perf: coalesce indicator recalculations on data updates

src/Store.ts

@@ -316,6 +316,13 @@ export default class StoreImp implements Store {
    */
   private readonly _taskScheduler: TaskScheduler
 
+  /**
+   * Indicators waiting for a coalesced recalculation flush
+   */
+  private readonly _pendingCalcIndicators = new Map<string, IndicatorImp>()
+
+  private _calcFlushScheduled = false
+
   /**
    * Overlay
    */
@@ -1343,11 +1350,31 @@ export default class StoreImp implements Store {
     let indicators: IndicatorImp[] = []
     indicators = indicators.concat(data)
     if (indicators.length > 0) {
-      const tasks: Record<string, Promise<unknown>> = {}
       indicators.forEach((indicator) => {
-        tasks[indicator.id] = indicator.calcImp(this._dataList)
+        this._pendingCalcIndicators.set(indicator.id, indicator)
       })
-      this._taskScheduler.add(tasks)
+      if (!this._calcFlushScheduled) {
+        this._calcFlushScheduled = true
+        // `calc` runs synchronously inside `calcImp`, so a burst of synchronous
+        // data updates (e.g. a websocket catch-up) would recalculate every
+        // indicator over the whole history once per update, in one blocking
+        // task. Defer the recalculation to a microtask: `calc` is a pure
+        // function of the current data list, so one flush after the last
+        // update of the tick produces the same result as recalculating after
+        // each of them.
+        void Promise.resolve().then(() => {
+          this._calcFlushScheduled = false
+          if (this._pendingCalcIndicators.size === 0) {
+            return
+          }
+          const tasks: Record<string, Promise<unknown>> = {}
+          this._pendingCalcIndicators.forEach((indicator) => {
+            tasks[indicator.id] = indicator.calcImp(this._dataList)
+          })
+          this._pendingCalcIndicators.clear()
+          this._taskScheduler.add(tasks)
+        })
+      }
     }
   }
 
@@ -1798,6 +1825,8 @@ export default class StoreImp implements Store {
   destroy(): void {
     this._clearData()
     this._clearLastPriceMarkExtendTextUpdateTimer()
+    this._calcFlushScheduled = false
+    this._pendingCalcIndicators.clear()
     this._taskScheduler.clear()
     this._overlays.clear()
     this._indicators.clear()