package handlers

import (
	"fmt"
	"html/template"
	"log"
	"net/http"
	"strconv"

	"shop/internal/auth"
	"shop/internal/compare"
	"shop/internal/heleket"
	"shop/internal/models"
	"shop/internal/repository"
	"shop/internal/version"
)

type CustomerHandler struct {
	products    *repository.ProductRepository
	categories  *repository.CategoryRepository
	users       *repository.UserRepository
	cart        *repository.CartRepository
	orders        *repository.OrderRepository
	priceHistory  *repository.PriceHistoryRepository
	reservations  *repository.ReservationRepository
	stats         *repository.StatsRepository
	userSession   *auth.Session
	cartSession   *auth.Session
	compareSession *auth.Session
	heleket        *heleket.Client
	heleketAPIKey  string
	publicBaseURL  string
	heleketCurrency string
	templates      *template.Template
}

type shopPage struct {
	Title      string
	User       *models.User
	CartCount    int
	CompareCount int
	Version      string
	Products   interface{}
	Categories interface{}
	Error      string
	Success    string
}

type cartPage struct {
	shopPage
	Items []models.CartItem
	Total float64
}

type checkoutPage struct {
	shopPage
	Items           []models.CartItem
	Total           float64
	Name            string
	Email           string
	Phone           string
	Address         string
	HeleketEnabled  bool
}

type accountPage struct {
	shopPage
	Orders  []models.Order
	Name    string
	Phone   string
	Address string
}

type productPage struct {
	shopPage
	Product         models.Product
	PriceHistory    []models.PriceHistoryEntry
	MaxHistoryPrice float64
	Reservation     *models.Reservation
	ReservedByOther bool
	CompareProducts []models.Product
	CompareCount    int
	Success         string
	Error           string
}

type comparePage struct {
	shopPage
	Products []models.Product
}

type categoryPage struct {
	shopPage
	Category models.Category
	Products []models.Product
}

func NewCustomerHandler(
	products *repository.ProductRepository,
	categories *repository.CategoryRepository,
	users *repository.UserRepository,
	cart *repository.CartRepository,
	orders *repository.OrderRepository,
	priceHistory *repository.PriceHistoryRepository,
	reservations *repository.ReservationRepository,
	stats *repository.StatsRepository,
	userSession, cartSession, compareSession *auth.Session,
	heleketClient *heleket.Client,
	heleketAPIKey, publicBaseURL, heleketCurrency string,
	templates *template.Template,
) *CustomerHandler {
	return &CustomerHandler{
		products: products, categories: categories, users: users, cart: cart, orders: orders,
		priceHistory: priceHistory, reservations: reservations, stats: stats,
		userSession: userSession, cartSession: cartSession, compareSession: compareSession,
		heleket: heleketClient, heleketAPIKey: heleketAPIKey,
		publicBaseURL: publicBaseURL, heleketCurrency: heleketCurrency,
		templates: templates,
	}
}

func (h *CustomerHandler) render(w http.ResponseWriter, name string, data any) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
	if err := h.templates.ExecuteTemplate(w, name, data); err != nil {
		log.Printf("render %s: %v", name, err)
	}
}

func (h *CustomerHandler) basePage(r *http.Request, w http.ResponseWriter, title string) shopPage {
	p := shopPage{Title: title, Version: version.Version}
	if uid, ok := auth.UserIDFromSession(h.userSession, r); ok {
		if u, err := h.users.GetByID(r.Context(), uid); err == nil {
			p.User = &u
		}
	}
	cartID, _ := h.resolveCart(r, w)
	if cartID > 0 {
		if n, err := h.cart.ItemCount(r.Context(), cartID); err == nil {
			p.CartCount = n
		}
	}
	p.CompareCount = h.compareCount(r)
	return p
}

func (h *CustomerHandler) resolveCart(r *http.Request, w http.ResponseWriter) (int, error) {
	ctx := r.Context()
	sessionKey := h.cartSession.EnsureKey(w, r)
	var userID *int
	if uid, ok := auth.UserIDFromSession(h.userSession, r); ok {
		userID = &uid
	}
	return h.cart.GetOrCreate(ctx, sessionKey, userID)
}

func (h *CustomerHandler) Home(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	_ = h.stats.IncrementHomeVisit(ctx)

