// Copyright 2019 The multi-geth Authors
// This file is part of the multi-geth library.
//
// The multi-geth 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 multi-geth 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 multi-geth library. If not, see <http://www.gnu.org/licenses/>.

package tconvert

import (
	"encoding/binary"
	"errors"

	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/params/types/coregeth"
	"github.com/ethereum/go-ethereum/params/types/genesisT"
	"github.com/ethereum/go-ethereum/params/types/pyethereum"
)

// NewPyEthereumGenesisSpec converts a go-ethereum genesis block into a Parity specific
// chain specification format.
func NewPyEthereumGenesisSpec(network string, genesis *genesisT.Genesis) (*pyethereum.PyEthereumGenesisSpec, error) {
	// Only ethash is currently supported between go-ethereum and pyethereum
	if genesis.Config.(*coregeth.CoreGethChainConfig).Ethash == nil {
		return nil, errors.New("unsupported consensus engine")
	}
	spec := &pyethereum.PyEthereumGenesisSpec{
		Timestamp:  (hexutil.Uint64)(genesis.Timestamp),
		ExtraData:  genesis.ExtraData,
		GasLimit:   (hexutil.Uint64)(genesis.GasLimit),
		Difficulty: (*hexutil.Big)(genesis.Difficulty),
		Mixhash:    genesis.Mixhash,
		Coinbase:   genesis.Coinbase,
		Alloc:      genesis.Alloc,
		ParentHash: genesis.ParentHash,
	}
	spec.Nonce = (hexutil.Bytes)(make([]byte, 8))
	binary.LittleEndian.PutUint64(spec.Nonce[:], genesis.Nonce)

	return spec, nil
}
