add useSessionForAcctStr

src/masto/clients.ts

@@ -1,6 +1,7 @@
 import {
   Accessor,
   createContext,
+  createMemo,
   createRenderEffect,
   createResource,
   Signal,
@@ -76,3 +77,39 @@ function useSessionsRaw() {
   }
   return store;
 }
+
+/**
+ * Get a session for the specific acct string.
+ *
+ * Acct string is a string in the pattern of `{username}@{site_with_protocol}`,
+ * like `@thislight@https://mastodon.social`, can be used to identify (tempoarily)
+ * an session on the tutu instance.
+ *
+ * The `site_with_protocol` is required.
+ *
+ * - If the username is present, the session matches the username and the site is returned; or,
+ * - If the username is not present, any session on the site is returned; or,
+ * - If no available session available for the pattern, an unauthorised session is returned.
+ *
+ * In an unauthorised session, the `.account` is `undefined` and the `client` is an
+ * unauthorised client for the site. This client may not available for some operations.
+ */
+export function useSessionForAcctStr(acct: Accessor<string>) {
+  const allSessions = useSessions()
+
+  return createMemo(() => {
+    const parts = acct().split("@", 2)
+    const [inputUsername, inputSite] = acct().split("@", 2);
+    const authedSession = allSessions().find(
+      (x) =>
+        x.account.site === inputSite &&
+        x.account.inf?.username === inputUsername,
+    );
+    return (
+      authedSession ?? {
+        client: createUnauthorizedClient(inputSite),
+        account: undefined,
+      }
+    );
+  });
+}