path: root/accounts/abi/bind/base.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 bind

import (
    "context"
    "errors"
    "fmt"
    "math/big"

    "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"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/event"
)

// SignerFn is a signer function callback when a contract requires a method to
// sign the transaction before submission.
type SignerFn func(types.Signer, common.Address, *types.Transaction) (*types.Transaction, error)

// CallOpts is the collection of options to fine tune a contract call request.
type CallOpts struct {
    Pending     bool            // Whether to operate on the pending state or the last known one
    From        common.Address  // Optional the sender address, otherwise the first account is used
    BlockNumber *big.Int        // Optional the block number on which the call should be performed
    Context     context.Context // Network context to support cancellation and timeouts (nil = no timeout)
}

// TransactOpts is the collection of authorization data required to create a
// valid Ethereum transaction.
type TransactOpts struct {
    From   common.Address // Ethereum account to send the transaction from
    Nonce  *big.Int       // Nonce to use for the transaction execution (nil = use pending state)
    Signer SignerFn       // Method to use for signing the transaction (mandatory)

    Value    *big.Int // Funds to transfer along along the transaction (nil = 0 = no funds)
    GasPrice *big.Int // Gas price to use for the transaction execution (nil = gas price oracle)
    GasLimit uint64   // Gas limit to set for the transaction execution (0 = estimate)

    Context context.Context // Network context to support cancellation and timeouts (nil = no timeout)
}

// FilterOpts is the collection of options to fine tune filtering for events
// within a bound contract.
type FilterOpts struct {
    Start uint64  // Start of the queried range
    End   *uint64 // End of the range (nil = latest)

    Context context.Context // Network context to support cancellation and timeouts (nil = no timeout)
}

// WatchOpts is the collection of options to fine tune subscribing for events
// within a bound contract.
type WatchOpts struct {
    Start   *uint64         // Start of the queried range (nil = latest)
    Context context.Context // Network context to support cancellation and timeouts (nil = no timeout)
}

// BoundContract is the base wrapper object that reflects a contract on the
// Ethereum network. It contains a collection of methods that are used by the
// higher level contract bindings to operate.
type BoundContract struct {
    address    common.Address     // Deployment address of the contract on the Ethereum blockchain
    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
    filterer   ContractFilterer   // Event filtering to interact with the blockchain
}

// NewBoundContract creates a low level contract interface through which calls
// and transactions may be made through.
func NewBoundContract(address common.Address, abi abi.ABI, caller ContractCaller, transactor ContractTransactor, filterer ContractFilterer) *BoundContract {
    return &BoundContract{
        address:    address,
        abi:        abi,
        caller:     caller,
        transactor: transactor,
        filterer:   filterer,
    }
}

// DeployContract deploys a contract onto the Ethereum blockchain and binds the
// deployment address with a Go wrapper.
func DeployContract(opts *TransactOpts, abi abi.ABI, bytecode []byte, backend ContractBackend, params ...interface{}) (common.Address, *types.Transaction, *BoundContract, error) {
    // Otherwise try to deploy the contract
    c := NewBoundContract(common.Address{}, abi, backend, backend, backend)

    input, err := c.abi.Pack("", params...)
    if err != nil {
        return common.Address{}, nil, nil, err
    }
    tx, err := c.transact(opts, nil, append(bytecode, input...))
    if err != nil {
        return common.Address{}, nil, nil, err
    }
    c.address = crypto.CreateAddress(opts.From, tx.Nonce())
    return c.address, tx, c, nil
}

// Call invokes the (constant) contract method with params as input values and
// sets the output to result. The result type might be a single field for simple
// returns, a slice of interfaces for anonymous returns and a struct for named
// returns.
func (c *BoundContract) Call(opts *CallOpts, result interface{}, method string, params ...interface{}) error {
    // Don't crash on a lazy user
    if opts == nil {
        opts = new(CallOpts)
    }
    // Pack the input, call and unpack the results
    input, err := c.abi.Pack(method, params...)
    if err != nil {
        return err
    }
    var (
        msg    = ethereum.CallMsg{From: opts.From, 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, opts.BlockNumber)
        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, opts.BlockNumber); err != nil {
                return err
            } else if len(code) == 0 {
                return ErrNoCode
            }
        }
    }
    if err != nil {
        return err
    }
    return c.abi.Unpack(result, method, output)
}

// Transact invokes the (paid) contract method with params as input values.
func (c *BoundContract) Transact(opts *TransactOpts, method string, params ...interface{}) (*types.Transaction, error) {
    // Otherwise pack up the parameters and invoke the contract
    input, err := c.abi.Pack(method, params...)
    if err != nil {
        return nil, err
    }
    return c.transact(opts, &c.address, input)
}

// Transfer initiates a plain transaction to move funds to the contract, calling
// its default method if one is available.
func (c *BoundContract) Transfer(opts *TransactOpts) (*types.Transaction, error) {
    return c.transact(opts, &c.address, nil)
}

// transact executes an actual transaction invocation, first deriving any missing
// authorization fields, and then scheduling the transaction for execution.
func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, input []byte) (*types.Transaction, error) {
    var err error

