package explorer

import (
	"context"
	"encoding/json"
	"fmt"
	"math/big"
	"net"
	"net/http"
	"strconv"
	"time"

	ethCommon "github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/rpc"
	"github.com/gorilla/mux"
	msg_pb "github.com/harmony-one/harmony/api/proto/message"
	"github.com/harmony-one/harmony/core"
	"github.com/harmony-one/harmony/hmy"
	"github.com/harmony-one/harmony/internal/chain"
	"github.com/harmony-one/harmony/internal/common"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/numeric"
	"github.com/harmony-one/harmony/p2p"
	stakingReward "github.com/harmony-one/harmony/staking/reward"
)

// Constants for explorer service.
const (
	explorerPortDifference = 4000
	defaultPageSize        = "1000"
	maxAddresses           = 100000
	nodeSyncTolerance      = 5
)

// HTTPError is an HTTP error.
type HTTPError struct {
	Code int
	Msg  string
}

// Service is the struct for explorer service.
type Service struct {
	router      *mux.Router
	IP          string
	Port        string
	Storage     *Storage
	server      *http.Server
	messageChan chan *msg_pb.Message
	blockchain  *core.BlockChain
	backend     hmy.NodeAPI
}

// New returns explorer service.
func New(selfPeer *p2p.Peer, bc *core.BlockChain, backend hmy.NodeAPI) *Service {
	return &Service{
		IP:         selfPeer.IP,
		Port:       selfPeer.Port,
		blockchain: bc,
		backend:    backend,
		Storage:    GetStorageInstance(selfPeer.IP, selfPeer.Port),
	}
}

// Start starts explorer service.
func (s *Service) Start() error {
	utils.Logger().Info().Msg("Starting explorer service.")
	s.Init()
	s.server = s.Run()
	s.Storage.Start()
	return nil
}

// Stop shutdowns explorer service.
func (s *Service) Stop() error {
	utils.Logger().Info().Msg("Shutting down explorer service.")
	if err := s.server.Shutdown(context.Background()); err != nil {
		utils.Logger().Error().Err(err).Msg("Error when shutting down explorer server")
	} else {
		utils.Logger().Info().Msg("Shutting down explorer server successfully")
	}
	s.Storage.Close()
	return nil
}

// GetExplorerPort returns the port serving explorer dashboard. This port is explorerPortDifference less than the node port.
func GetExplorerPort(nodePort string) string {
	if port, err := strconv.Atoi(nodePort); err == nil {
		return fmt.Sprintf("%d", port-explorerPortDifference)
	}
	utils.Logger().Error().Msg("error on parsing.")
	return ""
}

// Init is to initialize for ExplorerService.
func (s *Service) Init() {}

// Run is to run serving explorer.
func (s *Service) Run() *http.Server {
	// Init address.
	port := GetExplorerPort(s.Port)
	addr := net.JoinHostPort("", port)

	s.router = mux.NewRouter()

	// Set up router for addresses.
	// Fetch addresses request, accepts parameter size: how much addresses to read,
	// parameter prefix: from which address prefix start
	s.router.Path("/addresses").Queries("size", "{[0-9]*?}", "prefix", "{[a-zA-Z0-9]*?}").HandlerFunc(s.GetAddresses).Methods("GET")
	s.router.Path("/addresses").HandlerFunc(s.GetAddresses)

	// Set up router for supply info
	s.router.Path("/burn-addresses").Queries().HandlerFunc(s.GetInaccessibleAddressInfo).Methods("GET")
	s.router.Path("/burn-addresses").HandlerFunc(s.GetInaccessibleAddressInfo)
	s.router.Path("/circulating-supply").Queries().HandlerFunc(s.GetCirculatingSupply).Methods("GET")
	s.router.Path("/circulating-supply").HandlerFunc(s.GetCirculatingSupply)
	s.router.Path("/total-supply").Queries().HandlerFunc(s.GetTotalSupply).Methods("GET")
	s.router.Path("/total-supply").HandlerFunc(s.GetTotalSupply)

	// Set up router for node health check.
	s.router.Path("/node-sync").Queries().HandlerFunc(s.GetNodeSync).Methods("GET")
	s.router.Path("/node-sync").HandlerFunc(s.GetNodeSync)

	// Do serving now.
	utils.Logger().Info().Str("port", GetExplorerPort(s.Port)).Msg("[Explorer] Server started.")
	server := &http.Server{
		Addr:         addr,
		Handler:      s.router,
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  120 * time.Second,
	}
	go func() {
		defer func() { utils.Logger().Debug().Msg("[Explorer] Server closed.") }()
		if err := server.ListenAndServe(); err != nil {
			utils.Logger().Warn().Err(err).Msg("[Explorer] Server error.")
		}
	}()
	fmt.Printf("Started Explorer server at: %v:%v\n", s.IP, port)
	return server
}

// GetAddresses serves end-point /addresses, returns size of addresses from address with prefix.
func (s *Service) GetAddresses(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	sizeStr := r.FormValue("size")
	prefix := r.FormValue("prefix")
	if sizeStr == "" {
		sizeStr = defaultPageSize
	}
	data := &Data{}
	defer func() {
		if err := json.NewEncoder(w).Encode(data.Addresses); err != nil {
			utils.Logger().Warn().Err(err).Msg("cannot JSON-encode addresses")
		}
	}()

	size, err := strconv.Atoi(sizeStr)
	if err != nil || size > maxAddresses {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	data.Addresses, err = s.Storage.GetAddresses(size, oneAddress(prefix))
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		utils.Logger().Warn().Err(err).Msg("wasn't able to fetch addresses from storage")
		return
	}
}

var (
	// InaccessibleAddresses are a list of known eth addresses that cannot spend ONE tokens.
	InaccessibleAddresses = []ethCommon.Address{
		// one10000000000000000000000000000dead5shlag
		ethCommon.HexToAddress("0x7bDeF7Bdef7BDeF7BDEf7bDef7bdef7bdeF6E7AD"),
	}
)

