fix(match): prevent cached airing injection mutation regressions

4 files changed, 101 insertions, 30 deletions

diff --git a/src/lib/List/Anime/DueAnimeList.svelte b/src/lib/List/Anime/DueAnimeList.svelte
index 4da6836f..e170a81e 100644
--- a/src/lib/List/Anime/DueAnimeList.svelte
+++ b/src/lib/List/Anime/DueAnimeList.svelte
@@ -93,11 +93,17 @@ const cleanMedia = (
 			// Outdated media
 			hasDueEpisodes(media),
 		)
-		.map((media: Media) => {
-			if (hasNoAiredEpisodes(media)) media.nextAiringEpisode = { episode: -1 };
-
-			return media;
-		});
+		.map((media: Media) =>
+			hasNoAiredEpisodes(media)
+				? {
+						...media,
+						nextAiringEpisode: {
+							...(media.nextAiringEpisode || { episode: 0 }),
+							episode: -1,
+						},
+					}
+				: media,
+		);
 
 	if (!displayUnresolved)
 		dueAnime = dueAnime.filter(
diff --git a/src/lib/List/Anime/UpcomingAnimeList.svelte b/src/lib/List/Anime/UpcomingAnimeList.svelte
index 2dd69a68..4bd7a287 100644
--- a/src/lib/List/Anime/UpcomingAnimeList.svelte
+++ b/src/lib/List/Anime/UpcomingAnimeList.svelte
@@ -60,16 +60,19 @@ const cleanMedia = (
 						? media.mediaListEntry?.status === "PLANNING"
 						: false) || !hasDueEpisodes(media),
 			)
-			.map((media: Media) => {
+			.map((media: Media) =>
 				// Adjust for planned anime
-				if (
-					($settings.displayPlannedAnime ? media.episodes !== 1 : true) &&
-					hasNoAiredEpisodes(media)
-				)
-					media.nextAiringEpisode = { episode: -1 };
-
-				return media;
-			});
+				($settings.displayPlannedAnime ? media.episodes !== 1 : true) &&
+				hasNoAiredEpisodes(media)
+					? {
+							...media,
+							nextAiringEpisode: {
+								...(media.nextAiringEpisode || { episode: 0 }),
+								episode: -1,
+							},
+						}
+					: media,
+			);
 	let upcomingAnime = filterAnime(
 		plannedOnly ? "NOT_YET_RELEASED" : "RELEASING",
 	);
diff --git a/src/lib/Media/Anime/Airing/Subtitled/match.ts b/src/lib/Media/Anime/Airing/Subtitled/match.ts
index d3950948..0c91f3ac 100644
--- a/src/lib/Media/Anime/Airing/Subtitled/match.ts
+++ b/src/lib/Media/Anime/Airing/Subtitled/match.ts
@@ -171,6 +171,17 @@ const scheduleIndexCache = new WeakMap<SubsPlease, ScheduleIndex>();
 const closestMatchCache = new Map<string, Time | null>();
 const injectAiringTimeCache = new Map<string, Media>();
 
+const hashString = (input: string): string => {
+	let hash = 2166136261;
+
+	for (let index = 0; index < input.length; index += 1) {
+		hash ^= input.charCodeAt(index);
+		hash = Math.imul(hash, 16777619);
+	}
+
+	return (hash >>> 0).toString(36);
+};
+
 const setBoundedCacheValue = <T>(
 	cache: Map<string, T>,
 	key: string,
@@ -188,6 +199,12 @@ const animeTitleFingerprint = (anime: Media) =>
 		.map(preprocessTitle)
 		.join("|");
 
+const localTimeZone = () =>
+	Intl.DateTimeFormat().resolvedOptions().timeZone || "local";
+
+const airingDayOf = (airingAt: number | undefined) =>
+	new Date((airingAt || 0) * 1000).toLocaleString("en-US", { weekday: "long" });
+
 const fallbackClosestMatch = (
 	dayIndex: DayScheduleIndex,
 	searchTitles: string[],
@@ -230,14 +247,8 @@ const buildScheduleIndex = (subsPlease: SubsPlease): ScheduleIndex => {
 
 	for (const [day, value] of Object.entries(subsPlease.schedule)) {
 		const flattenedValue = Array.isArray(value) ? value.flat() : [];
-		const firstEntry = flattenedValue[0];
-		const lastEntry = flattenedValue[flattenedValue.length - 1];
 
