// sync databases every minute. If flushing fails we exit immediatly. The system
// may not continue under any circumstances.
func (s *Ethereum) syncDatabases() {
	ticker := time.NewTicker(1 * time.Minute)
done:
	for {
		select {
		case <-ticker.C:
			// don't change the order of database flushes
			if err := s.extraDb.Flush(); err != nil {
				glog.Fatalf("fatal error: flush extraDb: %v (Restart your node. We are aware of this issue)\n", err)
			}
			if err := s.stateDb.Flush(); err != nil {
				glog.Fatalf("fatal error: flush stateDb: %v (Restart your node. We are aware of this issue)\n", err)
			}
			if err := s.blockDb.Flush(); err != nil {
				glog.Fatalf("fatal error: flush blockDb: %v (Restart your node. We are aware of this issue)\n", err)
			}
		case <-s.shutdownChan:
			break done
		}
	}

	s.blockDb.Close()
	s.stateDb.Close()
	s.extraDb.Close()

	close(s.databasesClosed)
}

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *ChainManager) ResetWithGenesisBlock(genesis *types.Block) {
	bc.mu.Lock()
	defer bc.mu.Unlock()

	// Dump the entire block chain and purge the caches
	for block := bc.currentBlock; block != nil; block = bc.GetBlock(block.ParentHash()) {
		DeleteBlock(bc.chainDb, block.Hash())
	}
	bc.headerCache.Purge()
	bc.bodyCache.Purge()
	bc.bodyRLPCache.Purge()
	bc.blockCache.Purge()
	bc.futureBlocks.Purge()

	// Prepare the genesis block and reinitialize the chain
	if err := WriteTd(bc.chainDb, genesis.Hash(), genesis.Difficulty()); err != nil {
		glog.Fatalf("failed to write genesis block TD: %v", err)
	}
	if err := WriteBlock(bc.chainDb, genesis); err != nil {
		glog.Fatalf("failed to write genesis block: %v", err)
	}
	bc.genesisBlock = genesis
	bc.insert(bc.genesisBlock)
	bc.currentBlock = bc.genesisBlock
	bc.setTotalDifficulty(genesis.Difficulty())
}

// insert injects a new head block into the current block chain. This method
// assumes that the block is indeed a true head. It will also reset the head
// header and the head fast sync block to this very same block if they are older
// or if they are on a different side chain.
//
// Note, this function assumes that the `mu` mutex is held!
func (bc *BlockChain) insert(block *types.Block) {
	// If the block is on a side chain or an unknown one, force other heads onto it too
	updateHeads := GetCanonicalHash(bc.chainDb, block.NumberU64()) != block.Hash()

	// Add the block to the canonical chain number scheme and mark as the head
	if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
		glog.Fatalf("failed to insert block number: %v", err)
	}
	if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
		glog.Fatalf("failed to insert head block hash: %v", err)
	}
	bc.currentBlock = block

	// If the block is better than out head or is on a different chain, force update heads
	if updateHeads {
		if err := WriteHeadHeaderHash(bc.chainDb, block.Hash()); err != nil {
			glog.Fatalf("failed to insert head header hash: %v", err)
		}
		bc.currentHeader = block.Header()

		if err := WriteHeadFastBlockHash(bc.chainDb, block.Hash()); err != nil {
			glog.Fatalf("failed to insert head fast block hash: %v", err)
		}
		bc.currentFastBlock = block
	}
}

// NodeKey retrieves the currently configured private key of the node, checking
// first any manually set key, falling back to the one found in the configured
// data folder. If no key can be found, a new one is generated.
func (c *Config) NodeKey() *ecdsa.PrivateKey {
	// Use any specifically configured key
	if c.PrivateKey != nil {
		return c.PrivateKey
	}
	// Generate ephemeral key if no datadir is being used
	if c.DataDir == "" {
		key, err := crypto.GenerateKey()
		if err != nil {
			glog.Fatalf("Failed to generate ephemeral node key: %v", err)
		}
		return key
	}
	// Fall back to persistent key from the data directory
	keyfile := filepath.Join(c.DataDir, datadirPrivateKey)
	if key, err := crypto.LoadECDSA(keyfile); err == nil {
		return key
	}
	// No persistent key found, generate and store a new one
	key, err := crypto.GenerateKey()
	if err != nil {
		glog.Fatalf("Failed to generate node key: %v", err)
	}
	if err := crypto.SaveECDSA(keyfile, key); err != nil {
		glog.V(logger.Error).Infof("Failed to persist node key: %v", err)
	}
	return key
}

// WriteHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (hc *HeaderChain) WriteHeader(header *types.Header) (status WriteStatus, err error) {
	// Cache some values to prevent constant recalculation
	var (
		hash   = header.Hash()
		number = header.Number.Uint64()
	)
	// Calculate the total difficulty of the header
	ptd := hc.GetTd(header.ParentHash)
	if ptd == nil {
		return NonStatTy, ParentError(header.ParentHash)
	}
	localTd := hc.GetTd(hc.currentHeaderHash)
	externTd := new(big.Int).Add(header.Difficulty, ptd)

	// If the total difficulty is higher than our known, add it to the canonical chain
	// Second clause in the if statement reduces the vulnerability to selfish mining.
	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
	if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
		// Delete any canonical number assignments above the new head
		for i := number + 1; GetCanonicalHash(hc.chainDb, i) != (common.Hash{}); i++ {
			DeleteCanonicalHash(hc.chainDb, i)
		}
		// Overwrite any stale canonical number assignments
		var (
			headHash   = header.ParentHash
			headHeader = hc.GetHeader(headHash)
			headNumber = headHeader.Number.Uint64()
		)
		for GetCanonicalHash(hc.chainDb, headNumber) != headHash {
			WriteCanonicalHash(hc.chainDb, headHash, headNumber)

			headHash = headHeader.ParentHash
			headHeader = hc.GetHeader(headHash)
			headNumber = headHeader.Number.Uint64()
		}
		// Extend the canonical chain with the new header
		if err := WriteCanonicalHash(hc.chainDb, hash, number); err != nil {
			glog.Fatalf("failed to insert header number: %v", err)
		}
		if err := WriteHeadHeaderHash(hc.chainDb, hash); err != nil {
			glog.Fatalf("failed to insert head header hash: %v", err)
		}
		hc.currentHeaderHash, hc.currentHeader = hash, types.CopyHeader(header)

		status = CanonStatTy
	} else {
		status = SideStatTy
	}
	// Irrelevant of the canonical status, write the header itself to the database
	if err := hc.WriteTd(hash, externTd); err != nil {
		glog.Fatalf("failed to write header total difficulty: %v", err)
	}
	if err := WriteHeader(hc.chainDb, header); err != nil {
		glog.Fatalf("failed to write header contents: %v", err)
	}
	hc.headerCache.Add(hash, header)

	return
}

// writeHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (self *BlockChain) writeHeader(header *types.Header) error {
	self.wg.Add(1)
	defer self.wg.Done()

	// Calculate the total difficulty of the header
	ptd := self.GetTd(header.ParentHash)
	if ptd == nil {
		return ParentError(header.ParentHash)
	}

	localTd := self.GetTd(self.currentHeader.Hash())
	externTd := new(big.Int).Add(header.Difficulty, ptd)

	// Make sure no inconsistent state is leaked during insertion
	self.mu.Lock()
	defer self.mu.Unlock()

	// If the total difficulty is higher than our known, add it to the canonical chain
	// Second clause in the if statement reduces the vulnerability to selfish mining.
	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
	if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
		// Delete any canonical number assignments above the new head
		for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
			DeleteCanonicalHash(self.chainDb, i)
		}
		// Overwrite any stale canonical number assignments
		head := self.GetHeader(header.ParentHash)
		for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
			WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
			head = self.GetHeader(head.ParentHash)
		}
		// Extend the canonical chain with the new header
		if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
			glog.Fatalf("failed to insert header number: %v", err)
		}
		if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
			glog.Fatalf("failed to insert head header hash: %v", err)
		}
		self.currentHeader = types.CopyHeader(header)
	}
	// Irrelevant of the canonical status, write the header itself to the database
	if err := WriteTd(self.chainDb, header.Hash(), externTd); err != nil {
		glog.Fatalf("failed to write header total difficulty: %v", err)
	}
	if err := WriteHeader(self.chainDb, header); err != nil {
		glog.Fatalf("filed to write header contents: %v", err)
	}
	return nil
}

