// Copyright 2018 Vulcanize
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package dent

import (
	"encoding/json"
	"errors"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
)

type Converter interface {
	ToModel(ethLog types.Log) (DentModel, error)
}

type DentConverter struct{}

func NewDentConverter() DentConverter {
	return DentConverter{}
}

func (c DentConverter) ToModel(ethLog types.Log) (DentModel, error) {
	err := validateLog(ethLog)
	if err != nil {
		return DentModel{}, err
	}

	bidId := ethLog.Topics[2].Big()
	lot := ethLog.Topics[3].Big().String()
	bidValue := getBidValue(ethLog)
	guy := common.HexToAddress(ethLog.Topics[1].Hex()).String()
	tic := "0"
	//TODO: it is likely that the tic value will need to be added to an emitted event,
	//so this will need to be updated at that point

	transactionIndex := ethLog.TxIndex

	raw, err := json.Marshal(ethLog)
	if err != nil {
		return DentModel{}, err
	}

	return DentModel{
		BidId:            bidId.String(),
		Lot:              lot,
		Bid:              bidValue,
		Guy:              guy,
		Tic:              tic,
		TransactionIndex: transactionIndex,
		Raw:              raw,
	}, nil
}

func validateLog(ethLog types.Log) error {
	if len(ethLog.Data) <= 0 {
		return errors.New("dent log data is empty")
	}

	if len(ethLog.Topics) < 4 {
		return errors.New("dent log does not contain expected topics")
	}

	return nil
}

func getBidValue(ethLog types.Log) string {
	itemByteLength := 32
	lastDataItemStartIndex := len(ethLog.Data) - itemByteLength
	lastItem := ethLog.Data[lastDataItemStartIndex:]
	lastValue := big.NewInt(0).SetBytes(lastItem)

	return lastValue.String()
}