path: root/internal/ethapi/api.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package ethapi

import (
    "bytes"
    "context"
    "errors"
    "fmt"
    "math/big"
    "strings"
    "time"

    "github.com/davecgh/go-spew/spew"
    "github.com/dexon-foundation/dexon/accounts"
    "github.com/dexon-foundation/dexon/accounts/keystore"
    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/common/hexutil"
    "github.com/dexon-foundation/dexon/common/math"
    "github.com/dexon-foundation/dexon/consensus/ethash"
    "github.com/dexon-foundation/dexon/core"
    "github.com/dexon-foundation/dexon/core/rawdb"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/core/vm"
    "github.com/dexon-foundation/dexon/crypto"
    "github.com/dexon-foundation/dexon/log"
    "github.com/dexon-foundation/dexon/p2p"
    "github.com/dexon-foundation/dexon/params"
    "github.com/dexon-foundation/dexon/rlp"
    "github.com/dexon-foundation/dexon/rpc"
    "github.com/syndtr/goleveldb/leveldb"
    "github.com/syndtr/goleveldb/leveldb/util"
)

const (
    defaultGasPrice = params.GWei
)

// PublicEthereumAPI provides an API to access Ethereum related information.
// It offers only methods that operate on public data that is freely available to anyone.
type PublicEthereumAPI struct {
    b Backend
}

// NewPublicEthereumAPI creates a new Ethereum protocol API.
func NewPublicEthereumAPI(b Backend) *PublicEthereumAPI {
    return &PublicEthereumAPI{b}
}

// GasPrice returns a suggestion for a gas price.
func (s *PublicEthereumAPI) GasPrice(ctx context.Context) (*hexutil.Big, error) {
    price, err := s.b.SuggestPrice(ctx)
    return (*hexutil.Big)(price), err
}

// ProtocolVersion returns the current Ethereum protocol version this node supports
func (s *PublicEthereumAPI) ProtocolVersion() hexutil.Uint {
    return hexutil.Uint(s.b.ProtocolVersion())
}

// Syncing returns false in case the node is currently not syncing with the network. It can be up to date or has not
// yet received the latest block headers from its pears. In case it is synchronizing:
// - startingBlock: block number this node started to synchronise from
// - currentBlock:  block number this node is currently importing
// - highestBlock:  block number of the highest block header this node has received from peers
// - pulledStates:  number of state entries processed until now
// - knownStates:   number of known state entries that still need to be pulled
func (s *PublicEthereumAPI) Syncing() (interface{}, error) {
    progress := s.b.Downloader().Progress()

    // Return not syncing if the synchronisation already completed
    if progress.CurrentBlock >= progress.HighestBlock {
        return false, nil
    }
    // Otherwise gather the block sync stats
    return map[string]interface{}{
        "startingBlock": hexutil.Uint64(progress.StartingBlock),
        "currentBlock":  hexutil.Uint64(progress.CurrentBlock),
        "highestBlock":  hexutil.Uint64(progress.HighestBlock),
        "pulledStates":  hexutil.Uint64(progress.PulledStates),
        "knownStates":   hexutil.Uint64(progress.KnownStates),
    }, nil
}

// PublicTxPoolAPI offers and API for the transaction pool. It only operates on data that is non confidential.
type PublicTxPoolAPI struct {
    b Backend
}

// NewPublicTxPoolAPI creates a new tx pool service that gives information about the transaction pool.
func NewPublicTxPoolAPI(b Backend) *PublicTxPoolAPI {
    return &PublicTxPoolAPI{b}
}

// Content returns the transactions contained within the transaction pool.
func (s *PublicTxPoolAPI) Content() map[string]map[string]map[string]*RPCTransaction {
    content := map[string]map[string]map[string]*RPCTransaction{
        "pending": make(map[string]map[string]*RPCTransaction),
        "queued":  make(map[string]map[string]*RPCTransaction),
    }
    pending, queue := s.b.TxPoolContent()

    // Flatten the pending transactions
    for account, txs := range pending {
        dump := make(map[string]*RPCTransaction)
        for _, tx := range txs {
            dump[fmt.Sprintf("%d", tx.Nonce())] = newRPCPendingTransaction(tx)
        }
        content["pending"][account.Hex()] = dump
    }
    // Flatten the queued transactions
    for account, txs := range queue {
        dump := make(map[string]*RPCTransaction)
        for _, tx := range txs {
            dump[fmt.Sprintf("%d", tx.Nonce())] = newRPCPendingTransaction(tx)
        }
        content["queued"][account.Hex()] = dump
    }
    return content
}

// Status returns the number of pending and queued transaction in the pool.
func (s *PublicTxPoolAPI) Status() map[string]hexutil.Uint {
    pending, queue := s.b.Stats()
    return map[string]hexutil.Uint{
        "pending": hexutil.Uint(pending),
        "queued":  hexutil.Uint(queue),
    }
}

// Inspect retrieves the content of the transaction pool and flattens it into an
// easily inspectable list.
func (s *PublicTxPoolAPI) Inspect() map[string]map[string]map[string]string {
    content := map[string]map[string]map[string]string{
        "pending": make(map[string]map[string]string),
        "queued":  make(map[string]map[string]string),
    }
    pending, queue := s.b.TxPoolContent()

    // Define a formatter to flatten a transaction into a string
    var format = func(tx *types.Transaction) string {
        if to := tx.To(); to != nil {
            return fmt.Sprintf("%s: %v wei + %v gas × %v wei", tx.To().Hex(), tx.Value(), tx.Gas(), tx.GasPrice())
        }
        return fmt.Sprintf("contract creation: %v wei + %v gas × %v wei", tx.Value(), tx.Gas(), tx.GasPrice())
    }
    // Flatten the pending transactions
    for account, txs := range pending {
        dump := make(map[string]string)
        for _, tx := range txs {
            dump[fmt.Sprintf("%d", tx.Nonce())] = format(tx)
        }
        content["pending"][account.Hex()] = dump
    }
    // Flatten the queued transactions
    for account, txs := range queue {
        dump := make(map[string]string)
        for _, tx := range txs {
            dump[fmt.Sprintf("%d", tx.Nonce())] = format(tx)
        }
        content["queued"][account.Hex()] = dump
    }
    return content
}

// PublicAccountAPI provides an API to access accounts managed by this node.
// It offers only methods that can retrieve accounts.
type PublicAccountAPI struct {
    am *accounts.Manager
}

// NewPublicAccountAPI creates a new PublicAccountAPI.
func NewPublicAccountAPI(am *accounts.Manager) *PublicAccountAPI {
    return &PublicAccountAPI{am: am}
}

// Accounts returns the collection of accounts this node manages
func (s *PublicAccountAPI) Accounts() []common.Address {
    addresses := make([]common.Address, 0) // return [] instead of nil if empty
    for _, wallet := range s.am.Wallets() {
        for _, account := range wallet.Accounts() {
            addresses = append(addresses, account.Address)
        }
    }
    return addresses
}

// PrivateAccountAPI provides an API to access accounts managed by this node.
// It offers methods to create, (un)lock en list accounts. Some methods accept
// passwords and are therefore considered private by default.
type PrivateAccountAPI struct {
    am        *accounts.Manager
    nonceLock *AddrLocker
    b         Backend
}

// NewPrivateAccountAPI create a new PrivateAccountAPI.
func NewPrivateAccountAPI(b Backend, nonceLock *AddrLocker) *PrivateAccountAPI {
    return &PrivateAccountAPI{
        am:        b.AccountManager(),
        nonceLock: nonceLock,
        b:         b,
    }
}

