feat: Add identity URL validation utilities

src/lib/idURL.ts

@@ -0,0 +1,84 @@
+import {
+	BlahIdentity,
+	blahIdentityDescriptionSchema,
+	type BlahIdentityDescription
+} from '@blah-im/core/identity';
+
+export function idURLToUsername(idURL: string): string {
+	const url = new URL(idURL);
+	return url.host;
+}
+
+export type IDURLValidity =
+	| { valid: true }
+	| ({ valid: false } & (
+			| {
+					reason:
+						| 'invalid-url'
+						| 'profile-invalid'
+						| 'identity-mismatch'
+						| 'identity-missing-idurl';
+			  }
+			| {
+					reason: 'identity-request-failed';
+					status?: number;
+					errorText?: string;
+			  }
+	  ));
+export async function validateIDURL(url: string, identity: BlahIdentity): Promise<IDURLValidity> {
+	const idURL = URL.parse(url);
+	if (
+		!idURL ||
+		idURL.protocol !== 'https:' ||
+		idURL.pathname !== '/' ||
+		idURL.search ||
+		idURL.username ||
+		idURL.password
+	)
+		return { valid: false, reason: 'invalid-url' };
+
+	const profileFileURL = (() => {
+		let url = idURL;
+		url.pathname = '/.well-known/blah/identity.json';
+		return url.toString();
+	})();
+
+	try {
+		const response = await fetch(profileFileURL, {
+			method: 'GET',
+			headers: { Accept: 'application/json' }
+		});
+		if (!response.ok || response.status !== 200) {
+			return {
+				valid: false,
+				reason: 'identity-request-failed',
+				status: response.status,
+				errorText: await response.text()
+			};
+		}
+
+		const identityDescription = await response.json();
+		const { data: parsedIdentityDescription } =
+			blahIdentityDescriptionSchema.safeParse(identityDescription);
+		if (!parsedIdentityDescription) return { valid: false, reason: 'profile-invalid' };
+
+		if (parsedIdentityDescription.id_key !== identity.idPublicKey.id)
+			return { valid: false, reason: 'identity-mismatch' };
+
+		if (parsedIdentityDescription.profile.signee.payload.id_urls.findIndex((x) => x === url) === -1)
+			return { valid: false, reason: 'identity-missing-idurl' };
+
+		const identityFromDescription =
+			await BlahIdentity.fromIdentityDescription(parsedIdentityDescription);
+		if (!identityFromDescription.profileSigValid)
+			return { valid: false, reason: 'profile-invalid' };
+
+		return { valid: true };
+	} catch (e) {
+		return {
+			valid: false,
+			reason: 'identity-request-failed',
+			errorText: (e as Error).message
+		};
+	}
+}