package geth

import (
	"errors"
	"math/big"

	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/rpc"
	"github.com/vulcanize/vulcanizedb/pkg/core"
	vulcCommon "github.com/vulcanize/vulcanizedb/pkg/geth/converters/common"
	"golang.org/x/net/context"
	"strconv"
)

var ErrEmptyHeader = errors.New("empty header returned over RPC")

const MAX_BATCH_SIZE = 100

type BlockChain struct {
	blockConverter  vulcCommon.BlockConverter
	ethClient       core.EthClient
	headerConverter vulcCommon.HeaderConverter
	node            core.Node
	rpcClient       core.RpcClient
}

func NewBlockChain(ethClient core.EthClient, rpcClient core.RpcClient, node core.Node, converter vulcCommon.TransactionConverter) *BlockChain {
	return &BlockChain{
		blockConverter:  vulcCommon.NewBlockConverter(converter),
		ethClient:       ethClient,
		headerConverter: vulcCommon.HeaderConverter{},
		node:            node,
		rpcClient:       rpcClient,
	}
}

func (blockChain *BlockChain) GetBlockByNumber(blockNumber int64) (block core.Block, err error) {
	gethBlock, err := blockChain.ethClient.BlockByNumber(context.Background(), big.NewInt(blockNumber))
	if err != nil {
		return block, err
	}
	return blockChain.blockConverter.ToCoreBlock(gethBlock)
}

func (blockChain *BlockChain) GetHeaderByNumber(blockNumber int64) (header core.Header, err error) {
	if blockChain.node.NetworkID == core.KOVAN_NETWORK_ID {
		return blockChain.getPOAHeader(blockNumber)
	}
	return blockChain.getPOWHeader(blockNumber)
}

func (blockChain *BlockChain) GetHeaderByNumbers(blockNumbers []int64) (header []core.Header, err error) {
	if blockChain.node.NetworkID == core.KOVAN_NETWORK_ID {
		return blockChain.getPOAHeaders(blockNumbers)
	}
	return blockChain.getPOWHeaders(blockNumbers)
}

func (blockChain *BlockChain) getPOWHeader(blockNumber int64) (header core.Header, err error) {
	gethHeader, err := blockChain.ethClient.HeaderByNumber(context.Background(), big.NewInt(blockNumber))
	if err != nil {
		return header, err
	}
	return blockChain.headerConverter.Convert(gethHeader, gethHeader.Hash().String())
}

func (blockChain *BlockChain) getPOWHeaders(blockNumbers []int64) (headers []core.Header, err error) {
	var batch []rpc.BatchElem
	var POWHeaders [MAX_BATCH_SIZE]types.Header
	includeTransactions := false

	for index, blockNumber := range blockNumbers {

		if index >= MAX_BATCH_SIZE {
			break
		}

		blockNumberArg := hexutil.EncodeBig(big.NewInt(blockNumber))

		batchElem := rpc.BatchElem{
			Method: "eth_getBlockByNumber",
			Result: &POWHeaders[index],
			Args:   []interface{}{blockNumberArg, includeTransactions},
		}

		batch = append(batch, batchElem)
	}

	err = blockChain.rpcClient.BatchCall(batch)
	if err != nil {
		return headers, err
	}

	for _, POWHeader := range POWHeaders {
		if POWHeader.Number != nil {
			header, _ := blockChain.headerConverter.Convert(&POWHeader, POWHeader.Hash().String())

