spec loading cleanup (#858)

* spec loading cleanup in progress

* changed engine field in json spec

* refactored engine params

* polishing spec loading refactor

* fixed compiling json tests

* fixed compiling parity

* removed warnings

* removed commented out code

* fixed failing test

* bringing back removed TODO in spec.

json/src/spec/engine.rs

@@ -0,0 +1,63 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Engine deserialization.
+
+use serde::{Deserializer, Error};
+use serde::de::Visitor;
+use spec::Ethash;
+
+/// Engine deserialization.
+#[derive(Debug, PartialEq, Deserialize)]
+pub enum Engine {
+	/// Null engine.
+	Null,
+	/// Ethash engine.
+	Ethash(Ethash),
+}
+
+#[cfg(test)]
+mod tests {
+	use serde_json;
+	use spec::Engine;
+
+	#[test]
+	fn engine_deserialization() {
+		let s = r#"{
+			"Null": null
+		}"#;
+
+		let deserialized: Engine = serde_json::from_str(s).unwrap();
+		assert_eq!(Engine::Null, deserialized);
+
+		let s = r#"{
+			"Ethash": {
+				"params": {
+					"tieBreakingGas": false,
+					"gasLimitBoundDivisor": "0x0400",
+					"minimumDifficulty": "0x020000",
+					"difficultyBoundDivisor": "0x0800",
+					"durationLimit": "0x0d",
+					"blockReward": "0x4563918244F40000",
+					"registrar" : "0xc6d9d2cd449a754c494264e1809c50e34d64562b"
+				}
+			}
+		}"#;
+
+		let _deserialized: Engine = serde_json::from_str(s).unwrap();
+	}
+}
+