// InaccessibleAddressInfo ..
type InaccessibleAddressInfo struct {
	EthAddress ethCommon.Address `json:"eth-address"`
	Address    string            `json:"address"`
	Balance    numeric.Dec       `json:"balance"`
	Nonce      uint64            `json:"nonce"`
}

// getAllInaccessibleAddresses information according to InaccessibleAddresses
func (s *Service) getAllInaccessibleAddresses() ([]*InaccessibleAddressInfo, error) {
	state, err := s.blockchain.StateAt(s.blockchain.CurrentHeader().Root())
	if err != nil {
		return nil, err
	}

	accs := []*InaccessibleAddressInfo{}
	for _, addr := range InaccessibleAddresses {
		accs = append(accs, &InaccessibleAddressInfo{
			EthAddress: addr,
			Address:    common.MustAddressToBech32(addr),
			Balance:    numeric.NewDecFromBigIntWithPrec(state.GetBalance(addr), 18),
			Nonce:      state.GetNonce(addr),
		})
	}

	return accs, nil
}

// getTotalInaccessibleTokens in ONE at the latest header.
func (s *Service) getTotalInaccessibleTokens() (numeric.Dec, error) {
	addrInfos, err := s.getAllInaccessibleAddresses()
	if err != nil {
		return numeric.Dec{}, err
	}

	total := numeric.NewDecFromBigIntWithPrec(big.NewInt(0), 18)
	for _, addr := range addrInfos {
		total = total.Add(addr.Balance)
	}
	return total, nil
}

// GetInaccessibleAddressInfo serves /burn-addresses end-point.
func (s *Service) GetInaccessibleAddressInfo(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	accInfos, err := s.getAllInaccessibleAddresses()
	if err != nil {
		utils.Logger().Warn().Err(err).Msg("unable to fetch inaccessible addresses")
		w.WriteHeader(http.StatusInternalServerError)
	}
	if err := json.NewEncoder(w).Encode(accInfos); err != nil {
		utils.Logger().Warn().Msg("cannot JSON-encode inaccessible account info")
		w.WriteHeader(http.StatusInternalServerError)
	}
}

// GetCirculatingSupply serves /circulating-supply end-point.
// Note that known InaccessibleAddresses have their funds removed from the supply for this endpoint.
func (s *Service) GetCirculatingSupply(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	circulatingSupply, err := chain.GetCirculatingSupply(context.Background(), s.blockchain)
	if err != nil {
		utils.Logger().Warn().Err(err).Msg("unable to fetch circulating supply")
		w.WriteHeader(http.StatusInternalServerError)
	}
	totalInaccessible, err := s.getTotalInaccessibleTokens()
	if err != nil {
		utils.Logger().Warn().Err(err).Msg("unable to fetch inaccessible tokens")
		w.WriteHeader(http.StatusInternalServerError)
	}
	if err := json.NewEncoder(w).Encode(circulatingSupply.Sub(totalInaccessible)); err != nil {
		utils.Logger().Warn().Msg("cannot JSON-encode circulating supply")
		w.WriteHeader(http.StatusInternalServerError)
	}
}

// GetTotalSupply serves /total-supply end-point.
// Note that known InaccessibleAddresses have their funds removed from the supply for this endpoint.
func (s *Service) GetTotalSupply(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	totalSupply, err := stakingReward.GetTotalTokens(s.blockchain)
	if err != nil {
		utils.Logger().Warn().Err(err).Msg("unable to fetch total supply")
		w.WriteHeader(http.StatusInternalServerError)
	}
	totalInaccessible, err := s.getTotalInaccessibleTokens()
	if err != nil {
		utils.Logger().Warn().Err(err).Msg("unable to fetch inaccessible tokens")
		w.WriteHeader(http.StatusInternalServerError)
	}
	if err := json.NewEncoder(w).Encode(totalSupply.Sub(totalInaccessible)); err != nil {
		utils.Logger().Warn().Msg("cannot JSON-encode total supply")
		w.WriteHeader(http.StatusInternalServerError)
	}
}

// GetNodeSync returns status code Teapot 418 if node is not in sync
func (s *Service) GetNodeSync(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	sync, remote, diff := s.backend.SyncStatus(s.blockchain.ShardID())
	if !sync {
		utils.Logger().Debug().Uint64("remote", remote).Uint64("diff", diff).Msg("GetNodeSyncStatus")
		if remote == 0 || diff > nodeSyncTolerance {
			w.WriteHeader(http.StatusTeapot)
		} else {
			// return sync'ed if the diff is less than nodeSyncTolerance
			// this tolerance is only applicable to /node-sync API call
			sync = true
		}
	}
	if err := json.NewEncoder(w).Encode(sync); err != nil {
		utils.Logger().Warn().Msg("cannot JSON-encode total supply")
		w.WriteHeader(http.StatusInternalServerError)
	}
}

// NotifyService notify service.
func (s *Service) NotifyService(params map[string]interface{}) {}

// SetMessageChan sets up message channel to service.
func (s *Service) SetMessageChan(messageChan chan *msg_pb.Message) {
	s.messageChan = messageChan
}

// APIs for the services.
func (s *Service) APIs() []rpc.API {
	return nil
}