client.rs

// 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/>.

//! Blockchain database client.

use std::path::PathBuf;
use std::sync::atomic::{AtomicUsize, Ordering as AtomicOrdering};
use util::*;
use util::panics::*;
use views::BlockView;
use error::{ImportError, ExecutionError, BlockError, ImportResult};
use header::{BlockNumber, Header};
use state::State;
use spec::Spec;
use basic_types::Seal;
use engine::Engine;
use views::HeaderView;
use service::{NetSyncMessage, SyncMessage};
use env_info::LastHashes;
use verification;
use verification::{PreverifiedBlock, Verifier};
use block::*;
use transaction::{LocalizedTransaction, SignedTransaction, Action};
use blockchain::extras::TransactionAddress;
use filter::Filter;
use log_entry::LocalizedLogEntry;
use block_queue::{BlockQueue, BlockQueueInfo};
use blockchain::{BlockChain, BlockProvider, TreeRoute, ImportRoute};
use client::{BlockID, TransactionID, UncleID, TraceId, ClientConfig, DatabaseCompactionProfile,
	BlockChainClient, MiningBlockChainClient, TraceFilter, CallAnalytics };
use client::Error as ClientError;
use env_info::EnvInfo;
use executive::{Executive, Executed, TransactOptions, contract_address};
use receipt::LocalizedReceipt;
pub use blockchain::CacheSize as BlockChainCacheSize;
use trace::{TraceDB, ImportRequest as TraceImportRequest, LocalizedTrace, Database as TraceDatabase};
use trace;
use trace::FlatTransactionTraces;

// re-export
pub use types::blockchain_info::BlockChainInfo;
pub use types::block_status::BlockStatus;
use evm::Factory as EvmFactory;
use miner::{Miner, MinerService};

const MAX_TX_QUEUE_SIZE: usize = 4096;

impl fmt::Display for BlockChainInfo {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		write!(f, "#{}.{}", self.best_block_number, self.best_block_hash)
	}
}

/// Report on the status of a client.
#[derive(Default, Clone, Debug, Eq, PartialEq)]
pub struct ClientReport {
	/// How many blocks have been imported so far.
	pub blocks_imported: usize,
	/// How many transactions have been applied so far.
	pub transactions_applied: usize,
	/// How much gas has been processed so far.
	pub gas_processed: U256,
	/// Memory used by state DB
	pub state_db_mem: usize,
}

impl ClientReport {
	/// Alter internal reporting to reflect the additional `block` has been processed.
	pub fn accrue_block(&mut self, block: &PreverifiedBlock) {
		self.blocks_imported += 1;
		self.transactions_applied += block.transactions.len();
		self.gas_processed = self.gas_processed + block.header.gas_used;
	}
}

/// Blockchain database client backed by a persistent database. Owns and manages a blockchain and a block queue.
/// Call `import_block()` to import a block asynchronously; `flush_queue()` flushes the queue.
pub struct Client {
	chain: Arc<BlockChain>,
	tracedb: Arc<TraceDB<BlockChain>>,
	engine: Arc<Box<Engine>>,
	state_db: Mutex<Box<JournalDB>>,
	block_queue: BlockQueue,
	report: RwLock<ClientReport>,
	import_lock: Mutex<()>,
	panic_handler: Arc<PanicHandler>,
	verifier: Box<Verifier>,
	vm_factory: Arc<EvmFactory>,
	miner: Arc<Miner>,
	io_channel: IoChannel<NetSyncMessage>,
	queue_transactions: AtomicUsize,
}

const HISTORY: u64 = 1200;
// DO NOT TOUCH THIS ANY MORE UNLESS YOU REALLY KNOW WHAT YOU'RE DOING.
// Altering it will force a blanket DB update for *all* JournalDB-derived
//   databases.
// Instead, add/upgrade the version string of the individual JournalDB-derived database
// of which you actually want force an upgrade.
const CLIENT_DB_VER_STR: &'static str = "5.3";

