package handlers

import (
	"bookra/apps/auth-service/internal/auth"
	"bookra/apps/auth-service/internal/billing"
	"bookra/apps/auth-service/internal/config"
	"bookra/apps/auth-service/internal/db"
	"bookra/apps/auth-service/internal/email"
	"bookra/apps/auth-service/internal/oauth"
	"context"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
)

type Handler struct {
	authSvc    *auth.Service
	neon       *auth.NeonVerifier
	billingSvc *billing.Service
	google     *oauth.GoogleProvider
	cfg        *config.Config
	db         *db.DB
}

type LoginRequest struct {
	Email  string `json:"email" binding:"required,email"`
	Locale string `json:"locale,omitempty"`
}

type VerifyRequest struct {
	Token string `json:"token" binding:"required"`
}

type RefreshRequest struct {
	RefreshToken string `json:"refresh_token"`
}

type PasswordRegisterRequest struct {
	Email    string `json:"email" binding:"required,email"`
	Password string `json:"password" binding:"required,min=8"`
	Name     string `json:"name" binding:"required"`
}

type PasswordLoginRequest struct {
	Email    string `json:"email" binding:"required,email"`
	Password string `json:"password" binding:"required"`
}

type CheckoutRequest struct {
	PlanCode string `json:"planCode,omitempty"`
	Currency string `json:"currency,omitempty"`
}

func New(db *db.DB, emailSvc *email.Service, cfg *config.Config) (*Handler, error) {
	neonVerifier, err := auth.NewNeonVerifier(cfg.NeonAuthURL)
	if err != nil {
		return nil, err
	}
	return &Handler{
		authSvc:    auth.NewService(db, emailSvc, cfg.JWTSecret, cfg.FrontendURL),
		neon:       neonVerifier,
		billingSvc: billing.NewService(cfg, db),
		google:     oauth.NewGoogleProvider(cfg),
		cfg:        cfg,
		db:         db,
	}, nil
}

func (h *Handler) RegisterRoutes(r *gin.Engine) {
	// Auth API
	api := r.Group("/api/auth")
	{
		api.POST("/magic-link", h.SendMagicLink)
		api.POST("/verify", h.VerifyMagicLink)
		api.POST("/register", h.RegisterWithPassword)
		api.POST("/login", h.LoginWithPassword)
		api.POST("/refresh", h.RefreshToken)
		api.GET("/me", h.RequireAuth(), h.GetMe)
		api.POST("/logout", h.RequireAuth(), h.Logout)

		api.GET("/providers", h.ListProviders)
		api.GET("/oauth/google", h.GoogleAuth)
		api.GET("/oauth/google/callback", h.GoogleCallback)
	}

	// Billing API
	billingAPI := r.Group("/api/billing")
	{
		billingAPI.POST("/webhook", h.StripeWebhook)
		billingAPI.GET("/subscription", h.RequireAuth(), h.GetSubscription)
		billingAPI.POST("/checkout", h.RequireAuth(), h.CreateCheckoutSession)
		billingAPI.POST("/refresh", h.RequireAuth(), h.RefreshSubscription)
		billingAPI.GET("/plans", h.ListPlans)
	}

	// Admin Dashboard (Visual Management)
	admin := NewAdminDashboard(h.cfg, h.db)
	admin.RegisterRoutes(r)
}

func (h *Handler) SendMagicLink(c *gin.Context) {
	var req LoginRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	// Detect locale from request: JSON body > Accept-Language header > default "en"
	locale := req.Locale
	if locale == "" {
		locale = detectLocale(c)
	}

	if err := h.authSvc.GenerateMagicLink(c.Request.Context(), req.Email, locale); err != nil {
		log.Printf("magic link failed for %s: %v", req.Email, err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to send magic link"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "Magic link sent to your email"})
}

// detectLocale extracts locale from Accept-Language header
func detectLocale(c *gin.Context) string {
	acceptLang := c.GetHeader("Accept-Language")
	if strings.HasPrefix(acceptLang, "cs") || strings.Contains(acceptLang, "cs-") {
		return "cs"
	}
	// Default to English
	return "en"
}

func (h *Handler) VerifyMagicLink(c *gin.Context) {
	var req VerifyRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	tokens, err := h.authSvc.VerifyMagicLink(c.Request.Context(), req.Token)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid or expired token"})
		return
	}

	c.JSON(http.StatusOK, tokens)
}

func (h *Handler) RegisterWithPassword(c *gin.Context) {
	var req PasswordRegisterRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	tokens, err := h.authSvc.RegisterWithPassword(c.Request.Context(), req.Email, req.Password, req.Name)
	if err != nil {
		if strings.Contains(err.Error(), "already registered") {
			c.JSON(http.StatusConflict, gin.H{"error": "Email already registered"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Registration failed"})
		return
	}

	c.JSON(http.StatusCreated, tokens)
}

func (h *Handler) LoginWithPassword(c *gin.Context) {
	var req PasswordLoginRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	tokens, err := h.authSvc.LoginWithPassword(c.Request.Context(), req.Email, req.Password)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid credentials"})
		return
	}

