package rest

import (
	"context"
	"encoding/hex"
	"encoding/json"
	"errors"
	"math/big"
	"net/http"
	"strings"

	"github.com/gorilla/mux"

	"github.com/cosmos/cosmos-sdk/client"
	clientrest "github.com/cosmos/cosmos-sdk/client/rest"
	"github.com/cosmos/cosmos-sdk/types/rest"
	authrest "github.com/cosmos/cosmos-sdk/x/auth/client/rest"

	rpctypes "github.com/evmos/ethermint/rpc/types"
	feemarkettypes "github.com/evmos/ethermint/x/feemarket/types"

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

// RegisterTxRoutes - Central function to define routes that get registered by the main application
func RegisterTxRoutes(clientCtx client.Context, rtr *mux.Router) {
	r := clientrest.WithHTTPDeprecationHeaders(rtr)
	r.HandleFunc("/txs/{hash}", QueryTxRequestHandlerFn(clientCtx)).Methods("GET")
	r.HandleFunc("/txs", authrest.QueryTxsRequestHandlerFn(clientCtx)).Methods("GET")
	r.HandleFunc("/txs/decode", authrest.DecodeTxRequestHandlerFn(clientCtx)).Methods("POST")
}

// QueryTxRequestHandlerFn implements a REST handler that queries a transaction
// by hash in a committed block.
func QueryTxRequestHandlerFn(clientCtx client.Context) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		vars := mux.Vars(r)
		hashHexStr := vars["hash"]

		clientCtx, ok := rest.ParseQueryHeightOrReturnBadRequest(w, clientCtx, r)
		if !ok {
			return
		}

		ethHashPrefix := "0x"
		if !strings.HasPrefix(hashHexStr, ethHashPrefix) {
			authrest.QueryTxRequestHandlerFn(clientCtx)
			return
		}

		// eth Tx
		ethHashPrefixLength := len(ethHashPrefix)
		output, err := getEthTransactionByHash(clientCtx, hashHexStr[ethHashPrefixLength:])
		if err != nil {
			rest.WriteErrorResponse(w, http.StatusInternalServerError, err.Error())
			return
		}

		rest.PostProcessResponseBare(w, clientCtx, output)
	}
}

// GetTransactionByHash returns the transaction identified by hash.
func getEthTransactionByHash(clientCtx client.Context, hashHex string) ([]byte, error) {
	hash, err := hex.DecodeString(hashHex)
	if err != nil {
		return nil, err
	}
	node, err := clientCtx.GetNode()
	if err != nil {
		return nil, err
	}

	tx, err := node.Tx(context.Background(), hash, false)
	if err != nil {
		return nil, err
	}

	// Can either cache or just leave this out if not necessary
	block, err := node.Block(context.Background(), &tx.Height)
	if err != nil {
		return nil, err
	}

	client := feemarkettypes.NewQueryClient(clientCtx)
	res, err := client.BaseFee(context.Background(), &feemarkettypes.QueryBaseFeeRequest{})
	if err != nil {
		return nil, err
	}

	var baseFee *big.Int
	if res.BaseFee != nil {
		baseFee = res.BaseFee.BigInt()
	}

	blockHash := common.BytesToHash(block.Block.Header.Hash())

	ethTxs, err := rpctypes.RawTxToEthTx(clientCtx, tx.Tx)
	if err != nil {
		return nil, err
	}

	height := uint64(tx.Height)

	for _, ethTx := range ethTxs {
		if common.HexToHash(ethTx.Hash) == common.BytesToHash(hash) {
			rpcTx, err := rpctypes.NewRPCTransaction(ethTx.AsTransaction(), blockHash, height, uint64(tx.Index), baseFee)
			if err != nil {
				return nil, err
			}
			return json.Marshal(rpcTx)
		}
	}

	return nil, errors.New("eth tx not found")
}