wallet: Implement `z_getbalanceforaddress`

Closes zcash/zcash#5182.

qa/rpc-tests/wallet_accounts.py

@@ -40,6 +40,22 @@ class WalletAccountsTest(BitcoinTestFramework):
             assert_equal(expected[pool] * COIN, actual['pools'][pool]['valueZat'])
         assert_equal(actual['minimum_confirmations'], 1 if minconf is None else minconf)
 
+    # Check we only have balances in the expected pools.
+    # Remember that empty pools are omitted from the output.
+    def check_address_balance(self, address, expected, minconf=None):
+        if minconf is None:
+            actual = self.nodes[0].z_getbalanceforaddress(address)
+        else:
+            actual = self.nodes[0].z_getbalanceforaddress(address, minconf)
+        assert_equal(set(expected), set(actual['pools']))
+        for pool in expected:
+            assert_equal(expected[pool] * COIN, actual['pools'][pool]['valueZat'])
+        assert_equal(actual['minimum_confirmations'], 1 if minconf is None else minconf)
+
+    def check_balance(self, account, address, expected, minconf=None):
+        self.check_account_balance(account, expected, minconf)
+        self.check_address_balance(address, expected, minconf)
+
     def run_test(self):
         # With a new wallet, the first account will be 0.
         account0 = self.nodes[0].z_getnewaccount()
@@ -79,8 +95,8 @@ class WalletAccountsTest(BitcoinTestFramework):
         self.check_receiver_types(ua1, ['transparent', 'sapling'])
 
         # The balances of the accounts are all zero.
-        self.check_account_balance(0, {})
-        self.check_account_balance(1, {})
+        self.check_balance(0, ua0, {})
+        self.check_balance(1, ua1, {})
 
         # Manually send funds to one of the receivers in the UA.
         # TODO: Once z_sendmany supports UAs, receive to the UA instead of the receiver.
@@ -98,14 +114,14 @@ class WalletAccountsTest(BitcoinTestFramework):
         # The new balance should not be visible with the default minconf, but should be
         # visible with minconf=0.
         self.sync_all()
-        self.check_account_balance(0, {})
-        self.check_account_balance(0, {'sapling': 10}, 0)
+        self.check_balance(0, ua0, {})
+        self.check_balance(0, ua0, {'sapling': 10}, 0)
 
         self.nodes[2].generate(1)
         self.sync_all()
 
         # The default minconf should now detect the balance.
-        self.check_account_balance(0, {'sapling': 10})
+        self.check_balance(0, ua0, {'sapling': 10})
 
         # Manually send funds from the UA receiver.
         # TODO: Once z_sendmany supports UAs, send from the UA instead of the receiver.
@@ -125,8 +141,8 @@ class WalletAccountsTest(BitcoinTestFramework):
         # shown, as that transaction has been created and broadcast, and _might_ get mined
         # up until the transaction expires), or 9 (if we include the unmined transaction).
         self.sync_all()
-        self.check_account_balance(0, {})
-        self.check_account_balance(0, {'sapling': 9}, 0)
+        self.check_balance(0, ua0, {})
+        self.check_balance(0, ua0, {'sapling': 9}, 0)
 
 
 if __name__ == '__main__':

src/wallet/rpcwallet.cpp

@@ -3641,6 +3641,14 @@ UniValue z_getbalanceforaddress(const UniValue& params, bool fHelp)
     if (!fExperimentalOrchardWallet) {
         throw JSONRPCError(RPC_WALLET_ENCRYPTION_FAILED, "Error: the Orchard wallet experimental extensions are disabled.");
     }
+
+    KeyIO keyIO(Params());
+    auto decoded = keyIO.DecodePaymentAddress(params[0].get_str());
+    if (!decoded.has_value()) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
+    }
+    auto address = decoded.value();
+
     int minconf = 1;
     if (params.size() > 1) {
         minconf = params[1].get_int();
@@ -3648,11 +3656,45 @@ UniValue z_getbalanceforaddress(const UniValue& params, bool fHelp)
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Minimum number of confirmations cannot be less than 0");
         }
     }
+
+    LOCK(pwalletMain->cs_wallet);
+
+    // Get the receivers for this address.
+    auto selector = pwalletMain->ToZTXOSelector(address, false);
+    if (!selector.has_value()) {
+        // The only way we'd reach this is if the address is a unified address for which
+        // we do not know its UFVK.
+        throw JSONRPCError(
+            RPC_INVALID_PARAMETER,
+            "Error: wallet does not have the Unified Full Viewing Key for the given address");
+    }
+
+    auto spendableInputs = pwalletMain->FindSpendableInputs(selector.value(), true, minconf);
+
+    CAmount transparentBalance = 0;
+    CAmount sproutBalance = 0;
+    CAmount saplingBalance = 0;
+    for (const auto& t : spendableInputs.utxos) {
+        transparentBalance += t.Value();
+    }
+    for (const auto& t : spendableInputs.sproutNoteEntries) {
+        sproutBalance += t.note.value();
+    }
+    for (const auto& t : spendableInputs.saplingNoteEntries) {
+        saplingBalance += t.note.value();
+    }
+
     UniValue pools(UniValue::VOBJ);
-    pools.pushKV("transparent", 99999.99);
-    pools.pushKV("sprout", 99999.99);
-    pools.pushKV("sapling", 99999.99);
-    pools.pushKV("orchard", 99999.99);
+    auto renderBalance = [&](std::string poolName, CAmount balance) {
+        if (balance > 0) {
+            UniValue pool(UniValue::VOBJ);
+            pool.pushKV("valueZat", balance);
+            pools.pushKV(poolName, pool);
+        }
+    };
+    renderBalance("transparent", transparentBalance);
+    renderBalance("sprout", sproutBalance);
+    renderBalance("sapling", saplingBalance);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("pools", pools);