feat(webui): unread-cursor helpers for the error-log bell

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/errorLogUnread.test.ts

@@ -0,0 +1,68 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  LAST_SEEN_STORAGE_KEY,
+  countUnread,
+  formatBadgeCount,
+  latestLogId,
+  readLastSeenId,
+  writeLastSeenId,
+} from "./errorLogUnread";
+
+function fakeStorage(initial: Record<string, string> = {}) {
+  const map = new Map(Object.entries(initial));
+  return {
+    getItem: (key: string) => map.get(key) ?? null,
+    setItem: (key: string, value: string) => {
+      map.set(key, value);
+    },
+    map,
+  };
+}
+
+describe("errorLogUnread", () => {
+  it("latestLogId returns the max id, 0 for empty", () => {
+    expect(latestLogId([])).toBe(0);
+    expect(latestLogId([{ id: 3 }, { id: 9 }, { id: 5 }])).toBe(9);
+  });
+
+  it("countUnread counts entries newer than the cursor", () => {
+    const logs = [{ id: 10 }, { id: 8 }, { id: 4 }];
+    expect(countUnread(logs, 0)).toBe(3);
+    expect(countUnread(logs, 8)).toBe(1);
+    expect(countUnread(logs, 10)).toBe(0);
+  });
+
+  it("formatBadgeCount caps at 99+ and hides zero", () => {
+    expect(formatBadgeCount(0)).toBe("");
+    expect(formatBadgeCount(7)).toBe("7");
+    expect(formatBadgeCount(99)).toBe("99");
+    expect(formatBadgeCount(150)).toBe("99+");
+  });
+
+  it("readLastSeenId returns 0 for null storage, missing, or corrupt values", () => {
+    expect(readLastSeenId(null)).toBe(0);
+    expect(readLastSeenId(fakeStorage())).toBe(0);
+    expect(
+      readLastSeenId(fakeStorage({ [LAST_SEEN_STORAGE_KEY]: "abc" }))
+    ).toBe(0);
+    expect(
+      readLastSeenId(fakeStorage({ [LAST_SEEN_STORAGE_KEY]: "-5" }))
+    ).toBe(0);
+  });
+
+  it("writeLastSeenId round-trips through storage", () => {
+    const storage = fakeStorage();
+    writeLastSeenId(storage, 42);
+    expect(readLastSeenId(storage)).toBe(42);
+  });
+
+  it("writeLastSeenId swallows storage failures", () => {
+    const throwing = {
+      setItem: () => {
+        throw new Error("quota");
+      },
+    };
+    expect(() => writeLastSeenId(throwing, 1)).not.toThrow();
+  });
+});

src/lib/errorLogUnread.ts

@@ -0,0 +1,55 @@
+/** Unread-badge state for the error-log bell. The server assigns each entry a
+ * monotonically increasing id, so a single "last seen id" cursor is enough;
+ * the cursor lives in localStorage (per browser, per user is unnecessary
+ * because ids are global and monotonic). */
+
+export const LAST_SEEN_STORAGE_KEY = "evoscientist.errorLogs.lastSeenId";
+
+const BADGE_CAP = 99;
+
+export function latestLogId(logs: ReadonlyArray<{ id: number }>): number {
+  let max = 0;
+  for (const log of logs) {
+    if (log.id > max) max = log.id;
+  }
+  return max;
+}
+
+export function countUnread(
+  logs: ReadonlyArray<{ id: number }>,
+  lastSeenId: number
+): number {
+  let count = 0;
+  for (const log of logs) {
+    if (log.id > lastSeenId) count += 1;
+  }
+  return count;
+}
+
+export function formatBadgeCount(count: number): string {
+  if (count <= 0) return "";
+  return count > BADGE_CAP ? `${BADGE_CAP}+` : String(count);
+}
+
+export function readLastSeenId(
+  storage: Pick<Storage, "getItem"> | null
+): number {
+  if (!storage) return 0;
+  const raw = storage.getItem(LAST_SEEN_STORAGE_KEY);
+  if (raw === null) return 0;
+  const value = Number(raw);
+  if (!Number.isInteger(value) || value < 0) return 0;
+  return value;
+}
+
+export function writeLastSeenId(
+  storage: Pick<Storage, "setItem"> | null,
+  id: number
+): void {
+  if (!storage) return;
+  try {
+    storage.setItem(LAST_SEEN_STORAGE_KEY, String(id));
+  } catch {
+    // Private-mode quota errors must not break the bell.
+  }
+}