Add rest dice tracking for the Sync actors

module/documents/Actor/Sync.mjs

@@ -0,0 +1,60 @@
+import { syncMilestones, syncDice } from "../../config.mjs";
+
+/** @this {Actor} */
+async function useRestDie() {
+	let addToSync = await (new Roll(syncDice)).evaluate();
+	await addToSync.toMessage({
+		speaker: ChatMessage.getSpeaker({ actor: this.actor }),
+		flavor: `Sync Restoration`,
+	});
+	this.update({
+		"system.rest_dice": this.system.rest_dice - 1,
+		"system.value": this.system.value + addToSync.total,
+	});
+};
+
+/** @this {Actor} */
+async function _preUpdate(data, options) {
+	if (options.diff) {
+		if (data.system?.value != null) {
+			let currentSync = this.system.value;
+			let newSync = data.system.value;
+
+			let minSync = Math.min(currentSync, newSync);
+			let maxSync = Math.max(currentSync, newSync);
+			let milestones = syncMilestones.filter(
+				m => minSync < m.value && m.value <= maxSync
+			);
+
+			if (milestones.length > 0) data.system.rest_dice ??= this.system.rest_dice;
+
+			for (const milestone of milestones) {
+				// Damage
+				if (newSync < currentSync) {
+					if (!this.system.milestones_hit.has(milestone.value)) {
+						data.system.rest_dice += 1;
+						this.system.milestones_hit.add(milestone.value);
+					};
+				}
+
+				// Healing
+				else if (newSync > currentSync) {
+					if (
+						this.system.milestones_hit.has(milestone.value)
+						&& milestone.andReturn
+						&& milestone.value <= newSync
+					) {
+						this.system.milestones_hit.delete(milestone.value);
+					};
+				};
+			};
+
+			data.system.milestones_hit = [ ...this.system.milestones_hit ];
+		};
+	};
+};
+
+export default {
+	_preUpdate,
+	useRestDie,
+};