func (bc *ChainManager) setLastState() error {
	head := GetHeadBlockHash(bc.chainDb)
	if head != (common.Hash{}) {
		block := bc.GetBlock(head)
		if block != nil {
			bc.currentBlock = block
		} else {
			glog.Infof("LastBlock (%x) not found. Recovering...\n", head)
			if bc.recover() {
				glog.Infof("Recover successful")
			} else {
				glog.Fatalf("Recover failed. Please report")
			}
		}
	} else {
		bc.Reset()
	}
	bc.td = bc.GetTd(bc.currentBlock.Hash())
	bc.currentGasLimit = CalcGasLimit(bc.currentBlock)

	if glog.V(logger.Info) {
		glog.Infof("Last block (#%v) %x TD=%v\n", bc.currentBlock.Number(), bc.currentBlock.Hash(), bc.td)
	}

	return nil
}

// SetHead rewinds the local chain to a new head. Everything above the new head
// will be deleted and the new one set.
func (hc *HeaderChain) SetHead(head uint64, delFn DeleteCallback) {
	height := uint64(0)
	if hc.currentHeader != nil {
		height = hc.currentHeader.Number.Uint64()
	}

	for hc.currentHeader != nil && hc.currentHeader.Number.Uint64() > head {
		hash := hc.currentHeader.Hash()
		if delFn != nil {
			delFn(hash)
		}
		DeleteHeader(hc.chainDb, hash)
		DeleteTd(hc.chainDb, hash)
		hc.currentHeader = hc.GetHeader(hc.currentHeader.ParentHash)
	}
	// Roll back the canonical chain numbering
	for i := height; i > head; i-- {
		DeleteCanonicalHash(hc.chainDb, i)
	}
	// Clear out any stale content from the caches
	hc.headerCache.Purge()
	hc.tdCache.Purge()

	if hc.currentHeader == nil {
		hc.currentHeader = hc.genesisHeader
	}
	hc.currentHeaderHash = hc.currentHeader.Hash()

	if err := WriteHeadHeaderHash(hc.chainDb, hc.currentHeaderHash); err != nil {
		glog.Fatalf("failed to reset head header hash: %v", err)
	}
}

// SetCurrentHeader sets the current head header of the canonical chain.
func (hc *HeaderChain) SetCurrentHeader(head *types.Header) {
	if err := WriteHeadHeaderHash(hc.chainDb, head.Hash()); err != nil {
		glog.Fatalf("failed to insert head header hash: %v", err)
	}
	hc.currentHeader = head
	hc.currentHeaderHash = head.Hash()
}

// WriteHeadFastBlockHash stores the fast head block's hash.
func WriteHeadFastBlockHash(db ethdb.Database, hash common.Hash) error {
	if err := db.Put(headFastKey, hash.Bytes()); err != nil {
		glog.Fatalf("failed to store last fast block's hash into database: %v", err)
		return err
	}
	return nil
}

func (bc *ChainManager) setLastState() error {
	data, _ := bc.chainDb.Get([]byte("LastBlock"))
	if len(data) != 0 {
		block := bc.GetBlock(common.BytesToHash(data))
		if block != nil {
			bc.currentBlock = block
			bc.lastBlockHash = block.Hash()
		} else {
			glog.Infof("LastBlock (%x) not found. Recovering...\n", data)
			if bc.recover() {
				glog.Infof("Recover successful")
			} else {
				glog.Fatalf("Recover failed. Please report")
			}
		}
	} else {
		bc.Reset()
	}
	bc.td = bc.currentBlock.Td
	bc.currentGasLimit = CalcGasLimit(bc.currentBlock)

	if glog.V(logger.Info) {
		glog.Infof("Last block (#%v) %x TD=%v\n", bc.currentBlock.Number(), bc.currentBlock.Hash(), bc.td)
	}

	return nil
}

// WriteBlock writes the block to the chain.
func (self *ChainManager) WriteBlock(block *types.Block) (status writeStatus, err error) {
	self.wg.Add(1)
	defer self.wg.Done()

	// Calculate the total difficulty of the block
	ptd := self.GetTd(block.ParentHash())
	if ptd == nil {
		return NonStatTy, ParentError(block.ParentHash())
	}
	td := new(big.Int).Add(block.Difficulty(), ptd)

	self.mu.RLock()
	cblock := self.currentBlock
	self.mu.RUnlock()