    // Ensure a valid value field and resolve the account nonce
    value := opts.Value
    if value == nil {
        value = new(big.Int)
    }
    var nonce uint64
    if opts.Nonce == nil {
        nonce, err = c.transactor.PendingNonceAt(ensureContext(opts.Context), opts.From)
        if err != nil {
            return nil, fmt.Errorf("failed to retrieve account nonce: %v", err)
        }
    } else {
        nonce = opts.Nonce.Uint64()
    }
    // Figure out the gas allowance and gas price values
    gasPrice := opts.GasPrice
    if gasPrice == nil {
        gasPrice, err = c.transactor.SuggestGasPrice(ensureContext(opts.Context))
        if err != nil {
            return nil, fmt.Errorf("failed to suggest gas price: %v", err)
        }
    }
    gasLimit := opts.GasLimit
    if gasLimit == 0 {
        // Gas estimation cannot succeed without code for method invocations
        if contract != nil {
            if code, err := c.transactor.PendingCodeAt(ensureContext(opts.Context), c.address); err != nil {
                return nil, err
            } else if len(code) == 0 {
                return nil, ErrNoCode
            }
        }
        // If the contract surely has code (or code is not needed), estimate the transaction
        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 estimate gas needed: %v", err)
        }
    }
    // Create the transaction, sign it and schedule it for execution
    var rawTx *types.Transaction
    if contract == nil {
        rawTx = types.NewContractCreation(nonce, value, gasLimit, gasPrice, input)
    } else {
        rawTx = types.NewTransaction(nonce, c.address, value, gasLimit, gasPrice, input)
    }
    if opts.Signer == nil {
        return nil, errors.New("no signer to authorize the transaction with")
    }
    signedTx, err := opts.Signer(types.HomesteadSigner{}, opts.From, rawTx)
    if err != nil {
        return nil, err
    }
    if err := c.transactor.SendTransaction(ensureContext(opts.Context), signedTx); err != nil {
        return nil, err
    }
    return signedTx, nil
}

// FilterLogs filters contract logs for past blocks, returning the necessary
// channels to construct a strongly typed bound iterator on top of them.
func (c *BoundContract) FilterLogs(opts *FilterOpts, name string, query ...[]interface{}) (chan types.Log, event.Subscription, error) {
    // Don't crash on a lazy user
    if opts == nil {
        opts = new(FilterOpts)
    }
    // Append the event selector to the query parameters and construct the topic set
    query = append([][]interface{}{{c.abi.Events[name].Id()}}, query...)

    topics, err := makeTopics(query...)
    if err != nil {
        return nil, nil, err
    }
    // Start the background filtering
    logs := make(chan types.Log, 128)

    config := ethereum.FilterQuery{
        Addresses: []common.Address{c.address},
        Topics:    topics,
        FromBlock: new(big.Int).SetUint64(opts.Start),
    }
    if opts.End != nil {
        config.ToBlock = new(big.Int).SetUint64(*opts.End)
    }
    /* TODO(karalabe): Replace the rest of the method below with this when supported
    sub, err := c.filterer.SubscribeFilterLogs(ensureContext(opts.Context), config, logs)
    */
    buff, err := c.filterer.FilterLogs(ensureContext(opts.Context), config)
    if err != nil {
        return nil, nil, err
    }
    sub, err := event.NewSubscription(func(quit <-chan struct{}) error {
        for _, log := range buff {
            select {
            case logs <- log:
            case <-quit:
                return nil
            }
        }
        return nil
    }), nil

    if err != nil {
        return nil, nil, err
    }
    return logs, sub, nil
}

// WatchLogs filters subscribes to contract logs for future blocks, returning a
// subscription object that can be used to tear down the watcher.
func (c *BoundContract) WatchLogs(opts *WatchOpts, name string, query ...[]interface{}) (chan types.Log, event.Subscription, error) {
    // Don't crash on a lazy user
    if opts == nil {
        opts = new(WatchOpts)
    }
    // Append the event selector to the query parameters and construct the topic set
    query = append([][]interface{}{{c.abi.Events[name].Id()}}, query...)

    topics, err := makeTopics(query...)
    if err != nil {
        return nil, nil, err
    }
    // Start the background filtering
    logs := make(chan types.Log, 128)

    config := ethereum.FilterQuery{
        Addresses: []common.Address{c.address},
        Topics:    topics,
    }
    if opts.Start != nil {
        config.FromBlock = new(big.Int).SetUint64(*opts.Start)
    }
    sub, err := c.filterer.SubscribeFilterLogs(ensureContext(opts.Context), config, logs)
    if err != nil {
        return nil, nil, err
    }
    return logs, sub, nil
}

// UnpackLog unpacks a retrieved log into the provided output structure.
func (c *BoundContract) UnpackLog(out interface{}, event string, log types.Log) error {
    if len(log.Data) > 0 {
        if err := c.abi.Unpack(out, event, log.Data); err != nil {
            return err
        }
    }
    var indexed abi.Arguments
    for _, arg := range c.abi.Events[event].Inputs {
        if arg.Indexed {
            indexed = append(indexed, arg)
        }
    }
    return parseTopics(out, indexed, log.Topics[1:])
}

// ensureContext is a helper method to ensure a context is not nil, even if the
// user specified it as such.
func ensureContext(ctx context.Context) context.Context {
    if ctx == nil {
        return context.TODO()
    }
    return ctx
}