			headers = append(headers, header)
		}
	}

	return headers, err
}

func (blockChain *BlockChain) getPOAHeader(blockNumber int64) (header core.Header, err error) {
	var POAHeader core.POAHeader
	blockNumberArg := hexutil.EncodeBig(big.NewInt(blockNumber))
	includeTransactions := false
	err = blockChain.rpcClient.CallContext(context.Background(), &POAHeader, "eth_getBlockByNumber", blockNumberArg, includeTransactions)
	if err != nil {
		return header, err
	}
	if POAHeader.Number == nil {
		return header, ErrEmptyHeader
	}
	return blockChain.headerConverter.Convert(&types.Header{
		ParentHash:  POAHeader.ParentHash,
		UncleHash:   POAHeader.UncleHash,
		Coinbase:    POAHeader.Coinbase,
		Root:        POAHeader.Root,
		TxHash:      POAHeader.TxHash,
		ReceiptHash: POAHeader.ReceiptHash,
		Bloom:       POAHeader.Bloom,
		Difficulty:  POAHeader.Difficulty.ToInt(),
		Number:      POAHeader.Number.ToInt(),
		GasLimit:    uint64(POAHeader.GasLimit),
		GasUsed:     uint64(POAHeader.GasUsed),
		Time:        POAHeader.Time.ToInt(),
		Extra:       POAHeader.Extra,
	}, POAHeader.Hash.String())
}

func (blockChain *BlockChain) getPOAHeaders(blockNumbers []int64) (headers []core.Header, err error) {

	var batch []rpc.BatchElem
	var POAHeaders [MAX_BATCH_SIZE]core.POAHeader
	includeTransactions := false

	for index, blockNumber := range blockNumbers {

		if index >= MAX_BATCH_SIZE {
			break
		}

		blockNumberArg := hexutil.EncodeBig(big.NewInt(blockNumber))

		batchElem := rpc.BatchElem{
			Method: "eth_getBlockByNumber",
			Result: &POAHeaders[index],
			Args:   []interface{}{blockNumberArg, includeTransactions},
		}

		batch = append(batch, batchElem)
	}

	err = blockChain.rpcClient.BatchCall(batch)
	if err != nil {
		return headers, err
	}

	for _, POAHeader := range POAHeaders {
		var header core.Header
		//Header.Number of the newest block will return nil.
		if _, err := strconv.ParseUint(POAHeader.Number.ToInt().String(), 16, 64); err == nil {
			header, _ = blockChain.headerConverter.Convert(&types.Header{
				ParentHash:  POAHeader.ParentHash,
				UncleHash:   POAHeader.UncleHash,
				Coinbase:    POAHeader.Coinbase,
				Root:        POAHeader.Root,
				TxHash:      POAHeader.TxHash,
				ReceiptHash: POAHeader.ReceiptHash,
				Bloom:       POAHeader.Bloom,
				Difficulty:  POAHeader.Difficulty.ToInt(),
				Number:      POAHeader.Number.ToInt(),
				GasLimit:    uint64(POAHeader.GasLimit),
				GasUsed:     uint64(POAHeader.GasUsed),
				Time:        POAHeader.Time.ToInt(),
				Extra:       POAHeader.Extra,
			}, POAHeader.Hash.String())

			headers = append(headers, header)
		}
	}

	return headers, err
}

func (blockChain *BlockChain) GetLogs(contract core.Contract, startingBlockNumber, endingBlockNumber *big.Int) ([]core.Log, error) {
	if endingBlockNumber == nil {
		endingBlockNumber = startingBlockNumber
	}
	contractAddress := common.HexToAddress(contract.Hash)
	fc := ethereum.FilterQuery{
		FromBlock: startingBlockNumber,
		ToBlock:   endingBlockNumber,
		Addresses: []common.Address{contractAddress},
		Topics:    nil,
	}
	gethLogs, err := blockChain.GetEthLogsWithCustomQuery(fc)
	if err != nil {
		return []core.Log{}, err
	}
	logs := vulcCommon.ToCoreLogs(gethLogs)
	return logs, nil
}

func (blockChain *BlockChain) GetEthLogsWithCustomQuery(query ethereum.FilterQuery) ([]types.Log, error) {
	gethLogs, err := blockChain.ethClient.FilterLogs(context.Background(), query)
	if err != nil {
		return []types.Log{}, err
	}
	return gethLogs, nil
}

func (blockChain *BlockChain) LastBlock() *big.Int {
	block, _ := blockChain.ethClient.HeaderByNumber(context.Background(), nil)
	return block.Number
}

func (blockChain *BlockChain) Node() core.Node {
	return blockChain.node
}