// indexBlock extract all of the standard addresses from all of the transactions
// in the passed block and maps each of them to the assocaited transaction using
// the passed map.
func (idx *AddrIndex) indexBlock(data writeIndexData, block *btcutil.Block, view *blockchain.UtxoViewpoint) {
	for txIdx, tx := range block.Transactions() {
		// Coinbases do not reference any inputs.  Since the block is
		// required to have already gone through full validation, it has
		// already been proven on the first transaction in the block is
		// a coinbase.
		if txIdx != 0 {
			for _, txIn := range tx.MsgTx().TxIn {
				// The view should always have the input since
				// the index contract requires it, however, be
				// safe and simply ignore any missing entries.
				origin := &txIn.PreviousOutPoint
				entry := view.LookupEntry(&origin.Hash)
				if entry == nil {
					continue
				}

				pkScript := entry.PkScriptByIndex(origin.Index)
				idx.indexPkScript(data, pkScript, txIdx)
			}
		}

		for _, txOut := range tx.MsgTx().TxOut {
			idx.indexPkScript(data, txOut.PkScript, txIdx)
		}
	}
}

// ConnectBlock is invoked by the index manager when a new block has been
// connected to the main chain.  This indexer adds a mapping for each address
// the transactions in the block involve.
//
// This is part of the Indexer interface.
func (idx *AddrIndex) ConnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
	// The offset and length of the transactions within the serialized
	// block.
	txLocs, err := block.TxLoc()
	if err != nil {
		return err
	}

	// Get the internal block ID associated with the block.
	blockID, err := dbFetchBlockIDByHash(dbTx, block.Hash())
	if err != nil {
		return err
	}

	// Build all of the address to transaction mappings in a local map.
	addrsToTxns := make(writeIndexData)
	idx.indexBlock(addrsToTxns, block, view)

	// Add all of the index entries for each address.
	addrIdxBucket := dbTx.Metadata().Bucket(addrIndexKey)
	for addrKey, txIdxs := range addrsToTxns {
		for _, txIdx := range txIdxs {
			err := dbPutAddrIndexEntry(addrIdxBucket, addrKey,
				blockID, txLocs[txIdx])
			if err != nil {
				return err
			}
		}
	}

	return nil
}

// checkBIP0030 ensures blocks do not contain duplicate transactions which
// 'overwrite' older transactions that are not fully spent.  This prevents an
// attack where a coinbase and all of its dependent transactions could be
// duplicated to effectively revert the overwritten transactions to a single
// confirmation thereby making them vulnerable to a double spend.
//
// For more details, see https://en.bitcoin.it/wiki/BIP_0030 and
// http://r6.ca/blog/20120206T005236Z.html.
//
// This function MUST be called with the chain state lock held (for reads).
func (b *BlockChain) checkBIP0030(node *blockNode, block *btcutil.Block, view *UtxoViewpoint) error {
	// Fetch utxo details for all of the transactions in this block.
	// Typically, there will not be any utxos for any of the transactions.
	fetchSet := make(map[chainhash.Hash]struct{})
	for _, tx := range block.Transactions() {
		fetchSet[*tx.Hash()] = struct{}{}
	}
	err := view.fetchUtxos(b.db, fetchSet)
	if err != nil {
		return err
	}

	// Duplicate transactions are only allowed if the previous transaction
	// is fully spent.
	for _, tx := range block.Transactions() {
		txEntry := view.LookupEntry(tx.Hash())
		if txEntry != nil && !txEntry.IsFullySpent() {
			str := fmt.Sprintf("tried to overwrite transaction %v "+
				"at block height %d that is not fully spent",
				tx.Hash(), txEntry.blockHeight)
			return ruleError(ErrOverwriteTx, str)
		}
	}

	return nil
}

// makeUtxoView creates a mock unspent transaction output view by using the
// transaction index in order to look up all inputs referenced by the
// transactions in the block.  This is sometimes needed when catching indexes up
// because many of the txouts could actually already be spent however the
// associated scripts are still required to index them.
func makeUtxoView(dbTx database.Tx, block *btcutil.Block) (*blockchain.UtxoViewpoint, error) {
	view := blockchain.NewUtxoViewpoint()
	for txIdx, tx := range block.Transactions() {
		// Coinbases do not reference any inputs.  Since the block is
		// required to have already gone through full validation, it has
		// already been proven on the first transaction in the block is
		// a coinbase.
		if txIdx == 0 {
			continue
		}