/// Get the path for the databases given the root path and information on the databases.
pub fn get_db_path(path: &Path, pruning: journaldb::Algorithm, genesis_hash: H256) -> PathBuf {
	let mut dir = path.to_path_buf();
	dir.push(H64::from(genesis_hash).hex());
	//TODO: sec/fat: pruned/full versioning
	// version here is a bit useless now, since it's controlled only be the pruning algo.
	dir.push(format!("v{}-sec-{}", CLIENT_DB_VER_STR, pruning));
	dir
}

/// Append a path element to the given path and return the string.
pub fn append_path(path: &Path, item: &str) -> String {
	let mut p = path.to_path_buf();
	p.push(item);
	p.to_str().unwrap().to_owned()
}

impl Client {
	///  Create a new client with given spec and DB path and custom verifier.
	pub fn new(
		config: ClientConfig,
		spec: Spec,
		path: &Path,
		miner: Arc<Miner>,
		message_channel: IoChannel<NetSyncMessage>)
		-> Result<Arc<Client>, ClientError>
	{
		let path = get_db_path(path, config.pruning, spec.genesis_header().hash());
		let gb = spec.genesis_block();
		let chain = Arc::new(BlockChain::new(config.blockchain, &gb, &path));
		let tracedb = Arc::new(try!(TraceDB::new(config.tracing, &path, chain.clone())));

		let mut state_db_config = match config.db_cache_size {
			None => DatabaseConfig::default(),
			Some(cache_size) => DatabaseConfig::with_cache(cache_size),
		};

		if config.db_compaction == DatabaseCompactionProfile::HDD {
			state_db_config = state_db_config.compaction(CompactionProfile::hdd());
		}

		let mut state_db = journaldb::new(
			&append_path(&path, "state"),
			config.pruning,
			state_db_config
		);

		if state_db.is_empty() && spec.ensure_db_good(state_db.as_hashdb_mut()) {
			state_db.commit(0, &spec.genesis_header().hash(), None).expect("Error commiting genesis state to state DB");
		}

		let engine = Arc::new(spec.engine);

		let block_queue = BlockQueue::new(config.queue, engine.clone(), message_channel.clone());
		let panic_handler = PanicHandler::new_in_arc();
		panic_handler.forward_from(&block_queue);

		let client = Client {
			chain: chain,
			tracedb: tracedb,
			engine: engine,
			state_db: Mutex::new(state_db),
			block_queue: block_queue,
			report: RwLock::new(Default::default()),
			import_lock: Mutex::new(()),
			panic_handler: panic_handler,
			verifier: verification::new(config.verifier_type),
			vm_factory: Arc::new(EvmFactory::new(config.vm_type)),
			miner: miner,
			io_channel: message_channel,
			queue_transactions: AtomicUsize::new(0),
		};

		Ok(Arc::new(client))
	}

	/// Flush the block import queue.
	pub fn flush_queue(&self) {
		self.block_queue.flush();
	}

	fn build_last_hashes(&self, parent_hash: H256) -> LastHashes {
		let mut last_hashes = LastHashes::new();
		last_hashes.resize(256, H256::new());
		last_hashes[0] = parent_hash;
		for i in 0..255 {
			match self.chain.block_details(&last_hashes[i]) {
				Some(details) => {
					last_hashes[i + 1] = details.parent.clone();
				},
				None => break,
			}
		}
		last_hashes
	}

	fn check_and_close_block(&self, block: &PreverifiedBlock) -> Result<LockedBlock, ()> {
		let engine = self.engine.deref().deref();
		let header = &block.header;

		// Check the block isn't so old we won't be able to enact it.
		let best_block_number = self.chain.best_block_number();
		if best_block_number >= HISTORY && header.number() <= best_block_number - HISTORY {
			warn!(target: "client", "Block import failed for #{} ({})\nBlock is ancient (current best block: #{}).", header.number(), header.hash(), best_block_number);
			return Err(());
		}

		// Verify Block Family
		let verify_family_result = self.verifier.verify_block_family(&header, &block.bytes, engine, self.chain.deref());
		if let Err(e) = verify_family_result {
			warn!(target: "client", "Stage 3 block verification failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
			return Err(());
		};

