Define node_runtime compatible Runtime types (#23)

* Define default `node_runtime` compatible Runtime

* rustfmt

src/runtimes.rs

@@ -0,0 +1,54 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of substrate-subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with substrate-subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::srml::{
+    balances::Balances,
+    contracts::Contracts,
+    system::System,
+};
+use runtime_primitives::{
+    generic::Header,
+    traits::{
+        BlakeTwo256,
+        Verify,
+    },
+    AnySignature,
+};
+
+/// Concrete type definitions compatible with those in the default substrate `node_runtime`
+///
+/// # Note
+///
+/// If the concrete types in the target substrate runtime differ from these, a custom Runtime
+/// definition MUST be used to ensure type compatibility.
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct DefaultNodeRuntime;
+
+impl System for DefaultNodeRuntime {
+    type Index = u32;
+    type BlockNumber = u32;
+    type Hash = substrate_primitives::H256;
+    type Hashing = BlakeTwo256;
+    type AccountId = <AnySignature as Verify>::Signer;
+    type Address = srml_indices::address::Address<Self::AccountId, u32>;
+    type Header = Header<Self::BlockNumber, BlakeTwo256>;
+}
+
+impl Balances for DefaultNodeRuntime {
+    type Balance = u64;
+}
+
+impl Contracts for DefaultNodeRuntime {}