	// Compare the TD of the last known block in the canonical chain to make sure it's greater.
	// At this point it's possible that a different chain (fork) becomes the new canonical chain.
	if td.Cmp(self.Td()) > 0 {
		// chain fork
		if block.ParentHash() != cblock.Hash() {
			// during split we merge two different chains and create the new canonical chain
			err := self.reorg(cblock, block)
			if err != nil {
				return NonStatTy, err
			}
		}
		status = CanonStatTy

		self.mu.Lock()
		self.setTotalDifficulty(td)
		self.insert(block)
		self.mu.Unlock()
	} else {
		status = SideStatTy
	}

	if err := WriteTd(self.chainDb, block.Hash(), td); err != nil {
		glog.Fatalf("failed to write block total difficulty: %v", err)
	}
	if err := WriteBlock(self.chainDb, block); err != nil {
		glog.Fatalf("filed to write block contents: %v", err)
	}
	// Delete from future blocks
	self.futureBlocks.Remove(block.Hash())

	return
}

func (bc *ChainManager) recover() bool {
	data, _ := bc.chainDb.Get([]byte("checkpoint"))
	if len(data) != 0 {
		block := bc.GetBlock(common.BytesToHash(data))
		if block != nil {
			if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
				glog.Fatalf("failed to write database head number: %v", err)
			}
			if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
				glog.Fatalf("failed to write database head hash: %v", err)
			}
			bc.currentBlock = block
			return true
		}
	}
	return false
}

// WriteCanonicalHash stores the canonical hash for the given block number.
func WriteCanonicalHash(db ethdb.Database, hash common.Hash, number uint64) error {
	key := append(blockNumPrefix, big.NewInt(int64(number)).Bytes()...)
	if err := db.Put(key, hash.Bytes()); err != nil {
		glog.Fatalf("failed to store number to hash mapping into database: %v", err)
		return err
	}
	return nil
}

// WriteBlock writes the block to the chain.
func (self *BlockChain) WriteBlock(block *types.Block) (status WriteStatus, err error) {
	self.wg.Add(1)
	defer self.wg.Done()

	// Calculate the total difficulty of the block
	ptd := self.GetTd(block.ParentHash())
	if ptd == nil {
		return NonStatTy, ParentError(block.ParentHash())
	}

	localTd := self.GetTd(self.currentBlock.Hash())
	externTd := new(big.Int).Add(block.Difficulty(), ptd)

	// Make sure no inconsistent state is leaked during insertion
	self.mu.Lock()
	defer self.mu.Unlock()

	// If the total difficulty is higher than our known, add it to the canonical chain
	// Second clause in the if statement reduces the vulnerability to selfish mining.
	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
	if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
		// Reorganise the chain if the parent is not the head block
		if block.ParentHash() != self.currentBlock.Hash() {
			if err := self.reorg(self.currentBlock, block); err != nil {
				return NonStatTy, err
			}
		}
		// Insert the block as the new head of the chain
		self.insert(block)
		status = CanonStatTy
	} else {
		status = SideStatTy
	}
	// Irrelevant of the canonical status, write the block itself to the database
	if err := self.hc.WriteTd(block.Hash(), externTd); err != nil {
		glog.Fatalf("failed to write block total difficulty: %v", err)
	}
	if err := WriteBlock(self.chainDb, block); err != nil {
		glog.Fatalf("failed to write block contents: %v", err)
	}

	self.futureBlocks.Remove(block.Hash())

	return
}

// writeHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (self *BlockChain) writeHeader(header *types.Header) error {
	self.wg.Add(1)
	defer self.wg.Done()

	// Calculate the total difficulty of the header
	ptd := self.GetTd(header.ParentHash)
	if ptd == nil {
		return ParentError(header.ParentHash)
	}
	td := new(big.Int).Add(header.Difficulty, ptd)

	// Make sure no inconsistent state is leaked during insertion
	self.mu.Lock()
	defer self.mu.Unlock()

