package guest

import (
	"encoding/json"
	"errors"
	"net/http"
	"os"
	"regexp"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

var (
	guestRegex   = regexp.MustCompile(`^/guests/*$`)
	guestIDRegex = regexp.MustCompile(`^/guests/([0-9]+)$`)
)

type GuestHandler struct {
	guestStore GuestStore
}

type GuestStore interface {
	Find(credentials Credentials) (Guest, error)
	Get() ([]Guest, error)
	Add(guest Guest) error
	Update(guest Guest) error
}

type appError struct {
	Error   error
	Message string
	Code    int
}

func NewGuestHandler(guestStore GuestStore) *GuestHandler {
	return &GuestHandler{
		guestStore,
	}
}

func (guestHandler *GuestHandler) ServeHTTP(responseWriter http.ResponseWriter, request *http.Request) {
	switch {
	case request.Method == http.MethodOptions:
		responseWriter.WriteHeader(http.StatusOK)
	case request.Method == http.MethodPost && request.URL.Path == "/guests/login":
		guestHandler.handleLogIn(responseWriter, request)
	case request.Method == http.MethodPut && guestIDRegex.MatchString(request.URL.Path):
		guestHandler.handlePut(responseWriter, request)
	case request.Method == http.MethodGet && guestRegex.MatchString(request.URL.Path):
		guestHandler.handleGet(responseWriter, request)
	case request.Method == http.MethodPost && guestIDRegex.MatchString(request.URL.Path):
		guestHandler.handlePost(responseWriter, request)
	default:
		responseWriter.WriteHeader(http.StatusNotFound)
	}
}

func (guestHandler *GuestHandler) handleLogIn(responseWriter http.ResponseWriter, request *http.Request) {
	token, err := guestHandler.logIn(request)
	if err != nil {
		http.Error(responseWriter, err.Message, err.Code)
	} else {
		responseWriter.Write(token)
	}
}

func (guestHandler *GuestHandler) handlePut(responseWriter http.ResponseWriter, request *http.Request) {
	if err := guestHandler.putGuest(request); err != nil {
		http.Error(responseWriter, err.Message, err.Code)
	} else {
		responseWriter.WriteHeader(http.StatusOK)
	}
}

func (guestHandler *GuestHandler) handleGet(responseWriter http.ResponseWriter, request *http.Request) {
	guests, err := guestHandler.getGuests(request)
	if err != nil {
		http.Error(responseWriter, err.Message, err.Code)
	} else {
		responseWriter.Write(guests)
	}
}

func (guestHandler *GuestHandler) handlePost(responseWriter http.ResponseWriter, request *http.Request) {
	if err := guestHandler.postGuest(request); err != nil {
		http.Error(responseWriter, err.Message, err.Code)
	} else {
		responseWriter.WriteHeader(http.StatusOK)
	}
}

func (guestHandler *GuestHandler) logIn(request *http.Request) ([]byte, *appError) {
	credentials, err := guestHandler.decodeCredentials(request)
	if err != nil {
		return []byte{}, &appError{err, "failed to unmarshal credentials", http.StatusBadRequest}
	}
	guest, err := guestHandler.guestStore.Find(credentials)
	if err != nil {
		return []byte{}, &appError{err, "guest not found", http.StatusUnauthorized}
	}
	expirationTime := guestHandler.setExpirationTime()
	claims := guestHandler.createClaims(credentials, expirationTime)
	key, err := guestHandler.readGuestKey()
	if err != nil {
		return []byte{}, &appError{err, "failed to read secret key", http.StatusInternalServerError}
	}
	token, err := guestHandler.createToken(claims, key)
	if err != nil {
		return []byte{}, &appError{err, "failed to create token", http.StatusInternalServerError}
	}
	jsonBytes, err := guestHandler.marshalResponse(guest, token)
	if err != nil {
		return []byte{}, &appError{err, "failed to marshal response", http.StatusInternalServerError}
	}
	return jsonBytes, nil
}

func (guestHandler *GuestHandler) decodeCredentials(request *http.Request) (Credentials, error) {
	var credentials Credentials
	err := json.NewDecoder(request.Body).Decode(&credentials)
	defer request.Body.Close()
	return credentials, err
}

func (guestHandler *GuestHandler) setExpirationTime() time.Time {
	return time.Now().Add(15 * time.Minute)
}

func (guestHandler *GuestHandler) createClaims(credentials Credentials, expirationTime time.Time) *Claims {
	return &Claims{
		Credentials: credentials,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expirationTime),
		},
	}
}

func (guestHandler *GuestHandler) readGuestKey() ([]byte, error) {
	// TODO: use properties file
	return os.ReadFile("C:\\Users\\mhunt\\guest.pem")
}

func (guestHandler *GuestHandler) readAdminKey() ([]byte, error) {
	return os.ReadFile("C:\\Users\\mhunt\\admin.pem")
}