		// Use the transaction index to load all of the referenced
		// inputs and add their outputs to the view.
		for _, txIn := range tx.MsgTx().TxIn {
			originOut := &txIn.PreviousOutPoint
			originTx, err := dbFetchTx(dbTx, &originOut.Hash)
			if err != nil {
				return nil, err
			}

			view.AddTxOuts(btcutil.NewTx(originTx), 0)
		}
	}

	return view, nil
}

// GetBlockWeight computes the value of the weight metric for a given block.
// Currently the weight metric is simply the sum of the block's serialized size
// without any witness data scaled proportionally by the WitnessScaleFactor,
// and the block's serialized size including any witness data.
func GetBlockWeight(blk *btcutil.Block) int64 {
	msgBlock := blk.MsgBlock()

	baseSize := msgBlock.SerializeSizeStripped()
	totalSize := msgBlock.SerializeSize()

	// (baseSize * 3) + totalSize
	return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
}

func assertTxInBlock(t *harnessTest, block *btcutil.Block, txid *wire.ShaHash) {
	for _, tx := range block.Transactions() {
		if bytes.Equal(txid[:], tx.Sha()[:]) {
			return
		}
	}

	t.Fatalf("funding tx was not included in block")
}

// dbRemoveTxIndexEntries uses an existing database transaction to remove the
// latest transaction entry for every transaction in the passed block.
func dbRemoveTxIndexEntries(dbTx database.Tx, block *btcutil.Block) error {
	for _, tx := range block.Transactions() {
		err := dbRemoveTxIndexEntry(dbTx, tx.Hash())
		if err != nil {
			return err
		}
	}

	return nil
}

// DisconnectBlock is invoked by the index manager when a block has been
// disconnected from the main chain.  This indexer removes the
// hash-to-transaction mapping for every transaction in the block.
//
// This is part of the Indexer interface.
func (idx *TxIndex) DisconnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
	// Remove all of the transactions in the block from the index.
	if err := dbRemoveTxIndexEntries(dbTx, block); err != nil {
		return err
	}

	// Remove the block ID index entry for the block being disconnected and
	// decrement the current internal block ID to account for it.
	if err := dbRemoveBlockIDIndexEntry(dbTx, block.Hash()); err != nil {
		return err
	}
	idx.curBlockID--
	return nil
}

// dbIndexDisconnectBlock removes all of the index entries associated with the
// given block using the provided indexer and updates the tip of the indexer
// accordingly.  An error will be returned if the current tip for the indexer is
// not the passed block.
func dbIndexDisconnectBlock(dbTx database.Tx, indexer Indexer, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
	// Assert that the block being disconnected is the current tip of the
	// index.
	idxKey := indexer.Key()
	curTipHash, _, err := dbFetchIndexerTip(dbTx, idxKey)
	if err != nil {
		return err
	}
	if !curTipHash.IsEqual(block.Hash()) {
		return AssertError(fmt.Sprintf("dbIndexDisconnectBlock must "+
			"be called with the block at the current index tip "+
			"(%s, tip %s, block %s)", indexer.Name(),
			curTipHash, block.Hash()))
	}

	// Notify the indexer with the disconnected block so it can remove all
	// of the appropriate entries.
	if err := indexer.DisconnectBlock(dbTx, block, view); err != nil {
		return err
	}

	// Update the current index tip.
	prevHash := &block.MsgBlock().Header.PrevBlock
	return dbPutIndexerTip(dbTx, idxKey, prevHash, block.Height()-1)
}

// fetchInputUtxos loads utxo details about the input transactions referenced
// by the transactions in the given block into the view from the database as
// needed.  In particular, referenced entries that are earlier in the block are
// added to the view and entries that are already in the view are not modified.
func (view *UtxoViewpoint) fetchInputUtxos(db database.DB, block *btcutil.Block) error {
	// Build a map of in-flight transactions because some of the inputs in
	// this block could be referencing other transactions earlier in this
	// block which are not yet in the chain.
	txInFlight := map[chainhash.Hash]int{}
	transactions := block.Transactions()
	for i, tx := range transactions {
		txInFlight[*tx.Hash()] = i
	}

