package rpc

import (
	"fmt"
	"math/big"
	"os"
	"strconv"

	"github.com/tendermint/tendermint/libs/log"
	tmtypes "github.com/tendermint/tendermint/types"

	evmtypes "github.com/cosmos/ethermint/x/evm/types"

	"github.com/cosmos/cosmos-sdk/client/context"

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

// Backend implements the functionality needed to filter changes.
// Implemented by EthermintBackend.
type Backend interface {
	// Used by block filter; also used for polling
	BlockNumber() (hexutil.Uint64, error)
	HeaderByNumber(blockNum BlockNumber) (*ethtypes.Header, error)
	HeaderByHash(blockHash common.Hash) (*ethtypes.Header, error)
	GetBlockByNumber(blockNum BlockNumber, fullTx bool) (map[string]interface{}, error)
	GetBlockByHash(hash common.Hash, fullTx bool) (map[string]interface{}, error)
	getEthBlockByNumber(height int64, fullTx bool) (map[string]interface{}, error)
	getGasLimit() (int64, error)
	// returns the logs of a given block
	GetLogs(blockHash common.Hash) ([][]*ethtypes.Log, error)

	// Used by pending transaction filter
	PendingTransactions() ([]*Transaction, error)

	// Used by log filter
	GetTransactionLogs(txHash common.Hash) ([]*ethtypes.Log, error)
	BloomStatus() (uint64, uint64)
}

var _ Backend = (*EthermintBackend)(nil)

// EthermintBackend implements the Backend interface
type EthermintBackend struct {
	cliCtx   context.CLIContext
	logger   log.Logger
	gasLimit int64
}

// NewEthermintBackend creates a new EthermintBackend instance
func NewEthermintBackend(cliCtx context.CLIContext) *EthermintBackend {
	return &EthermintBackend{
		cliCtx:   cliCtx,
		logger:   log.NewTMLogger(log.NewSyncWriter(os.Stdout)).With("module", "json-rpc"),
		gasLimit: int64(^uint32(0)),
	}
}

// BlockNumber returns the current block number.
func (e *EthermintBackend) BlockNumber() (hexutil.Uint64, error) {
	res, height, err := e.cliCtx.QueryWithData(fmt.Sprintf("custom/%s/blockNumber", evmtypes.ModuleName), nil)
	if err != nil {
		return hexutil.Uint64(0), err
	}

	var out evmtypes.QueryResBlockNumber
	e.cliCtx.Codec.MustUnmarshalJSON(res, &out)

	e.cliCtx.WithHeight(height)
	return hexutil.Uint64(out.Number), nil
}

// GetBlockByNumber returns the block identified by number.
func (e *EthermintBackend) GetBlockByNumber(blockNum BlockNumber, fullTx bool) (map[string]interface{}, error) {
	value := blockNum.Int64()
	return e.getEthBlockByNumber(value, fullTx)
}

// GetBlockByHash returns the block identified by hash.
func (e *EthermintBackend) GetBlockByHash(hash common.Hash, fullTx bool) (map[string]interface{}, error) {
	res, height, err := e.cliCtx.Query(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryHashToHeight, hash.Hex()))
	if err != nil {
		return nil, err
	}

	var out evmtypes.QueryResBlockNumber
	if err := e.cliCtx.Codec.UnmarshalJSON(res, &out); err != nil {
		return nil, err
	}

	e.cliCtx = e.cliCtx.WithHeight(height)
	return e.getEthBlockByNumber(out.Number, fullTx)
}

// HeaderByNumber returns the block header identified by height.
func (e *EthermintBackend) HeaderByNumber(blockNum BlockNumber) (*ethtypes.Header, error) {
	return e.getBlockHeader(blockNum.Int64())
}

