package eth

import (
	"errors"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/sirupsen/logrus"
)

// TransactionArgs represents the arguments to construct a new transaction
// or a message call.
type TransactionArgs struct {
	From                 *common.Address `json:"from"`
	To                   *common.Address `json:"to"`
	Gas                  *hexutil.Uint64 `json:"gas"`
	GasPrice             *hexutil.Big    `json:"gasPrice"`
	MaxFeePerGas         *hexutil.Big    `json:"maxFeePerGas"`
	MaxPriorityFeePerGas *hexutil.Big    `json:"maxPriorityFeePerGas"`
	Value                *hexutil.Big    `json:"value"`
	Nonce                *hexutil.Uint64 `json:"nonce"`

	// We accept "data" and "input" for backwards-compatibility reasons.
	// "input" is the newer name and should be preferred by clients.
	// Issue detail: https://github.com/ethereum/go-ethereum/issues/15628
	Data  *hexutil.Bytes `json:"data"`
	Input *hexutil.Bytes `json:"input"`

	// Introduced by AccessListTxType transaction.
	AccessList *types.AccessList `json:"accessList,omitempty"`
	ChainID    *hexutil.Big      `json:"chainId,omitempty"`
}

// from retrieves the transaction sender address.
func (args *TransactionArgs) from() common.Address {
	if args.From == nil {
		return common.Address{}
	}
	return *args.From
}

// data retrieves the transaction calldata. Input field is preferred.
func (args *TransactionArgs) data() []byte {
	if args.Input != nil {
		return *args.Input
	}
	if args.Data != nil {
		return *args.Data
	}
	return nil
}

// ToMessage converts the transaction arguments to the Message type used by the
// core evm. This method is used in calls and traces that do not require a real
// live transaction.
func (args *TransactionArgs) ToMessage(globalGasCap uint64, baseFee *big.Int) (*core.Message, error) {
	// Reject invalid combinations of pre- and post-1559 fee styles
	if args.GasPrice != nil && (args.MaxFeePerGas != nil || args.MaxPriorityFeePerGas != nil) {
		return nil, errors.New("both gasPrice and (maxFeePerGas or maxPriorityFeePerGas) specified")
	}
	// Set sender address or use zero address if none specified.
	addr := args.from()

	// Set default gas & gas price if none were set
	gas := globalGasCap
	if gas == 0 {
		gas = uint64(math.MaxUint64 / 2)
	}
	if args.Gas != nil {
		gas = uint64(*args.Gas)
	}
	if globalGasCap != 0 && globalGasCap < gas {
		logrus.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
		gas = globalGasCap
	}
	var (
		gasPrice  *big.Int
		gasFeeCap *big.Int
		gasTipCap *big.Int
	)
	if baseFee == nil {
		// If there's no basefee, then it must be a non-1559 execution
		gasPrice = new(big.Int)
		if args.GasPrice != nil {
			gasPrice = args.GasPrice.ToInt()
		}
		gasFeeCap, gasTipCap = gasPrice, gasPrice
	} else {
		// A basefee is provided, necessitating 1559-type execution
		if args.GasPrice != nil {
			// User specified the legacy gas field, convert to 1559 gas typing
			gasPrice = args.GasPrice.ToInt()
			gasFeeCap, gasTipCap = gasPrice, gasPrice
		} else {
			// User specified 1559 gas fields (or none), use those
			gasFeeCap = new(big.Int)
			if args.MaxFeePerGas != nil {
				gasFeeCap = args.MaxFeePerGas.ToInt()
			}
			gasTipCap = new(big.Int)
			if args.MaxPriorityFeePerGas != nil {
				gasTipCap = args.MaxPriorityFeePerGas.ToInt()
			}
			// Backfill the legacy gasPrice for EVM execution, unless we're all zeroes
			gasPrice = new(big.Int)
			if gasFeeCap.BitLen() > 0 || gasTipCap.BitLen() > 0 {
				gasPrice = math.BigMin(new(big.Int).Add(gasTipCap, baseFee), gasFeeCap)
			}
		}
	}
	value := new(big.Int)
	if args.Value != nil {
		value = args.Value.ToInt()
	}
	data := args.data()
	var accessList types.AccessList
	if args.AccessList != nil {
		accessList = *args.AccessList
	}
	msg := &core.Message{
		From:              addr,
		To:                args.To,
		Value:             value,
		GasLimit:          gas,
		GasPrice:          gasPrice,
		GasFeeCap:         gasFeeCap,
		GasTipCap:         gasTipCap,
		Data:              data,
		AccessList:        accessList,
		SkipAccountChecks: true,
	}
	return msg, nil
}