history == ["north", "take lamp", "inventory"]
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def test_empty_input_not_stored(self):
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h = FakeInputHistory(ENTER)
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assert h.input() == ""
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assert h._history == []
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def test_grows_unbounded(self):
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h = FakeInputHistory()
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for i in range(500):
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h.feed(f"cmd{i}" + ENTER)
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h.input()
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assert len(h._history) == 500
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assert h._history[0] == "cmd0"
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assert h._history[499] == "cmd499"
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# ---------------------------------------------------------------------------
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# Up/Down arrow navigation
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# ---------------------------------------------------------------------------
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class TestUpDownNavigation:
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def _make_history(self, *commands: str) -> FakeInputHistory:
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h = FakeInputHistory()
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for cmd in commands:
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h.feed(cmd + ENTER)
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h.input()
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return h
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def test_up_recalls_last_command(self):
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h = self._make_history("look", "north")
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h.feed(UP + ENTER)
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assert h.input() == "north"
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def test_up_twice_recalls_older(self):
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h = self._make_history("look", "north", "take lamp")
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h.feed(UP + UP + ENTER)
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assert h.input() == "north"
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def test_up_then_down_returns_to_newer(self):
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h = self._make_history("look", "north")
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h.feed(UP + UP + DOWN + ENTER)
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assert h.input() == "north"
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def test_down_past_end_restores_current_input(self):
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h = self._make_history("look")
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# Type "hel", arrow up (recalls "look"), arrow down (restores "hel")
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h.feed("hel" + UP + DOWN + ENTER)
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assert h.input() == "hel"
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def test_up_at_top_stays_at_oldest(self):
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h = self._make_history("only")
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h.feed(UP + UP + UP + ENTER)
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assert h.input() == "only"
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def test_down_with_no_history_is_noop(self):
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h = FakeInputHistory(DOWN + "hello" + ENTER)
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assert h.input() == "hello"
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def test_up_with_no_history_is_noop(self):
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h = FakeInputHistory(UP + "hello" + ENTER)
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assert h.input() == "hello"
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def test_browse_full_history(self):
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h = self._make_history("a", "b", "c")
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# Go all the way up (c -> b -> a), then submit
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h.feed(UP + UP + UP + ENTER)
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assert h.input() == "a"
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def test_recalled_command_added_to_history(self):
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h = self._make_history("look")
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h.feed(UP + ENTER)
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result = h.input()
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assert result == "look"
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# "look" is now in history twice (original + re-submitted)
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assert h._history == ["look", "look"]
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# ---------------------------------------------------------------------------
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# Line editing
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# ---------------------------------------------------------------------------
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class TestLineEditing:
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def test_backspace_deletes_char(self):
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h = FakeInputHistory("helloo" + BACKSPACE + ENTER)
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assert h.input() == "hello"
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def test_backspace_at_start_is_noop(self):
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h = FakeInputHistory(BACKSPACE + "hi" + ENTER)
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assert h.input() == "hi"
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def test_left_arrow_and_insert(self):
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# Type "hllo", left 3 times to position after 'h', insert 'e'
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h = FakeInputHistory("hllo" + LEFT + LEFT + LEFT + "e" + ENTER)
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assert h.input() == "hello"
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def test_right_arrow(self):
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# Type "hllo", left 3, right 1, insert 'e' (between l and l)
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h = FakeInputHistory("hllo" + LEFT + LEFT + LEFT + RIGHT + "e" + ENTER)
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assert h.input() == "hlelo"
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def test_home_moves_to_start(self):
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h = FakeInputHistory("ello" + HOME + "h" + ENTER)
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assert h.input() == "hello"
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def test_end_moves_to_end(self):
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h = FakeInputHistory("hel" + HOME + END + "lo" + ENTER)
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assert h.input() == "hello"
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def test_delete_key(self):
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# Type "hello", left twice (cursor before 'l' 'o'), delete removes 'l'
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h = FakeInputHistory("hello" + LEFT + LEFT + DELETE + ENTER)
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assert h.input() == "helo"
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def test_delete_at_end_is_noop(self):
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h = FakeInputHistory("hi" + DELETE + ENTER)
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assert h.input() == "hi"
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def test_backspace_mid_line(self):
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# Type "helxlo", left 2 (before 'l' 'o'), backspace removes 'x'...
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# Actually: "helxlo" then LEFT LEFT puts cursor before "lo", backspace removes 'x'
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h = FakeInputHistory("helxlo" + LEFT + LEFT + BACKSPACE + ENTER)
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assert h.input() == "hello"
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# ---------------------------------------------------------------------------
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# Ctrl-D / Ctrl-C
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# ---------------------------------------------------------------------------
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class TestControlKeys:
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def test_ctrl_d_on_empty_raises_eof(self):
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h = FakeInputHistory(CTRL_D)
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with pytest.raises(EOFError):
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h.input()
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def test_ctrl_d_with_content_is_ignored(self):
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h = FakeInputHistory("hi" + CTRL_D + ENTER)
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assert h.input() == "hi"
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def test_ctrl_c_raises_keyboard_interrupt(self):
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h = FakeInputHistory(CTRL_C)
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with pytest.raises(KeyboardInterrupt):
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h.input()
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