chore: global sync per minute safety limit (#2765)

packages/snjs/lib/Services/Sync/SyncFrequencyGuard.ts

@@ -0,0 +1,40 @@
+import { SyncFrequencyGuardInterface } from './SyncFrequencyGuardInterface'
+
+export class SyncFrequencyGuard implements SyncFrequencyGuardInterface {
+  private callsPerMinuteMap: Map<string, number>
+
+  constructor(private syncCallsThresholdPerMinute: number) {
+    this.callsPerMinuteMap = new Map<string, number>()
+  }
+
+  isSyncCallsThresholdReachedThisMinute(): boolean {
+    const stringDateToTheMinute = this.getCallsPerMinuteKey()
+    const persistedCallsCount = this.callsPerMinuteMap.get(stringDateToTheMinute) || 0
+
+    return persistedCallsCount >= this.syncCallsThresholdPerMinute
+  }
+
+  incrementCallsPerMinute(): void {
+    const stringDateToTheMinute = this.getCallsPerMinuteKey()
+    const persistedCallsCount = this.callsPerMinuteMap.get(stringDateToTheMinute)
+    const newMinuteStarted = persistedCallsCount === undefined
+
+    if (newMinuteStarted) {
+      this.clear()
+
+      this.callsPerMinuteMap.set(stringDateToTheMinute, 1)
+    } else {
+      this.callsPerMinuteMap.set(stringDateToTheMinute, persistedCallsCount + 1)
+    }
+  }
+
+  clear(): void {
+    this.callsPerMinuteMap.clear()
+  }
+
+  private getCallsPerMinuteKey(): string {
+    const now = new Date()
+
+    return `${now.getFullYear()}-${now.getMonth()}-${now.getDate()}T${now.getHours()}:${now.getMinutes()}`
+  }
+}