api log implementation

src/services/spaced_update.js

@@ -0,0 +1,67 @@
+class SpacedUpdate {
+    constructor(updater, updateInterval = 1000) {
+        this.updater = updater;
+        this.lastUpdated = Date.now();
+        this.changed = false;
+        this.updateInterval = updateInterval;
+    }
+
+    scheduleUpdate() {
+        if (!this.changeForbidden) {
+            this.changed = true;
+            setTimeout(() => this.triggerUpdate());
+        }
+    }
+
+    async updateNowIfNecessary() {
+        if (this.changed) {
+            this.changed = false; // optimistic...
+
+            try {
+                await this.updater();
+            }
+            catch (e) {
+                this.changed = true;
+
+                throw e;
+            }
+        }
+    }
+
+    isAllSavedAndTriggerUpdate() {
+        const allSaved = !this.changed;
+
+        this.updateNowIfNecessary();
+
+        return allSaved;
+    }
+
+    triggerUpdate() {
+        if (!this.changed) {
+            return;
+        }
+
+        if (Date.now() - this.lastUpdated > this.updateInterval) {
+            this.updater();
+            this.lastUpdated = Date.now();
+            this.changed = false;
+        }
+        else {
+            // update not triggered but changes are still pending so we need to schedule another check
+            this.scheduleUpdate();
+        }
+    }
+
+    async allowUpdateWithoutChange(callback) {
+        this.changeForbidden = true;
+
+        try {
+            await callback();
+        }
+        finally {
+            this.changeForbidden = false;
+        }
+    }
+}
+
+module.exports = SpacedUpdate;