// Copyright 2014 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 vm

import (
	"math/big"
	"strings"
	"sync/atomic"
	"time"

	"github.com/PlatONnetwork/PlatON-Go/x/plugin"

	"github.com/PlatONnetwork/PlatON-Go/common"
	"github.com/PlatONnetwork/PlatON-Go/crypto"
	"github.com/PlatONnetwork/PlatON-Go/params"
)

// emptyCodeHash is used by create to ensure deployment is disallowed to already
// deployed contract addresses (relevant after the account abstraction). 
var emptyCodeHash = crypto. Keccak256Hash(nil)

type (
	// CanTransferFunc is the signature of a transfer guard function
	CanTransferFunc func(StateDB, common. Address, *big. Int) bool
	// TransferFunc is the signature of a transfer function
	TransferFunc func(StateDB, common. Address, common. Address, *big. Int)
	// GetHashFunc returns the nth block hash in the blockchain
	// and is used by the BLOCKHASH EVM op code. 
	GetHashFunc func(uint64) common. Hash
)

// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter. 
func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, error) {
	if contract. CodeAddr ! = nil {
		precompiles := PrecompiledContractsHomestead

		if p := precompiles[*contract. CodeAddr]; p ! = nil {
			return RunPrecompiledContract(p, input, contract)
		}

		if p := PlatONPrecompiledContracts[*contract. CodeAddr]; p ! = nil {
			switch p.(type) {

			case *validatorInnerContract:
				vic := &validatorInnerContract{
					Contract: contract,
					Evm:      evm,
				}
				return RunPrecompiledContract(vic, input, contract)

			case *StakingContract:
				staking := &StakingContract{
					Plugin:   plugin. StakingInstance(),
					Contract: contract,
					Evm:      evm,
				}
				return RunPlatONPrecompiledContract(staking, input, contract)
			case *RestrictingContract:
				restricting := &RestrictingContract{
					Plugin:   plugin. RestrictingInstance(),
					Contract: contract,
					Evm:      evm,
				}
				return RunPlatONPrecompiledContract(restricting, input, contract)
			case *SlashingContract:
				slashing := &SlashingContract{
					Plugin:   plugin. SlashInstance(),
					Contract: contract,
					Evm:      evm,
				}
				return RunPlatONPrecompiledContract(slashing, input, contract)
			case *GovContract:
				govContract := &GovContract{
					Plugin:   plugin. GovPluginInstance(),
					Contract: contract,
					Evm:      evm,
				}
				return RunPlatONPrecompiledContract(govContract, input, contract)
			}
		}

	}

	for _, interpreter := range evm.interpreters {
		if interpreter. CanRun(contract. Code) {
			if evm.interpreter ! = interpreter {
				// Ensure that the interpreter pointer is set back
				// to its current value upon return. 
				defer func(i Interpreter) {
					evm.interpreter = i
				}(evm.interpreter)
				evm.interpreter = interpreter
			}
			return interpreter. Run(contract, input, readOnly)
		}
	}
	return nil, ErrNoCompatibleInterpreter
}

// Context provides the EVM with auxiliary information.  Once provided
// it shouldn't be modified. 
type Context struct {
	// CanTransfer returns whether the account contains
	// sufficient ether to transfer the value
	CanTransfer CanTransferFunc
	// Transfer transfers ether from one account to the other
	Transfer TransferFunc
	// GetHash returns the hash corresponding to n
	GetHash GetHashFunc

	// Message information
	Origin   common. Address // Provides information for ORIGIN
	GasPrice *big. Int       // Provides information for GASPRICE

	// Block information
	Coinbase    common. Address // Provides information for COINBASE
	GasLimit    uint64         // Provides information for GASLIMIT
	BlockNumber *big. Int       // Provides information for NUMBER
	Time        *big. Int       // Provides information for TIME
	Difficulty  *big. Int       // Provides information for DIFFICULTY

	BlockHash common. Hash // Only, the value will be available after the current block has been sealed. 
}

// EVM is the Ethereum Virtual Machine base object and provides
// the necessary tools to run a contract on the given state with
// the provided context.  It should be noted that any error
// generated through any of the calls should be considered a
// revert-state-and-consume-all-gas operation, no checks on
// specific errors should ever be performed.  The interpreter makes
// sure that any errors generated are to be considered faulty code. 
//
// The EVM should never be reused and is not thread safe. 
type EVM struct {
	// Context provides auxiliary blockchain related information
	Context
	// StateDB gives access to the underlying state
	StateDB StateDB
	// Depth is the current call stack
	depth int

