Adds the foundation for canvas undo/redo. UI wiring, keyboard shortcuts,
toolbar buttons and agent-tools refactor land in follow-up commits.
useSimulatorStore.ts:
- New CanvasCommand type — { description, execute, undo }.
- HISTORY_MAX = 50 (oldest entries dropped on overflow).
- New state: history[] + historyIndex (-1 = empty).
- New APIs: pushCommand(cmd, {applyNow?}), undo, redo, canUndo, canRedo,
clearHistory.
- New "recorded" actions that wrap raw mutators with a CanvasCommand:
recordAddComponent, recordRemoveComponent, recordMove, recordRotate,
recordSetProperty, recordAddWire, recordRemoveWire, recordUpdateWire.
- recordRemoveComponent captures both the component AND any wires that
cascade with it, so undo restores both atomically.
- recordMove also re-runs updateWirePositions on undo/redo so wire
endpoints follow the component back/forward.
- setComponents and setWires (project-load / clear paths) now call
clearHistory inline — leaving stale commands pointing at IDs that no
longer exist would crash on undo.
Why custom Command pattern over zundo / travels:
- The store has 30+ ephemeral fields (simulator instances, serialOutput
growing byte-by-byte, hexEpoch counter, wireInProgress that ticks 60×/s
on drag). Snapshot/diff middleware would either burn memory tracking
them or need a fragile partialize allow-list.
- Per-op descriptions ("Add LED", "Move resistor") for tooltips come for
free with this approach; zundo/travels would need to infer them.
Tests: 15/15 in src/__tests__/undo-redo.test.ts — covers cap-at-50,
redo-truncation, cascade undo of remove-component, move/rotate/property
round trips, bulk-setter clearing.
Raw mutators (addComponent / removeComponent / updateComponent / addWire /
removeWire / updateWire) are unchanged. UI handlers can keep using them
during live drags for preview frames without spamming history; the
record* actions are what drag-end, click-finish and agent tools should
call going forward.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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