package backend

import (
	"fmt"
	"math/big"

	"github.com/cosmos/cosmos-sdk/client/flags"
	sdk "github.com/cosmos/cosmos-sdk/types"
	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
	"github.com/ethereum/go-ethereum/accounts/keystore"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	ethtypes "github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/signer/core/apitypes"
	"github.com/evmos/ethermint/ethereum/eip712"
	evmtypes "github.com/evmos/ethermint/x/evm/types"
	"github.com/pkg/errors"
)

// SendTransaction sends transaction based on received args using Node's key to sign it
func (b *Backend) SendTransaction(args evmtypes.TransactionArgs) (common.Hash, error) {
	// Look up the wallet containing the requested signer
	_, err := b.clientCtx.Keyring.KeyByAddress(sdk.AccAddress(args.From.Bytes()))
	if err != nil {
		b.logger.Error("failed to find key in keyring", "address", args.From, "error", err.Error())
		return common.Hash{}, fmt.Errorf("%s; %s", keystore.ErrNoMatch, err.Error())
	}

	args, err = b.SetTxDefaults(args)
	if err != nil {
		return common.Hash{}, err
	}

	msg := args.ToTransaction()
	if err := msg.ValidateBasic(); err != nil {
		b.logger.Debug("tx failed basic validation", "error", err.Error())
		return common.Hash{}, err
	}

	bn, err := b.BlockNumber()
	if err != nil {
		b.logger.Debug("failed to fetch latest block number", "error", err.Error())
		return common.Hash{}, err
	}

	signer := ethtypes.MakeSigner(b.ChainConfig(), new(big.Int).SetUint64(uint64(bn)))

	// Sign transaction
	if err := msg.Sign(signer, b.clientCtx.Keyring); err != nil {
		b.logger.Debug("failed to sign tx", "error", err.Error())
		return common.Hash{}, err
	}

	// Query params to use the EVM denomination
	res, err := b.queryClient.QueryClient.Params(b.ctx, &evmtypes.QueryParamsRequest{})
	if err != nil {
		b.logger.Error("failed to query evm params", "error", err.Error())
		return common.Hash{}, err
	}

	// Assemble transaction from fields
	tx, err := msg.BuildTx(b.clientCtx.TxConfig.NewTxBuilder(), res.Params.EvmDenom)
	if err != nil {
		b.logger.Error("build cosmos tx failed", "error", err.Error())
		return common.Hash{}, err
	}

	// Encode transaction by default Tx encoder
	txEncoder := b.clientCtx.TxConfig.TxEncoder()
	txBytes, err := txEncoder(tx)
	if err != nil {
		b.logger.Error("failed to encode eth tx using default encoder", "error", err.Error())
		return common.Hash{}, err
	}

	ethTx := msg.AsTransaction()

	// check the local node config in case unprotected txs are disabled
	if !b.UnprotectedAllowed() && !ethTx.Protected() {
		// Ensure only eip155 signed transactions are submitted if EIP155Required is set.
		return common.Hash{}, errors.New("only replay-protected (EIP-155) transactions allowed over RPC")
	}

	txHash := ethTx.Hash()

	// Broadcast transaction in sync mode (default)
	// NOTE: If error is encountered on the node, the broadcast will not return an error
	syncCtx := b.clientCtx.WithBroadcastMode(flags.BroadcastSync)
	rsp, err := syncCtx.BroadcastTx(txBytes)
	if rsp != nil && rsp.Code != 0 {
		err = sdkerrors.ABCIError(rsp.Codespace, rsp.Code, rsp.RawLog)
	}
	if err != nil {
		b.logger.Error("failed to broadcast tx", "error", err.Error())
		return txHash, err
	}

	// Return transaction hash
	return txHash, nil
}

// Sign signs the provided data using the private key of address via Geth's signature standard.
func (b *Backend) Sign(address common.Address, data hexutil.Bytes) (hexutil.Bytes, error) {
	from := sdk.AccAddress(address.Bytes())

	_, err := b.clientCtx.Keyring.KeyByAddress(from)
	if err != nil {
		b.logger.Error("failed to find key in keyring", "address", address.String())
		return nil, fmt.Errorf("%s; %s", keystore.ErrNoMatch, err.Error())
	}

	// Sign the requested hash with the wallet
	signature, _, err := b.clientCtx.Keyring.SignByAddress(from, data)
	if err != nil {
		b.logger.Error("keyring.SignByAddress failed", "address", address.Hex())
		return nil, err
	}

	signature[crypto.RecoveryIDOffset] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
	return signature, nil
}

// SignTypedData signs EIP-712 conformant typed data
func (b *Backend) SignTypedData(address common.Address, typedData apitypes.TypedData) (hexutil.Bytes, error) {
	from := sdk.AccAddress(address.Bytes())

	_, err := b.clientCtx.Keyring.KeyByAddress(from)
	if err != nil {
		b.logger.Error("failed to find key in keyring", "address", address.String())
		return nil, fmt.Errorf("%s; %s", keystore.ErrNoMatch, err.Error())
	}

	sigHash, err := eip712.ComputeTypedDataHash(typedData)
	if err != nil {
		return nil, err
	}

	// Sign the requested hash with the wallet
	signature, _, err := b.clientCtx.Keyring.SignByAddress(from, sigHash)
	if err != nil {
		b.logger.Error("keyring.SignByAddress failed", "address", address.Hex())
		return nil, err
	}

	signature[crypto.RecoveryIDOffset] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
	return signature, nil
}