bug: fix cashu wallet not being loaded all the time

src/lib/cashu.svelte.ts

@@ -188,28 +188,46 @@ async function tryRedeemUnredeemedCashuQuotes() {
   return quotes;
 }
 
-let wallet: CashuWallet | undefined;
+let wallet: CashuWallet | null = null;
+let walletPromise: Promise<CashuWallet> | null = null;
 
-const walletReady = (async () => {
+export async function getWallet(): Promise<CashuWallet> {
   if (wallet) return wallet;
-  await loadProofs();
-  try {
-    await getMnemonic();
-  } catch (_) {}
+  if (walletPromise) return walletPromise;
 
-  const mint = new CashuMint(MINT_URL);
-  wallet = new CashuWallet(mint);
-  await wallet.loadMint();
-  await tryRedeemUnredeemedCashuQuotes();
+  walletPromise = (async () => {
+    try {
+      await loadProofs();
+      try {
+        await getMnemonic();
+      } catch (_) {}
 
-  try {
-    console.log(`cashu addr: ${await getCashuAddress()}`);
-  } catch (_) {
-  }
+      const mint = new CashuMint(MINT_URL);
+      const w = new CashuWallet(mint);
+      await w.loadMint();
 
-  await persistProofs();
-  return wallet;
-})();
+      tryRedeemUnredeemedCashuQuotes()
+        .then(() => persistProofs())
+        .catch((err) => console.error("Failed background redemption", err));
+
+      getCashuAddress()
+        .then((addr) => console.log(`cashu addr: ${addr}`))
+        .catch(() => {});
+
+      wallet = w;
+      return w;
+    } catch (err) {
+      walletPromise = null;
+      throw err;
+    } finally {
+      setTimeout(() => {
+        if (wallet) walletPromise = null;
+      }, 0);
+    }
+  })();
+
+  return walletPromise;
+}
 
 let quoteRedeemInterval: ReturnType<typeof setInterval> | undefined;
 if (quoteRedeemInterval) clearInterval(quoteRedeemInterval);
@@ -275,7 +293,7 @@ async function maybeMelt() {
   if (balance < meltThreshold) return;
 
   try {
-    const wallet = await walletReady;
+    const wallet = await getWallet();
     const invoice = await createMeltInvoice(balance - (balance % 2000));
     const meltQuote = await wallet.createMeltQuote(invoice);
 
@@ -337,7 +355,7 @@ loadCashuTxns();
 export async function payBolt11Invoice(invoice: string): Promise<void> {
   if (!invoice.trim()) throw new Error("Invoice is empty");
 
-  const wallet = await walletReady;
+  const wallet = await getWallet();
   const meltQuote = await wallet.createMeltQuote(invoice);
 
   const amountToMelt = meltQuote.amount + meltQuote.fee_reserve;