	// If the total difficulty is higher than our known, add it to the canonical chain
	if td.Cmp(self.GetTd(self.currentHeader.Hash())) > 0 {
		// Delete any canonical number assignments above the new head
		for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
			DeleteCanonicalHash(self.chainDb, i)
		}
		// Overwrite any stale canonical number assignments
		head := self.GetHeader(header.ParentHash)
		for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
			WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
			head = self.GetHeader(head.ParentHash)
		}
		// Extend the canonical chain with the new header
		if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
			glog.Fatalf("failed to insert header number: %v", err)
		}
		if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
			glog.Fatalf("failed to insert head header hash: %v", err)
		}
		self.currentHeader = types.CopyHeader(header)
	}
	// Irrelevant of the canonical status, write the header itself to the database
	if err := WriteTd(self.chainDb, header.Hash(), td); err != nil {
		glog.Fatalf("failed to write header total difficulty: %v", err)
	}
	if err := WriteHeader(self.chainDb, header); err != nil {
		glog.Fatalf("filed to write header contents: %v", err)
	}
	return nil
}

// insert injects a block into the current chain block chain. Note, this function
// assumes that the `mu` mutex is held!
func (bc *ChainManager) insert(block *types.Block) {
	// Add the block to the canonical chain number scheme and mark as the head
	if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
		glog.Fatalf("failed to insert block number: %v", err)
	}
	if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
		glog.Fatalf("failed to insert block number: %v", err)
	}
	// Add a new restore point if we reached some limit
	bc.checkpoint++
	if bc.checkpoint > checkpointLimit {
		if err := bc.chainDb.Put([]byte("checkpoint"), block.Hash().Bytes()); err != nil {
			glog.Fatalf("failed to create checkpoint: %v", err)
		}
		bc.checkpoint = 0
	}
	// Update the internal internal state with the head block
	bc.currentBlock = block
}

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) {
	// Dump the entire block chain and purge the caches
	bc.SetHead(0)

	bc.mu.Lock()
	defer bc.mu.Unlock()

	// Prepare the genesis block and reinitialise the chain
	if err := WriteTd(bc.chainDb, genesis.Hash(), genesis.Difficulty()); err != nil {
		glog.Fatalf("failed to write genesis block TD: %v", err)
	}
	if err := WriteBlock(bc.chainDb, genesis); err != nil {
		glog.Fatalf("failed to write genesis block: %v", err)
	}
	bc.genesisBlock = genesis
	bc.insert(bc.genesisBlock)
	bc.currentBlock = bc.genesisBlock
	bc.currentHeader = bc.genesisBlock.Header()
	bc.currentFastBlock = bc.genesisBlock
}

// WriteBlock writes the block to the chain.
func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err error) {
	self.wg.Add(1)
	defer self.wg.Done()

	// Calculate the total difficulty of the block
	ptd := self.GetTd(block.ParentHash())
	if ptd == nil {
		return NonStatTy, ParentError(block.ParentHash())
	}
	td := new(big.Int).Add(block.Difficulty(), ptd)

	// Make sure no inconsistent state is leaked during insertion
	self.mu.Lock()
	defer self.mu.Unlock()

	// If the total difficulty is higher than our known, add it to the canonical chain
	if td.Cmp(self.GetTd(self.currentBlock.Hash())) > 0 {
		// Reorganize the chain if the parent is not the head block
		if block.ParentHash() != self.currentBlock.Hash() {
			if err := self.reorg(self.currentBlock, block); err != nil {
				return NonStatTy, err
			}
		}
		// Insert the block as the new head of the chain
		self.insert(block)
		status = CanonStatTy
	} else {
		status = SideStatTy
	}
	// Irrelevant of the canonical status, write the block itself to the database
	if err := WriteTd(self.chainDb, block.Hash(), td); err != nil {
		glog.Fatalf("failed to write block total difficulty: %v", err)
	}
	if err := WriteBlock(self.chainDb, block); err != nil {
		glog.Fatalf("filed to write block contents: %v", err)
	}
	self.futureBlocks.Remove(block.Hash())

	return
}

// WriteTd serializes the total difficulty of a block into the database.
func WriteTd(db ethdb.Database, hash common.Hash, td *big.Int) error {
	data, err := rlp.EncodeToBytes(td)
	if err != nil {
		return err
	}
	key := append(append(blockPrefix, hash.Bytes()...), tdSuffix...)
	if err := db.Put(key, data); err != nil {
		glog.Fatalf("failed to store block total difficulty into database: %v", err)
		return err
	}
	glog.V(logger.Debug).Infof("stored block total difficulty [%x…]: %v", hash.Bytes()[:4], td)
	return nil
}