	products, _ := h.products.Featured(ctx, 8)
	categories, _ := h.products.Categories(ctx)

	p := h.basePage(r, w, "Shop — Интернет-магазин")
	p.Products = products
	p.Categories = categories
	h.render(w, "home.html", p)
}

func (h *CustomerHandler) ProductPage(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.Atoi(r.PathValue("id"))
	if err != nil {
		http.NotFound(w, r)
		return
	}
	ctx := r.Context()
	product, err := h.products.GetActiveByID(ctx, id)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	p := productPage{
		shopPage: h.basePage(r, w, product.Name),
		Product:  product,
	}
	p.PriceHistory, _ = h.priceHistory.ByProduct(ctx, id, 12)
	for _, e := range p.PriceHistory {
		if e.Price > p.MaxHistoryPrice {
			p.MaxHistoryPrice = e.Price
		}
	}

	sessionKey := h.cartSession.EnsureKey(w, r)
	if res, err := h.reservations.ActiveByProduct(ctx, id); err == nil {
		p.Reservation = res
		if res.SessionKey != sessionKey {
			var uid int
			if u, ok := auth.UserIDFromSession(h.userSession, r); ok {
				uid = u
			}
			if res.UserID == nil || uid == 0 || *res.UserID != uid {
				p.ReservedByOther = true
			}
		}
	}

	compareRaw, _ := h.compareSession.FromRequest(r)
	compareIDs := compare.Parse(compareRaw)
	p.CompareCount = len(compareIDs)

	var others []models.Product
	if product.CategoryID != nil {
		others, _ = h.products.ByCategoryID(ctx, *product.CategoryID)
	} else {
		others, _ = h.products.Featured(ctx, 50)
	}
	for _, o := range others {
		if o.ID != id {
			p.CompareProducts = append(p.CompareProducts, o)
		}
	}

	switch r.URL.Query().Get("ok") {
	case "reserve":
		p.Success = "Товар забронирован на 24 часа"
	case "compare":
		p.Success = "Товар добавлен к сравнению"
	}
	if r.URL.Query().Get("err") == "reserved" {
		p.Error = "Товар уже забронирован другим покупателем"
	}

	h.render(w, "product.html", p)
}

func (h *CustomerHandler) CategoryPage(w http.ResponseWriter, r *http.Request) {
	slug := r.PathValue("slug")
	cat, err := h.categories.GetBySlug(r.Context(), slug)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	products, _ := h.products.ByCategoryID(r.Context(), cat.ID)
	p := categoryPage{
		shopPage: h.basePage(r, w, cat.Name),
		Category: cat,
		Products: products,
	}
	h.render(w, "category.html", p)
}

func (h *CustomerHandler) RegisterPage(w http.ResponseWriter, r *http.Request) {
	if _, ok := auth.UserIDFromSession(h.userSession, r); ok {
		http.Redirect(w, r, "/account", http.StatusSeeOther)
		return
	}
	h.render(w, "register.html", h.basePage(r, w, "Регистрация"))
}

func (h *CustomerHandler) Register(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	ctx := r.Context()
	email := r.FormValue("email")
	password := r.FormValue("password")
	name := r.FormValue("name")

	p := h.basePage(r, w, "Регистрация")
	if email == "" || password == "" || name == "" {
		p.Error = "Заполните все поля"
		h.render(w, "register.html", p)
		return
	}
	if len(password) < 6 {
		p.Error = "Пароль минимум 6 символов"
		h.render(w, "register.html", p)
		return
	}
	exists, _ := h.users.EmailExists(ctx, email)
	if exists {
		p.Error = "Email уже зарегистрирован"
		h.render(w, "register.html", p)
		return
	}

	u, err := h.users.Create(ctx, email, password, name)
	if err != nil {
		log.Printf("register: %v", err)
		p.Error = "Ошибка регистрации"
		h.render(w, "register.html", p)
		return
	}

	sessionKey := h.cartSession.EnsureKey(w, r)
	_ = h.cart.MergeToUser(ctx, sessionKey, u.ID)
	_ = auth.SetUserSession(h.userSession, w, r, u.ID)
	http.Redirect(w, r, "/account", http.StatusSeeOther)
}

