From bb8a71326a85a3d70bad36a35d300c614d8e8b7f Mon Sep 17 00:00:00 2001
From: Fuwn <contact@fuwn.net>
Date: Tue, 3 Mar 2026 08:57:37 -0800
Subject: chore(effect): add v4 cookie decode foundation and tests

---
 src/lib/Effect/authCookie.ts | 45 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 src/lib/Effect/authCookie.ts

(limited to 'src/lib/Effect/authCookie.ts')

diff --git a/src/lib/Effect/authCookie.ts b/src/lib/Effect/authCookie.ts
new file mode 100644
index 00000000..e716f5e9
--- /dev/null
+++ b/src/lib/Effect/authCookie.ts
@@ -0,0 +1,45 @@
+import type { AniListAuthorisation } from "$lib/Data/AniList/identity";
+import { Effect, Result, Schema } from "effect";
+
+const UserCookieSchema = Schema.Struct({
+	token_type: Schema.String,
+	expires_in: Schema.Number,
+	access_token: Schema.String,
+	refresh_token: Schema.String,
+});
+
+export const decodeAuthCookieEffect = (cookie: string) =>
+	Effect.gen(function* () {
+		const parsedCookie = yield* Effect.try({
+			try: () => JSON.parse(cookie) as unknown,
+			catch: (cause) => new Error("Invalid user cookie JSON", { cause }),
+		});
+		const decodedCookie = yield* Effect.try({
+			try: () => Schema.decodeUnknownSync(UserCookieSchema)(parsedCookie),
+			catch: (cause) => new Error("Invalid user cookie payload", { cause }),
+		});
+
+		return {
+			tokenType: decodedCookie.token_type,
+			expiresIn: decodedCookie.expires_in,
+			accessToken: decodedCookie.access_token,
+			refreshToken: decodedCookie.refresh_token,
+		} as AniListAuthorisation;
+	});
+
+export const decodeAuthCookieEither = (cookie: string) =>
+	Result.try({
+		try: () => Effect.runSync(decodeAuthCookieEffect(cookie)),
+		catch: (cause) =>
+			cause instanceof Error
+				? cause
+				: new Error("Failed to decode user cookie", { cause }),
+	});
+
+export const decodeAuthCookieOrThrow = (
+	cookie: string,
+): AniListAuthorisation => {
+	const decoded = decodeAuthCookieEither(cookie);
+
+	return Result.getOrThrow(decoded);
+};
-- 
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