package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"regexp"
	"slices"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"git.huntm.net/wedding/server/guest"
)

type guestHandler struct {
	store guestStore
}

type guestStore interface {
	FindGuest(creds guest.Credentials) (guest.Guest, error)
	Get() ([]guest.Guest, error)
	Add(guest guest.Guest) error
	Update(guest guest.Guest) error
}

var (
	user     = os.Getenv("USER")
	pass     = os.Getenv("PASS")
	host     = "localhost"
	port     = "5432"
	database = "postgres"

	guestRe   = regexp.MustCompile(`^/guest/*$`)
	guestIdRe = regexp.MustCompile(`^/guest/([0-9]+)$`)
)

func newGuestHandler(s guestStore) *guestHandler {
	return &guestHandler{
		store: s,
	}
}

func (h *guestHandler) login(w http.ResponseWriter, r *http.Request) {
	var creds guest.Credentials
	err := json.NewDecoder(r.Body).Decode(&creds)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	weddingGuest, err := h.store.FindGuest(creds)
	if err != nil {
		http.Error(w, err.Error(), http.StatusUnauthorized)
		return
	}

	expirationTime := time.Now().Add(15 * time.Minute)
	claims := &guest.Claims{
		Credentials: creds,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expirationTime),
		},
	}

	key, err := os.ReadFile("C:\\Users\\mhunt\\skey.pem")
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(key)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	loginResponse := &guest.LoginResponse{
		Guest: weddingGuest,
		Token: tokenString,
	}

	jsonBytes, err := json.Marshal(loginResponse)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func (h *guestHandler) getGuests(w http.ResponseWriter, _ *http.Request) {
	guests, err := h.store.Get()
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	jsonBytes, err := json.Marshal(guests)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func (h *guestHandler) createGuest(w http.ResponseWriter, r *http.Request) {
	var guest guest.Guest
	err := json.NewDecoder(r.Body).Decode(&guest)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	guestSlice, err := h.store.Get()
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	for _, g := range guestSlice {
		if g.Id == guest.Id {
			http.Error(w, "Id already exists", http.StatusBadRequest)
			return
		}
	}

	err = h.store.Add(guest)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	w.WriteHeader(http.StatusOK)
}

func (h *guestHandler) updateGuest(w http.ResponseWriter, r *http.Request) {
	tokenString := r.Header.Get("Authorization")
	claims := &guest.Claims{}

	key, err := os.ReadFile("C:\\Users\\mhunt\\skey.pem")
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	token, err := jwt.ParseWithClaims(tokenString, claims, func(token *jwt.Token) (any, error) {
		return key, nil
	})
	if err != nil {
		if err == jwt.ErrSignatureInvalid {
			w.WriteHeader(http.StatusUnauthorized)
			return
		}
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if !token.Valid {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	matches := guestIdRe.FindStringSubmatch(r.URL.Path)
	if len(matches) < 2 {
		http.Error(w, "No id found", http.StatusBadRequest)
		return
	}

	var guest guest.Guest
	err = json.NewDecoder(r.Body).Decode(&guest)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	err = h.store.Update(guest)
	if err != nil {
		http.Error(w, "Cannot update guest", http.StatusBadRequest)
		return
	}
}

func (h *guestHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	switch {
	case r.Method == http.MethodOptions:
		w.WriteHeader(http.StatusOK)
	case r.Method == http.MethodPost && r.URL.Path == "/guest/login":
		h.login(w, r)
	case r.Method == http.MethodGet && guestRe.MatchString(r.URL.Path):
		h.getGuests(w, r)
	case r.Method == http.MethodPost && guestRe.MatchString(r.URL.Path):
		h.createGuest(w, r)
	case r.Method == http.MethodPut && guestIdRe.MatchString(r.URL.Path):
		h.updateGuest(w, r)
	default:
		w.WriteHeader(http.StatusNotFound)
	}
}

func enableCors(next http.Handler) http.Handler {
	allowedOrigins := []string{"http://localhost:5173", "http://192.168.1.41:5173"}
	allowedMethods := []string{"OPTIONS", "POST", "PUT"}
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		method := r.Header.Get("Method")
		if isPreflight(r) && slices.Contains(allowedMethods, method) {
			w.Header().Add("Access-Control-Allow-Methods", method)
		}

		origin := r.Header.Get("Origin")
		if slices.Contains(allowedOrigins, origin) {
			w.Header().Add("Access-Control-Allow-Origin", origin)
		}

		w.Header().Add("Access-Control-Allow-Headers", "*")
		next.ServeHTTP(w, r)
	})
}

func isPreflight(r *http.Request) bool {
	return r.Method == "OPTIONS" &&
		r.Header.Get("Origin") != "" &&
		r.Header.Get("Access-Control-Request-Method") != ""
}

func main() {
	db, err := pgxpool.New(context.Background(), fmt.Sprintf("postgres://%s:%s@%s:%s/%s", user, pass, host, port, database))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	store := guest.NewMemStore(db)
	guestHandler := newGuestHandler(store)

	mux := http.NewServeMux()
	mux.Handle("/guest/", guestHandler)
	log.Fatal(http.ListenAndServe(":8080", enableCors(mux)))
}