func (h *CustomerHandler) LoginPage(w http.ResponseWriter, r *http.Request) {
	if _, ok := auth.UserIDFromSession(h.userSession, r); ok {
		http.Redirect(w, r, "/account", http.StatusSeeOther)
		return
	}
	h.render(w, "login.html", h.basePage(r, w, "Вход"))
}

func (h *CustomerHandler) Login(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	ctx := r.Context()
	u, err := h.users.Authenticate(ctx, r.FormValue("email"), r.FormValue("password"))
	p := h.basePage(r, w, "Вход")
	if err != nil {
		p.Error = "Неверный email или пароль"
		h.render(w, "login.html", p)
		return
	}
	sessionKey := h.cartSession.EnsureKey(w, r)
	_ = h.cart.MergeToUser(ctx, sessionKey, u.ID)
	_ = auth.SetUserSession(h.userSession, w, r, u.ID)
	http.Redirect(w, r, "/account", http.StatusSeeOther)
}

func (h *CustomerHandler) Logout(w http.ResponseWriter, r *http.Request) {
	h.userSession.ClearCookie(w, r)
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

func (h *CustomerHandler) CartAdd(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	productID, _ := strconv.Atoi(r.FormValue("product_id"))
	qty, _ := strconv.Atoi(r.FormValue("quantity"))
	if qty < 1 {
		qty = 1
	}
	if productID <= 0 {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}
	cartID, err := h.resolveCart(r, w)
	if err == nil {
		_ = h.cart.AddItem(r.Context(), cartID, productID, qty)
	}
	http.Redirect(w, r, "/cart", http.StatusSeeOther)
}

func (h *CustomerHandler) CartPage(w http.ResponseWriter, r *http.Request) {
	cartID, err := h.resolveCart(r, w)
	p := cartPage{shopPage: h.basePage(r, w, "Корзина")}
	if err != nil || cartID == 0 {
		h.render(w, "cart.html", p)
		return
	}
	ctx := r.Context()
	p.Items, _ = h.cart.Items(ctx, cartID)
	p.Total, _ = h.cart.Total(ctx, cartID)
	h.render(w, "cart.html", p)
}

func (h *CustomerHandler) CartUpdate(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	productID, _ := strconv.Atoi(r.FormValue("product_id"))
	qty, _ := strconv.Atoi(r.FormValue("quantity"))
	cartID, _ := h.resolveCart(r, w)
	if cartID > 0 {
		_ = h.cart.UpdateItem(r.Context(), cartID, productID, qty)
	}
	http.Redirect(w, r, "/cart", http.StatusSeeOther)
}

func (h *CustomerHandler) CartRemove(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	productID, _ := strconv.Atoi(r.FormValue("product_id"))
	cartID, _ := h.resolveCart(r, w)
	if cartID > 0 {
		_ = h.cart.RemoveItem(r.Context(), cartID, productID)
	}
	http.Redirect(w, r, "/cart", http.StatusSeeOther)
}

func (h *CustomerHandler) CheckoutPage(w http.ResponseWriter, r *http.Request) {
	cartID, _ := h.resolveCart(r, w)
	ctx := r.Context()
	items, _ := h.cart.Items(ctx, cartID)
	if len(items) == 0 {
		http.Redirect(w, r, "/cart", http.StatusSeeOther)
		return
	}
	total, _ := h.cart.Total(ctx, cartID)
	p := checkoutPage{
		shopPage:       h.basePage(r, w, "Оформление заказа"),
		Items:          items,
		Total:          total,
		HeleketEnabled: h.heleket.Enabled(),
	}
	if p.User != nil {
		p.Name = p.User.Name
		p.Email = p.User.Email
		p.Phone = p.User.Phone
		p.Address = p.User.Address
	}
	h.render(w, "checkout.html", p)
}

func (h *CustomerHandler) Checkout(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	ctx := r.Context()
	cartID, _ := h.resolveCart(r, w)
	items, _ := h.cart.Items(ctx, cartID)
	if len(items) == 0 {
		http.Redirect(w, r, "/cart", http.StatusSeeOther)
		return
	}
	total, _ := h.cart.Total(ctx, cartID)

	name := r.FormValue("name")
	email := r.FormValue("email")
	phone := r.FormValue("phone")
	address := r.FormValue("address")