// ListAccounts will return a list of addresses for accounts this node manages.
func (s *PrivateAccountAPI) ListAccounts() []common.Address {
    addresses := make([]common.Address, 0) // return [] instead of nil if empty
    for _, wallet := range s.am.Wallets() {
        for _, account := range wallet.Accounts() {
            addresses = append(addresses, account.Address)
        }
    }
    return addresses
}

// rawWallet is a JSON representation of an accounts.Wallet interface, with its
// data contents extracted into plain fields.
type rawWallet struct {
    URL      string             `json:"url"`
    Status   string             `json:"status"`
    Failure  string             `json:"failure,omitempty"`
    Accounts []accounts.Account `json:"accounts,omitempty"`
}

// ListWallets will return a list of wallets this node manages.
func (s *PrivateAccountAPI) ListWallets() []rawWallet {
    wallets := make([]rawWallet, 0) // return [] instead of nil if empty
    for _, wallet := range s.am.Wallets() {
        status, failure := wallet.Status()

        raw := rawWallet{
            URL:      wallet.URL().String(),
            Status:   status,
            Accounts: wallet.Accounts(),
        }
        if failure != nil {
            raw.Failure = failure.Error()
        }
        wallets = append(wallets, raw)
    }
    return wallets
}

// OpenWallet initiates a hardware wallet opening procedure, establishing a USB
// connection and attempting to authenticate via the provided passphrase. Note,
// the method may return an extra challenge requiring a second open (e.g. the
// Trezor PIN matrix challenge).
func (s *PrivateAccountAPI) OpenWallet(url string, passphrase *string) error {
    wallet, err := s.am.Wallet(url)
    if err != nil {
        return err
    }
    pass := ""
    if passphrase != nil {
        pass = *passphrase
    }
    return wallet.Open(pass)
}

// DeriveAccount requests a HD wallet to derive a new account, optionally pinning
// it for later reuse.
func (s *PrivateAccountAPI) DeriveAccount(url string, path string, pin *bool) (accounts.Account, error) {
    wallet, err := s.am.Wallet(url)
    if err != nil {
        return accounts.Account{}, err
    }
    derivPath, err := accounts.ParseDerivationPath(path)
    if err != nil {
        return accounts.Account{}, err
    }
    if pin == nil {
        pin = new(bool)
    }
    return wallet.Derive(derivPath, *pin)
}

// NewAccount will create a new account and returns the address for the new account.
func (s *PrivateAccountAPI) NewAccount(password string) (common.Address, error) {
    acc, err := fetchKeystore(s.am).NewAccount(password)
    if err == nil {
        return acc.Address, nil
    }
    return common.Address{}, err
}

// fetchKeystore retrives the encrypted keystore from the account manager.
func fetchKeystore(am *accounts.Manager) *keystore.KeyStore {
    return am.Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
}

// ImportRawKey stores the given hex encoded ECDSA key into the key directory,
// encrypting it with the passphrase.
func (s *PrivateAccountAPI) ImportRawKey(privkey string, password string) (common.Address, error) {
    key, err := crypto.HexToECDSA(privkey)
    if err != nil {
        return common.Address{}, err
    }
    acc, err := fetchKeystore(s.am).ImportECDSA(key, password)
    return acc.Address, err
}

// UnlockAccount will unlock the account associated with the given address with
// the given password for duration seconds. If duration is nil it will use a
// default of 300 seconds. It returns an indication if the account was unlocked.
func (s *PrivateAccountAPI) UnlockAccount(addr common.Address, password string, duration *uint64) (bool, error) {
    const max = uint64(time.Duration(math.MaxInt64) / time.Second)
    var d time.Duration
    if duration == nil {
        d = 300 * time.Second
    } else if *duration > max {
        return false, errors.New("unlock duration too large")
    } else {
        d = time.Duration(*duration) * time.Second
    }
    err := fetchKeystore(s.am).TimedUnlock(accounts.Account{Address: addr}, password, d)
    if err != nil {
        log.Warn("Failed account unlock attempt", "address", addr, "err", err)
    }
    return err == nil, err
}

// LockAccount will lock the account associated with the given address when it's unlocked.
func (s *PrivateAccountAPI) LockAccount(addr common.Address) bool {
    return fetchKeystore(s.am).Lock(addr) == nil
}

// signTransaction sets defaults and signs the given transaction
// NOTE: the caller needs to ensure that the nonceLock is held, if applicable,
// and release it after the transaction has been submitted to the tx pool
func (s *PrivateAccountAPI) signTransaction(ctx context.Context, args *SendTxArgs, passwd string) (*types.Transaction, error) {
    // Look up the wallet containing the requested signer
    account := accounts.Account{Address: args.From}
    wallet, err := s.am.Find(account)
    if err != nil {
        return nil, err
    }
    // Set some sanity defaults and terminate on failure
    if err := args.setDefaults(ctx, s.b); err != nil {
        return nil, err
    }
    // Assemble the transaction and sign with the wallet
    tx := args.toTransaction()

    var chainID *big.Int
    if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
        chainID = config.ChainID
    }
    return wallet.SignTxWithPassphrase(account, passwd, tx, chainID)
}

// SendTransaction will create a transaction from the given arguments and
// tries to sign it with the key associated with args.To. If the given passwd isn't
// able to decrypt the key it fails.
func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
    if args.Nonce == nil {
        // Hold the addresse's mutex around signing to prevent concurrent assignment of
        // the same nonce to multiple accounts.
        s.nonceLock.LockAddr(args.From)
        defer s.nonceLock.UnlockAddr(args.From)
    }
    signed, err := s.signTransaction(ctx, &args, passwd)
    if err != nil {
        log.Warn("Failed transaction send attempt", "from", args.From, "to", args.To, "value", args.Value.ToInt(), "err", err)
        return common.Hash{}, err
    }
    return submitTransaction(ctx, s.b, signed)
}

// SignTransaction will create a transaction from the given arguments and
// tries to sign it with the key associated with args.To. If the given passwd isn't
// able to decrypt the key it fails. The transaction is returned in RLP-form, not broadcast
// to other nodes
func (s *PrivateAccountAPI) SignTransaction(ctx context.Context, args SendTxArgs, passwd string) (*SignTransactionResult, error) {
    // No need to obtain the noncelock mutex, since we won't be sending this
    // tx into the transaction pool, but right back to the user
    if args.Gas == nil {
        return nil, fmt.Errorf("gas not specified")
    }
    if args.GasPrice == nil {
        return nil, fmt.Errorf("gasPrice not specified")
    }
    if args.Nonce == nil {
        return nil, fmt.Errorf("nonce not specified")
    }
    signed, err := s.signTransaction(ctx, &args, passwd)
    if err != nil {
        log.Warn("Failed transaction sign attempt", "from", args.From, "to", args.To, "value", args.Value.ToInt(), "err", err)
        return nil, err
    }
    data, err := rlp.EncodeToBytes(signed)
    if err != nil {
        return nil, err
    }
    return &SignTransactionResult{data, signed}, nil
}

// signHash is a helper function that calculates a hash for the given message that can be
// safely used to calculate a signature from.
//
// The hash is calulcated as
//   keccak256("\x19Ethereum Signed Message:\n"${message length}${message}).
//
// This gives context to the signed message and prevents signing of transactions.
func signHash(data []byte) []byte {
    msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
    return crypto.Keccak256([]byte(msg))
}