		// Check if Parent is in chain
		let chain_has_parent = self.chain.block_header(&header.parent_hash);
		if let None = chain_has_parent {
			warn!(target: "client", "Block import failed for #{} ({}): Parent not found ({}) ", header.number(), header.hash(), header.parent_hash);
			return Err(());
		};

		// Enact Verified Block
		let parent = chain_has_parent.unwrap();
		let last_hashes = self.build_last_hashes(header.parent_hash.clone());
		let db = self.state_db.lock().unwrap().boxed_clone();

		let enact_result = enact_verified(&block, engine, self.tracedb.tracing_enabled(), db, &parent, last_hashes, &self.vm_factory);
		if let Err(e) = enact_result {
			warn!(target: "client", "Block import failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
			return Err(());
		};

		// Final Verification
		let locked_block = enact_result.unwrap();
		if let Err(e) = self.verifier.verify_block_final(&header, locked_block.block().header()) {
			warn!(target: "client", "Stage 4 block verification failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
			return Err(());
		}

		Ok(locked_block)
	}

	fn calculate_enacted_retracted(&self, import_results: &[ImportRoute]) -> (Vec<H256>, Vec<H256>) {
		fn map_to_vec(map: Vec<(H256, bool)>) -> Vec<H256> {
			map.into_iter().map(|(k, _v)| k).collect()
		}

		// In ImportRoute we get all the blocks that have been enacted and retracted by single insert.
		// Because we are doing multiple inserts some of the blocks that were enacted in import `k`
		// could be retracted in import `k+1`. This is why to understand if after all inserts
		// the block is enacted or retracted we iterate over all routes and at the end final state
		// will be in the hashmap
		let map = import_results.iter().fold(HashMap::new(), |mut map, route| {
			for hash in &route.enacted {
				map.insert(hash.clone(), true);
			}
			for hash in &route.retracted {
				map.insert(hash.clone(), false);
			}
			map
		});

		// Split to enacted retracted (using hashmap value)
		let (enacted, retracted) = map.into_iter().partition(|&(_k, v)| v);
		// And convert tuples to keys
		(map_to_vec(enacted), map_to_vec(retracted))
	}

	/// This is triggered by a message coming from a block queue when the block is ready for insertion
	pub fn import_verified_blocks(&self, io: &IoChannel<NetSyncMessage>) -> usize {
		let max_blocks_to_import = 64;

		let mut imported_blocks = Vec::with_capacity(max_blocks_to_import);
		let mut invalid_blocks = HashSet::new();
		let mut import_results = Vec::with_capacity(max_blocks_to_import);

		let _import_lock = self.import_lock.lock();
		let _timer = PerfTimer::new("import_verified_blocks");
		let blocks = self.block_queue.drain(max_blocks_to_import);

		let original_best = self.chain_info().best_block_hash;

		for block in blocks {
			let header = &block.header;

			if invalid_blocks.contains(&header.parent_hash) {
				invalid_blocks.insert(header.hash());
				continue;
			}
			let closed_block = self.check_and_close_block(&block);
			if let Err(_) = closed_block {
				invalid_blocks.insert(header.hash());
				continue;
			}
			let closed_block = closed_block.unwrap();
			imported_blocks.push(header.hash());

			let route = self.commit_block(closed_block, &header.hash(), &block.bytes);
			import_results.push(route);

			self.report.write().unwrap().accrue_block(&block);
			trace!(target: "client", "Imported #{} ({})", header.number(), header.hash());
		}

		let imported = imported_blocks.len();
		let invalid_blocks = invalid_blocks.into_iter().collect::<Vec<H256>>();

		{
			if !invalid_blocks.is_empty() {
				self.block_queue.mark_as_bad(&invalid_blocks);
			}
			if !imported_blocks.is_empty() {
				self.block_queue.mark_as_good(&imported_blocks);
			}
		}