	// chainConfig contains information about the current chain
	chainConfig *params. ChainConfig
	// chain rules contains the chain rules for the current epoch
	chainRules params. Rules
	// virtual machine configuration options used to initialise the
	// evm. 
	vmConfig Config
	// global (to this context) ethereum virtual machine
	// used throughout the execution of the tx. 
	interpreters []Interpreter
	interpreter  Interpreter
	// abort is used to abort the EVM calling operations
	// NOTE: must be set atomically
	abort int32
	// callGasTemp holds the gas available for the current call.  This is needed because the
	// available gas is calculated in gasCall* according to the 63/64 rule and later
	// applied in opCall*. 
	callGasTemp uint64
}

// NewEVM returns a new EVM.  The returned EVM is not thread safe and should
// only ever be used *once*. 
func NewEVM(ctx Context, statedb StateDB, chainConfig *params. ChainConfig, vmConfig Config) *EVM {
	evm := &EVM{
		Context:      ctx,
		StateDB:      statedb,
		vmConfig:     vmConfig,
		chainConfig:  chainConfig,
		chainRules:   chainConfig. Rules(ctx. BlockNumber),
		interpreters: make([]Interpreter, 0, 1),
	}

	// vmConfig. EVMInterpreter will be used by EVM-C, it won't be checked here
	// as we always want to have the built-in EVM as the failover option. 
	// todo: replace the evm to wasm for the interpreter. 
	if strings. EqualFold("evm", chainConfig. VMInterpreter) {
		evm.interpreters = append(evm.interpreters, NewEVMInterpreter(evm, vmConfig))
	} else {
		evm.interpreters = append(evm.interpreters, NewWASMInterpreter(evm, vmConfig))
	}
	evm.interpreter = evm.interpreters[0]
	return evm
}

// Cancel cancels any running EVM operation.  This may be called concurrently and
// it's safe to be called multiple times. 
func (evm *EVM) Cancel() {
	atomic. StoreInt32(&evm.abort, 1)
}

// Interpreter returns the current interpreter
func (evm *EVM) Interpreter() Interpreter {
	return evm.interpreter
}

// Call executes the contract associated with the addr with the given input as
// parameters.  It also handles any necessary value transfer required and takes
// the necessary steps to create accounts and reverses the state in case of an
// execution error or failed value transfer. 
func (evm *EVM) Call(caller ContractRef, addr common. Address, input []byte, gas uint64, value *big. Int) (ret []byte, leftOverGas uint64, err error) {
	if evm.vmConfig. NoRecursion && evm.depth > 0 {
		return nil, gas, nil
	}

	// Fail if we're trying to execute above the call depth limit
	if evm.depth > int(params. CallCreateDepth) {
		return nil, gas, ErrDepth
	}
	// Fail if we're trying to transfer more than the available balance
	if ! evm. Context. CanTransfer(evm. StateDB, caller. Address(), value) {
		return nil, gas, ErrInsufficientBalance
	}

	var (
		to       = AccountRef(addr)
		snapshot = evm. StateDB.Snapshot() // - snapshot. 
	)
	if ! evm. StateDB.Exist(addr) {
		precompiles := PrecompiledContractsHomestead

		if precompiles[addr] == nil && PlatONPrecompiledContracts[addr] == nil && value. Sign() == 0 {
			// Calling a non existing account, don't do anything, but ping the tracer
			if evm.vmConfig. Debug && evm.depth == 0 {
				evm.vmConfig. Tracer. CaptureStart(caller. Address(), addr, false, input, gas, value)
				evm.vmConfig. Tracer. CaptureEnd(ret, 0, 0, nil)
			}
			return nil, gas, nil
		}
		evm. StateDB.CreateAccount(addr)
	}
	evm. Transfer(evm. StateDB, caller. Address(), to. Address(), value)

	// Initialise a new contract and set the code that is to be used by the EVM. 
	// The contract is a scoped environment for this execution context only. 
	contract := NewContract(caller, to, value, gas)

	contract. SetCallCode(&addr, evm. StateDB.GetCodeHash(addr), evm. StateDB.GetCode(addr))
	start := time. Now()

	// Capture the tracer start/end events in debug mode
	if evm.vmConfig. Debug && evm.depth == 0 {
		evm.vmConfig. Tracer. CaptureStart(caller. Address(), addr, false, input, gas, value)

		defer func() { // Lazy evaluation of the parameters
			evm.vmConfig. Tracer. CaptureEnd(ret, gas-contract. Gas, time. Since(start), err)
		}()
	}
	ret, err = run(evm, contract, input, false)

