Trav
f6d35fa594
Snapshot of the existing codebase before working through the TASKS.md backlog. Real library data (data/) and the iTunes import fixture (itunes-test-library/) are gitignored. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
72 lines
1.9 KiB
Python
72 lines
1.9 KiB
Python
"""A tiny closure-based undo/redo stack.
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Each Command stores a human label plus two zero-arg callables — one to undo the
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change and one to redo it. The change is assumed to have already been applied by
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the caller, so push() only records it. The stack keeps a bounded history (10
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levels by default); pushing past the limit silently drops the oldest entry.
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"""
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import collections
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from PyQt6.QtCore import QObject, pyqtSignal
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class Command:
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def __init__(self, label: str, undo, redo):
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self.label = label
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self._undo = undo
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self._redo = redo
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def undo(self):
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self._undo()
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def redo(self):
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self._redo()
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class UndoStack(QObject):
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changed = pyqtSignal()
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def __init__(self, maxlen: int = 10, parent=None):
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super().__init__(parent)
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self._undo: collections.deque[Command] = collections.deque(maxlen=maxlen)
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self._redo: list[Command] = []
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def push(self, command: Command):
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"""Record an already-applied change; clears the redo branch."""
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self._undo.append(command)
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self._redo.clear()
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self.changed.emit()
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def undo(self):
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if not self._undo:
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return
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command = self._undo.pop()
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command.undo()
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self._redo.append(command)
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self.changed.emit()
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def redo(self):
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if not self._redo:
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return
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command = self._redo.pop()
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command.redo()
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self._undo.append(command)
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self.changed.emit()
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def can_undo(self) -> bool:
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return bool(self._undo)
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def can_redo(self) -> bool:
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return bool(self._redo)
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def undo_label(self) -> str:
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return self._undo[-1].label if self._undo else ""
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def redo_label(self) -> str:
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return self._redo[-1].label if self._redo else ""
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def clear(self):
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self._undo.clear()
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self._redo.clear()
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self.changed.emit()
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