Undo, Redo 기능 추가

src/renderer/history.js

@@ -0,0 +1,33 @@
+const MAX = 50;
+let _stack  = [];  // each entry: { files: [], affectedPaths: Set | null }
+let _cursor = -1;
+
+export function push(files, affectedPaths = null) {
+  _stack = _stack.slice(0, _cursor + 1);
+  _stack.push({ files: [...files], affectedPaths: affectedPaths ? new Set(affectedPaths) : null });
+  if (_stack.length > MAX) _stack.shift();
+  _cursor = _stack.length - 1;
+}
+
+// Returns { files, affectedPaths } where affectedPaths are from the entry being undone
+export function undo() {
+  if (!canUndo()) return null;
+  const affectedPaths = _stack[_cursor].affectedPaths;
+  --_cursor;
+  return { files: [..._stack[_cursor].files], affectedPaths };
+}
+
+// Returns { files, affectedPaths } from the entry being redone
+export function redo() {
+  if (!canRedo()) return null;
+  ++_cursor;
+  return { files: [..._stack[_cursor].files], affectedPaths: _stack[_cursor].affectedPaths };
+}
+
+export function canUndo() { return _cursor > 0; }
+export function canRedo() { return _cursor < _stack.length - 1; }
+
+export function reset() {
+  _stack  = [];
+  _cursor = -1;
+}