		{
			if !imported_blocks.is_empty() && self.block_queue.queue_info().is_empty() {
				let (enacted, retracted) = self.calculate_enacted_retracted(&import_results);

				if self.queue_info().is_empty() {
					self.miner.chain_new_blocks(self, &imported_blocks, &invalid_blocks, &enacted, &retracted);
				}

				io.send(NetworkIoMessage::User(SyncMessage::NewChainBlocks {
					imported: imported_blocks,
					invalid: invalid_blocks,
					enacted: enacted,
					retracted: retracted,
					sealed: Vec::new(),
				})).unwrap_or_else(|e| warn!("Error sending IO notification: {:?}", e));
			}
		}

		if self.chain_info().best_block_hash != original_best {
			self.miner.update_sealing(self);
		}

		imported
	}

	fn commit_block<B>(&self, block: B, hash: &H256, block_data: &Bytes) -> ImportRoute where B: IsBlock + Drain {
		let number = block.header().number();
		// Are we committing an era?
		let ancient = if number >= HISTORY {
			let n = number - HISTORY;
			Some((n, self.chain.block_hash(n).unwrap()))
		} else {
			None
		};

		// Commit results
		let receipts = block.receipts().to_owned();
		let traces = block.traces().clone().unwrap_or_else(Vec::new);
		let traces: Vec<FlatTransactionTraces> = traces.into_iter()
			.map(Into::into)
			.collect();

		//let traces = From::from(block.traces().clone().unwrap_or_else(Vec::new));

		// CHECK! I *think* this is fine, even if the state_root is equal to another
		// already-imported block of the same number.
		// TODO: Prove it with a test.
		block.drain().commit(number, hash, ancient).expect("State DB commit failed.");

		// And update the chain after commit to prevent race conditions
		// (when something is in chain but you are not able to fetch details)
		let route = self.chain.insert_block(block_data, receipts);
		self.tracedb.import(TraceImportRequest {
			traces: traces.into(),
			block_hash: hash.clone(),
			block_number: number,
			enacted: route.enacted.clone(),
			retracted: route.retracted.len()
		});
		route
	}

	/// Import transactions from the IO queue
	pub fn import_queued_transactions(&self, transactions: &[Bytes]) -> usize {
		let _timer = PerfTimer::new("import_queued_transactions");
		self.queue_transactions.fetch_sub(transactions.len(), AtomicOrdering::SeqCst);
		let txs = transactions.iter().filter_map(|bytes| UntrustedRlp::new(&bytes).as_val().ok()).collect();
		let results = self.miner.import_external_transactions(self, txs);
		results.len()
	}

	/// Attempt to get a copy of a specific block's state.
	///
	/// This will not fail if given BlockID::Latest.
	/// Otherwise, this can fail (but may not) if the DB prunes state.
	pub fn state_at(&self, id: BlockID) -> Option<State> {
		// fast path for latest state.
		match id.clone() {
			BlockID::Pending => return self.miner.pending_state().or_else(|| Some(self.state())),
			BlockID::Latest => return Some(self.state()),
			_ => {},
		}

		let block_number = match self.block_number(id.clone()) {
			Some(num) => num,
			None => return None,
		};

		self.block_header(id).and_then(|header| {
			let db = self.state_db.lock().unwrap().boxed_clone();

			// early exit for pruned blocks
			if db.is_pruned() && self.chain.best_block_number() >= block_number + HISTORY {
				return None;
			}

			let root = HeaderView::new(&header).state_root();

			State::from_existing(db, root, self.engine.account_start_nonce()).ok()
		})
	}

	/// 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())
			.expect("State root of best block header always valid.")
	}

	/// Get info on the cache.
	pub fn blockchain_cache_info(&self) -> BlockChainCacheSize {
		self.chain.cache_size()
	}

	/// Get the report.
	pub fn report(&self) -> ClientReport {
		let mut report = self.report.read().unwrap().clone();
		report.state_db_mem = self.state_db.lock().unwrap().mem_used();
		report
	}

	/// Tick the client.
	pub fn tick(&self) {
		self.chain.collect_garbage();
		self.block_queue.collect_garbage();
	}