// Sign calculates an Ethereum ECDSA signature for:
// keccack256("\x19Ethereum Signed Message:\n" + len(message) + message))
//
// Note, the produced signature conforms to the secp256k1 curve R, S and V values,
// where the V value will be 27 or 28 for legacy reasons.
//
// The key used to calculate the signature is decrypted with the given password.
//
// https://github.com/dexon-foundation/dexon/wiki/Management-APIs#personal_sign
func (s *PrivateAccountAPI) Sign(ctx context.Context, data hexutil.Bytes, addr common.Address, passwd string) (hexutil.Bytes, error) {
    // Look up the wallet containing the requested signer
    account := accounts.Account{Address: addr}

    wallet, err := s.b.AccountManager().Find(account)
    if err != nil {
        return nil, err
    }
    // Assemble sign the data with the wallet
    signature, err := wallet.SignHashWithPassphrase(account, passwd, signHash(data))
    if err != nil {
        log.Warn("Failed data sign attempt", "address", addr, "err", err)
        return nil, err
    }
    signature[64] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
    return signature, nil
}

// EcRecover returns the address for the account that was used to create the signature.
// Note, this function is compatible with eth_sign and personal_sign. As such it recovers
// the address of:
// hash = keccak256("\x19Ethereum Signed Message:\n"${message length}${message})
// addr = ecrecover(hash, signature)
//
// Note, the signature must conform to the secp256k1 curve R, S and V values, where
// the V value must be 27 or 28 for legacy reasons.
//
// https://github.com/dexon-foundation/dexon/wiki/Management-APIs#personal_ecRecover
func (s *PrivateAccountAPI) EcRecover(ctx context.Context, data, sig hexutil.Bytes) (common.Address, error) {
    if len(sig) != 65 {
        return common.Address{}, fmt.Errorf("signature must be 65 bytes long")
    }
    if sig[64] != 27 && sig[64] != 28 {
        return common.Address{}, fmt.Errorf("invalid Ethereum signature (V is not 27 or 28)")
    }
    sig[64] -= 27 // Transform yellow paper V from 27/28 to 0/1

    rpk, err := crypto.SigToPub(signHash(data), sig)
    if err != nil {
        return common.Address{}, err
    }
    return crypto.PubkeyToAddress(*rpk), nil
}

// SignAndSendTransaction was renamed to SendTransaction. This method is deprecated
// and will be removed in the future. It primary goal is to give clients time to update.
func (s *PrivateAccountAPI) SignAndSendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
    return s.SendTransaction(ctx, args, passwd)
}

// PublicBlockChainAPI provides an API to access the Ethereum blockchain.
// It offers only methods that operate on public data that is freely available to anyone.
type PublicBlockChainAPI struct {
    b Backend
}

// NewPublicBlockChainAPI creates a new Ethereum blockchain API.
func NewPublicBlockChainAPI(b Backend) *PublicBlockChainAPI {
    return &PublicBlockChainAPI{b}
}

// BlockNumber returns the block number of the chain head.
func (s *PublicBlockChainAPI) BlockNumber() hexutil.Uint64 {
    header, _ := s.b.HeaderByNumber(context.Background(), rpc.LatestBlockNumber) // latest header should always be available
    return hexutil.Uint64(header.Number.Uint64())
}

// GetBalance returns the amount of wei for the given address in the state of the
// given block number. The rpc.LatestBlockNumber and rpc.PendingBlockNumber meta
// block numbers are also allowed.
func (s *PublicBlockChainAPI) GetBalance(ctx context.Context, address common.Address, blockNr rpc.BlockNumber) (*hexutil.Big, error) {
    state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, err
    }
    return (*hexutil.Big)(state.GetBalance(address)), state.Error()
}

// Result structs for GetProof
type AccountResult struct {
    Address      common.Address  `json:"address"`
    AccountProof []string        `json:"accountProof"`
    Balance      *hexutil.Big    `json:"balance"`
    CodeHash     common.Hash     `json:"codeHash"`
    Nonce        hexutil.Uint64  `json:"nonce"`
    StorageHash  common.Hash     `json:"storageHash"`
    StorageProof []StorageResult `json:"storageProof"`
}
type StorageResult struct {
    Key   string       `json:"key"`
    Value *hexutil.Big `json:"value"`
    Proof []string     `json:"proof"`
}

// GetProof returns the Merkle-proof for a given account and optionally some storage keys.
func (s *PublicBlockChainAPI) GetProof(ctx context.Context, address common.Address, storageKeys []string, blockNr rpc.BlockNumber) (*AccountResult, error) {
    state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, err
    }

    storageTrie := state.StorageTrie(address)
    storageHash := types.EmptyRootHash
    codeHash := state.GetCodeHash(address)
    storageProof := make([]StorageResult, len(storageKeys))

    // if we have a storageTrie, (which means the account exists), we can update the storagehash
    if storageTrie != nil {
        storageHash = storageTrie.Hash()
    } else {
        // no storageTrie means the account does not exist, so the codeHash is the hash of an empty bytearray.
        codeHash = crypto.Keccak256Hash(nil)
    }

    // create the proof for the storageKeys
    for i, key := range storageKeys {
        if storageTrie != nil {
            proof, storageError := state.GetStorageProof(address, common.HexToHash(key))
            if storageError != nil {
                return nil, storageError
            }
            storageProof[i] = StorageResult{key, (*hexutil.Big)(state.GetState(address, common.HexToHash(key)).Big()), common.ToHexArray(proof)}
        } else {
            storageProof[i] = StorageResult{key, &hexutil.Big{}, []string{}}
        }
    }

    // create the accountProof
    accountProof, proofErr := state.GetProof(address)
    if proofErr != nil {
        return nil, proofErr
    }

    return &AccountResult{
        Address:      address,
        AccountProof: common.ToHexArray(accountProof),
        Balance:      (*hexutil.Big)(state.GetBalance(address)),
        CodeHash:     codeHash,
        Nonce:        hexutil.Uint64(state.GetNonce(address)),
        StorageHash:  storageHash,
        StorageProof: storageProof,
    }, state.Error()
}

// GetBlockByNumber returns the requested block. When blockNr is -1 the chain head is returned. When fullTx is true all
// transactions in the block are returned in full detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetBlockByNumber(ctx context.Context, blockNr rpc.BlockNumber, fullTx bool) (map[string]interface{}, error) {
    block, err := s.b.BlockByNumber(ctx, blockNr)
    if block != nil {
        response, err := s.rpcOutputBlock(block, true, fullTx)
        if err == nil && blockNr == rpc.PendingBlockNumber {
            // Pending blocks need to nil out a few fields
            for _, field := range []string{"hash", "nonce", "miner"} {
                response[field] = nil
            }
        }
        return response, err
    }
    return nil, err
}

// GetBlockByHash returns the requested block. When fullTx is true all transactions in the block are returned in full
// detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetBlockByHash(ctx context.Context, blockHash common.Hash, fullTx bool) (map[string]interface{}, error) {
    block, err := s.b.GetBlock(ctx, blockHash)
    if block != nil {
        return s.rpcOutputBlock(block, true, fullTx)
    }
    return nil, err
}

