package sign

import (
	"crypto/ecdsa"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/fbsobreira/gotron-sdk/pkg/proto/core"
	"google.golang.org/protobuf/proto"
)

// SignTransaction
//
//	@Description:
//	@param transaction
//	@param privateKey
//	@return *core.Transaction
//	@return error
func SignTransaction(transaction *core.Transaction, privateKey string) (*core.Transaction, error) {
	privateBytes, err := hex.DecodeString(privateKey)
	if err != nil {
		return nil, errors.New(fmt.Errorf("hex decode private key error:%v", err).Error())
	}
	prIv := crypto.ToECDSAUnsafe(privateBytes)
	defer zeroKey(prIv)

	rawData, err := proto.Marshal(transaction.GetRawData())
	if err != nil {
		return nil, errors.New(fmt.Errorf("proto marshal tx raw data error:%v", err).Error())
	}

	h256h := sha256.New()
	h256h.Write(rawData)
	hash := h256h.Sum(nil)
	signature, err := crypto.Sign(hash, prIv)
	if err != nil {
		return nil, errors.New(err.Error())
	}
	transaction.Signature = append(transaction.Signature, signature)

	return transaction, nil
}

// zeroKey
//
//	@Description:
//	@param k
func zeroKey(k *ecdsa.PrivateKey) {
	b := k.D.Bits()
	for i := range b {
		b[i] = 0
	}
}