	// Loop through all of the transaction inputs (except for the coinbase
	// which has no inputs) collecting them into sets of what is needed and
	// what is already known (in-flight).
	txNeededSet := make(map[chainhash.Hash]struct{})
	for i, tx := range transactions[1:] {
		for _, txIn := range tx.MsgTx().TxIn {
			// It is acceptable for a transaction input to reference
			// the output of another transaction in this block only
			// if the referenced transaction comes before the
			// current one in this block.  Add the outputs of the
			// referenced transaction as available utxos when this
			// is the case.  Otherwise, the utxo details are still
			// needed.
			//
			// NOTE: The >= is correct here because i is one less
			// than the actual position of the transaction within
			// the block due to skipping the coinbase.
			originHash := &txIn.PreviousOutPoint.Hash
			if inFlightIndex, ok := txInFlight[*originHash]; ok &&
				i >= inFlightIndex {

				originTx := transactions[inFlightIndex]
				view.AddTxOuts(originTx, block.Height())
				continue
			}

			// Don't request entries that are already in the view
			// from the database.
			if _, ok := view.entries[*originHash]; ok {
				continue
			}

			txNeededSet[*originHash] = struct{}{}
		}
	}

	// Request the input utxos from the database.
	return view.fetchUtxosMain(db, txNeededSet)
}

// CheckConnectBlock performs several checks to confirm connecting the passed
// block to the main chain does not violate any rules.  An example of some of
// the checks performed are ensuring connecting the block would not cause any
// duplicate transaction hashes for old transactions that aren't already fully
// spent, double spends, exceeding the maximum allowed signature operations
// per block, invalid values in relation to the expected block subsidy, or fail
// transaction script validation.
//
// This function is safe for concurrent access.
func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
	b.chainLock.Lock()
	defer b.chainLock.Unlock()

	prevNode := b.bestNode
	newNode := newBlockNode(&block.MsgBlock().Header, block.Hash(),
		prevNode.height+1)
	newNode.parent = prevNode
	newNode.workSum.Add(prevNode.workSum, newNode.workSum)

	// Leave the spent txouts entry nil in the state since the information
	// is not needed and thus extra work can be avoided.
	view := NewUtxoViewpoint()
	view.SetBestHash(prevNode.hash)
	return b.checkConnectBlock(newNode, block, view, nil)
}

// ConnectBlock is invoked by the index manager when a new block has been
// connected to the main chain.  This indexer adds a hash-to-transaction mapping
// for every transaction in the passed block.
//
// This is part of the Indexer interface.
func (idx *TxIndex) ConnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
	// Increment the internal block ID to use for the block being connected
	// and add all of the transactions in the block to the index.
	newBlockID := idx.curBlockID + 1
	if err := dbAddTxIndexEntries(dbTx, block, newBlockID); err != nil {
		return err
	}

	// Add the new block ID index entry for the block being connected and
	// update the current internal block ID accordingly.
	err := dbPutBlockIDIndexEntry(dbTx, block.Hash(), newBlockID)
	if err != nil {
		return err
	}
	idx.curBlockID = newBlockID
	return nil
}

// LogBlockHeight logs a new block height as an information message to show
// progress to the user. In order to prevent spam, it limits logging to one
// message every 10 seconds with duration and totals included.
func (b *blockProgressLogger) LogBlockHeight(block *btcutil.Block) {
	b.Lock()
	defer b.Unlock()

	b.receivedLogBlocks++
	b.receivedLogTx += int64(len(block.MsgBlock().Transactions))

	now := time.Now()
	duration := now.Sub(b.lastBlockLogTime)
	if duration < time.Second*10 {
		return
	}

	// Truncate the duration to 10s of milliseconds.
	durationMillis := int64(duration / time.Millisecond)
	tDuration := 10 * time.Millisecond * time.Duration(durationMillis/10)