	p := checkoutPage{
		shopPage:       h.basePage(r, w, "Оформление заказа"),
		Items:          items,
		Total:          total,
		Name:           name,
		Email:          email,
		Phone:          phone,
		Address:        address,
		HeleketEnabled: h.heleket.Enabled(),
	}
	if name == "" || email == "" || phone == "" || address == "" {
		p.Error = "Заполните все поля доставки"
		h.render(w, "checkout.html", p)
		return
	}

	paymentMethod := r.FormValue("payment_method")
	if paymentMethod != "heleket" {
		paymentMethod = "cod"
	}
	if paymentMethod == "heleket" && !h.heleket.Enabled() {
		p.Error = "Онлайн-оплата временно недоступна"
		h.render(w, "checkout.html", p)
		return
	}

	order := models.Order{
		GuestName: name, GuestEmail: email, GuestPhone: phone,
		Address: address, Total: total, PaymentMethod: paymentMethod,
	}
	if paymentMethod == "heleket" {
		order.Status = "unpaid"
	}
	if uid, ok := auth.UserIDFromSession(h.userSession, r); ok {
		order.UserID = &uid
		_ = h.users.UpdateProfile(ctx, &models.User{ID: uid, Name: name, Phone: phone, Address: address})
	}

	if err := h.orders.Create(ctx, &order, items); err != nil {
		log.Printf("checkout: %v", err)
		p.Error = "Ошибка оформления заказа"
		h.render(w, "checkout.html", p)
		return
	}

	if paymentMethod == "heleket" {
		externalID := heleket.OrderExternalID(order.ID)
		base := h.publicBaseURL
		if base == "" {
			base = "http://" + r.Host
		}
		invoice, err := h.heleket.CreateInvoice(ctx, heleket.InvoiceRequest{
			Amount:         heleket.FormatAmount(total),
			Currency:       h.heleketCurrency,
			OrderID:        externalID,
			URLReturn:      base + "/cart",
			URLSuccess:     base + "/order/" + strconv.Itoa(order.ID) + "/success",
			URLCallback:    base + "/webhooks/heleket",
			PayerEmail:     email,
			Lifetime:       3600,
			AdditionalData: "order:" + strconv.Itoa(order.ID),
		})
		if err != nil {
			log.Printf("heleket invoice: %v", err)
			p.Error = "Заказ #" + strconv.Itoa(order.ID) + " создан, но счёт не выдан. Попробуйте оплатить из личного кабинета."
			h.render(w, "checkout.html", p)
			return
		}
		_ = h.orders.UpdateHeleketPayment(ctx, order.ID, invoice.UUID, externalID, invoice.URL, invoice.PaymentStatus)
		_ = h.cart.Clear(ctx, cartID)
		http.Redirect(w, r, invoice.URL, http.StatusSeeOther)
		return
	}

	_ = h.cart.Clear(ctx, cartID)

	success := h.basePage(r, w, "Заказ оформлен")
	success.Success = "Заказ #" + strconv.Itoa(order.ID) + " успешно создан!"
	h.render(w, "order_success.html", success)
}

func (h *CustomerHandler) Account(w http.ResponseWriter, r *http.Request) {
	uid, ok := auth.UserIDFromSession(h.userSession, r)
	if !ok {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	ctx := r.Context()
	u, err := h.users.GetByID(ctx, uid)
	if err != nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	if r.Method == http.MethodPost {
		_ = r.ParseForm()
		u.Name = r.FormValue("name")
		u.Phone = r.FormValue("phone")
		u.Address = r.FormValue("address")
		_ = h.users.UpdateProfile(ctx, &u)
	}

	orders, _ := h.orders.ByUser(ctx, uid)
	p := accountPage{
		shopPage: h.basePage(r, w, "Личный кабинет"),
		Orders:   orders,
		Name:     u.Name,
		Phone:    u.Phone,
		Address:  u.Address,
	}
	p.User = &u
	if r.Method == http.MethodPost {
		p.Success = "Профиль сохранён"
	}
	h.render(w, "account.html", p)
}

func (h *CustomerHandler) Health(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	fmt.Fprintf(w, `{"status":"ok","version":%q}`, version.Version)
}