	/// Set up the cache behaviour.
	pub fn configure_cache(&self, pref_cache_size: usize, max_cache_size: usize) {
		self.chain.configure_cache(pref_cache_size, max_cache_size);
	}

	/// Look up the block number for the given block ID.
	pub fn block_number(&self, id: BlockID) -> Option<BlockNumber> {
		match id {
			BlockID::Number(number) => Some(number),
			BlockID::Hash(ref hash) => self.chain.block_number(hash),
			BlockID::Earliest => Some(0),
			BlockID::Latest | BlockID::Pending => Some(self.chain.best_block_number()),
		}
	}

	fn block_hash(chain: &BlockChain, id: BlockID) -> Option<H256> {
		match id {
			BlockID::Hash(hash) => Some(hash),
			BlockID::Number(number) => chain.block_hash(number),
			BlockID::Earliest => chain.block_hash(0),
			BlockID::Latest | BlockID::Pending => Some(chain.best_block_hash()),
		}
	}

	fn transaction_address(&self, id: TransactionID) -> Option<TransactionAddress> {
		match id {
			TransactionID::Hash(ref hash) => self.chain.transaction_address(hash),
			TransactionID::Location(id, index) => Self::block_hash(&self.chain, id).map(|hash| TransactionAddress {
				block_hash: hash,
				index: index,
			})
		}
	}
}

impl BlockChainClient for Client {
	fn call(&self, t: &SignedTransaction, analytics: CallAnalytics) -> Result<Executed, ExecutionError> {
		let header = self.block_header(BlockID::Latest).unwrap();
		let view = HeaderView::new(&header);
		let last_hashes = self.build_last_hashes(view.hash());
		let env_info = EnvInfo {
			number: view.number(),
			author: view.author(),
			timestamp: view.timestamp(),
			difficulty: view.difficulty(),
			last_hashes: last_hashes,
			gas_used: U256::zero(),
			gas_limit: U256::max_value(),
		};
		// that's just a copy of the state.
		let mut state = self.state();
		let sender = try!(t.sender().map_err(|e| {
			let message = format!("Transaction malformed: {:?}", e);
			ExecutionError::TransactionMalformed(message)
		}));
		let balance = state.balance(&sender);
		let needed_balance = t.value + t.gas * t.gas_price;
		if balance < needed_balance {
			// give the sender a sufficient balance
			state.add_balance(&sender, &(needed_balance - balance));
		}
		let options = TransactOptions { tracing: analytics.transaction_tracing, vm_tracing: analytics.vm_tracing, check_nonce: false };
		let mut ret = Executive::new(&mut state, &env_info, self.engine.deref().deref(), &self.vm_factory).transact(t, options);

		// TODO gav move this into Executive.
		if analytics.state_diffing {
			if let Ok(ref mut x) = ret {
				x.state_diff = Some(state.diff_from(self.state()));
			}
		}
		ret
	}


	fn block_header(&self, id: BlockID) -> Option<Bytes> {
		Self::block_hash(&self.chain, id).and_then(|hash| self.chain.block(&hash).map(|bytes| BlockView::new(&bytes).rlp().at(0).as_raw().to_vec()))
	}

	fn block_body(&self, id: BlockID) -> Option<Bytes> {
		Self::block_hash(&self.chain, id).and_then(|hash| {
			self.chain.block(&hash).map(|bytes| {
				let rlp = Rlp::new(&bytes);
				let mut body = RlpStream::new_list(2);
				body.append_raw(rlp.at(1).as_raw(), 1);
				body.append_raw(rlp.at(2).as_raw(), 1);
				body.out()
			})
		})
	}

	fn block(&self, id: BlockID) -> Option<Bytes> {
		if let &BlockID::Pending = &id {
			if let Some(block) = self.miner.pending_block() { 
				return Some(block.rlp_bytes(Seal::Without));
			}
		}
		Self::block_hash(&self.chain, id).and_then(|hash| {
			self.chain.block(&hash)
		})
	}

	fn block_status(&self, id: BlockID) -> BlockStatus {
		match Self::block_hash(&self.chain, id) {
			Some(ref hash) if self.chain.is_known(hash) => BlockStatus::InChain,
			Some(hash) => self.block_queue.block_status(&hash),
			None => BlockStatus::Unknown
		}
	}