-		versionParts.push(
-			`${day}:${flattenedValue.length}:${firstEntry?.title || ""}:${firstEntry?.time || ""}:${
-				lastEntry?.title || ""
-			}:${lastEntry?.time || ""}`,
-		);
+		versionParts.push(day);
 
 		const dayIndex: DayScheduleIndex = {
 			entries: [],
@@ -251,6 +262,9 @@ const buildScheduleIndex = (subsPlease: SubsPlease): ScheduleIndex => {
 				time: scheduleTime.time,
 				day,
 			};
+
+			versionParts.push(`${day}\u001f${time.title}\u001f${time.time}`);
+
 			const normalizedTitle = preprocessTitle(time.title);
 			const tokens = normalizedTitle.split(" ").filter(isMeaningfulToken);
 			const entryIndex = dayIndex.entries.length;
@@ -271,7 +285,7 @@ const buildScheduleIndex = (subsPlease: SubsPlease): ScheduleIndex => {
 
 	return {
 		byDay,
-		version: `${subsPlease.tz}:${versionParts.join("|")}`,
+		version: hashString(`${subsPlease.tz}\u001e${versionParts.join("\u001d")}`),
 	};
 };
 
@@ -290,16 +304,13 @@ export const findClosestMatch = (
 		return null;
 	}
 
+	const airingDay = airingDayOf(anime.nextAiringEpisode?.airingAt);
 	const cacheKey = `${anime.id}:${anime.nextAiringEpisode?.airingAt || 0}:${animeTitleFingerprint(
 		anime,
-	)}:${scheduleIndex.version}`;
+	)}:${airingDay}:${localTimeZone()}:${scheduleIndex.version}`;
 	const cached = closestMatchCache.get(cacheKey);
 
 	if (cached !== undefined) return cached;
-
-	const airingDay = new Date(
-		(anime.nextAiringEpisode?.airingAt || 0) * 1000,
-	).toLocaleString("en-US", { weekday: "long" });
 	const dayIndex = scheduleIndex.byDay.get(airingDay);
 
 	if (!dayIndex || dayIndex.entries.length === 0) {
@@ -526,6 +537,14 @@ const buildInjectAiringTimeCacheKey = (
 		animeTitleFingerprint(anime),
 	].join(":");
 
+const cloneInjectedMedia = (media: Media): Media =>
+	({
+		...media,
+		nextAiringEpisode: media.nextAiringEpisode
+			? { ...media.nextAiringEpisode }
+			: undefined,
+	}) as Media;
+
 export const injectAiringTime = (
 	anime: Media,
 	subsPlease: SubsPlease | null,
@@ -543,7 +562,7 @@ export const injectAiringTime = (
 	);
 	const cached = injectAiringTimeCache.get(cacheKey);
 
-	if (cached) return cached;
+	if (cached) return cloneInjectedMedia(cached);
 
 	const airingAt = anime.nextAiringEpisode?.airingAt;
 	const now = new Date();
@@ -604,12 +623,14 @@ export const injectAiringTime = (
 		},
 	} as Media;
 
+	const cachedValue = cloneInjectedMedia(injected);
+
 	setBoundedCacheValue(
 		injectAiringTimeCache,
 		cacheKey,
-		injected,
+		cachedValue,
 		MAX_INJECT_CACHE_ENTRIES,
 	);
 
-	return injected;
+	return cloneInjectedMedia(cachedValue);
 };
diff --git a/src/lib/Media/Anime/Airing/classify.test.ts b/src/lib/Media/Anime/Airing/classify.test.ts
index 6af36b77..fb7f2c8f 100644
--- a/src/lib/Media/Anime/Airing/classify.test.ts
+++ b/src/lib/Media/Anime/Airing/classify.test.ts
@@ -156,3 +156,44 @@ describe("native countdown toggle parity", () => {
 		});
 	}
 });
+
+describe("injectAiringTime cache safety", () => {
+	it("does not let caller mutation poison cached injected media", () => {
+		const media = baseMedia(444444);
+		const subtitledAiringAt = Math.floor(Date.now() / 1000) + 24 * 60 * 60;
+		const nativeAiringAt = subtitledAiringAt + 12 * 60 * 60;
+		const nativeAiringDate = new Date(nativeAiringAt * 1000);
+		const airingDay = nativeAiringDate.toLocaleString("en-US", {
+			weekday: "long",
+		});
+		const subsPlease = {
+			tz: "America/Los_Angeles",
+			schedule: {
+				[airingDay]: [
+					{
+						title: media.title.romaji,
+						page: "",
+						image_url: "",
+						time: toScheduleTime(subtitledAiringAt),
+					},
+				],
+			},
+		} as unknown as SubsPlease;
+
+		media.nextAiringEpisode = {
+			episode: 8,
+			airingAt: nativeAiringAt,
+		};
+		settings.setKey("displayNativeCountdown", false);
+
+		const first = injectAiringTime(media, subsPlease);
+
+		first.nextAiringEpisode = { episode: -1 };
+
+		const second = injectAiringTime(media, subsPlease);
+
+		expect(second.nextAiringEpisode?.episode).not.toBe(-1);
+		expect(typeof second.nextAiringEpisode?.airingAt).toBe("number");
+		expect(typeof second.nextAiringEpisode?.nativeAiringAt).toBe("number");
+	});
+});