Optimize explore data worker transfer with lightweight video objects

- Implements `toLightweightVideo` helper in `js/services/exploreDataService.js` to strip large fields (content, signatures, etc.) from video objects before sending to the worker.
- Updates `buildWatchHistoryTagCounts` and `buildTagIdf` to use lightweight objects.
- Adds `tests/services/exploreDataService.optimization.test.mjs` to verify correctness.
- Adds `benchmarks/worker_transfer_lightweight_bench.js` demonstrating ~40% improvement in transfer time.

Co-authored-by: PR0M3TH3AN <[email protected]>

tests/services/exploreDataService.optimization.test.mjs

@@ -0,0 +1,93 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { toLightweightVideo } from "../../js/services/exploreDataService.js";
+import { collectVideoTags } from "../../js/utils/videoTags.js";
+import { buildVideoAddressPointer } from "../../js/utils/videoPointer.js";
+
+test("exploreDataService optimization", async (t) => {
+  await t.test("toLightweightVideo extracts necessary fields", () => {
+    const fullVideo = {
+      id: "video-id",
+      kind: 30078,
+      pubkey: "pubkey-123",
+      content: "some long content",
+      sig: "signature",
+      created_at: 1234567890,
+      tags: [
+        ["t", "tag1"],
+        ["t", "tag2"],
+        ["p", "mention"],
+        ["d", "identifier"],
+        ["e", "reply"],
+      ],
+      nip71: {
+        hashtags: ["tag3"],
+        t: ["tag4"],
+      },
+      relays: ["wss://relay"],
+    };
+
+    const lightweight = toLightweightVideo(fullVideo);
+
+    assert.equal(lightweight.id, "video-id");
+    assert.equal(lightweight.kind, 30078);
+    assert.equal(lightweight.pubkey, "pubkey-123");
+    assert.deepEqual(lightweight.nip71, { hashtags: ["tag3"], t: ["tag4"] });
+
+    // Check tags filtering
+    assert.equal(lightweight.tags.length, 3);
+    assert.deepEqual(lightweight.tags, [
+      ["t", "tag1"],
+      ["t", "tag2"],
+      ["d", "identifier"],
+    ]);
+
+    // Check excluded fields
+    assert.equal(lightweight.content, undefined);
+    assert.equal(lightweight.sig, undefined);
+    assert.equal(lightweight.created_at, undefined);
+    assert.equal(lightweight.relays, undefined);
+  });
+
+  await t.test("collectVideoTags works with lightweight object", () => {
+    const lightweight = {
+      id: "video-id",
+      tags: [
+        ["t", "tag1"],
+        ["d", "identifier"],
+      ],
+      nip71: {
+        hashtags: ["tag2"],
+      },
+    };
+
+    const tags = collectVideoTags(lightweight);
+    // Should collect tag1 and tag2. tag2 from nip71.
+    // And d tag is NOT collected by collectVideoTags (it only collects hashtags).
+
+    assert.ok(tags.includes("tag1"));
+    assert.ok(tags.includes("tag2"));
+    assert.equal(tags.length, 2);
+  });
+
+  await t.test("buildVideoAddressPointer works with lightweight object", () => {
+    const lightweight = {
+      id: "video-id",
+      kind: 30078,
+      pubkey: "pubkey-123",
+      tags: [
+        ["t", "tag1"],
+        ["d", "identifier"],
+      ],
+    };
+
+    const pointer = buildVideoAddressPointer(lightweight);
+    assert.equal(pointer, "30078:pubkey-123:identifier");
+  });
+
+  await t.test("toLightweightVideo handles invalid input", () => {
+    assert.equal(toLightweightVideo(null), null);
+    assert.equal(toLightweightVideo(undefined), null);
+    assert.equal(toLightweightVideo("string"), null);
+  });
+});