	fn block_total_difficulty(&self, id: BlockID) -> Option<U256> {
		if let &BlockID::Pending = &id {
			if let Some(block) = self.miner.pending_block() {
				return Some(*block.header.difficulty() + self.block_total_difficulty(BlockID::Latest).expect("blocks in chain have details; qed"));
			} 
		}
		Self::block_hash(&self.chain, id).and_then(|hash| self.chain.block_details(&hash)).map(|d| d.total_difficulty)
	}

	fn nonce(&self, address: &Address, id: BlockID) -> Option<U256> {
		self.state_at(id).map(|s| s.nonce(address))
	}

	fn block_hash(&self, id: BlockID) -> Option<H256> {
		Self::block_hash(&self.chain, id)
	}

	fn code(&self, address: &Address) -> Option<Bytes> {
		self.state().code(address)
	}

	fn balance(&self, address: &Address, id: BlockID) -> Option<U256> {
		self.state_at(id).map(|s| s.balance(address))
	}

	fn storage_at(&self, address: &Address, position: &H256, id: BlockID) -> Option<H256> {
		self.state_at(id).map(|s| s.storage_at(address, position))
	}

	fn transaction(&self, id: TransactionID) -> Option<LocalizedTransaction> {
		self.transaction_address(id).and_then(|address| self.chain.transaction(&address))
	}

	fn uncle(&self, id: UncleID) -> Option<Header> {
		let index = id.1;
		self.block(id.0).and_then(|block| BlockView::new(&block).uncle_at(index))
	}

	fn transaction_receipt(&self, id: TransactionID) -> Option<LocalizedReceipt> {
		self.transaction_address(id).and_then(|address| {
			let t = self.chain.block(&address.block_hash)
				.and_then(|block| BlockView::new(&block).localized_transaction_at(address.index));

			match (t, self.chain.transaction_receipt(&address)) {
				(Some(tx), Some(receipt)) => {
					let block_hash = tx.block_hash.clone();
					let block_number = tx.block_number.clone();
					let transaction_hash = tx.hash();
					let transaction_index = tx.transaction_index;
					let prior_gas_used = match tx.transaction_index {
						0 => U256::zero(),
						i => {
							let prior_address = TransactionAddress { block_hash: address.block_hash, index: i - 1 };
							let prior_receipt = self.chain.transaction_receipt(&prior_address).expect("Transaction receipt at `address` exists; `prior_address` has lower index in same block; qed");
							prior_receipt.gas_used
						}
					};
					Some(LocalizedReceipt {
						transaction_hash: tx.hash(),
						transaction_index: tx.transaction_index,
						block_hash: tx.block_hash,
						block_number: tx.block_number,
						cumulative_gas_used: receipt.gas_used,
						gas_used: receipt.gas_used - prior_gas_used,
						contract_address: match tx.action {
							Action::Call(_) => None,
							Action::Create => Some(contract_address(&tx.sender().unwrap(), &tx.nonce))
						},
						logs: receipt.logs.into_iter().enumerate().map(|(i, log)| LocalizedLogEntry {
							entry: log,
							block_hash: block_hash.clone(),
							block_number: block_number,
							transaction_hash: transaction_hash.clone(),
							transaction_index: transaction_index,
							log_index: i
						}).collect()
					})
				},
				_ => None
			}
		})
	}

	fn tree_route(&self, from: &H256, to: &H256) -> Option<TreeRoute> {
		match self.chain.is_known(from) && self.chain.is_known(to) {
			true => Some(self.chain.tree_route(from.clone(), to.clone())),
			false => None
		}
	}

	fn find_uncles(&self, hash: &H256) -> Option<Vec<H256>> {
		self.chain.find_uncle_hashes(hash, self.engine.maximum_uncle_age())
	}

	fn state_data(&self, hash: &H256) -> Option<Bytes> {
		self.state_db.lock().unwrap().state(hash)
	}

