path: root/accounts/abi/bind/backends/simulated.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 backends

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

	"github.com/ava-labs/coreth/accounts/abi/bind"
	"github.com/ava-labs/coreth/consensus/ethash"
	"github.com/ava-labs/coreth/core"
	"github.com/ava-labs/coreth/core/bloombits"
	"github.com/ava-labs/coreth/core/rawdb"
	"github.com/ava-labs/coreth/core/state"
	"github.com/ava-labs/coreth/core/types"
	"github.com/ava-labs/coreth/core/vm"
	"github.com/ava-labs/coreth/params"
	"github.com/ava-labs/coreth/rpc"
	"github.com/ava-labs/go-ethereum"
	"github.com/ava-labs/go-ethereum/common"
	"github.com/ava-labs/go-ethereum/common/math"
	"github.com/ava-labs/go-ethereum/eth/filters"
	"github.com/ava-labs/go-ethereum/ethdb"
	"github.com/ava-labs/go-ethereum/event"
)

// This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
var _ bind.ContractBackend = (*SimulatedBackend)(nil)

var (
	errBlockNumberUnsupported = errors.New("simulatedBackend cannot access blocks other than the latest block")
	errGasEstimationFailed    = errors.New("gas required exceeds allowance or always failing transaction")
)

// SimulatedBackend implements bind.ContractBackend, simulating a blockchain in
// the background. Its main purpose is to allow easily testing contract bindings.
type SimulatedBackend struct {
	database   ethdb.Database   // In memory database to store our testing data
	blockchain *core.BlockChain // Ethereum blockchain to handle the consensus

	mu           sync.Mutex
	pendingBlock *types.Block   // Currently pending block that will be imported on request
	pendingState *state.StateDB // Currently pending state that will be the active on on request

	events *filters.EventSystem // Event system for filtering log events live

	config *params.ChainConfig
}

// NewSimulatedBackendWithDatabase creates a new binding backend based on the given database
// and uses a simulated blockchain for testing purposes.
func NewSimulatedBackendWithDatabase(database ethdb.Database, alloc core.GenesisAlloc, gasLimit uint64) *SimulatedBackend {
	genesis := core.Genesis{Config: params.AllEthashProtocolChanges, GasLimit: gasLimit, Alloc: alloc}
	genesis.MustCommit(database)
	blockchain, _ := core.NewBlockChain(database, nil, genesis.Config, ethash.NewFaker(), vm.Config{}, nil)

	backend := &SimulatedBackend{
		database:   database,
		blockchain: blockchain,
		config:     genesis.Config,
		events:     filters.NewEventSystem(new(event.TypeMux), &filterBackend{database, blockchain}, false),
	}
	backend.rollback()
	return backend
}

// NewSimulatedBackend creates a new binding backend using a simulated blockchain
// for testing purposes.
func NewSimulatedBackend(alloc core.GenesisAlloc, gasLimit uint64) *SimulatedBackend {
	return NewSimulatedBackendWithDatabase(rawdb.NewMemoryDatabase(), alloc, gasLimit)
}

// Close terminates the underlying blockchain's update loop.
func (b *SimulatedBackend) Close() error {
	b.blockchain.Stop()
	return nil
}

// Commit imports all the pending transactions as a single block and starts a
// fresh new state.
func (b *SimulatedBackend) Commit() {
	b.mu.Lock()
	defer b.mu.Unlock()

	if _, err := b.blockchain.InsertChain([]*types.Block{b.pendingBlock}); err != nil {
		panic(err) // This cannot happen unless the simulator is wrong, fail in that case
	}
	b.rollback()
}

// Rollback aborts all pending transactions, reverting to the last committed state.
func (b *SimulatedBackend) Rollback() {
	b.mu.Lock()
	defer b.mu.Unlock()

	b.rollback()
}

func (b *SimulatedBackend) rollback() {
	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(int, *core.BlockGen) {})
	statedb, _ := b.blockchain.State()

	b.pendingBlock = blocks[0]
	b.pendingState, _ = state.New(b.pendingBlock.Root(), statedb.Database())
}

// CodeAt returns the code associated with a certain account in the blockchain.
func (b *SimulatedBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
		return nil, errBlockNumberUnsupported
	}
	statedb, _ := b.blockchain.State()
	return statedb.GetCode(contract), nil
}

// BalanceAt returns the wei balance of a certain account in the blockchain.
func (b *SimulatedBackend) BalanceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (*big.Int, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
		return nil, errBlockNumberUnsupported
	}
	statedb, _ := b.blockchain.State()
	return statedb.GetBalance(contract), nil
}

// NonceAt returns the nonce of a certain account in the blockchain.
func (b *SimulatedBackend) NonceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (uint64, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
		return 0, errBlockNumberUnsupported
	}
	statedb, _ := b.blockchain.State()
	return statedb.GetNonce(contract), nil
}

// StorageAt returns the value of key in the storage of an account in the blockchain.
func (b *SimulatedBackend) StorageAt(ctx context.Context, contract common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
		return nil, errBlockNumberUnsupported
	}
	statedb, _ := b.blockchain.State()
	val := statedb.GetState(contract, key)
	return val[:], nil
}

// TransactionReceipt returns the receipt of a transaction.
func (b *SimulatedBackend) TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error) {
	receipt, _, _, _ := rawdb.ReadReceipt(b.database, txHash, b.config)
	return receipt, nil
}

// TransactionByHash checks the pool of pending transactions in addition to the
// blockchain. The isPending return value indicates whether the transaction has been
// mined yet. Note that the transaction may not be part of the canonical chain even if
// it's not pending.
func (b *SimulatedBackend) TransactionByHash(ctx context.Context, txHash common.Hash) (*types.Transaction, bool, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	tx := b.pendingBlock.Transaction(txHash)
	if tx != nil {
		return tx, true, nil
	}
	tx, _, _, _ = rawdb.ReadTransaction(b.database, txHash)
	if tx != nil {
		return tx, false, nil
	}
	return nil, false, ethereum.NotFound
}

// PendingCodeAt returns the code associated with an account in the pending state.
func (b *SimulatedBackend) PendingCodeAt(ctx context.Context, contract common.Address) ([]byte, error) {
	b.mu.Lock()
	defer b.mu.Unlock()

	return b.pendingState.GetCode(contract), nil
}

// CallContract executes a contract call.
func (b *SimulatedBackend)