feat: parse both-year ranges and open-ended events

Honkai: Star Rail and Wuthering Waves state a year on each side of a range
("Aug. 14, 2026 - Aug. 24, 2026"), which the year-on-the-end parser cannot
read.

Both also publish genuinely open-ended events — "Jul. 24, 2026 - End of
4.6", "July 10, 2026 - Permanent". Those keep their real start and report no
end, rather than being dropped or given a guessed one.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

src/ingest/dates.ts

@@ -83,6 +83,52 @@ export function parseMonthDayRange(
   };
 }
 
+/**
+ * "Aug. 14, 2026 - Aug. 24, 2026" → both instants.
+ *
+ * Distinct from parseMonthDayRange, where the single stated year belongs to the
+ * end. Here both sides carry their own year, so nothing has to be inferred.
+ * Trailing prose after the range is ignored.
+ */
+export function parseFullRange(
+  input: string,
+): { start: ParsedInstant; end: ParsedInstant } | null {
+  const re =
+    /([A-Za-z]+)\.?\s+(\d{1,2}),\s*(\d{4})\s*[-–—]\s*([A-Za-z]+)\.?\s+(\d{1,2}),\s*(\d{4})/;
+  const m = re.exec(input);
+  if (!m) return null;
+
+  const startMonth = monthNumber(m[1] ?? "");
+  const endMonth = monthNumber(m[4] ?? "");
+  if (startMonth === null || endMonth === null) return null;
+
+  const startIso = iso(Number(m[3]), startMonth, Number(m[2]));
+  const endIso = iso(Number(m[6]), endMonth, Number(m[5]));
+  if (startIso === null || endIso === null) return null;
+
+  return {
+    start: { iso: startIso, precision: "day" },
+    end: { iso: endIso, precision: "day" },
+  };
+}
+
+/**
+ * A range whose start is a real date but whose end is not: "July 10, 2026 -
+ * Permanent", "Jul. 24, 2026 - End of 4.6", or a lone start date.
+ *
+ * Returns a null end rather than inventing one. These are common and correct —
+ * the source genuinely has not announced an end — and the UI renders them
+ * distinctly from an event ending far in the future.
+ *
+ * Deliberately the last parser tried, because it is the most permissive.
+ */
+export function parseOpenRange(
+  input: string,
+): { start: ParsedInstant; end: null } | null {
+  const start = parseMonthDayYear(input);
+  return start === null ? null : { start, end: null };
+}
+
 /**
  * "2021/01/16 04:00 - 2021/01/31 03:59" → both instants, exact precision.
  * Trailing prose after the range (e.g. "Currently Unavailable") is ignored.

test/dates.test.ts

@@ -1,7 +1,9 @@
 import { describe, expect, test } from "bun:test";
 import {
+  parseFullRange,
   parseMonthDayRange,
   parseMonthDayYear,
+  parseOpenRange,
   parseSlashDateTimeRange,
 } from "../src/ingest/dates.ts";
 
@@ -84,3 +86,44 @@ describe("parseSlashDateTimeRange", () => {
     expect(parseSlashDateTimeRange("Permanently Available")).toBeNull();
   });
 });
+
+describe("parseFullRange", () => {
+  test("reads a year from each side", () => {
+    expect(parseFullRange("Aug. 14, 2026 - Aug. 24, 2026")).toEqual({
+      start: { iso: "2026-08-14T00:00:00.000Z", precision: "day" },
+      end: { iso: "2026-08-24T00:00:00.000Z", precision: "day" },
+    });
+  });
+
+  test("ignores prose trailing the range", () => {
+    const r = parseFullRange(
+      "July 30, 2026 - August 13, 2026 Reach Union Level 8 to unlock",
+    );
+    expect(r?.end.iso).toBe("2026-08-13T00:00:00.000Z");
+  });
+
+  test("does not fire on a range with the year only at the end", () => {
+    // That shape belongs to parseMonthDayRange, which rolls the start year.
+    expect(parseFullRange("August 12 - September 21, 2026")).toBeNull();
+  });
+});
+
+describe("parseOpenRange", () => {
+  test("keeps a real start when the end is not a date", () => {
+    // "End of 4.6" and "Permanent" are honest unknowns, not parse failures.
+    for (const input of [
+      "Jul. 24, 2026 - End of 4.6",
+      "July 10, 2026 - Permanent",
+      "August 3, 2026",
+    ]) {
+      const r = parseOpenRange(input);
+      expect(r?.end).toBeNull();
+      expect(r?.start.iso.slice(0, 4)).toBe("2026");
+    }
+  });
+
+  test("returns null when there is no full date at all", () => {
+    expect(parseOpenRange("08/12 - 08/24")).toBeNull();
+    expect(parseOpenRange("Releases in Version 3.6")).toBeNull();
+  });
+});