	fn block_receipts(&self, hash: &H256) -> Option<Bytes> {
		self.chain.block_receipts(hash).map(|receipts| rlp::encode(&receipts).to_vec())
	}

	fn import_block(&self, bytes: Bytes) -> ImportResult {
		{
			let header = BlockView::new(&bytes).header_view();
			if self.chain.is_known(&header.sha3()) {
				return Err(ImportError::AlreadyInChain.into());
			}
			if self.block_status(BlockID::Hash(header.parent_hash())) == BlockStatus::Unknown {
				return Err(BlockError::UnknownParent(header.parent_hash()).into());
			}
		}
		self.block_queue.import_block(bytes)
	}

	fn queue_info(&self) -> BlockQueueInfo {
		self.block_queue.queue_info()
	}

	fn clear_queue(&self) {
		self.block_queue.clear();
	}

	fn chain_info(&self) -> BlockChainInfo {
		BlockChainInfo {
			total_difficulty: self.chain.best_block_total_difficulty(),
			pending_total_difficulty: self.chain.best_block_total_difficulty(),
			genesis_hash: self.chain.genesis_hash(),
			best_block_hash: self.chain.best_block_hash(),
			best_block_number: From::from(self.chain.best_block_number())
		}
	}

	fn blocks_with_bloom(&self, bloom: &H2048, from_block: BlockID, to_block: BlockID) -> Option<Vec<BlockNumber>> {
		match (self.block_number(from_block), self.block_number(to_block)) {
			(Some(from), Some(to)) => Some(self.chain.blocks_with_bloom(bloom, from, to)),
			_ => None
		}
	}

	fn logs(&self, filter: Filter) -> Vec<LocalizedLogEntry> {
		// TODO: lock blockchain only once

		let mut blocks = filter.bloom_possibilities().iter()
			.filter_map(|bloom| self.blocks_with_bloom(bloom, filter.from_block.clone(), filter.to_block.clone()))
			.flat_map(|m| m)
			// remove duplicate elements
			.collect::<HashSet<u64>>()
			.into_iter()
			.collect::<Vec<u64>>();

		blocks.sort();

		blocks.into_iter()
			.filter_map(|number| self.chain.block_hash(number).map(|hash| (number, hash)))
			.filter_map(|(number, hash)| self.chain.block_receipts(&hash).map(|r| (number, hash, r.receipts)))
			.filter_map(|(number, hash, receipts)| self.chain.block(&hash).map(|ref b| (number, hash, receipts, BlockView::new(b).transaction_hashes())))
			.flat_map(|(number, hash, receipts, hashes)| {
				let mut log_index = 0;
				receipts.into_iter()
					.enumerate()
					.flat_map(|(index, receipt)| {
						log_index += receipt.logs.len();
						receipt.logs.into_iter()
							.enumerate()
							.filter(|tuple| filter.matches(&tuple.1))
						 	.map(|(i, log)| LocalizedLogEntry {
							 	entry: log,
								block_hash: hash.clone(),
								block_number: number,
								transaction_hash: hashes.get(index).cloned().unwrap_or_else(H256::new),
								transaction_index: index,
								log_index: log_index + i
							})
							.collect::<Vec<LocalizedLogEntry>>()
					})
					.collect::<Vec<LocalizedLogEntry>>()

			})
			.collect()
	}

	fn filter_traces(&self, filter: TraceFilter) -> Option<Vec<LocalizedTrace>> {
		let start = self.block_number(filter.range.start);
		let end = self.block_number(filter.range.end);

		if start.is_some() && end.is_some() {
			let filter = trace::Filter {
				range: start.unwrap() as usize..end.unwrap() as usize,
				from_address: From::from(filter.from_address),
				to_address: From::from(filter.to_address),
			};

			let traces = self.tracedb.filter(&filter);
			Some(traces)
		} else {
			None
		}
	}

	fn trace(&self, trace: TraceId) -> Option<LocalizedTrace> {
		let trace_address = trace.address;
		self.transaction_address(trace.transaction)
			.and_then(|tx_address| {
				self.block_number(BlockID::Hash(tx_address.block_hash))
					.and_then(|number| self.tracedb.trace(number, tx_address.index, trace_address))
			})
	}

