[APP-1776] Refactor Live Now config, reorg files (#9871)

src/state/appConfig.tsx

@@ -0,0 +1,87 @@
+import {createContext, useContext} from 'react'
+import {QueryClient, useQuery} from '@tanstack/react-query'
+
+import {APP_CONFIG_URL} from '#/env'
+
+const qc = new QueryClient()
+const appConfigQueryKey = ['app-config']
+
+/**
+ * Matches the types defined in our `app-config` worker
+ */
+type AppConfigResponse = {
+  liveNow: {
+    allow: string[]
+    exceptions: {
+      did: string
+      allow: string[]
+    }[]
+  }
+}
+
+export const DEFAULT_APP_CONFIG_RESPONSE: AppConfigResponse = {
+  liveNow: {
+    allow: [],
+    exceptions: [],
+  },
+}
+
+let fetchAppConfigPromise: Promise<AppConfigResponse> | undefined
+
+async function fetchAppConfig(): Promise<AppConfigResponse | null> {
+  try {
+    if (!fetchAppConfigPromise) {
+      fetchAppConfigPromise = (async () => {
+        const r = await fetch(`${APP_CONFIG_URL}/config`)
+        if (!r.ok) throw new Error(await r.text())
+        const data = await r.json()
+        return data
+      })()
+    }
+    return await fetchAppConfigPromise
+  } catch (e) {
+    fetchAppConfigPromise = undefined
+    throw e
+  }
+}
+
+const Context = createContext<AppConfigResponse>(DEFAULT_APP_CONFIG_RESPONSE)
+
+export function Provider({children}: React.PropsWithChildren<{}>) {
+  const {data} = useQuery<AppConfigResponse | null>(
+    {
+      staleTime: Infinity,
+      queryKey: appConfigQueryKey,
+      refetchInterval: query => {
+        // refetch regularly if fetch failed, otherwise never refetch
+        return query.state.status === 'error' ? 60e3 : Infinity
+      },
+      async queryFn() {
+        return fetchAppConfig()
+      },
+    },
+    qc,
+  )
+  return (
+    <Context.Provider value={data ?? DEFAULT_APP_CONFIG_RESPONSE}>
+      {children}
+    </Context.Provider>
+  )
+}
+
+export async function prefetchAppConfig() {
+  try {
+    const data = await fetchAppConfig()
+    if (data) {
+      qc.setQueryData(appConfigQueryKey, data)
+    }
+  } catch {}
+}
+
+export function useAppConfig() {
+  const ctx = useContext(Context)
+  if (!ctx) {
+    throw new Error('useAppConfig must be used within a Provider')
+  }
+  return ctx
+}