package transactions

import (
	"context"
	"math/big"

	ethereum "github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/status-im/status-go/geth/rpc"
)

// EthTransactor provides methods to create transactions for ethereum network.
type EthTransactor interface {
	PendingNonceAt(ctx context.Context, account common.Address) (uint64, error)
	ethereum.GasEstimator
	ethereum.GasPricer
	ethereum.TransactionSender
}

// EthTxClient wraps common API methods that are used to send transaction.
type EthTxClient struct {
	c *rpc.Client
}

// NewEthTxClient returns a new EthTxClient for client
func NewEthTxClient(client *rpc.Client) *EthTxClient {
	return &EthTxClient{c: client}
}

// PendingNonceAt returns the account nonce of the given account in the pending state.
// This is the nonce that should be used for the next transaction.
func (ec *EthTxClient) PendingNonceAt(ctx context.Context, account common.Address) (uint64, error) {
	var result hexutil.Uint64
	err := ec.c.CallContext(ctx, &result, "eth_getTransactionCount", account, "pending")
	return uint64(result), err
}

// SuggestGasPrice retrieves the currently suggested gas price to allow a timely
// execution of a transaction.
func (ec *EthTxClient) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
	var hex hexutil.Big
	if err := ec.c.CallContext(ctx, &hex, "eth_gasPrice"); err != nil {
		return nil, err
	}
	return (*big.Int)(&hex), nil
}

// EstimateGas tries to estimate the gas needed to execute a specific transaction based on
// the current pending state of the backend blockchain. There is no guarantee that this is
// the true gas limit requirement as other transactions may be added or removed by miners,
// but it should provide a basis for setting a reasonable default.
func (ec *EthTxClient) EstimateGas(ctx context.Context, msg ethereum.CallMsg) (*big.Int, error) {
	var hex hexutil.Big
	err := ec.c.CallContext(ctx, &hex, "eth_estimateGas", toCallArg(msg))
	if err != nil {
		return nil, err
	}
	return (*big.Int)(&hex), nil
}

// SendTransaction injects a signed transaction into the pending pool for execution.
//
// If the transaction was a contract creation use the TransactionReceipt method to get the
// contract address after the transaction has been mined.
func (ec *EthTxClient) SendTransaction(ctx context.Context, tx *types.Transaction) error {
	data, err := rlp.EncodeToBytes(tx)
	if err != nil {
		return err
	}
	return ec.c.CallContext(ctx, nil, "eth_sendRawTransaction", common.ToHex(data))
}

func toCallArg(msg ethereum.CallMsg) interface{} {
	arg := map[string]interface{}{
		"from": msg.From,
		"to":   msg.To,
	}
	if len(msg.Data) > 0 {
		arg["data"] = hexutil.Bytes(msg.Data)
	}
	if msg.Value != nil {
		arg["value"] = (*hexutil.Big)(msg.Value)
	}
	if msg.Gas != nil {
		arg["gas"] = (*hexutil.Big)(msg.Gas)
	}
	if msg.GasPrice != nil {
		arg["gasPrice"] = (*hexutil.Big)(msg.GasPrice)
	}
	return arg
}