	fn transaction_traces(&self, transaction: TransactionID) -> Option<Vec<LocalizedTrace>> {
		self.transaction_address(transaction)
			.and_then(|tx_address| {
				self.block_number(BlockID::Hash(tx_address.block_hash))
					.and_then(|number| self.tracedb.transaction_traces(number, tx_address.index))
			})
	}

	fn block_traces(&self, block: BlockID) -> Option<Vec<LocalizedTrace>> {
		self.block_number(block)
			.and_then(|number| self.tracedb.block_traces(number))
	}

	fn last_hashes(&self) -> LastHashes {
		self.build_last_hashes(self.chain.best_block_hash())
	}

	fn queue_transactions(&self, transactions: Vec<Bytes>) {
		if self.queue_transactions.load(AtomicOrdering::Relaxed) > MAX_TX_QUEUE_SIZE {
			debug!("Ignoring {} transactions: queue is full", transactions.len());
		} else {
			let len = transactions.len();
			match self.io_channel.send(NetworkIoMessage::User(SyncMessage::NewTransactions(transactions))) {
				Ok(_) => {
					self.queue_transactions.fetch_add(len, AtomicOrdering::SeqCst);
				}
				Err(e) => {
					debug!("Ignoring {} transactions: error queueing: {}", len, e);
				}
			}
		}
	}

	fn pending_transactions(&self) -> Vec<SignedTransaction> {
		self.miner.pending_transactions()
	}
}

impl MiningBlockChainClient for Client {
	fn prepare_open_block(&self, author: Address, gas_range_target: (U256, U256), extra_data: Bytes) -> OpenBlock {
		let engine = self.engine.deref().deref();
		let h = self.chain.best_block_hash();

		let mut open_block = OpenBlock::new(
			engine,
			&self.vm_factory,
			false,	// TODO: this will need to be parameterised once we want to do immediate mining insertion.
			self.state_db.lock().unwrap().boxed_clone(),
			&self.chain.block_header(&h).expect("h is best block hash: so it's header must exist: qed"),
			self.build_last_hashes(h.clone()),
			author,
			gas_range_target,
			extra_data,
		).expect("OpenBlock::new only fails if parent state root invalid; state root of best block's header is never invalid; qed");

		// Add uncles
		self.chain
			.find_uncle_headers(&h, engine.maximum_uncle_age())
			.unwrap()
			.into_iter()
			.take(engine.maximum_uncle_count())
			.foreach(|h| {
				open_block.push_uncle(h).unwrap();
			});

		open_block
	}

	fn vm_factory(&self) -> &EvmFactory {
		&self.vm_factory
	}

	fn import_sealed_block(&self, block: SealedBlock) -> ImportResult {
		let _import_lock = self.import_lock.lock();
		let _timer = PerfTimer::new("import_sealed_block");

		let original_best = self.chain_info().best_block_hash;

		let h = block.header().hash();
		let number = block.header().number();

		let block_data = block.rlp_bytes();
		let route = self.commit_block(block, &h, &block_data);
		trace!(target: "client", "Imported sealed block #{} ({})", number, h);

		{
			let (enacted, retracted) = self.calculate_enacted_retracted(&[route]);
			self.miner.chain_new_blocks(self, &[h.clone()], &[], &enacted, &retracted);

			self.io_channel.send(NetworkIoMessage::User(SyncMessage::NewChainBlocks {
				imported: vec![h.clone()],
				invalid: vec![],
				enacted: enacted,
				retracted: retracted,
				sealed: vec![h.clone()],
			})).unwrap_or_else(|e| warn!("Error sending IO notification: {:?}", e));
		}

		if self.chain_info().best_block_hash != original_best {
			self.miner.update_sealing(self);
		}

		Ok(h)
	}
}

impl MayPanic for Client {
	fn on_panic<F>(&self, closure: F) where F: OnPanicListener {
		self.panic_handler.on_panic(closure);
	}
}