	// Log information about new block height.
	blockStr := "blocks"
	if b.receivedLogBlocks == 1 {
		blockStr = "block"
	}
	txStr := "transactions"
	if b.receivedLogTx == 1 {
		txStr = "transaction"
	}
	b.subsystemLogger.Infof("%s %d %s in the last %s (%d %s, height %d, %s)",
		b.progressAction, b.receivedLogBlocks, blockStr, tDuration, b.receivedLogTx,
		txStr, block.Height(), block.MsgBlock().Header.Timestamp)

	b.receivedLogBlocks = 0
	b.receivedLogTx = 0
	b.lastBlockLogTime = now
}

// dbAddTxIndexEntries uses an existing database transaction to add a
// transaction index entry for every transaction in the passed block.
func dbAddTxIndexEntries(dbTx database.Tx, block *btcutil.Block, blockID uint32) error {
	// The offset and length of the transactions within the serialized
	// block.
	txLocs, err := block.TxLoc()
	if err != nil {
		return err
	}

	// As an optimization, allocate a single slice big enough to hold all
	// of the serialized transaction index entries for the block and
	// serialize them directly into the slice.  Then, pass the appropriate
	// subslice to the database to be written.  This approach significantly
	// cuts down on the number of required allocations.
	offset := 0
	serializedValues := make([]byte, len(block.Transactions())*txEntrySize)
	for i, tx := range block.Transactions() {
		putTxIndexEntry(serializedValues[offset:], blockID, txLocs[i])
		endOffset := offset + txEntrySize
		err := dbPutTxIndexEntry(dbTx, tx.Hash(),
			serializedValues[offset:endOffset:endOffset])
		if err != nil {
			return err
		}
		offset += txEntrySize
	}

	return nil
}

// ValidateWitnessCommitment validates the witness commitment (if any) found
// within the coinbase transaction of the passed block.
func ValidateWitnessCommitment(blk *btcutil.Block) error {
	coinbaseTx := blk.Transactions()[0]
	witnessCommitment, witnessFound := ExtractWitnessCommitment(coinbaseTx)

	// If we can't find a witness commitment in any of the coinbase's
	// outputs, then the block MUST NOT contain any transactions with
	// witness data.
	if !witnessFound {
		for _, tx := range blk.Transactions() {
			msgTx := tx.MsgTx()
			if msgTx.HasWitness() {
				str := fmt.Sprintf("block contains transaction with witness" +
					" data, yet no witness commitment present")
				return ruleError(ErrUnexpectedWitness, str)
			}
		}
		return nil
	}

	// At this point the block contains a witness commitment, so the
	// coinbase transaction MUST have exactly one witness element within
	// its witness data and that element must be exactly
	// CoinbaseWitnessDataLen bytes.
	coinbaseWitness := coinbaseTx.MsgTx().TxIn[0].Witness
	if len(coinbaseWitness) != 1 {
		str := fmt.Sprintf("the coinbase transaction has %d items in "+
			"its witness stack when only one is allowed",
			len(coinbaseWitness))
		return ruleError(ErrInvalidWitnessCommitment, str)
	}
	witnessNonce := coinbaseWitness[0]
	if len(witnessNonce) != CoinbaseWitnessDataLen {
		str := fmt.Sprintf("the coinbase transaction witness nonce "+
			"has %d bytes when it must be %d bytes",
			len(witnessNonce), CoinbaseWitnessDataLen)
		return ruleError(ErrInvalidWitnessCommitment, str)
	}

	// Finally, with the preliminary checks out of the way, we can check if
	// the extracted witnessCommitment is equal to:
	// SHA256(witnessMerkleRoot || witnessNonce). Where witnessNonce is the
	// coinbase transaction's only witness item.
	witnessMerkleTree := BuildMerkleTreeStore(blk.Transactions(), true)
	witnessMerkleRoot := witnessMerkleTree[len(witnessMerkleTree)-1]

	witnessPreimage := make([]byte, 64)
	copy(witnessPreimage[:], witnessMerkleRoot[:])
	copy(witnessPreimage[32:], witnessNonce)

	if !bytes.Equal(chainhash.DoubleHashB(witnessPreimage), witnessCommitment) {
		str := "witness commitment does not match"
		return ruleError(ErrWitnessCommitmentMismatch, str)
	}

	return nil
}

// maybeAcceptBlock potentially accepts a block into the block chain and, if
// accepted, returns whether or not it is on the main chain.  It performs
// several validation checks which depend on its position within the block chain
// before adding it.  The block is expected to have already gone through
// ProcessBlock before calling this function with it.
//
// The flags modify the behavior of this function as follows:
//  - BFDryRun: The memory chain index will not be pruned and no accept
//    notification will be sent since the block is not being accepted.
//
// The flags are also passed to checkBlockContext and connectBestChain.  See
// their documentation for how the flags modify their behavior.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) (bool, error) {
	dryRun := flags&BFDryRun == BFDryRun

