Extrinsic pool (#182)

* Use latest version of txpool.

* Initial version of the pool.

* Fix abstraction.

* Implement watchers and notifications.

* Return hash from RPC.

* Remove commented code.

* Remove client dep.

* Fix tests.

substrate/polkadot/transaction-pool/src/error.rs

@@ -0,0 +1,61 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+use extrinsic_pool::{self, txpool};
+use primitives::Hash;
+use runtime::UncheckedExtrinsic;
+
+error_chain! {
+	links {
+		Pool(txpool::Error, txpool::ErrorKind);
+	}
+	errors {
+		/// Unexpected extrinsic format submitted
+		InvalidExtrinsicFormat {
+			description("Invalid extrinsic format."),
+			display("Invalid extrinsic format."),
+		}
+		/// Attempted to queue an inherent transaction.
+		IsInherent(xt: UncheckedExtrinsic) {
+			description("Inherent transactions cannot be queued."),
+			display("Inehrent transactions cannot be queued."),
+		}
+		/// Attempted to queue a transaction with bad signature.
+		BadSignature(xt: UncheckedExtrinsic) {
+			description("Transaction had bad signature."),
+			display("Transaction had bad signature."),
+		}
+		/// Attempted to queue a transaction that is already in the pool.
+		AlreadyImported(hash: Hash) {
+			description("Transaction is already in the pool."),
+			display("Transaction {:?} is already in the pool.", hash),
+		}
+		/// Import error.
+		Import(err: Box<::std::error::Error + Send>) {
+			description("Error importing transaction"),
+			display("Error importing transaction: {}", err.description()),
+		}
+	}
+}
+
+impl extrinsic_pool::api::Error for Error {
+	fn into_pool_error(self) -> ::std::result::Result<txpool::Error, Self> {
+		match self {
+			Error(ErrorKind::Pool(e), c) => Ok(txpool::Error(e, c)),
+			e => Err(e),
+		}
+	}
+}