// Copyright 2017 AMIS Technologies
// 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 container

import (
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/consensus/istanbul"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto/sha3"
	"github.com/ethereum/go-ethereum/rlp"

	"github.com/jpmorganchase/istanbul-tools/cmd/istanbul/extra"
)

func sigHash(header *types.Header) (hash common.Hash) {
	hasher := sha3.NewKeccak256()

	// Clean seal is required for calculating proposer seal.
	rlp.Encode(hasher, types.IstanbulFilteredHeader(header, false))
	hasher.Sum(hash[:0])
	return hash
}

func GetProposer(header *types.Header) common.Address {
	if header == nil {
		return common.Address{}
	}

	_, istanbulExtra, err := extra.Decode(common.ToHex(header.Extra))
	if err != nil {
		return common.Address{}
	}

	addr, err := istanbul.GetSignatureAddress(sigHash(header).Bytes(), istanbulExtra.Seal)
	if err != nil {
		return common.Address{}
	}
	return addr
}