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, 48 insertions, 27 deletions

diff --git a/accounts/abi/bind/base.go b/accounts/abi/bind/base.go
index 80948d3f1..965f51e85 100644
--- a/accounts/abi/bind/base.go
+++ b/accounts/abi/bind/base.go
@@ -20,8 +20,8 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
-	"sync/atomic"
 
+	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -62,9 +62,6 @@ type BoundContract struct {
 	abi        abi.ABI            // Reflect based ABI to access the correct Ethereum methods
 	caller     ContractCaller     // Read interface to interact with the blockchain
 	transactor ContractTransactor // Write interface to interact with the blockchain
-
-	latestHasCode  uint32 // Cached verification that the latest state contains code for this contract
-	pendingHasCode uint32 // Cached verification that the pending state contains code for this contract
 }
 
 // NewBoundContract creates a low level contract interface through which calls
@@ -105,25 +102,42 @@ func (c *BoundContract) Call(opts *CallOpts, result interface{}, method string,
 	if opts == nil {
 		opts = new(CallOpts)
 	}
-	// Make sure we have a contract to operate on, and bail out otherwise
-	if (opts.Pending && atomic.LoadUint32(&c.pendingHasCode) == 0) || (!opts.Pending && atomic.LoadUint32(&c.latestHasCode) == 0) {
-		if code, err := c.caller.HasCode(opts.Context, c.address, opts.Pending); err != nil {
-			return err
-		} else if !code {
-			return ErrNoCode
-		}
-		if opts.Pending {
-			atomic.StoreUint32(&c.pendingHasCode, 1)
-		} else {
-			atomic.StoreUint32(&c.latestHasCode, 1)
-		}
-	}
 	// Pack the input, call and unpack the results
 	input, err := c.abi.Pack(method, params...)
 	if err != nil {
 		return err
 	}
-	output, err := c.caller.ContractCall(opts.Context, c.address, input, opts.Pending)
+	var (
+		msg    = ethereum.CallMsg{To: &c.address, Data: input}
+		ctx    = ensureContext(opts.Context)
+		code   []byte
+		output []byte
+	)
+	if opts.Pending {
+		pb, ok := c.caller.(PendingContractCaller)
+		if !ok {
+			return ErrNoPendingState
+		}
+		output, err = pb.PendingCallContract(ctx, msg)
+		if err == nil && len(output) == 0 {
+			// Make sure we have a contract to operate on, and bail out otherwise.
+			if code, err = pb.PendingCodeAt(ctx, c.address); err != nil {
+				return err
+			} else if len(code) == 0 {
+				return ErrNoCode
+			}
+		}
+	} else {
+		output, err = c.caller.CallContract(ctx, msg, nil)
+		if err == nil && len(output) == 0 {
+			// Make sure we have a contract to operate on, and bail out otherwise.
+			if code, err = c.caller.CodeAt(ctx, c.address, nil); err != nil {
+				return err
+			} else if len(code) == 0 {
+				return ErrNoCode
+			}
+		}
+	}
 	if err != nil {
 		return err
 	}
@@ -158,7 +172,7 @@ func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, i
 	}
 	nonce := uint64(0)
 	if opts.Nonce == nil {
-		nonce, err = c.transactor.PendingAccountNonce(opts.Context, opts.From)
+		nonce, err = c.transactor.PendingNonceAt(ensureContext(opts.Context), opts.From)
 		if err != nil {
 			return nil, fmt.Errorf("failed to retrieve account nonce: %v", err)
 		}
@@ -168,7 +182,7 @@ func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, i
 	// Figure out the gas allowance and gas price values
 	gasPrice := opts.GasPrice
 	if gasPrice == nil {
-		gasPrice, err = c.transactor.SuggestGasPrice(opts.Context)
+		gasPrice, err = c.transactor.SuggestGasPrice(ensureContext(opts.Context))
 		if err != nil {
 			return nil, fmt.Errorf("failed to suggest gas price: %v", err)
 		}
@@ -176,18 +190,18 @@ func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, i
 	gasLimit := opts.GasLimit
 	if gasLimit == nil {
 		// Gas estimation cannot succeed without code for method invocations
-		if contract != nil && atomic.LoadUint32(&c.pendingHasCode) == 0 {
-			if code, err := c.transactor.HasCode(opts.Context, c.address, true); err != nil {
+		if contract != nil {
+			if code, err := c.transactor.PendingCodeAt(ensureContext(opts.Context), c.address); err != nil {
 				return nil, err
-			} else if !code {
+			} else if len(code) == 0 {
 				return nil, ErrNoCode
 			}
-			atomic.StoreUint32(&c.pendingHasCode, 1)
 		}
 		// If the contract surely has code (or code is not needed), estimate the transaction
-		gasLimit, err = c.transactor.EstimateGasLimit(opts.Context, opts.From, contract, value, input)
+		msg := ethereum.CallMsg{From: opts.From, To: contract, Value: value, Data: input}
+		gasLimit, err = c.transactor.EstimateGas(ensureContext(opts.Context), msg)
 		if err != nil {
-			return nil, fmt.Errorf("failed to exstimate gas needed: %v", err)
+			return nil, fmt.Errorf("failed to estimate gas needed: %v", err)
 		}
 	}
 	// Create the transaction, sign it and schedule it for execution
@@ -204,8 +218,15 @@ func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, i
 	if err != nil {
 		return nil, err
 	}
-	if err := c.transactor.SendTransaction(opts.Context, signedTx); err != nil {
+	if err := c.transactor.SendTransaction(ensureContext(opts.Context), signedTx); err != nil {
 		return nil, err
 	}
 	return signedTx, nil
 }
+
+func ensureContext(ctx context.Context) context.Context {
+	if ctx == nil {
+		return context.TODO()
+	}
+	return ctx
+}