func (guestHandler *GuestHandler) createToken(claims *Claims, key []byte) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(key)
}

func (guestHandler *GuestHandler) marshalResponse(guest Guest, token string) ([]byte, error) {
	loginResponse := guestHandler.createLoginResponse(guest, token)
	return json.Marshal(loginResponse)
}

func (guestHandler *GuestHandler) createLoginResponse(weddingGuest Guest, token string) *LoginResponse {
	return &LoginResponse{
		Guest: weddingGuest,
		Token: token,
	}
}

func (guestHandler *GuestHandler) putGuest(request *http.Request) *appError {
	guestKey, err := guestHandler.readGuestKey()
	if err != nil {
		return &appError{err, "failed to read secret key", http.StatusInternalServerError}
	}
	if err := guestHandler.validateToken(request, guestKey); err != nil {
		return err
	}
	if guestHandler.findID(request) {
		return &appError{errors.New("id not found"), "id not found", http.StatusNotFound}
	}
	guest, err := guestHandler.decodeGuest(request)
	if err != nil {
		return &appError{err, "invalid guest", http.StatusBadRequest}
	}
	if err := guestHandler.guestStore.Update(guest); err != nil {
		return &appError{err, "failed to update guest", http.StatusInternalServerError}
	}
	return nil
}

func (guestHandler *GuestHandler) validateToken(request *http.Request, key []byte) *appError {
	authorizationHeader := guestHandler.getToken(request)
	claims := guestHandler.newClaims()
	token, err := guestHandler.parseWithClaims(authorizationHeader, claims, key)
	if err != nil {
		if err == jwt.ErrSignatureInvalid {
			return &appError{err, "invalid signature", http.StatusUnauthorized}
		}
		return &appError{err, "failed to parse claims", http.StatusBadRequest}
	}
	if !token.Valid {
		return &appError{err, "invalid token", http.StatusUnauthorized}
	}
	return nil
}

func (guestHandler *GuestHandler) getToken(request *http.Request) string {
	return request.Header.Get("Authorization")
}

func (guestHandler *GuestHandler) newClaims() *Claims {
	return &Claims{}
}

func (guestHandler *GuestHandler) parseWithClaims(token string, claims *Claims, key []byte) (*jwt.Token, error) {
	return jwt.ParseWithClaims(token, claims, func(token *jwt.Token) (any, error) {
		return key, nil
	})
}

func (guestHandler *GuestHandler) findID(request *http.Request) bool {
	matches := guestIDRegex.FindStringSubmatch(request.URL.Path)
	return len(matches) < 2
}

func (guestHandler *GuestHandler) decodeGuest(request *http.Request) (Guest, error) {
	var guest Guest
	err := json.NewDecoder(request.Body).Decode(&guest)
	defer request.Body.Close()
	return guest, err
}

func (guestHandler *GuestHandler) getGuests(request *http.Request) ([]byte, *appError) {
	adminKey, err := guestHandler.readAdminKey()
	if err != nil {
		return []byte{}, &appError{err, "failed to read secret key", http.StatusInternalServerError}
	}
	if err := guestHandler.validateToken(request, adminKey); err != nil {
		return []byte{}, err
	}
	guests, err := guestHandler.guestStore.Get()
	if err != nil {
		return []byte{}, &appError{err, "failed to get guests", http.StatusInternalServerError}
	}
	jsonBytes, err := json.Marshal(guests)
	if err != nil {
		return []byte{}, &appError{err, "failed to marshal guests", http.StatusInternalServerError}
	}
	return jsonBytes, nil
}

func (guestHandler *GuestHandler) postGuest(request *http.Request) *appError {
	adminKey, err := guestHandler.readAdminKey()
	if err != nil {
		return &appError{err, "failed to read secret key", http.StatusInternalServerError}
	}
	if err := guestHandler.validateToken(request, adminKey); err != nil {
		return err
	}
	guest, err := guestHandler.decodeGuest(request)
	if err != nil {
		return &appError{err, "invalid guest", http.StatusBadRequest}
	}
	guests, err := guestHandler.guestStore.Get()
	if err != nil {
		return &appError{err, "failed to get guests", http.StatusInternalServerError}
	}
	if err := guestHandler.checkExistingGuests(guests, guest); err != nil {
		return &appError{err, "id already exists", http.StatusConflict}
	}
	if err := guestHandler.guestStore.Add(guest); err != nil {
		return &appError{err, "failed to add guest", http.StatusInternalServerError}
	}
	return nil
}

func (guestHandler *GuestHandler) checkExistingGuests(guests []Guest, newGuest Guest) error {
	for _, guest := range guests {
		if guest.ID == newGuest.ID {
			return errors.New("id already exists")
		}
	}
	return nil
}