// GetUncleByBlockNumberAndIndex returns the uncle block for the given block hash and index. When fullTx is true
// all transactions in the block are returned in full detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetUncleByBlockNumberAndIndex(ctx context.Context, blockNr rpc.BlockNumber, index hexutil.Uint) (map[string]interface{}, error) {
    block, err := s.b.BlockByNumber(ctx, blockNr)
    if block != nil {
        uncles := block.Uncles()
        if index >= hexutil.Uint(len(uncles)) {
            log.Debug("Requested uncle not found", "number", blockNr, "hash", block.Hash(), "index", index)
            return nil, nil
        }
        block = types.NewBlockWithHeader(uncles[index])
        return s.rpcOutputBlock(block, false, false)
    }
    return nil, err
}

// GetUncleByBlockHashAndIndex returns the uncle block for the given block hash and index. When fullTx is true
// all transactions in the block are returned in full detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetUncleByBlockHashAndIndex(ctx context.Context, blockHash common.Hash, index hexutil.Uint) (map[string]interface{}, error) {
    block, err := s.b.GetBlock(ctx, blockHash)
    if block != nil {
        uncles := block.Uncles()
        if index >= hexutil.Uint(len(uncles)) {
            log.Debug("Requested uncle not found", "number", block.Number(), "hash", blockHash, "index", index)
            return nil, nil
        }
        block = types.NewBlockWithHeader(uncles[index])
        return s.rpcOutputBlock(block, false, false)
    }
    return nil, err
}

// GetUncleCountByBlockNumber returns number of uncles in the block for the given block number
func (s *PublicBlockChainAPI) GetUncleCountByBlockNumber(ctx context.Context, blockNr rpc.BlockNumber) *hexutil.Uint {
    if block, _ := s.b.BlockByNumber(ctx, blockNr); block != nil {
        n := hexutil.Uint(len(block.Uncles()))
        return &n
    }
    return nil
}

// GetUncleCountByBlockHash returns number of uncles in the block for the given block hash
func (s *PublicBlockChainAPI) GetUncleCountByBlockHash(ctx context.Context, blockHash common.Hash) *hexutil.Uint {
    if block, _ := s.b.GetBlock(ctx, blockHash); block != nil {
        n := hexutil.Uint(len(block.Uncles()))
        return &n
    }
    return nil
}

// GetCode returns the code stored at the given address in the state for the given block number.
func (s *PublicBlockChainAPI) GetCode(ctx context.Context, address common.Address, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
    state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, err
    }
    code := state.GetCode(address)
    return code, state.Error()
}

// GetStorageAt returns the storage from the state at the given address, key and
// block number. The rpc.LatestBlockNumber and rpc.PendingBlockNumber meta block
// numbers are also allowed.
func (s *PublicBlockChainAPI) GetStorageAt(ctx context.Context, address common.Address, key string, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
    state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, err
    }
    res := state.GetState(address, common.HexToHash(key))
    return res[:], state.Error()
}

// CallArgs represents the arguments for a call.
type CallArgs struct {
    From     common.Address  `json:"from"`
    To       *common.Address `json:"to"`
    Gas      hexutil.Uint64  `json:"gas"`
    GasPrice hexutil.Big     `json:"gasPrice"`
    Value    hexutil.Big     `json:"value"`
    Data     hexutil.Bytes   `json:"data"`
}

func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber, timeout time.Duration, globalGasCap *big.Int) ([]byte, uint64, bool, error) {
    defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())

    state, header, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, 0, false, err
    }
    // Set sender address or use a default if none specified
    addr := args.From
    if addr == (common.Address{}) {
        if wallets := s.b.AccountManager().Wallets(); len(wallets) > 0 {
            if accounts := wallets[0].Accounts(); len(accounts) > 0 {
                addr = accounts[0].Address
            }
        }
    }
    // Set default gas & gas price if none were set
    gas := uint64(args.Gas)
    if gas == 0 {
        gas = math.MaxUint64 / 2
    }
    if globalGasCap != nil && globalGasCap.Uint64() < gas {
        log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
        gas = globalGasCap.Uint64()
    }
    gasPrice := args.GasPrice.ToInt()
    if gasPrice.Sign() == 0 {
        gasPrice = new(big.Int).SetUint64(defaultGasPrice)
    }
    // Create new call message
    msg := types.NewMessage(addr, args.To, 0, args.Value.ToInt(), gas, gasPrice, args.Data, false)

    // Setup context so it may be cancelled the call has completed
    // or, in case of unmetered gas, setup a context with a timeout.
    var cancel context.CancelFunc
    if timeout > 0 {
        ctx, cancel = context.WithTimeout(ctx, timeout)
    } else {
        ctx, cancel = context.WithCancel(ctx)
    }
    // Make sure the context is cancelled when the call has completed
    // this makes sure resources are cleaned up.
    defer cancel()

    // Get a new instance of the EVM.
    evm, vmError, err := s.b.GetEVM(ctx, msg, state, header)
    if err != nil {
        return nil, 0, false, err
    }
    // Wait for the context to be done and cancel the evm. Even if the
    // EVM has finished, cancelling may be done (repeatedly)
    go func() {
        <-ctx.Done()
        evm.Cancel()
    }()

    // Setup the gas pool (also for unmetered requests)
    // and apply the message.
    gp := new(core.GasPool).AddGas(math.MaxUint64)
    res, gas, failed, err := core.ApplyMessage(evm, msg, gp)
    if err := vmError(); err != nil {
        return nil, 0, false, err
    }
    return res, gas, failed, err
}

// Call executes the given transaction on the state for the given block number.
// It doesn't make and changes in the state/blockchain and is useful to execute and retrieve values.
func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
    result, _, _, err := s.doCall(ctx, args, blockNr, 5*time.Second, s.b.RPCGasCap())
    return (hexutil.Bytes)(result), err
}

// EstimateGas returns an estimate of the amount of gas needed to execute the
// given transaction against the current pending block.
func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs) (hexutil.Uint64, error) {
    // Binary search the gas requirement, as it may be higher than the amount used
    var (
        lo  uint64 = params.TxGas - 1
        hi  uint64
        cap uint64
    )
    if uint64(args.Gas) >= params.TxGas {
        hi = uint64(args.Gas)
    } else {
        // Retrieve the current pending block to act as the gas ceiling
        block, err := s.b.BlockByNumber(ctx, rpc.PendingBlockNumber)
        if err != nil {
            return 0, err
        }
        hi = block.GasLimit()
    }
    gasCap := s.b.RPCGasCap()
    if gasCap != nil && hi > gasCap.Uint64() {
        log.Warn("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
        hi = gasCap.Uint64()
    }
    cap = hi

    // Create a helper to check if a gas allowance results in an executable transaction
    executable := func(gas uint64) bool {
        args.Gas = hexutil.Uint64(gas)

        _, _, failed, err := s.doCall(ctx, args, rpc.PendingBlockNumber, 0, gasCap)
        if err != nil || failed {
            return false
        }
        return true
    }
    // Execute the binary search and hone in on an executable gas limit
    for lo+1 < hi {
        mid := (hi + lo) / 2
        if !executable(mid) {
            lo = mid
        } else {
            hi = mid
        }
    }
    // Reject the transaction as invalid if it still fails at the highest allowance
    if hi == cap {
        if !executable(hi) {
            return 0, fmt.Errorf("gas required exceeds allowance (%d) or always failing transaction", cap)
        }
    }
    return hexutil.Uint64(hi), nil
}

// ExecutionResult groups all structured logs emitted by the EVM
// while replaying a transaction in debug mode as well as transaction
// execution status, the amount of gas used and the return value
type ExecutionResult struct {
    Gas         uint64         `json:"gas"`
    Failed      bool           `json:"failed"`
    ReturnValue string         `json:"returnValue"`
    StructLogs  []StructLogRes `json:"structLogs"`
}

