feat: add multi-token batch payment support to pool_pay

contracts/sharpy/src/lib.rs

@@ -245,20 +245,26 @@ impl SharpyContract {
         payer.require_auth();
         assert!(!payments.is_empty(), "payments must not be empty");
 
-        let mut total: i128 = 0;
+        // Phase 1: Validate all invoices and group totals by token
+        let mut token_totals: Map<Address, i128> = Map::new(&env);
         for p in payments.iter() {
             let inv = load_invoice(&env, p.invoice_id);
             assert!(inv.status == InvoiceStatus::Pending, "invoice is not pending");
             assert!(p.amount > 0, "payment amount must be positive");
             let inv_total: i128 = inv.amounts.iter().sum();
             assert!(inv.funded + p.amount <= inv_total, "payment exceeds remaining balance");
-            total += p.amount;
+            let token = inv.tokens.get(0).expect("no token");
+            let prev = token_totals.get(token.clone()).unwrap_or(0);
+            token_totals.set(token, prev + p.amount);
         }
 
-        let first = load_invoice(&env, payments.get(0).unwrap().invoice_id);
-        let token_client = token::Client::new(&env, &first.tokens.get(0).expect("no token"));
-        token_client.transfer(&payer, &env.current_contract_address(), &total);
+        // Phase 2: Transfer tokens — one transfer per unique token
+        for (token, amount) in token_totals.iter() {
+            let token_client = token::Client::new(&env, &token);
+            token_client.transfer(&payer, &env.current_contract_address(), &amount);
+        }
 
+        // Phase 3: Update each invoice's state
         for p in payments.iter() {
             let mut inv = load_invoice(&env, p.invoice_id);
             inv.payments.push_back(Payment { payer: payer.clone(), amount: p.amount, tip: 0 });

contracts/sharpy/src/test.rs

@@ -7,6 +7,21 @@ mod tests {
         SharpyContractClient,
     };
 
+    fn setup_with_tokens(
+        env: &Env,
+        payer: &Address,
+        amounts: &[i128],
+    ) -> (Address, Address) {
+        let admin = Address::generate(env);
+        let token_a = env.register_stellar_asset_contract(admin.clone());
+        let token_b = env.register_stellar_asset_contract(admin);
+        let sac_a = token::StellarAssetClient::new(env, &token_a);
+        let sac_b = token::StellarAssetClient::new(env, &token_b);
+        sac_a.mint(payer, &amounts[0]);
+        sac_b.mint(payer, &amounts[1]);
+        (token_a, token_b)
+    }
+
     fn setup() -> (Env, SharpyContractClient<'static>) {
         let env = Env::default();
         env.mock_all_auths();