accounts/abi/bind: use ethereum interfaces

In this commit, contract bindings and their backend start using the
Ethereum Go API interfaces offered by ethclient. This makes ethclient a
suitable replacement for the old remote backend and gets us one step
closer to the final stable Go API that is planned for go-ethereum 1.5.

The changes in detail:

* Pending state is optional for read only contract bindings.
  BoundContract attempts to discover the Pending* methods via an
  interface assertion. There are a couple of advantages to this:
  ContractCaller is just two methods and can be implemented on top of
  pretty much anything that provides Ethereum data. Since the backend
  interfaces are now disjoint, ContractBackend can simply be declared as
  a union of the reader and writer side.

* Caching of HasCode is removed. The caching could go wrong in case of
  chain reorganisations and removing it simplifies the code a lot.
  We'll figure out a performant way of providing ErrNoCode before the
  1.5 release.

* BoundContract now ensures that the backend receives a non-nil context
  with every call.

1 files changed, 74 insertions, 88 deletions

diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index 687a31bf1..c2542f40e 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -17,8 +17,10 @@
 package backends
 
 import (
+	"fmt"
 	"math/big"
 
+	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
@@ -79,58 +81,44 @@ func (b *SimulatedBackend) Rollback() {
 	b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
 }
 
-// HasCode implements ContractVerifier.HasCode, checking whether there is any
-// code associated with a certain account in the blockchain.
-func (b *SimulatedBackend) HasCode(ctx context.Context, contract common.Address, pending bool) (bool, error) {
-	if pending {
-		return len(b.pendingState.GetCode(contract)) > 0, nil
+// CodeAt implements ChainStateReader.CodeAt, returning the code associated with
+// a certain account at a given block number in the blockchain.
+func (b *SimulatedBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
+	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
+		return nil, fmt.Errorf("SimulatedBackend cannot access blocks other than the latest block")
 	}
 	statedb, _ := b.blockchain.State()
-	return len(statedb.GetCode(contract)) > 0, nil
+	return statedb.GetCode(contract), nil
 }
 
-// ContractCall implements ContractCaller.ContractCall, executing the specified
-// contract with the given input data.
-func (b *SimulatedBackend) ContractCall(ctx context.Context, contract common.Address, data []byte, pending bool) ([]byte, error) {
-	// Create a copy of the current state db to screw around with
-	var (
-		block   *types.Block
-		statedb *state.StateDB
-	)
-	if pending {
-		block, statedb = b.pendingBlock, b.pendingState.Copy()
-	} else {
-		block = b.blockchain.CurrentBlock()
-		statedb, _ = b.blockchain.State()
-	}
-	// If there's no code to interact with, respond with an appropriate error
-	if code := statedb.GetCode(contract); len(code) == 0 {
-		return nil, bind.ErrNoCode
-	}
-	// Set infinite balance to the a fake caller account
-	from := statedb.GetOrNewStateObject(common.Address{})
-	from.SetBalance(common.MaxBig)
+// PendingCodeAt implements PendingStateReader.PendingCodeAt, returning the
+// code associated with a certain account in the pending state of the blockchain.
+func (b *SimulatedBackend) PendingCodeAt(ctx context.Context, contract common.Address) ([]byte, error) {
+	return b.pendingState.GetCode(contract), nil
+}
 
-	// Assemble the call invocation to measure the gas usage
-	msg := callmsg{
-		from:     from,
-		to:       &contract,
-		gasPrice: new(big.Int),
-		gasLimit: common.MaxBig,
-		value:    new(big.Int),
-		data:     data,
+// CallContract executes a contract call.
+func (b *SimulatedBackend) CallContract(ctx context.Context, call ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
+	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
+		return nil, fmt.Errorf("SimulatedBackend cannot access blocks other than the latest block")
 	}
-	// Execute the call and return
-	vmenv := core.NewEnv(statedb, chainConfig, b.blockchain, msg, block.Header(), vm.Config{})
-	gaspool := new(core.GasPool).AddGas(common.MaxBig)
+	state, err := b.blockchain.State()
+	if err != nil {
+		return nil, err
+	}
+	rval, _, err := b.callContract(ctx, call, b.blockchain.CurrentBlock(), state)
+	return rval, err
+}
 
-	out, _, err := core.ApplyMessage(vmenv, msg, gaspool)
-	return out, err
+// PendingCallContract executes a contract call on the pending state.
+func (b *SimulatedBackend) PendingCallContract(ctx context.Context, call ethereum.CallMsg) ([]byte, error) {
+	rval, _, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState.Copy())
+	return rval, err
 }
 
-// PendingAccountNonce implements ContractTransactor.PendingAccountNonce, retrieving
+// PendingNonceAt implements PendingStateReader.PendingNonceAt, retrieving
 // the nonce currently pending for the account.
-func (b *SimulatedBackend) PendingAccountNonce(ctx context.Context, account common.Address) (uint64, error) {
+func (b *SimulatedBackend) PendingNonceAt(ctx context.Context, account common.Address) (uint64, error) {
 	return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
 }
 