// StructLogRes stores a structured log emitted by the EVM while replaying a
// transaction in debug mode
type StructLogRes struct {
    Pc      uint64             `json:"pc"`
    Op      string             `json:"op"`
    Gas     uint64             `json:"gas"`
    GasCost uint64             `json:"gasCost"`
    Depth   int                `json:"depth"`
    Error   error              `json:"error,omitempty"`
    Stack   *[]string          `json:"stack,omitempty"`
    Memory  *[]string          `json:"memory,omitempty"`
    Storage *map[string]string `json:"storage,omitempty"`
}

// formatLogs formats EVM returned structured logs for json output
func FormatLogs(logs []vm.StructLog) []StructLogRes {
    formatted := make([]StructLogRes, len(logs))
    for index, trace := range logs {
        formatted[index] = StructLogRes{
            Pc:      trace.Pc,
            Op:      trace.Op.String(),
            Gas:     trace.Gas,
            GasCost: trace.GasCost,
            Depth:   trace.Depth,
            Error:   trace.Err,
        }
        if trace.Stack != nil {
            stack := make([]string, len(trace.Stack))
            for i, stackValue := range trace.Stack {
                stack[i] = fmt.Sprintf("%x", math.PaddedBigBytes(stackValue, 32))
            }
            formatted[index].Stack = &stack
        }
        if trace.Memory != nil {
            memory := make([]string, 0, (len(trace.Memory)+31)/32)
            for i := 0; i+32 <= len(trace.Memory); i += 32 {
                memory = append(memory, fmt.Sprintf("%x", trace.Memory[i:i+32]))
            }
            formatted[index].Memory = &memory
        }
        if trace.Storage != nil {
            storage := make(map[string]string)
            for i, storageValue := range trace.Storage {
                storage[fmt.Sprintf("%x", i)] = fmt.Sprintf("%x", storageValue)
            }
            formatted[index].Storage = &storage
        }
    }
    return formatted
}

// RPCMarshalBlock converts the given block to the RPC output which depends on fullTx. If inclTx is true transactions are
// returned. When fullTx is true the returned block contains full transaction details, otherwise it will only contain
// transaction hashes.
func RPCMarshalBlock(b *types.Block, inclTx bool, fullTx bool) (map[string]interface{}, error) {
    head := b.Header() // copies the header once
    fields := map[string]interface{}{
        "number":           (*hexutil.Big)(head.Number),
        "hash":             b.Hash(),
        "parentHash":       head.ParentHash,
        "nonce":            head.Nonce,
        "mixHash":          head.MixDigest,
        "sha3Uncles":       head.UncleHash,
        "logsBloom":        head.Bloom,
        "stateRoot":        head.Root,
        "miner":            head.Coinbase,
        "difficulty":       (*hexutil.Big)(head.Difficulty),
        "extraData":        hexutil.Bytes(head.Extra),
        "size":             hexutil.Uint64(b.Size()),
        "gasLimit":         hexutil.Uint64(head.GasLimit),
        "gasUsed":          hexutil.Uint64(head.GasUsed),
        "timestamp":        hexutil.Uint64(head.Time),
        "transactionsRoot": head.TxHash,
        "receiptsRoot":     head.ReceiptHash,
    }

    if inclTx {
        formatTx := func(tx *types.Transaction) (interface{}, error) {
            return tx.Hash(), nil
        }
        if fullTx {
            formatTx = func(tx *types.Transaction) (interface{}, error) {
                return newRPCTransactionFromBlockHash(b, tx.Hash()), nil
            }
        }
        txs := b.Transactions()
        transactions := make([]interface{}, len(txs))
        var err error
        for i, tx := range txs {
            if transactions[i], err = formatTx(tx); err != nil {
                return nil, err
            }
        }
        fields["transactions"] = transactions
    }

    uncles := b.Uncles()
    uncleHashes := make([]common.Hash, len(uncles))
    for i, uncle := range uncles {
        uncleHashes[i] = uncle.Hash()
    }
    fields["uncles"] = uncleHashes

    return fields, nil
}

// rpcOutputBlock uses the generalized output filler, then adds the total difficulty field, which requires
// a `PublicBlockchainAPI`.
func (s *PublicBlockChainAPI) rpcOutputBlock(b *types.Block, inclTx bool, fullTx bool) (map[string]interface{}, error) {
    fields, err := RPCMarshalBlock(b, inclTx, fullTx)
    if err != nil {
        return nil, err
    }
    fields["totalDifficulty"] = (*hexutil.Big)(s.b.GetTd(b.Hash()))
    return fields, err
}

// RPCTransaction represents a transaction that will serialize to the RPC representation of a transaction
type RPCTransaction struct {
    BlockHash        common.Hash     `json:"blockHash"`
    BlockNumber      *hexutil.Big    `json:"blockNumber"`
    From             common.Address  `json:"from"`
    Gas              hexutil.Uint64  `json:"gas"`
    GasPrice         *hexutil.Big    `json:"gasPrice"`
    Hash             common.Hash     `json:"hash"`
    Input            hexutil.Bytes   `json:"input"`
    Nonce            hexutil.Uint64  `json:"nonce"`
    To               *common.Address `json:"to"`
    TransactionIndex hexutil.Uint    `json:"transactionIndex"`
    Value            *hexutil.Big    `json:"value"`
    V                *hexutil.Big    `json:"v"`
    R                *hexutil.Big    `json:"r"`
    S                *hexutil.Big    `json:"s"`
}

// newRPCTransaction returns a transaction that will serialize to the RPC
// representation, with the given location metadata set (if available).
func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber uint64, index uint64) *RPCTransaction {
    var signer types.Signer = types.FrontierSigner{}
    if tx.Protected() {
        signer = types.NewEIP155Signer(tx.ChainId())
    }
    from, _ := types.Sender(signer, tx)
    v, r, s := tx.RawSignatureValues()

    result := &RPCTransaction{
        From:     from,
        Gas:      hexutil.Uint64(tx.Gas()),
        GasPrice: (*hexutil.Big)(tx.GasPrice()),
        Hash:     tx.Hash(),
        Input:    hexutil.Bytes(tx.Data()),
        Nonce:    hexutil.Uint64(tx.Nonce()),
        To:       tx.To(),
        Value:    (*hexutil.Big)(tx.Value()),
        V:        (*hexutil.Big)(v),
        R:        (*hexutil.Big)(r),
        S:        (*hexutil.Big)(s),
    }
    if blockHash != (common.Hash{}) {
        result.BlockHash = blockHash
        result.BlockNumber = (*hexutil.Big)(new(big.Int).SetUint64(blockNumber))
        result.TransactionIndex = hexutil.Uint(index)
    }
    return result
}

// newRPCPendingTransaction returns a pending transaction that will serialize to the RPC representation
func newRPCPendingTransaction(tx *types.Transaction) *RPCTransaction {
    return newRPCTransaction(tx, common.Hash{}, 0, 0)
}

// newRPCTransactionFromBlockIndex returns a transaction that will serialize to the RPC representation.
func newRPCTransactionFromBlockIndex(b *types.Block, index uint64) *RPCTransaction {
    txs := b.Transactions()
    if index >= uint64(len(txs)) {
        return nil
    }
    return newRPCTransaction(txs[index], b.Hash(), b.NumberU64(), index)
}