// HeaderByHash returns the block header identified by hash.
func (e *EthermintBackend) HeaderByHash(blockHash common.Hash) (*ethtypes.Header, error) {
	res, height, err := e.cliCtx.Query(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryHashToHeight, blockHash.Hex()))
	if err != nil {
		return nil, err
	}
	var out evmtypes.QueryResBlockNumber
	if err := e.cliCtx.Codec.UnmarshalJSON(res, &out); err != nil {
		return nil, err
	}

	e.cliCtx = e.cliCtx.WithHeight(height)
	return e.getBlockHeader(out.Number)
}

func (e *EthermintBackend) getBlockHeader(height int64) (*ethtypes.Header, error) {
	if height <= 0 {
		// get latest block height
		num, err := e.BlockNumber()
		if err != nil {
			return nil, err
		}

		height = int64(num)
	}

	block, err := e.cliCtx.Client.Block(&height)
	if err != nil {
		return nil, err
	}

	res, _, err := e.cliCtx.Query(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryBloom, strconv.FormatInt(height, 10)))
	if err != nil {
		return nil, err
	}

	var bloomRes evmtypes.QueryBloomFilter
	e.cliCtx.Codec.MustUnmarshalJSON(res, &bloomRes)

	ethHeader := EthHeaderFromTendermint(block.Block.Header)
	ethHeader.Bloom = bloomRes.Bloom

	return ethHeader, nil
}

func (e *EthermintBackend) getEthBlockByNumber(height int64, fullTx bool) (map[string]interface{}, error) {
	// Remove this check when 0 query is fixed ref: (https://github.com/tendermint/tendermint/issues/4014)
	var blkNumPtr *int64
	if height != 0 {
		blkNumPtr = &height
	}

	block, err := e.cliCtx.Client.Block(blkNumPtr)
	if err != nil {
		return nil, err
	}
	header := block.Block.Header

	gasLimit, err := e.getGasLimit()
	if err != nil {
		return nil, err
	}

	var (
		gasUsed      *big.Int
		transactions []common.Hash
	)

	if fullTx {
		// Populate full transaction data
		transactions, gasUsed, err = convertTransactionsToRPC(
			e.cliCtx, block.Block.Txs, common.BytesToHash(header.Hash()), uint64(header.Height),
		)
		if err != nil {
			return nil, err
		}
	} else {
		// TODO: Gas used not saved and cannot be calculated by hashes
		// Return slice of transaction hashes
		transactions = make([]common.Hash, len(block.Block.Txs))
		for i, tx := range block.Block.Txs {
			transactions[i] = common.BytesToHash(tx.Hash())
		}
	}

	res, _, err := e.cliCtx.Query(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryBloom, strconv.FormatInt(block.Block.Height, 10)))
	if err != nil {
		return nil, err
	}

	var out evmtypes.QueryBloomFilter
	e.cliCtx.Codec.MustUnmarshalJSON(res, &out)
	return formatBlock(header, block.Block.Size(), gasLimit, gasUsed, transactions, out.Bloom), nil
}

// getGasLimit returns the gas limit per block set in genesis
func (e *EthermintBackend) getGasLimit() (int64, error) {
	// Retrieve from gasLimit variable cache
	if e.gasLimit != -1 {
		return e.gasLimit, nil
	}

	// Query genesis block if hasn't been retrieved yet
	genesis, err := e.cliCtx.Client.Genesis()
	if err != nil {
		return 0, err
	}

	// Save value to gasLimit cached value
	gasLimit := genesis.Genesis.ConsensusParams.Block.MaxGas
	if gasLimit == -1 {
		// Sets gas limit to max uint32 to not error with javascript dev tooling
		// This -1 value indicating no block gas limit is set to max uint64 with geth hexutils
		// which errors certain javascript dev tooling which only supports up to 53 bits
		gasLimit = int64(^uint32(0))
	}
	e.gasLimit = gasLimit
	return gasLimit, nil
}

