Refactor: extract functions and types for creating extrinsics (#138)

* Extract extrinsic

* Extract extrinsic types to own module

* Fix compiler errors

* Fix warnings

* Fmt

* Pin wabt-sys to 0.7.1, it fails (on my machine) with 0.7.2

* Fix up tests

* Fmt

* Reexport RuntimeVersion

src/extrinsic/mod.rs

@@ -0,0 +1,82 @@
+// Copyright 2019-2020 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/>.
+
+//! Create signed or unsigned extrinsics.
+
+mod extra;
+mod signer;
+
+pub use self::{
+    extra::{
+        DefaultExtra,
+        Extra,
+        SignedExtra,
+    },
+    signer::{
+        PairSigner,
+        Signer,
+    },
+};
+
+use sp_runtime::traits::SignedExtension;
+use sp_version::RuntimeVersion;
+
+use crate::{
+    frame::system::System,
+    runtimes::Runtime,
+    Encoded,
+    Error,
+};
+
+/// UncheckedExtrinsic type.
+pub type UncheckedExtrinsic<T> = sp_runtime::generic::UncheckedExtrinsic<
+    <T as System>::Address,
+    Encoded,
+    <T as Runtime>::Signature,
+    Extra<T>,
+>;
+
+/// SignedPayload type.
+pub type SignedPayload<T> = sp_runtime::generic::SignedPayload<Encoded, Extra<T>>;
+
+/// Creates a signed extrinsic
+pub async fn create_signed<T>(
+    runtime_version: &RuntimeVersion,
+    genesis_hash: T::Hash,
+    nonce: T::Index,
+    call: Encoded,
+    signer: &(dyn Signer<T> + Send + Sync),
+) -> Result<UncheckedExtrinsic<T>, Error>
+where
+    T: Runtime,
+    <<T::Extra as SignedExtra<T>>::Extra as SignedExtension>::AdditionalSigned:
+        Send + Sync,
+{
+    let spec_version = runtime_version.spec_version;
+    let tx_version = runtime_version.transaction_version;
+    let extra: T::Extra = T::Extra::new(spec_version, tx_version, nonce, genesis_hash);
+    let payload = SignedPayload::<T>::new(call, extra.extra())?;
+    let signed = signer.sign(payload).await?;
+    Ok(signed)
+}
+
+/// Creates an unsigned extrinsic
+pub fn create_unsigned<T>(call: Encoded) -> UncheckedExtrinsic<T>
+where
+    T: Runtime,
+{
+    UncheckedExtrinsic::<T>::new_unsigned(call)
+}