	// When an error was returned by the EVM or when setting the creation code
	// above we revert to the snapshot and consume any gas remaining.  Additionally
	// when we're in homestead this also counts for code storage gas errors. 
	if err ! = nil {
		evm. StateDB.RevertToSnapshot(snapshot)
		if err ! = errExecutionReverted {
			contract. UseGas(contract. Gas)
		}
	}
	return ret, contract. Gas, err
}

// CallCode executes the contract associated with the addr with the given input
// as parameters.  It also handles any necessary value transfer required and takes
// the necessary steps to create accounts and reverses the state in case of an
// execution error or failed value transfer. 
//
// CallCode differs from Call in the sense that it executes the given address'
// code with the caller as context. 
func (evm *EVM) CallCode(caller ContractRef, addr common. Address, input []byte, gas uint64, value *big. Int) (ret []byte, leftOverGas uint64, err error) {
	if evm.vmConfig. NoRecursion && evm.depth > 0 {
		return nil, gas, nil
	}

	// Fail if we're trying to execute above the call depth limit
	if evm.depth > int(params. CallCreateDepth) {
		return nil, gas, ErrDepth
	}
	// Fail if we're trying to transfer more than the available balance
	if ! evm. CanTransfer(evm. StateDB, caller. Address(), value) {
		return nil, gas, ErrInsufficientBalance
	}

	var (
		snapshot = evm. StateDB.Snapshot()
		to       = AccountRef(caller. Address())
	)
	// initialise a new contract and set the code that is to be used by the
	// EVM.  The contract is a scoped environment for this execution context
	// only. 
	contract := NewContract(caller, to, value, gas)
	contract. SetCallCode(&addr, evm. StateDB.GetCodeHash(addr), evm. StateDB.GetCode(addr))

	ret, err = run(evm, contract, input, false)
	if err ! = nil {
		evm. StateDB.RevertToSnapshot(snapshot)
		if err ! = errExecutionReverted {
			contract. UseGas(contract. Gas)
		}
	}
	return ret, contract. Gas, err
}

// DelegateCall executes the contract associated with the addr with the given input
// as parameters.  It reverses the state in case of an execution error. 
//
// DelegateCall differs from CallCode in the sense that it executes the given address'
// code with the caller as context and the caller is set to the caller of the caller. 
func (evm *EVM) DelegateCall(caller ContractRef, addr common. Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error) {
	if evm.vmConfig. NoRecursion && evm.depth > 0 {
		return nil, gas, nil
	}
	// Fail if we're trying to execute above the call depth limit
	if evm.depth > int(params. CallCreateDepth) {
		return nil, gas, ErrDepth
	}

	var (
		snapshot = evm. StateDB.Snapshot()
		to       = AccountRef(caller. Address())
	)

	// Initialise a new contract and make initialise the delegate values
	contract := NewContract(caller, to, nil, gas).AsDelegate()
	contract. SetCallCode(&addr, evm. StateDB.GetCodeHash(addr), evm. StateDB.GetCode(addr))

	ret, err = run(evm, contract, input, false)
	if err ! = nil {
		evm. StateDB.RevertToSnapshot(snapshot)
		if err ! = errExecutionReverted {
			contract. UseGas(contract. Gas)
		}
	}
	return ret, contract. Gas, err
}

// StaticCall executes the contract associated with the addr with the given input
// as parameters while disallowing any modifications to the state during the call. 
// Opcodes that attempt to perform such modifications will result in exceptions
// instead of performing the modifications. 
func (evm *EVM) StaticCall(caller ContractRef, addr common. Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error) {
	if evm.vmConfig. NoRecursion && evm.depth > 0 {
		return nil, gas, nil
	}
	// Fail if we're trying to execute above the call depth limit
	if evm.depth > int(params. CallCreateDepth) {
		return nil, gas, ErrDepth
	}

	var (
		to       = AccountRef(addr)
		snapshot = evm. StateDB.Snapshot()
	)
	// Initialise a new contract and set the code that is to be used by the
	// EVM.  The contract is a scoped environment for this execution context
	// only. 
	contract := NewContract(caller, to, new(big. Int), gas)
	contract. SetCallCode(&addr, evm. StateDB.GetCodeHash(addr), evm. StateDB.GetCode(addr))

	// When an error was returned by the EVM or when setting the creation code
	// above we revert to the snapshot and consume any gas remaining.  Additionally
	// when we're in Homestead this also counts for code storage gas errors. 
	ret, err = run(evm, contract, input, true)
	if err ! = nil {
		evm. StateDB.RevertToSnapshot(snapshot)
		if err ! = errExecutionReverted {
			contract. UseGas(contract. Gas)
		}
	}
	return ret, contract. Gas, err
}

