From 08a23d87334c5dc7f284fe89bc39cc681f645320 Mon Sep 17 00:00:00 2001
From: Manav Rathi <manav@mrmr.io>
Date: Wed, 3 Jul 2024 10:22:11 +0530
Subject: [PATCH] Sketch

---
 web/packages/new/photos/services/ml/worker.ts | 84 ++++++++++++++++++-
 1 file changed, 80 insertions(+), 4 deletions(-)

diff --git a/web/packages/new/photos/services/ml/worker.ts b/web/packages/new/photos/services/ml/worker.ts
index 3fe960773a..a854bfa6e3 100644
--- a/web/packages/new/photos/services/ml/worker.ts
+++ b/web/packages/new/photos/services/ml/worker.ts
@@ -6,6 +6,25 @@ import log from "@/next/log";
 import { fileLogID } from "../../utils/file";
 import { pullFaceEmbeddings, putFaceIndex } from "./embedding";
 import { indexFaces } from "./index-face";
+import { wait } from "@/utils/promise";
+
+/**
+ * The MLWorker state machine.
+ *
+ *     ext. event      state           then state
+ *    ------------- --------------- --------------
+ *     sync         -> "pull"       -> "idle"
+ *     upload       -> "liveq"      -> "idle"
+ *     idleTimeout  -> "backfillq"  -> "idle"
+ *
+ * where
+ *
+ * -   "pull": pulling embeddings from remote
+ * -   "liveq": indexing items that are being uploaded
+ * -   "backfillq": indexing unindexed items otherwise
+ * -   "idle": in between state transitions
+ */
+type MLWorkerState = "idle" | "pull" | "liveq" | "backfillq";
 
 /**
  * Run operations related to machine learning (e.g. indexing) in a Web Worker.
@@ -15,16 +34,73 @@ import { indexFaces } from "./index-face";
  * tasks that might degrade interactivity.
  */
 export class MLWorker {
+    private state: MLWorkerState = "idle";
     private isSyncing = false;
+    private shouldSync = false;
+    private liveQ: EnteFile[] = [];
+    private idleTimeout: ReturnType<typeof setTimeout> | undefined;
 
     /**
      * Pull embeddings from remote, and start backfilling if needed.
+     *
+     * This function enqueues the pull and returns immediately without waiting
+     * for the pull to complete.
      */
-    async sync() {
-        if (this.isSyncing) return;
-        this.isSyncing = true;
+    sync() {
+        this.shouldSync = true;
+        if (this.idleTimeout) {
+            clearTimeout(this.idleTimeout);
+            this.idleTimeout = undefined;
+            this.tick();
+        } else {
+            // this.tick will get run when the current task finishes.
+        }
+    }
+
+    private tick() {
+        // Schedule a new macrotask (by using setTimeout) instead of scheduling
+        // a new microtask (by directly resolving the promise). This is likely
+        // unnecessary; I'm doing this as a partially out of superstition aiming
+        // to to give GC a chance to run if needed and generally ease execution
+        // / memory pressure.
+        const next = () => setTimeout(() => this.tick(), 0);
+
+        // If we've been asked to sync, do that irrespective of anything else.
+        if (this.shouldSync) {
+            this.shouldSync = false;
+            this.state = "pull";
+            void this.pull().then(next);
+            return;
+        }
+
+        // Otherwise see if there is something in the live queue.
+        if (this.liveQ.length > 0) {
+            this.state = "liveq";
+            void this.liveq().then(next);
+            return;
+        }
+
+        // // Otherwise check to see if there is something to backfill.
+        // const { indexableCount } = await indexedAndIndexableCounts();
+        // if (indexableCount > 0) {
+        //     this.state = "backfillq";
+        //     void this.liveq().then(() => this.tick());
+        //     return;
+        // }
+
+        // if (this.isSyncing) return;
+        // this.isSyncing = true;
+        // this.isSyncing = false;
+        // void this.next();
+    }
+
+    async pull() {
         await pullFaceEmbeddings();
-        this.isSyncing = false;
+    }
+
+    async liveq() {
+        console.log("liveq");
+        await wait(0);
     }
 }