// GetTransactionLogs returns the logs given a transaction hash.
// It returns an error if there's an encoding error.
// If no logs are found for the tx hash, the error is nil.
func (e *EthermintBackend) GetTransactionLogs(txHash common.Hash) ([]*ethtypes.Log, error) {
	ctx := e.cliCtx

	res, height, err := ctx.QueryWithData(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryTransactionLogs, txHash.Hex()), nil)
	if err != nil {
		return nil, err
	}

	out := new(evmtypes.QueryETHLogs)
	if err := e.cliCtx.Codec.UnmarshalJSON(res, &out); err != nil {
		return nil, err
	}

	e.cliCtx = e.cliCtx.WithHeight(height)
	return out.Logs, nil
}

// PendingTransactions returns the transactions that are in the transaction pool
// and have a from address that is one of the accounts this node manages.
func (e *EthermintBackend) PendingTransactions() ([]*Transaction, error) {
	pendingTxs, err := e.cliCtx.Client.UnconfirmedTxs(100)
	if err != nil {
		return nil, err
	}

	transactions := make([]*Transaction, pendingTxs.Count)
	for _, tx := range pendingTxs.Txs {
		ethTx, err := bytesToEthTx(e.cliCtx, tx)
		if err != nil {
			return nil, err
		}

		// * Should check signer and reference against accounts the node manages in future
		rpcTx, err := newRPCTransaction(*ethTx, common.BytesToHash(tx.Hash()), common.Hash{}, nil, 0)
		if err != nil {
			return nil, err
		}

		transactions = append(transactions, rpcTx)
	}

	return transactions, nil
}

// GetLogs returns all the logs from all the ethreum transactions in a block.
func (e *EthermintBackend) GetLogs(blockHash common.Hash) ([][]*ethtypes.Log, error) {
	res, _, err := e.cliCtx.Query(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryHashToHeight, blockHash.Hex()))
	if err != nil {
		return nil, err
	}

	var out evmtypes.QueryResBlockNumber
	if err := e.cliCtx.Codec.UnmarshalJSON(res, &out); err != nil {
		return nil, err
	}

	block, err := e.cliCtx.Client.Block(&out.Number)
	if err != nil {
		return nil, err
	}

	var blockLogs = [][]*ethtypes.Log{}
	for _, tx := range block.Block.Txs {
		// NOTE: we query the state in case the tx result logs are not persisted after an upgrade.
		res, _, err := e.cliCtx.QueryWithData(fmt.Sprintf("custom/%s/%s/%s", evmtypes.ModuleName, evmtypes.QueryTransactionLogs, common.BytesToHash(tx.Hash()).Hex()), nil)
		if err != nil {
			continue
		}

		out := new(evmtypes.QueryETHLogs)
		if err := e.cliCtx.Codec.UnmarshalJSON(res, &out); err != nil {
			return nil, err
		}

		blockLogs = append(blockLogs, out.Logs)
	}

	return blockLogs, nil
}

// BloomStatus returns the BloomBitsBlocks and the number of processed sections maintained
// by the chain indexer.
func (e *EthermintBackend) BloomStatus() (uint64, uint64) {
	return 4096, 0
}

// EthHeaderFromTendermint is an util function that returns an Ethereum Header
// from a tendermint Header.
func EthHeaderFromTendermint(header tmtypes.Header) *ethtypes.Header {
	return &ethtypes.Header{
		ParentHash:  common.BytesToHash(header.LastBlockID.Hash.Bytes()),
		UncleHash:   common.Hash{},
		Coinbase:    common.Address{},
		Root:        common.BytesToHash(header.AppHash),
		TxHash:      common.BytesToHash(header.DataHash),
		ReceiptHash: common.Hash{},
		Difficulty:  nil,
		Number:      big.NewInt(header.Height),
		Time:        uint64(header.Time.Unix()),
		Extra:       nil,
		MixDigest:   common.Hash{},
		Nonce:       ethtypes.BlockNonce{},
	}
}