feat: add SSE parser and in-flight request tracker

tests/inflight-tracker.test.ts

@@ -0,0 +1,50 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { InflightTracker, type FeedEvent } from "../src/lib/inflight-tracker";
+
+test("snapshot rebuilds counts for all in-flight requests", () => {
+  const tracker = new InflightTracker();
+  tracker.apply({
+    type: "inflight",
+    operation: "snapshot",
+    requests: [
+      { model: "A", id: "1" },
+      { model: "A", id: "2" },
+      { model: "B", id: "3" },
+    ],
+  });
+  assert.equal(tracker.count("A"), 2);
+  assert.equal(tracker.count("B"), 1);
+  assert.equal(tracker.count("C"), 0);
+});
+
+test("add and remove adjust per-model counts", () => {
+  const tracker = new InflightTracker();
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }] });
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "2" }] });
+  assert.equal(tracker.count("A"), 2);
+  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "1" }] });
+  assert.equal(tracker.count("A"), 1);
+  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "2" }] });
+  assert.equal(tracker.count("A"), 0);
+  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "9" }] });
+  assert.equal(tracker.count("A"), 0);
+});
+
+test("modelStatus normalizes states", () => {
+  const tracker = new InflightTracker();
+  tracker.apply({
+    type: "modelStatus",
+    models: [
+      { id: "A", state: "ready" },
+      { id: "B", state: "loading" },
+      { id: "C", state: "stopped" },
+      { id: "D", state: "weird" },
+    ],
+  });
+  assert.equal(tracker.state("A"), "ready");
+  assert.equal(tracker.state("B"), "loading");
+  assert.equal(tracker.state("C"), "stopped");
+  assert.equal(tracker.state("D"), "stopped");
+  assert.equal(tracker.state("missing"), undefined);
+});

tests/sse.test.ts

@@ -0,0 +1,24 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { parseSse } from "../src/lib/sse";
+
+test("parseSse extracts event + data blocks separated by blank lines", () => {
+  const { messages, rest } = parseSse('event:message\ndata:{"a":1}\n\nevent:message\ndata:hello\n\n');
+  assert.equal(rest, "");
+  assert.equal(messages.length, 2);
+  assert.equal(messages[0].event, "message");
+  assert.equal(messages[0].data, '{"a":1}');
+  assert.equal(messages[1].data, "hello");
+});
+
+test("parseSse keeps a trailing partial event in rest", () => {
+  const { messages, rest } = parseSse("event:message\ndata:par");
+  assert.equal(messages.length, 0);
+  assert.equal(rest, "event:message\ndata:par");
+});
+
+test("parseSse joins multi-line data fields with newline", () => {
+  const { messages } = parseSse("data:line1\ndata:line2\n\n");
+  assert.equal(messages.length, 1);
+  assert.equal(messages[0].data, "line1\nline2");
+});