// newRPCRawTransactionFromBlockIndex returns the bytes of a transaction given a block and a transaction index.
func newRPCRawTransactionFromBlockIndex(b *types.Block, index uint64) hexutil.Bytes {
    txs := b.Transactions()
    if index >= uint64(len(txs)) {
        return nil
    }
    blob, _ := rlp.EncodeToBytes(txs[index])
    return blob
}

// newRPCTransactionFromBlockHash returns a transaction that will serialize to the RPC representation.
func newRPCTransactionFromBlockHash(b *types.Block, hash common.Hash) *RPCTransaction {
    for idx, tx := range b.Transactions() {
        if tx.Hash() == hash {
            return newRPCTransactionFromBlockIndex(b, uint64(idx))
        }
    }
    return nil
}

// PublicTransactionPoolAPI exposes methods for the RPC interface
type PublicTransactionPoolAPI struct {
    b         Backend
    nonceLock *AddrLocker
}

// NewPublicTransactionPoolAPI creates a new RPC service with methods specific for the transaction pool.
func NewPublicTransactionPoolAPI(b Backend, nonceLock *AddrLocker) *PublicTransactionPoolAPI {
    return &PublicTransactionPoolAPI{b, nonceLock}
}

// GetBlockTransactionCountByNumber returns the number of transactions in the block with the given block number.
func (s *PublicTransactionPoolAPI) GetBlockTransactionCountByNumber(ctx context.Context, blockNr rpc.BlockNumber) *hexutil.Uint {
    if block, _ := s.b.BlockByNumber(ctx, blockNr); block != nil {
        n := hexutil.Uint(len(block.Transactions()))
        return &n
    }
    return nil
}

// GetBlockTransactionCountByHash returns the number of transactions in the block with the given hash.
func (s *PublicTransactionPoolAPI) GetBlockTransactionCountByHash(ctx context.Context, blockHash common.Hash) *hexutil.Uint {
    if block, _ := s.b.GetBlock(ctx, blockHash); block != nil {
        n := hexutil.Uint(len(block.Transactions()))
        return &n
    }
    return nil
}

// GetTransactionByBlockNumberAndIndex returns the transaction for the given block number and index.
func (s *PublicTransactionPoolAPI) GetTransactionByBlockNumberAndIndex(ctx context.Context, blockNr rpc.BlockNumber, index hexutil.Uint) *RPCTransaction {
    if block, _ := s.b.BlockByNumber(ctx, blockNr); block != nil {
        return newRPCTransactionFromBlockIndex(block, uint64(index))
    }
    return nil
}

// GetTransactionByBlockHashAndIndex returns the transaction for the given block hash and index.
func (s *PublicTransactionPoolAPI) GetTransactionByBlockHashAndIndex(ctx context.Context, blockHash common.Hash, index hexutil.Uint) *RPCTransaction {
    if block, _ := s.b.GetBlock(ctx, blockHash); block != nil {
        return newRPCTransactionFromBlockIndex(block, uint64(index))
    }
    return nil
}

// GetRawTransactionByBlockNumberAndIndex returns the bytes of the transaction for the given block number and index.
func (s *PublicTransactionPoolAPI) GetRawTransactionByBlockNumberAndIndex(ctx context.Context, blockNr rpc.BlockNumber, index hexutil.Uint) hexutil.Bytes {
    if block, _ := s.b.BlockByNumber(ctx, blockNr); block != nil {
        return newRPCRawTransactionFromBlockIndex(block, uint64(index))
    }
    return nil
}

// GetRawTransactionByBlockHashAndIndex returns the bytes of the transaction for the given block hash and index.
func (s *PublicTransactionPoolAPI) GetRawTransactionByBlockHashAndIndex(ctx context.Context, blockHash common.Hash, index hexutil.Uint) hexutil.Bytes {
    if block, _ := s.b.GetBlock(ctx, blockHash); block != nil {
        return newRPCRawTransactionFromBlockIndex(block, uint64(index))
    }
    return nil
}

// GetTransactionCount returns the number of transactions the given address has sent for the given block number
func (s *PublicTransactionPoolAPI) GetTransactionCount(ctx context.Context, address common.Address, blockNr rpc.BlockNumber) (*hexutil.Uint64, error) {
    // Ask transaction pool for the nonce which includes pending transactions
    if blockNr == rpc.PendingBlockNumber {
        nonce, err := s.b.GetPoolNonce(ctx, address)
        if err != nil {
            return nil, err
        }
        return (*hexutil.Uint64)(&nonce), nil
    }
    // Resolve block number and use its state to ask for the nonce
    state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
    if state == nil || err != nil {
        return nil, err
    }
    nonce := state.GetNonce(address)
    return (*hexutil.Uint64)(&nonce), state.Error()
}

// GetTransactionByHash returns the transaction for the given hash
func (s *PublicTransactionPoolAPI) GetTransactionByHash(ctx context.Context, hash common.Hash) *RPCTransaction {
    // Try to return an already finalized transaction
    if tx, blockHash, blockNumber, index := rawdb.ReadTransaction(s.b.ChainDb(), hash); tx != nil {
        return newRPCTransaction(tx, blockHash, blockNumber, index)
    }
    // No finalized transaction, try to retrieve it from the pool
    if tx := s.b.GetPoolTransaction(hash); tx != nil {
        return newRPCPendingTransaction(tx)
    }
    // Transaction unknown, return as such
    return nil
}

// GetRawTransactionByHash returns the bytes of the transaction for the given hash.
func (s *PublicTransactionPoolAPI) GetRawTransactionByHash(ctx context.Context, hash common.Hash) (hexutil.Bytes, error) {
    var tx *types.Transaction

    // Retrieve a finalized transaction, or a pooled otherwise
    if tx, _, _, _ = rawdb.ReadTransaction(s.b.ChainDb(), hash); tx == nil {
        if tx = s.b.GetPoolTransaction(hash); tx == nil {
            // Transaction not found anywhere, abort
            return nil, nil
        }
    }
    // Serialize to RLP and return
    return rlp.EncodeToBytes(tx)
}

// GetTransactionReceipt returns the transaction receipt for the given transaction hash.
func (s *PublicTransactionPoolAPI) GetTransactionReceipt(ctx context.Context, hash common.Hash) (map[string]interface{}, error) {
    tx, blockHash, blockNumber, index := rawdb.ReadTransaction(s.b.ChainDb(), hash)
    if tx == nil {
        return nil, nil
    }
    receipts, err := s.b.GetReceipts(ctx, blockHash)
    if err != nil {
        return nil, err
    }
    if len(receipts) <= int(index) {
        return nil, nil
    }
    receipt := receipts[index]

    var signer types.Signer = types.FrontierSigner{}
    if tx.Protected() {
        signer = types.NewEIP155Signer(tx.ChainId())
    }
    from, _ := types.Sender(signer, tx)

    fields := map[string]interface{}{
        "blockHash":         blockHash,
        "blockNumber":       hexutil.Uint64(blockNumber),
        "transactionHash":   hash,
        "transactionIndex":  hexutil.Uint64(index),
        "from":              from,
        "to":                tx.To(),
        "gasUsed":           hexutil.Uint64(receipt.GasUsed),
        "cumulativeGasUsed": hexutil.Uint64(receipt.CumulativeGasUsed),
        "contractAddress":   nil,
        "logs":              receipt.Logs,
        "logsBloom":         receipt.Bloom,
    }

