🎸 feat|Token|Wrap Token Layer to access undo history

When history is added, add information on token movement.
When history is deleted, revert to prior movement.

scripts/TokenLayer.js

@@ -0,0 +1,64 @@
+/* globals
+canvas,
+foundry
+*/
+/* eslint no-unused-vars: ["error", { "argsIgnorePattern": "^_" }] */
+
+import { MODULE_ID } from "./const.js";
+
+// Patches for the TokenLayer class
+export const PATCHES = {};
+PATCHES.MOVEMENT_TRACKING = {};
+
+// ----- NOTE: Wraps ----- //
+
+/**
+ * Wrap TokenLayer.prototype.storeHistory
+ * Add token movement data if the token moved so combat move history can be undone.
+ * @param {string} type   The event type (create, update, delete)
+ * @param {Object[]} data   The object data
+ */
+function storeHistory(wrapped, type, data) {
+  wrapped(type, data);
+  if ( type === "create" ) return;
+  data = data.filter(d => Object.keys(d).length > 1); // Filter entries without changes
+  if ( !data.length ) return;
+  const addedObj = this.history.at(-1);
+  const tokenMap = new Map(canvas.tokens.placeables.map(token => [token.id, token]));
+  for ( const datum of data ) {
+    addedObj[MODULE_ID] ??= {};
+    const token = tokenMap.get(datum._id);
+    if ( !token ) continue;
+
+    // Copy the current move data.
+    token._combatMoveData ??= new Map();
+    const lastMoveDistance = token._lastMoveDistance ?? 0;
+    const combatMoveData = foundry.utils.duplicate([...token._combatMoveData.entries()]);
+    addedObj[MODULE_ID][datum._id] = { lastMoveDistance, combatMoveData };
+  }
+}
+
+/**
+ * Wrap TokenLayer.prototype.undoHistory
+ * Reset the tokens' movement data to the previous history.
+ * @returns {Promise<Document[]>}     An array of documents which were modified by the undo operation
+ */
+async function undoHistory(wrapped) {
+  const event = this.history.at(-1);
+  const res = await wrapped();
+  if ( !event || event.type === "create" ) return res; // Create would be undone with deletion, which we can ignore.
+
+  // If deletion event, a new token would be created upon undo. Update with its previous event movement data.
+  // If update event, update with previous event movement data.
+  if ( !event[MODULE_ID] ) return res;
+  const tokenMap = new Map(canvas.tokens.placeables.map(token => [token.id, token]));
+  for ( const [id, { lastMoveDistance, combatMoveData }] of Object.entries(event[MODULE_ID]) ) {
+    const token = tokenMap.get(id);
+    if ( !token ) continue;
+    token._lastMoveDistance = lastMoveDistance;
+    token._combatMoveData = new Map(combatMoveData);
+  }
+  return res;
+}
+
+PATCHES.MOVEMENT_TRACKING.WRAPS = { storeHistory, undoHistory };

scripts/patching.js

@@ -18,6 +18,7 @@ import { PATCHES as PATCHES_TokenPF } from "./pathfinding/Token.js";
 
 // Movement tracking
 import { PATCHES as PATCHES_TokenHUD } from "./token_hud.js";
+import { PATCHES as PATCHES_TokenLayer } from "./TokenLayer.js";
 
 // Settings
 import { PATCHES as PATCHES_ClientSettings } from "./ModuleSettingsAbstract.js";
@@ -31,6 +32,7 @@ const PATCHES = {
   DrawingConfig: PATCHES_DrawingConfig,
   Ruler: PATCHES_Ruler,
   Token: mergeObject(mergeObject(PATCHES_Token, PATCHES_TokenPF), PATCHES_TokenHUD),
+  TokenLayer: PATCHES_TokenLayer,
   Wall: PATCHES_Wall
 };