func hasAllBlocks(chain *core.BlockChain, bs []*types.Block) bool {
	for _, b := range bs {
		if !chain.HasBlock(b.Hash()) {
			return false
		}
	}
	return true
}

// blockByNumber is a commonly used helper function which retrieves and returns the block for the given block number. It
// returns nil when no block could be found.
func blockByNumber(m *miner.Miner, bc *core.BlockChain, blockNr rpc.BlockNumber) *types.Block {
	if blockNr == rpc.PendingBlockNumber {
		return m.PendingBlock()
	}
	if blockNr == rpc.LatestBlockNumber {
		return bc.CurrentBlock()
	}

	return bc.GetBlockByNumber(uint64(blockNr))
}

func ExportChain(blockchain *core.BlockChain, fn string) error {
	glog.Infoln("Exporting blockchain to", fn)
	fh, err := os.OpenFile(fn, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.ModePerm)
	if err != nil {
		return err
	}
	defer fh.Close()
	if err := blockchain.Export(fh); err != nil {
		return err
	}
	glog.Infoln("Exported blockchain to", fn)
	return nil
}

func ExportAppendChain(blockchain *core.BlockChain, fn string, first uint64, last uint64) error {
	glog.Infoln("Exporting blockchain to", fn)
	// TODO verify mode perms
	fh, err := os.OpenFile(fn, os.O_CREATE|os.O_APPEND|os.O_WRONLY, os.ModePerm)
	if err != nil {
		return err
	}
	defer fh.Close()
	if err := blockchain.ExportN(fh, first, last); err != nil {
		return err
	}
	glog.Infoln("Exported blockchain to", fn)
	return nil
}

func (self *GasPriceOracle) processPastBlocks(chain *core.BlockChain) {
	last := int64(-1)
	cblock := chain.CurrentBlock()
	if cblock != nil {
		last = int64(cblock.NumberU64())
	}
	first := int64(0)
	if last > gpoProcessPastBlocks {
		first = last - gpoProcessPastBlocks
	}
	self.firstProcessed = uint64(first)
	for i := first; i <= last; i++ {
		block := chain.GetBlockByNumber(uint64(i))
		if block != nil {
			self.processBlock(block)
		}
	}

}

func ImportChain(chain *core.BlockChain, fn string) error {
	// Watch for Ctrl-C while the import is running.
	// If a signal is received, the import will stop at the next batch.
	interrupt := make(chan os.Signal, 1)
	stop := make(chan struct{})
	signal.Notify(interrupt, os.Interrupt)
	defer signal.Stop(interrupt)
	defer close(interrupt)
	go func() {
		if _, ok := <-interrupt; ok {
			glog.Info("caught interrupt during import, will stop at next batch")
		}
		close(stop)
	}()
	checkInterrupt := func() bool {
		select {
		case <-stop:
			return true
		default:
			return false
		}
	}

	glog.Infoln("Importing blockchain", fn)
	fh, err := os.Open(fn)
	if err != nil {
		return err
	}
	defer fh.Close()
	stream := rlp.NewStream(fh, 0)

	// Run actual the import.
	blocks := make(types.Blocks, importBatchSize)
	n := 0
	for batch := 0; ; batch++ {
		// Load a batch of RLP blocks.
		if checkInterrupt() {
			return fmt.Errorf("interrupted")
		}
		i := 0
		for ; i < importBatchSize; i++ {
			var b types.Block
			if err := stream.Decode(&b); err == io.EOF {
				break
			} else if err != nil {
				return fmt.Errorf("at block %d: %v", n, err)
			}
			// don't import first block
			if b.NumberU64() == 0 {
				i--
				continue
			}
			blocks[i] = &b
			n++
		}
		if i == 0 {
			break
		}
		// Import the batch.
		if checkInterrupt() {
			return fmt.Errorf("interrupted")
		}
		if hasAllBlocks(chain, blocks[:i]) {
			glog.Infof("skipping batch %d, all blocks present [%x / %x]",
				batch, blocks[0].Hash().Bytes()[:4], blocks[i-1].Hash().Bytes()[:4])
			continue
		}

		if _, err := chain.InsertChain(blocks[:i]); err != nil {
			return fmt.Errorf("invalid block %d: %v", n, err)
		}
	}
	return nil
}

// NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
// with the ethereum network.
func NewProtocolManager(fastSync bool, networkId int, mux *event.TypeMux, txpool txPool, pow pow.PoW, blockchain *core.BlockChain, chaindb ethdb.Database) (*ProtocolManager, error) {
	// Figure out whether to allow fast sync or not
	if fastSync && blockchain.CurrentBlock().NumberU64() > 0 {
		glog.V(logger.Info).Infof("blockchain not empty, fast sync disabled")
		fastSync = false
	}
	// Create the protocol manager with the base fields
	manager := &ProtocolManager{
		networkId:  networkId,
		fastSync:   fastSync,
		eventMux:   mux,
		txpool:     txpool,
		blockchain: blockchain,
		chaindb:    chaindb,
		peers:      newPeerSet(),
		newPeerCh:  make(chan *peer, 1),
		txsyncCh:   make(chan *txsync),
		quitSync:   make(chan struct{}),
	}
	// Initiate a sub-protocol for every implemented version we can handle
	manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
	for i, version := range ProtocolVersions {
		// Skip protocol version if incompatible with the mode of operation
		if fastSync && version < eth63 {
			continue
		}
		// Compatible; initialise the sub-protocol
		version := version // Closure for the run
		manager.SubProtocols = append(manager.SubProtocols, p2p.Protocol{
			Name:    ProtocolName,
			Version: version,
			Length:  ProtocolLengths[i],
			Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
				peer := manager.newPeer(int(version), p, rw)
				manager.newPeerCh <- peer
				return manager.handle(peer)
			},
			NodeInfo: func() interface{} {
				return manager.NodeInfo()
			},
			PeerInfo: func(id discover.NodeID) interface{} {
				if p := manager.peers.Peer(fmt.Sprintf("%x", id[:8])); p != nil {
					return p.Info()
				}
				return nil
			},
		})
	}
	if len(manager.SubProtocols) == 0 {
		return nil, errIncompatibleConfig
	}
	// Construct the different synchronisation mechanisms
	manager.downloader = downloader.New(chaindb, manager.eventMux, blockchain.HasHeader, blockchain.HasBlockAndState, blockchain.GetHeader,
		blockchain.GetBlock, blockchain.CurrentHeader, blockchain.CurrentBlock, blockchain.CurrentFastBlock, blockchain.FastSyncCommitHead,
		blockchain.GetTd, blockchain.InsertHeaderChain, blockchain.InsertChain, blockchain.InsertReceiptChain, blockchain.Rollback,
		manager.removePeer)

	validator := func(block *types.Block, parent *types.Block) error {
		return core.ValidateHeader(pow, block.Header(), parent.Header(), true, false)
	}
	heighter := func() uint64 {
		return blockchain.CurrentBlock().NumberU64()
	}
	manager.fetcher = fetcher.New(blockchain.GetBlock, validator, manager.BroadcastBlock, heighter, blockchain.InsertChain, manager.removePeer)

	return manager, nil
}