    // Assign receipt status or post state.
    if len(receipt.PostState) > 0 {
        fields["root"] = hexutil.Bytes(receipt.PostState)
    } else {
        fields["status"] = hexutil.Uint(receipt.Status)
    }
    if receipt.Logs == nil {
        fields["logs"] = [][]*types.Log{}
    }
    // If the ContractAddress is 20 0x0 bytes, assume it is not a contract creation
    if receipt.ContractAddress != (common.Address{}) {
        fields["contractAddress"] = receipt.ContractAddress
    }
    return fields, nil
}

// sign is a helper function that signs a transaction with the private key of the given address.
func (s *PublicTransactionPoolAPI) sign(addr common.Address, tx *types.Transaction) (*types.Transaction, error) {
    // Look up the wallet containing the requested signer
    account := accounts.Account{Address: addr}

    wallet, err := s.b.AccountManager().Find(account)
    if err != nil {
        return nil, err
    }
    // Request the wallet to sign the transaction
    var chainID *big.Int
    if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
        chainID = config.ChainID
    }
    return wallet.SignTx(account, tx, chainID)
}

// SendTxArgs represents the arguments to sumbit a new transaction into the transaction pool.
type SendTxArgs struct {
    From     common.Address  `json:"from"`
    To       *common.Address `json:"to"`
    Gas      *hexutil.Uint64 `json:"gas"`
    GasPrice *hexutil.Big    `json:"gasPrice"`
    Value    *hexutil.Big    `json:"value"`
    Nonce    *hexutil.Uint64 `json:"nonce"`
    // We accept "data" and "input" for backwards-compatibility reasons. "input" is the
    // newer name and should be preferred by clients.
    Data  *hexutil.Bytes `json:"data"`
    Input *hexutil.Bytes `json:"input"`
}

// setDefaults is a helper function that fills in default values for unspecified tx fields.
func (args *SendTxArgs) setDefaults(ctx context.Context, b Backend) error {
    if args.Gas == nil {
        args.Gas = new(hexutil.Uint64)
        *(*uint64)(args.Gas) = 90000
    }
    if args.GasPrice == nil {
        price, err := b.SuggestPrice(ctx)
        if err != nil {
            return err
        }
        args.GasPrice = (*hexutil.Big)(price)
    }
    if args.Value == nil {
        args.Value = new(hexutil.Big)
    }
    if args.Nonce == nil {
        nonce, err := b.GetPoolNonce(ctx, args.From)
        if err != nil {
            return err
        }
        args.Nonce = (*hexutil.Uint64)(&nonce)
    }
    if args.Data != nil && args.Input != nil && !bytes.Equal(*args.Data, *args.Input) {
        return errors.New(`Both "data" and "input" are set and not equal. Please use "input" to pass transaction call data.`)
    }
    if args.To == nil {
        // Contract creation
        var input []byte
        if args.Data != nil {
            input = *args.Data
        } else if args.Input != nil {
            input = *args.Input
        }
        if len(input) == 0 {
            return errors.New(`contract creation without any data provided`)
        }
    }
    return nil
}

func (args *SendTxArgs) toTransaction() *types.Transaction {
    var input []byte
    if args.Data != nil {
        input = *args.Data
    } else if args.Input != nil {
        input = *args.Input
    }
    if args.To == nil {
        return types.NewContractCreation(uint64(*args.Nonce), (*big.Int)(args.Value), uint64(*args.Gas), (*big.Int)(args.GasPrice), input)
    }
    return types.NewTransaction(uint64(*args.Nonce), *args.To, (*big.Int)(args.Value), uint64(*args.Gas), (*big.Int)(args.GasPrice), input)
}

// submitTransaction is a helper function that submits tx to txPool and logs a message.
func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (common.Hash, error) {
    if err := b.SendTx(ctx, tx); err != nil {
        return common.Hash{}, err
    }
    if tx.To() == nil {
        signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
        from, err := types.Sender(signer, tx)
        if err != nil {
            return common.Hash{}, err
        }
        addr := crypto.CreateAddress(from, tx.Nonce())
        log.Info("Submitted contract creation", "fullhash", tx.Hash().Hex(), "contract", addr.Hex())
    } else {
        log.Info("Submitted transaction", "fullhash", tx.Hash().Hex(), "recipient", tx.To())
    }
    return tx.Hash(), nil
}

// SendTransaction creates a transaction for the given argument, sign it and submit it to the
// transaction pool.
func (s *PublicTransactionPoolAPI) SendTransaction(ctx context.Context, args SendTxArgs) (common.Hash, error) {

    // Look up the wallet containing the requested signer
    account := accounts.Account{Address: args.From}

    wallet, err := s.b.AccountManager().Find(account)
    if err != nil {
        return common.Hash{}, err
    }

    if args.Nonce == nil {
        // Hold the addresse's mutex around signing to prevent concurrent assignment of
        // the same nonce to multiple accounts.
        s.nonceLock.LockAddr(args.From)
        defer s.nonceLock.UnlockAddr(args.From)
    }

    // Set some sanity defaults and terminate on failure
    if err := args.setDefaults(ctx, s.b); err != nil {
        return common.Hash{}, err
    }
    // Assemble the transaction and sign with the wallet
    tx := args.toTransaction()

    var chainID *big.Int
    if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
        chainID = config.ChainID
    }
    signed, err := wallet.SignTx(account, tx, chainID)
    if err != nil {
        return common.Hash{}, err
    }
    return submitTransaction(ctx, s.b, signed)
}

// SendRawTransaction will add the signed transaction to the transaction pool.
// The sender is responsible for signing the transaction and using the correct nonce.
func (s *PublicTransactionPoolAPI) SendRawTransaction(ctx context.Context, encodedTx hexutil.Bytes) (common.Hash, error) {
    tx := new(types.Transaction)
    if err := rlp.DecodeBytes(encodedTx, tx); err != nil {
        return common.Hash{}, err
    }
    return submitTransaction(ctx, s.b, tx)
}

// Sign calculates an ECDSA signature for:
// keccack256("\x19Ethereum Signed Message:\n" + len(message) + message).
//
// Note, the produced signature conforms to the secp256k1 curve R, S and V values,
// where the V value will be 27 or 28 for legacy reasons.
//
// The account associated with addr must be unlocked.
//
// https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign
func (s *PublicTransactionPoolAPI) Sign(addr common.Address, data hexutil.Bytes) (hexutil.Bytes, error) {
    // Look up the wallet containing the requested signer
    account := accounts.Account{Address: addr}

    wallet, err := s.b.AccountManager().Find(account)
    if err != nil {
        return nil, err
    }
    // Sign the requested hash with the wallet
    signature, err := wallet.SignHash(account, signHash(data))
    if err == nil {
        signature[64] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
    }
    return signature, err
}

// SignTransactionResult represents a RLP encoded signed transaction.
type SignTransactionResult struct {
    Raw hexutil.Bytes      `json:"raw"`
    Tx  *types.Transaction `json:"tx"`
}

// SignTransaction will sign the given transaction with the from account.
// The node needs to have the private key of the account corresponding with
// the given from address and it needs to be unlocked.
func (s *PublicTransactionPoolAPI) SignTransaction(ctx context.Context, args SendTxArgs) (*SignTransactionResult, error) {
    if args.Gas == nil {
        return nil, fmt.Errorf("gas not specified")
    }
    if args.GasPrice == nil {
        return nil, fmt.Errorf("gasPrice not specified")
    }
    if args.Nonce == nil {
        return nil, fmt.Errorf("nonce not specified")
    }
    if err := args.setDefaults(ctx, s.b); err != nil {
        return nil, err
    }
    tx, err := s.sign(args.From, args.toTransaction())
    if err != nil {
        return nil, err
    }
    data, err := rlp.EncodeToBytes(tx)
    if err != nil {
        return nil, err
    }
    return &SignTransactionResult{data, tx}, nil
}

