add state_at_id and balance_at_id, integrate with RPC

ethcore/src/client/client.rs

@@ -346,6 +346,16 @@ impl<V> Client<V> where V: Verifier {
 		imported
 	}
 
+	/// Attempt to get a copy of a specific block's state.
+	///
+	/// This can fail (but may not) if the DB prunes state.
+	pub fn state_at_id(&self, id: BlockID) -> Option<State> {
+		self.block_header(id).map(|header| {
+			let db = self.state_db.lock().unwrap().boxed_clone();
+			State::from_existing(db, HeaderView::new(&header).state_root(), self.engine.account_start_nonce())
+		})
+	}
+
 	/// Get a copy of the best block's state.
 	pub fn state(&self) -> State {
 		State::from_existing(self.state_db.lock().unwrap().boxed_clone(), HeaderView::new(&self.best_block_header()).state_root(), self.engine.account_start_nonce())
@@ -557,6 +567,13 @@ impl<V> BlockChainClient for Client<V> where V: Verifier {
 		self.state().balance(address)
 	}
 
+	fn balance_at_id(&self, address: &Address, id: BlockID) -> Option<U256> {
+		match id {
+			BlockID::Latest => Some(self.balance(address)),
+			id => self.state_at_id(id).map(|s| s.balance(address)),
+		}
+	}
+
 	fn storage_at(&self, address: &Address, position: &H256) -> H256 {
 		self.state().storage_at(address, position)
 	}

ethcore/src/client/mod.rs

@@ -74,9 +74,21 @@ pub trait BlockChainClient : Sync + Send {
 	/// Get address code.
 	fn code(&self, address: &Address) -> Option<Bytes>;
 
-	/// Get address balance.
+	/// Get address balance at latest state.
 	fn balance(&self, address: &Address) -> U256;
 
+	/// Account balance at a specific block ID.
+	///
+	/// Will fail if the block is not valid or the block's root hash has been
+	/// pruned from the DB.
+	fn balance_at_id(&self, address: &Address, id: BlockID) -> Option<U256> {
+		if let BlockID::Latest = id {
+			Some(self.balance(address))
+		} else {
+			None
+		}
+	}
+
 	/// Get value of the storage at given position.
 	fn storage_at(&self, address: &Address, position: &H256) -> H256;
 

miner/src/lib.rs

@@ -63,8 +63,8 @@ pub use external::{ExternalMiner, ExternalMinerService};
 use std::collections::BTreeMap;
 use util::{H256, U256, Address, Bytes};
 use ethcore::client::{BlockChainClient, Executed};
-use ethcore::block::{ClosedBlock};
-use ethcore::receipt::{Receipt};
+use ethcore::block::ClosedBlock;
+use ethcore::receipt::Receipt;
 use ethcore::error::{Error, ExecutionError};
 use ethcore::transaction::SignedTransaction;
 
@@ -154,7 +154,7 @@ pub trait MinerService : Send + Sync {
 	/// Suggested gas limit.
 	fn sensible_gas_limit(&self) -> U256 { x!(21000) }
 
-	/// Account balance
+	/// Latest account balance in pending state.
 	fn balance(&self, chain: &BlockChainClient, address: &Address) -> U256;
 
 	/// Call into contract code using pending state.

rpc/src/v1/impls/eth.rs

@@ -26,9 +26,9 @@ use ethminer::{MinerService, AccountDetails, ExternalMinerService};
 use jsonrpc_core::*;
 use util::numbers::*;
 use util::sha3::*;
-use util::bytes::{ToPretty};
+use util::bytes::ToPretty;
 use util::rlp::{encode, decode, UntrustedRlp, View};
-use ethcore::client::{BlockChainClient, BlockID, TransactionID, UncleID};
+use ethcore::client::{self, BlockChainClient, BlockID, TransactionID, UncleID};
 use ethcore::block::IsBlock;
 use ethcore::views::*;
 use ethcore::ethereum::Ethash;
@@ -257,6 +257,17 @@ fn pending_logs<M>(miner: &M, filter: &EthcoreFilter) -> Vec<Log> where M: Miner
 	result
 }
 
+// must be in range [-32099, -32000]
+const UNSUPPORTED_REQUEST_CODE: i64 = -32000;
+
+fn make_unsupported_err() -> Error {
+	Error {
+			code: ErrorCode::ServerError(UNSUPPORTED_REQUEST_CODE),
+			message: "Unsupported request.".into(),
+			data: None
+	}
+}
+
 impl<C, S, A, M, EM> Eth for EthClient<C, S, A, M, EM> where
 	C: BlockChainClient + 'static,
 	S: SyncProvider + 'static,
@@ -343,7 +354,7 @@ impl<C, S, A, M, EM> Eth for EthClient<C, S, A, M, EM> where
 			.and_then(|(address, block_number,)| match block_number {
 				BlockNumber::Latest => to_value(&take_weak!(self.client).balance(&address)),
 				BlockNumber::Pending => to_value(&take_weak!(self.miner).balance(take_weak!(self.client).deref(), &address)),
-				_ => Err(Error::invalid_params()),
+				id => to_value(&try!(take_weak!(self.client).balance_at_id(&address, id.into()).ok_or_else(make_unsupported_err))),
 			})
 	}