Squash Odysseus development history

static/js/editor/history-budget.js

@@ -0,0 +1,39 @@
+/** Adaptive bounds for raw ImageData history snapshots. */
+
+export const MAX_HISTORY_ENTRIES = 30;
+export const MAX_HISTORY_BYTES = 192 * 1024 * 1024;
+
+function imageDataBytes(imageData) {
+  return Number(imageData?.data?.byteLength || imageData?.data?.length || 0);
+}
+
+export function snapshotByteSize(snapshot) {
+  if (!snapshot) return 0;
+  if (Number.isFinite(snapshot._bytes)) return snapshot._bytes;
+  let bytes = imageDataBytes(snapshot.wand?.imageData);
+  bytes += imageDataBytes(snapshot.lastSelection?.imageData);
+  for (const selection of snapshot.savedSelections || []) bytes += imageDataBytes(selection.imageData);
+  for (const group of snapshot.layerGroups || []) {
+    for (const mask of group.masks || []) bytes += imageDataBytes(mask.imageData);
+  }
+  for (const layer of snapshot.layers || []) {
+    bytes += imageDataBytes(layer.imageData);
+    bytes += imageDataBytes(layer.placed?.sourceImageData);
+    for (const mask of layer.masks || []) bytes += imageDataBytes(mask.imageData);
+  }
+  return bytes;
+}
+
+export function trimHistoryStack(
+  stack,
+  maxEntries = MAX_HISTORY_ENTRIES,
+  maxBytes = MAX_HISTORY_BYTES,
+) {
+  while (stack.length > maxEntries) stack.shift();
+  let bytes = stack.reduce((total, snapshot) => total + snapshotByteSize(snapshot), 0);
+  // Keep the newest state even when one snapshot alone exceeds the budget.
+  while (stack.length > 1 && bytes > maxBytes) {
+    bytes -= snapshotByteSize(stack.shift());
+  }
+  return bytes;
+}