rpc/chain_spec: Implement chainSpec RPC methods

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

client/rpc-spec/src/chain_spec/chain_spec.rs

@@ -0,0 +1,68 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020-2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! API implementation for the specification of a chain.
+
+use crate::chain_spec::api::ChainSpecApiServer;
+use jsonrpsee::core::RpcResult;
+use sc_chain_spec::Properties;
+
+/// An API for chain spec RPC calls.
+pub struct ChainSpec {
+	/// The name of the chain.
+	name: String,
+	/// The hexadecimal encoded hash of the genesis block.
+	///
+	/// # Note
+	///
+	/// This can be empty, or prefixed with "0x".
+	genesis_hash: String,
+	/// Chain properties.
+	properties: Properties,
+}
+
+impl ChainSpec {
+	/// Creates a new [`ChainSpec`].
+	pub fn new<Hash: AsRef<[u8]>>(
+		name: String,
+		genesis_hash: Hash,
+		properties: Properties,
+	) -> Self {
+		let genesis_hash = if genesis_hash.as_ref().is_empty() {
+			"".into()
+		} else {
+			format!("0x{}", hex::encode(genesis_hash))
+		};
+
+		Self { name, properties, genesis_hash }
+	}
+}
+
+impl ChainSpecApiServer for ChainSpec {
+	fn chain_spec_unstable_chain_name(&self) -> RpcResult<String> {
+		Ok(self.name.clone())
+	}
+
+	fn chain_spec_unstable_genesis_hash(&self) -> RpcResult<String> {
+		Ok(self.genesis_hash.clone())
+	}
+
+	fn chain_spec_unstable_properties(&self) -> RpcResult<Properties> {
+		Ok(self.properties.clone())
+	}
+}

client/rpc-spec/src/chain_spec/mod.rs

@@ -29,5 +29,7 @@
 //! Methods are prefixed by `chainSpec`.
 
 pub mod api;
+pub mod chain_spec;
 
 pub use api::ChainSpecApiServer;
+pub use chain_spec::ChainSpec;