// PendingTransactions returns the transactions that are in the transaction pool
// and have a from address that is one of the accounts this node manages.
func (s *PublicTransactionPoolAPI) PendingTransactions() ([]*RPCTransaction, error) {
    pending, err := s.b.GetPoolTransactions()
    if err != nil {
        return nil, err
    }
    accounts := make(map[common.Address]struct{})
    for _, wallet := range s.b.AccountManager().Wallets() {
        for _, account := range wallet.Accounts() {
            accounts[account.Address] = struct{}{}
        }
    }
    transactions := make([]*RPCTransaction, 0, len(pending))
    for _, tx := range pending {
        var signer types.Signer = types.HomesteadSigner{}
        if tx.Protected() {
            signer = types.NewEIP155Signer(tx.ChainId())
        }
        from, _ := types.Sender(signer, tx)
        if _, exists := accounts[from]; exists {
            transactions = append(transactions, newRPCPendingTransaction(tx))
        }
    }
    return transactions, nil
}

// Resend accepts an existing transaction and a new gas price and limit. It will remove
// the given transaction from the pool and reinsert it with the new gas price and limit.
func (s *PublicTransactionPoolAPI) Resend(ctx context.Context, sendArgs SendTxArgs, gasPrice *hexutil.Big, gasLimit *hexutil.Uint64) (common.Hash, error) {
    if sendArgs.Nonce == nil {
        return common.Hash{}, fmt.Errorf("missing transaction nonce in transaction spec")
    }
    if err := sendArgs.setDefaults(ctx, s.b); err != nil {
        return common.Hash{}, err
    }
    matchTx := sendArgs.toTransaction()
    pending, err := s.b.GetPoolTransactions()
    if err != nil {
        return common.Hash{}, err
    }

    for _, p := range pending {
        var signer types.Signer = types.HomesteadSigner{}
        if p.Protected() {
            signer = types.NewEIP155Signer(p.ChainId())
        }
        wantSigHash := signer.Hash(matchTx)

        if pFrom, err := types.Sender(signer, p); err == nil && pFrom == sendArgs.From && signer.Hash(p) == wantSigHash {
            // Match. Re-sign and send the transaction.
            if gasPrice != nil && (*big.Int)(gasPrice).Sign() != 0 {
                sendArgs.GasPrice = gasPrice
            }
            if gasLimit != nil && *gasLimit != 0 {
                sendArgs.Gas = gasLimit
            }
            signedTx, err := s.sign(sendArgs.From, sendArgs.toTransaction())
            if err != nil {
                return common.Hash{}, err
            }
            if err = s.b.SendTx(ctx, signedTx); err != nil {
                return common.Hash{}, err
            }
            return signedTx.Hash(), nil
        }
    }

    return common.Hash{}, fmt.Errorf("Transaction %#x not found", matchTx.Hash())
}

// PublicDebugAPI is the collection of Ethereum APIs exposed over the public
// debugging endpoint.
type PublicDebugAPI struct {
    b Backend
}

// NewPublicDebugAPI creates a new API definition for the public debug methods
// of the Ethereum service.
func NewPublicDebugAPI(b Backend) *PublicDebugAPI {
    return &PublicDebugAPI{b: b}
}

// GetBlockRlp retrieves the RLP encoded for of a single block.
func (api *PublicDebugAPI) GetBlockRlp(ctx context.Context, number uint64) (string, error) {
    block, _ := api.b.BlockByNumber(ctx, rpc.BlockNumber(number))
    if block == nil {
        return "", fmt.Errorf("block #%d not found", number)
    }
    encoded, err := rlp.EncodeToBytes(block)
    if err != nil {
        return "", err
    }
    return fmt.Sprintf("%x", encoded), nil
}

// PrintBlock retrieves a block and returns its pretty printed form.
func (api *PublicDebugAPI) PrintBlock(ctx context.Context, number uint64) (string, error) {
    block, _ := api.b.BlockByNumber(ctx, rpc.BlockNumber(number))
    if block == nil {
        return "", fmt.Errorf("block #%d not found", number)
    }
    return spew.Sdump(block), nil
}

// SeedHash retrieves the seed hash of a block.
func (api *PublicDebugAPI) SeedHash(ctx context.Context, number uint64) (string, error) {
    block, _ := api.b.BlockByNumber(ctx, rpc.BlockNumber(number))
    if block == nil {
        return "", fmt.Errorf("block #%d not found", number)
    }
    return fmt.Sprintf("0x%x", ethash.SeedHash(number)), nil
}

// PrivateDebugAPI is the collection of Ethereum APIs exposed over the private
// debugging endpoint.
type PrivateDebugAPI struct {
    b Backend
}

// NewPrivateDebugAPI creates a new API definition for the private debug methods
// of the Ethereum service.
func NewPrivateDebugAPI(b Backend) *PrivateDebugAPI {
    return &PrivateDebugAPI{b: b}
}

// ChaindbProperty returns leveldb properties of the chain database.
func (api *PrivateDebugAPI) ChaindbProperty(property string) (string, error) {
    ldb, ok := api.b.ChainDb().(interface {
        LDB() *leveldb.DB
    })
    if !ok {
        return "", fmt.Errorf("chaindbProperty does not work for memory databases")
    }
    if property == "" {
        property = "leveldb.stats"
    } else if !strings.HasPrefix(property, "leveldb.") {
        property = "leveldb." + property
    }
    return ldb.LDB().GetProperty(property)
}

func (api *PrivateDebugAPI) ChaindbCompact() error {
    ldb, ok := api.b.ChainDb().(interface {
        LDB() *leveldb.DB
    })
    if !ok {
        return fmt.Errorf("chaindbCompact does not work for memory databases")
    }
    for b := byte(0); b < 255; b++ {
        log.Info("Compacting chain database", "range", fmt.Sprintf("0x%0.2X-0x%0.2X", b, b+1))
        err := ldb.LDB().CompactRange(util.Range{Start: []byte{b}, Limit: []byte{b + 1}})
        if err != nil {
            log.Error("Database compaction failed", "err", err)
            return err
        }
    }
    return nil
}

// SetHead rewinds the head of the blockchain to a previous block.
func (api *PrivateDebugAPI) SetHead(number hexutil.Uint64) {
    api.b.SetHead(uint64(number))
}

// PublicNetAPI offers network related RPC methods
type PublicNetAPI struct {
    net            *p2p.Server
    networkVersion uint64
}

// NewPublicNetAPI creates a new net API instance.
func NewPublicNetAPI(net *p2p.Server, networkVersion uint64) *PublicNetAPI {
    return &PublicNetAPI{net, networkVersion}
}

// Listening returns an indication if the node is listening for network connections.
func (s *PublicNetAPI) Listening() bool {
    return true // always listening
}

// PeerCount returns the number of connected peers
func (s *PublicNetAPI) PeerCount() hexutil.Uint {
    return hexutil.Uint(s.net.PeerCount())
}

// Version returns the current ethereum protocol version.
func (s *PublicNetAPI) Version() string {
    return fmt.Sprintf("%d", s.networkVersion)
}