@@ -140,45 +128,49 @@ func (b *SimulatedBackend) SuggestGasPrice(ctx context.Context) (*big.Int, error
 	return big.NewInt(1), nil
 }
 
-// EstimateGasLimit implements ContractTransactor.EstimateGasLimit, executing the
-// requested code against the currently pending block/state and returning the used
-// gas.
-func (b *SimulatedBackend) EstimateGasLimit(ctx context.Context, sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
-	// Create a copy of the currently pending state db to screw around with
-	var (
-		block   = b.pendingBlock
-		statedb = b.pendingState.Copy()
-	)
-	// If there's no code to interact with, respond with an appropriate error
-	if contract != nil {
-		if code := statedb.GetCode(*contract); len(code) == 0 {
-			return nil, bind.ErrNoCode
-		}
-	}
-	// Set infinite balance to the a fake caller account
-	from := statedb.GetOrNewStateObject(sender)
-	from.SetBalance(common.MaxBig)
+// EstimateGas executes the requested code against the currently pending block/state and
+// returns the used amount of gas.
+func (b *SimulatedBackend) EstimateGas(ctx context.Context, call ethereum.CallMsg) (*big.Int, error) {
+	_, gas, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState.Copy())
+	return gas, err
+}
 
-	// Assemble the call invocation to measure the gas usage
-	msg := callmsg{
-		from:     from,
-		to:       contract,
-		gasPrice: new(big.Int),
-		gasLimit: common.MaxBig,
-		value:    value,
-		data:     data,
+// callContract implemens common code between normal and pending contract calls.
+// state is modified during execution, make sure to copy it if necessary.
+func (b *SimulatedBackend) callContract(ctx context.Context, call ethereum.CallMsg, block *types.Block, statedb *state.StateDB) ([]byte, *big.Int, error) {
+	// Ensure message is initialized properly.
+	if call.GasPrice == nil {
+		call.GasPrice = big.NewInt(1)
+	}
+	if call.Gas == nil || call.Gas.BitLen() == 0 {
+		call.Gas = big.NewInt(50000000)
 	}
-	// Execute the call and return
+	if call.Value == nil {
+		call.Value = new(big.Int)
+	}
+	// Set infinite balance to the fake caller account.
+	from := statedb.GetOrNewStateObject(call.From)
+	from.SetBalance(common.MaxBig)
+	// Execute the call.
+	msg := callmsg{call}
 	vmenv := core.NewEnv(statedb, chainConfig, b.blockchain, msg, block.Header(), vm.Config{})
 	gaspool := new(core.GasPool).AddGas(common.MaxBig)
-
-	_, gas, _, err := core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
-	return gas, err
+	ret, gasUsed, _, err := core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
+	return ret, gasUsed, err
 }
 
-// SendTransaction implements ContractTransactor.SendTransaction, delegating the raw
-// transaction injection to the remote node.
+// SendTransaction updates the pending block to include the given transaction.
+// It panics if the transaction is invalid.
 func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transaction) error {
+	sender, err := tx.From()
+	if err != nil {
+		panic(fmt.Errorf("invalid transaction: %v", err))
+	}
+	nonce := b.pendingState.GetNonce(sender)
+	if tx.Nonce() != nonce {
+		panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
+	}
+
 	blocks, _ := core.GenerateChain(nil, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
 		for _, tx := range b.pendingBlock.Transactions() {
 			block.AddTx(tx)
@@ -187,26 +179,20 @@ func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transa
 	})
 	b.pendingBlock = blocks[0]
 	b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
-
 	return nil
 }
 
 // callmsg implements core.Message to allow passing it as a transaction simulator.
 type callmsg struct {
-	from     *state.StateObject
-	to       *common.Address
-	gasLimit *big.Int
-	gasPrice *big.Int
-	value    *big.Int
-	data     []byte
+	ethereum.CallMsg
 }
 
-func (m callmsg) From() (common.Address, error)         { return m.from.Address(), nil }
-func (m callmsg) FromFrontier() (common.Address, error) { return m.from.Address(), nil }
+func (m callmsg) From() (common.Address, error)         { return m.CallMsg.From, nil }
+func (m callmsg) FromFrontier() (common.Address, error) { return m.CallMsg.From, nil }
 func (m callmsg) Nonce() uint64                         { return 0 }
 func (m callmsg) CheckNonce() bool                      { return false }
-func (m callmsg) To() *common.Address                   { return m.to }
-func (m callmsg) GasPrice() *big.Int                    { return m.gasPrice }
-func (m callmsg) Gas() *big.Int                         { return m.gasLimit }
-func (m callmsg) Value() *big.Int                       { return m.value }
-func (m callmsg) Data() []byte                          { return m.data }
+func (m callmsg) To() *common.Address                   { return m.CallMsg.To }
+func (m callmsg) GasPrice() *big.Int                    { return m.CallMsg.GasPrice }
+func (m callmsg) Gas() *big.Int                         { return m.CallMsg.Gas }
+func (m callmsg) Value() *big.Int                       { return m.CallMsg.Value }
+func (m callmsg) Data() []byte                          { return m.CallMsg.Data }