feat(admin): add authenticated fetch helper

src/lib/server/admin/authenticated-fetch.ts

@@ -0,0 +1,83 @@
+import { error, redirect } from '@sveltejs/kit'
+import type { RequestEvent } from '@sveltejs/kit'
+import { getSessionUser } from '$lib/server/admin/session'
+
+type FetchInput = Parameters<typeof fetch>[0]
+
+export type AdminFetchOptions = RequestInit
+
+export interface AdminFetchJsonOptions extends AdminFetchOptions {
+	parse?: 'json' | 'text' | 'response'
+}
+
+function adminPassword(): string {
+	return process.env.ADMIN_PASSWORD ?? 'changeme'
+}
+
+function withAuthHeader(init: RequestInit = {}): RequestInit {
+	const headers = new Headers(init.headers ?? {})
+	if (!headers.has('Authorization')) {
+		const credentials = Buffer.from(`admin:${adminPassword()}`).toString('base64')
+		headers.set('Authorization', `Basic ${credentials}`)
+	}
+
+	return {
+		...init,
+		headers
+	}
+}
+
+export async function adminFetch(
+	event: RequestEvent,
+	input: FetchInput,
+	options: AdminFetchOptions = {}
+): Promise<Response> {
+	const user = getSessionUser(event.cookies)
+	if (!user) {
+		throw redirect(303, '/admin/login')
+	}
+
+	const init = withAuthHeader(options)
+	const response = await event.fetch(input, init)
+
+	if (response.status === 401) {
+		throw redirect(303, '/admin/login')
+	}
+
+	if (!response.ok) {
+		let detail: string | undefined
+		try {
+			const json = await response.clone().json()
+			detail = typeof json === 'object' && json !== null && 'error' in json ? String(json.error) : undefined
+		} catch {
+			try {
+				detail = await response.clone().text()
+			} catch {
+				detail = undefined
+			}
+		}
+
+		throw error(response.status, detail || 'Admin request failed')
+	}
+
+	return response
+}
+
+export async function adminFetchJson<T>(
+	event: RequestEvent,
+	input: FetchInput,
+	options: AdminFetchJsonOptions = {}
+): Promise<T> {
+	const { parse = 'json', ...fetchOptions } = options
+	const response = await adminFetch(event, input, fetchOptions)
+
+	if (parse === 'text') {
+		return (await response.text()) as unknown as T
+	}
+
+	if (parse === 'response') {
+		return response as unknown as T
+	}
+
+	return response.json() as Promise<T>
+}