	// Get a block node for the block previous to this one.  Will be nil
	// if this is the genesis block.
	prevNode, err := b.getPrevNodeFromBlock(block)
	if err != nil {
		log.Errorf("getPrevNodeFromBlock: %v", err)
		return false, err
	}

	// The height of this block is one more than the referenced previous
	// block.
	blockHeight := int32(0)
	if prevNode != nil {
		blockHeight = prevNode.height + 1
	}
	block.SetHeight(blockHeight)

	// The block must pass all of the validation rules which depend on the
	// position of the block within the block chain.
	err = b.checkBlockContext(block, prevNode, flags)
	if err != nil {
		return false, err
	}

	// Create a new block node for the block and add it to the in-memory
	// block chain (could be either a side chain or the main chain).
	blockHeader := &block.MsgBlock().Header
	newNode := newBlockNode(blockHeader, block.Hash(), blockHeight)
	if prevNode != nil {
		newNode.parent = prevNode
		newNode.height = blockHeight
		newNode.workSum.Add(prevNode.workSum, newNode.workSum)
	}

	// Connect the passed block to the chain while respecting proper chain
	// selection according to the chain with the most proof of work.  This
	// also handles validation of the transaction scripts.
	isMainChain, err := b.connectBestChain(newNode, block, flags)
	if err != nil {
		return false, err
	}

	// Notify the caller that the new block was accepted into the block
	// chain.  The caller would typically want to react by relaying the
	// inventory to other peers.
	if !dryRun {
		b.chainLock.Unlock()
		b.sendNotification(NTBlockAccepted, block)
		b.chainLock.Lock()
	}

	return isMainChain, nil
}

// connectTransactions updates the view by adding all new utxos created by all
// of the transactions in the passed block, marking all utxos the transactions
// spend as spent, and setting the best hash for the view to the passed block.
// In addition, when the 'stxos' argument is not nil, it will be updated to
// append an entry for each spent txout.
func (view *UtxoViewpoint) connectTransactions(block *btcutil.Block, stxos *[]spentTxOut) error {
	for _, tx := range block.Transactions() {
		err := view.connectTransaction(tx, block.Height(), stxos)
		if err != nil {
			return err
		}
	}

	// Update the best hash for view to include this block since all of its
	// transactions have been connected.
	view.SetBestHash(block.Hash())
	return nil
}

// dbIndexConnectBlock adds all of the index entries associated with the
// given block using the provided indexer and updates the tip of the indexer
// accordingly.  An error will be returned if the current tip for the indexer is
// not the previous block for the passed block.
func dbIndexConnectBlock(dbTx database.Tx, indexer Indexer, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
	// Assert that the block being connected properly connects to the
	// current tip of the index.
	idxKey := indexer.Key()
	curTipHash, _, err := dbFetchIndexerTip(dbTx, idxKey)
	if err != nil {
		return err
	}
	if !curTipHash.IsEqual(&block.MsgBlock().Header.PrevBlock) {
		return AssertError(fmt.Sprintf("dbIndexConnectBlock must be "+
			"called with a block that extends the current index "+
			"tip (%s, tip %s, block %s)", indexer.Name(),
			curTipHash, block.Hash()))
	}

	// Notify the indexer with the connected block so it can index it.
	if err := indexer.ConnectBlock(dbTx, block, view); err != nil {
		return err
	}

	// Update the current index tip.
	return dbPutIndexerTip(dbTx, idxKey, block.Hash(), block.Height())
}

// submitBlock submits the passed block to network after ensuring it passes all
// of the consensus validation rules.
func (m *CPUMiner) submitBlock(block *btcutil.Block) bool {
	m.submitBlockLock.Lock()
	defer m.submitBlockLock.Unlock()

