refactor(effect): harden settings and media cache json parsing

3 files changed, 54 insertions, 1 deletions

diff --git a/src/lib/Data/AniList/media.ts b/src/lib/Data/AniList/media.ts
index 7a9fe810..f2a4aad6 100644
--- a/src/lib/Data/AniList/media.ts
+++ b/src/lib/Data/AniList/media.ts
@@ -1,4 +1,5 @@
 import type { AniListAuthorisation } from "$lib/Data/AniList/identity";
+import { parseJsonStringOrDefault } from "$lib/Effect/json";
 import type { UserIdentity } from "./identity";
 import anime from "$stores/anime";
 import manga from "$stores/manga";
@@ -271,7 +272,7 @@ export const mediaListCollection = async (
 	}
 
 	if (mediaCache !== undefined && mediaCache !== "")
-		return JSON.parse(mediaCache);
+		return parseJsonStringOrDefault<Media[]>(mediaCache, []);
 
 	const userIdResponse = await (
 		await fetch("https://graphql.anilist.co", {
diff --git a/src/lib/Effect/json.test.ts b/src/lib/Effect/json.test.ts
new file mode 100644
index 00000000..b315fe61
--- /dev/null
+++ b/src/lib/Effect/json.test.ts
@@ -0,0 +1,24 @@
+import { describe, expect, it } from "vitest";
+import {
+	parseJsonStringOrDefault,
+	parseJsonStringOrThrow,
+} from "$lib/Effect/json";
+
+describe("effect json parsing", () => {
+	it("parses valid json strings", () => {
+		expect(parseJsonStringOrThrow(`{"ok":true,"value":3}`)).toEqual({
+			ok: true,
+			value: 3,
+		});
+	});
+
+	it("throws for invalid json strings", () => {
+		expect(() => parseJsonStringOrThrow("{nope}")).toThrowError();
+	});
+
+	it("returns fallback for invalid json", () => {
+		expect(parseJsonStringOrDefault("{nope}", { ok: false })).toEqual({
+			ok: false,
+		});
+	});
+});
diff --git a/src/lib/Effect/json.ts b/src/lib/Effect/json.ts
new file mode 100644
index 00000000..b905cc41
--- /dev/null
+++ b/src/lib/Effect/json.ts
@@ -0,0 +1,28 @@
+import { Effect, Result } from "effect";
+
+export const parseJsonStringEffect = (value: string) =>
+	Effect.try({
+		try: () => JSON.parse(value) as unknown,
+		catch: (cause) => new Error("Invalid JSON payload", { cause }),
+	});
+
+export const parseJsonStringEither = (value: string) =>
+	Result.try({
+		try: () => Effect.runSync(parseJsonStringEffect(value)),
+		catch: (cause) =>
+			cause instanceof Error
+				? cause
+				: new Error("Failed to parse JSON payload", { cause }),
+	});
+
+export const parseJsonStringOrThrow = <T = unknown>(value: string): T =>
+	Result.getOrThrow(parseJsonStringEither(value)) as T;
+
+export const parseJsonStringOrDefault = <T>(value: string, fallback: T): T => {
+	const parsed = parseJsonStringEither(value);
+
+	return Result.match(parsed, {
+		onSuccess: (decoded) => decoded as T,
+		onFailure: () => fallback,
+	});
+};