// create creates a new contract using code as deployment code. 
func (evm *EVM) create(caller ContractRef, code []byte, gas uint64, value *big. Int, address common. Address) ([]byte, common. Address, uint64, error) {
	// Depth check execution.  Fail if we're trying to execute above the
	// limit. 
	if evm.depth > int(params. CallCreateDepth) {
		return nil, common. Address{}, gas, ErrDepth
	}
	if ! evm. CanTransfer(evm. StateDB, caller. Address(), value) {
		return nil, common. Address{}, gas, ErrInsufficientBalance
	}
	nonce := evm. StateDB.GetNonce(caller. Address())
	evm. StateDB.SetNonce(caller. Address(), nonce+1)

	// Ensure there's no existing contract already at the designated address
	contractHash := evm. StateDB.GetCodeHash(address)
	if evm. StateDB.GetNonce(address) ! = 0 || (contractHash ! = (common. Hash{}) && contractHash ! = emptyCodeHash) {
		return nil, common. Address{}, 0, ErrContractAddressCollision
	}
	// Create a new account on the state
	snapshot := evm. StateDB.Snapshot()
	evm. StateDB.CreateAccount(address)
	evm. StateDB.SetNonce(address, 1)
	evm. Transfer(evm. StateDB, caller. Address(), address, value)

	// initialise a new contract and set the code that is to be used by the
	// EVM.  The contract is a scoped environment for this execution context
	// only. 
	contract := NewContract(caller, AccountRef(address), value, gas)
	contract. SetCallCode(&address, crypto. Keccak256Hash(code), code)

	if evm.vmConfig. NoRecursion && evm.depth > 0 {
		return nil, address, gas, nil
	}

	if evm.vmConfig. Debug && evm.depth == 0 {
		evm.vmConfig. Tracer. CaptureStart(caller. Address(), address, true, code, gas, value)
	}
	start := time. Now()

	ret, err := run(evm, contract, nil, false)

	// check whether the max code size has been exceeded
	maxCodeSizeExceeded := len(ret) > params. MaxCodeSize
	// if the contract creation ran successfully and no errors were returned
	// calculate the gas required to store the code.  If the code could not
	// be stored due to not enough gas set an error and let it be handled
	// by the error checking condition below. 
	if err == nil && ! maxCodeSizeExceeded {
		createDataGas := uint64(len(ret)) * params. CreateDataGas
		if contract. UseGas(createDataGas) {
			evm. StateDB.SetCode(address, ret)
		} else {
			err = ErrCodeStoreOutOfGas
		}
	}

	// When an error was returned by the EVM or when setting the creation code
	// above we revert to the snapshot and consume any gas remaining.  Additionally
	// when we're in homestead this also counts for code storage gas errors. 
	if maxCodeSizeExceeded || (err ! = nil && err ! = ErrCodeStoreOutOfGas) {
		evm. StateDB.RevertToSnapshot(snapshot)
		if err ! = errExecutionReverted {
			contract. UseGas(contract. Gas)
		}
	}
	// Assign err if contract code size exceeds the max while the err is still empty. 
	if maxCodeSizeExceeded && err == nil {
		err = errMaxCodeSizeExceeded
	}
	if evm.vmConfig. Debug && evm.depth == 0 {
		evm.vmConfig. Tracer. CaptureEnd(ret, gas-contract. Gas, time. Since(start), err)
	}
	return ret, address, contract. Gas, err

}

// Create creates a new contract using code as deployment code. 
func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big. Int) (ret []byte, contractAddr common. Address, leftOverGas uint64, err error) {
	contractAddr = crypto. CreateAddress(caller. Address(), evm. StateDB.GetNonce(caller. Address()))
	return evm.create(caller, code, gas, value, contractAddr)
}

// Create2 creates a new contract using code as deployment code. 
//
// The different between Create2 with Create is Create2 uses sha3(0xff ++ msg.sender ++ salt ++ sha3(init_code))[12:]
// instead of the usual sender-and-nonce-hash as the address where the contract is initialized at. 
func (evm *EVM) Create2(caller ContractRef, code []byte, gas uint64, endowment *big. Int, salt *big. Int) (ret []byte, contractAddr common. Address, leftOverGas uint64, err error) {
	contractAddr = crypto. CreateAddress2(caller. Address(), common. BigToHash(salt), code)
	return evm.create(caller, code, gas, endowment, contractAddr)
}

// ChainConfig returns the environment's chain configuration
func (evm *EVM) ChainConfig() *params. ChainConfig { return evm.chainConfig }

func (evm *EVM) GetStateDB() StateDB {
	return evm. StateDB
}

func (evm *EVM) GetEvm() *EVM {
	return evm
}

func (evm *EVM) GetConfig() Config {
	return evm.vmConfig
}