	// Ensure the block is not stale since a new block could have shown up
	// while the solution was being found.  Typically that condition is
	// detected and all work on the stale block is halted to start work on
	// a new block, but the check only happens periodically, so it is
	// possible a block was found and submitted in between.
	msgBlock := block.MsgBlock()
	if !msgBlock.Header.PrevBlock.IsEqual(m.g.BestSnapshot().Hash) {
		log.Debugf("Block submitted via CPU miner with previous "+
			"block %s is stale", msgBlock.Header.PrevBlock)
		return false
	}

	// Process this block using the same rules as blocks coming from other
	// nodes.  This will in turn relay it to the network like normal.
	isOrphan, err := m.cfg.ProcessBlock(block, blockchain.BFNone)
	if err != nil {
		// Anything other than a rule violation is an unexpected error,
		// so log that error as an internal error.
		if _, ok := err.(blockchain.RuleError); !ok {
			log.Errorf("Unexpected error while processing "+
				"block submitted via CPU miner: %v", err)
			return false
		}

		log.Debugf("Block submitted via CPU miner rejected: %v", err)
		return false
	}
	if isOrphan {
		log.Debugf("Block submitted via CPU miner is an orphan")
		return false
	}

	// The block was accepted.
	coinbaseTx := block.MsgBlock().Transactions[0].TxOut[0]
	log.Infof("Block submitted via CPU miner accepted (hash %s, "+
		"amount %v)", block.Hash(), btcutil.Amount(coinbaseTx.Value))
	return true
}

// CreateBlock creates a new block building from the previous block with a
// specified blockversion and timestamp. If the timestamp passed is zero (not
// initialized), then the timestamp of the previous block will be used plus 1
// second is used. Passing nil for the previous block results in a block that
// builds off of the genesis block for the specified chain.
func CreateBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
	blockVersion int32, blockTime time.Time,
	miningAddr btcutil.Address, net *chaincfg.Params) (*btcutil.Block, error) {

	var (
		prevHash      *chainhash.Hash
		blockHeight   int32
		prevBlockTime time.Time
	)

	// If the previous block isn't specified, then we'll construct a block
	// that builds off of the genesis block for the chain.
	if prevBlock == nil {
		prevHash = net.GenesisHash
		blockHeight = 1
		prevBlockTime = net.GenesisBlock.Header.Timestamp.Add(time.Minute)
	} else {
		prevHash = prevBlock.Hash()
		blockHeight = prevBlock.Height() + 1
		prevBlockTime = prevBlock.MsgBlock().Header.Timestamp
	}

	// If a target block time was specified, then use that as the header's
	// timestamp. Otherwise, add one second to the previous block unless
	// it's the genesis block in which case use the current time.
	var ts time.Time
	switch {
	case !blockTime.IsZero():
		ts = blockTime
	default:
		ts = prevBlockTime.Add(time.Second)
	}

	extraNonce := uint64(0)
	coinbaseScript, err := standardCoinbaseScript(blockHeight, extraNonce)
	if err != nil {
		return nil, err
	}
	coinbaseTx, err := createCoinbaseTx(coinbaseScript, blockHeight,
		miningAddr, net)
	if err != nil {
		return nil, err
	}

	// Create a new block ready to be solved.
	blockTxns := []*btcutil.Tx{coinbaseTx}
	if inclusionTxs != nil {
		blockTxns = append(blockTxns, inclusionTxs...)
	}
	merkles := blockchain.BuildMerkleTreeStore(blockTxns, false)
	var block wire.MsgBlock
	block.Header = wire.BlockHeader{
		Version:    blockVersion,
		PrevBlock:  *prevHash,
		MerkleRoot: *merkles[len(merkles)-1],
		Timestamp:  ts,
		Bits:       net.PowLimitBits,
	}
	for _, tx := range blockTxns {
		if err := block.AddTransaction(tx.MsgTx()); err != nil {
			return nil, err
		}
	}

	found := solveBlock(&block.Header, net.PowLimit)
	if !found {
		return nil, errors.New("Unable to solve block")
	}

	utilBlock := btcutil.NewBlock(&block)
	utilBlock.SetHeight(blockHeight)
	return utilBlock, nil
}