	c.JSON(http.StatusOK, tokens)
}

func (h *Handler) RefreshToken(c *gin.Context) {
	var req RefreshRequest
	if err := c.ShouldBindJSON(&req); err != nil && !errors.Is(err, io.EOF) {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	refreshToken := strings.TrimSpace(req.RefreshToken)
	if refreshToken == "" {
		authHeader := c.GetHeader("Authorization")
		if strings.HasPrefix(authHeader, "Bearer ") {
			refreshToken = strings.TrimSpace(strings.TrimPrefix(authHeader, "Bearer "))
		}
	}
	if refreshToken == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing refresh token"})
		return
	}

	tokens, err := h.authSvc.RefreshTokens(c.Request.Context(), refreshToken)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid refresh token"})
		return
	}

	c.JSON(http.StatusOK, tokens)
}

func (h *Handler) GetMe(c *gin.Context) {
	claims, exists := c.Get("claims")
	if !exists {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "claims not found"})
		return
	}

	userClaims := claims.(*auth.Claims)
	c.JSON(http.StatusOK, gin.H{
		"id":    userClaims.UserID,
		"email": userClaims.Email,
		"name":  userClaims.Name,
		"role":  userClaims.Role,
	})
}

func (h *Handler) Logout(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"message": "Logged out"})
}

func (h *Handler) ListProviders(c *gin.Context) {
	providers := []gin.H{}

	if h.google.Enabled() {
		providers = append(providers, gin.H{
			"id":   "google",
			"name": "Google",
			"url":  "/api/auth/oauth/google",
		})
	}

	providers = append(providers, gin.H{
		"id":   "email",
		"name": "Email Magic Link",
	})

	c.JSON(http.StatusOK, gin.H{"providers": providers})
}

func (h *Handler) GoogleAuth(c *gin.Context) {
	if !h.google.Enabled() {
		c.JSON(http.StatusNotFound, gin.H{"error": "Google OAuth not configured"})
		return
	}

	state := generateState()
	url := h.google.GetAuthURL(state)

	c.SetCookie("oauth_state", state, 600, "/", "", oauthCookieSecure(c, h.cfg), true)
	c.Redirect(http.StatusTemporaryRedirect, url)
}

func (h *Handler) GoogleCallback(c *gin.Context) {
	if !h.google.Enabled() {
		c.JSON(http.StatusNotFound, gin.H{"error": "Google OAuth not configured"})
		return
	}

	state := c.Query("state")
	expectedState, err := c.Cookie("oauth_state")
	if err != nil || state == "" || state != expectedState {
		c.SetCookie("oauth_state", "", -1, "/", "", oauthCookieSecure(c, h.cfg), true)
		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid OAuth state"})
		return
	}
	c.SetCookie("oauth_state", "", -1, "/", "", oauthCookieSecure(c, h.cfg), true)

	code := c.Query("code")
	if code == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing code"})
		return
	}

	user, err := h.google.ExchangeCode(c.Request.Context(), code)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "OAuth failed"})
		return
	}

	providerID, email, name := h.google.ParseUser(user)
	tokens, err := h.authSvc.OAuthLoginOrCreate(c.Request.Context(), "google", providerID, email, name)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to process login"})
		return
	}

	redirectURL := h.cfg.FrontendURL + "/auth/callback?token=" + url.QueryEscape(tokens.AccessToken)
	if tokens.RefreshToken != "" {
		redirectURL += "&refresh_token=" + url.QueryEscape(tokens.RefreshToken)
	}
	c.Redirect(http.StatusTemporaryRedirect, redirectURL)
}

func (h *Handler) GetSubscription(c *gin.Context) {
	claims, ok := h.claimsFromContext(c)
	if !ok {
		return
	}

	snapshot, err := h.billingSvc.GetSubscription(c.Request.Context(), claims.UserID)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to load subscription"})
		return
	}

	c.JSON(http.StatusOK, snapshot)
}

func (h *Handler) CreateCheckoutSession(c *gin.Context) {
	claims, ok := h.claimsFromContext(c)
	if !ok {
		return
	}

	var req CheckoutRequest
	if err := c.ShouldBindJSON(&req); err != nil && !errors.Is(err, io.EOF) {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	response, err := h.billingSvc.CreateCheckoutSession(c.Request.Context(), billing.UserIdentity{
		ID:    claims.UserID,
		Email: claims.Email,
		Name:  claims.Name,
	}, req.PlanCode, req.Currency)
	if err != nil {
		switch {
		case errors.Is(err, billing.ErrPlanNotConfigured):
			c.JSON(http.StatusBadRequest, gin.H{"error": "Billing plan is not configured"})
		case errors.Is(err, billing.ErrStripeNotConfigured):
			c.JSON(http.StatusServiceUnavailable, gin.H{"error": "Stripe is not configured"})
		default:
			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create checkout session"})
		}
		return
	}

	c.JSON(http.StatusOK, response)
}

func (h *Handler) RefreshSubscription(c *gin.Context) {
	claims, ok := h.claimsFromContext(c)
	if !ok {
		return
	}

	snapshot, err := h.billingSvc.Refresh(c.Request.Context(), claims.UserID)
	if err != nil {
		if errors.Is(err, billing.ErrStripeNotConfigured) {
			c.JSON(http.StatusServiceUnavailable, gin.H{"error": "Stripe is not configured"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to refresh subscription"})
		return
	}

	c.JSON(http.StatusOK, snapshot)
}

// ListPlans returns available billing plans and their configuration status
func (h *Handler) ListPlans(c *gin.Context) {
	plans := []gin.H{
		{"code": "starter", "name": "Starter", "description": "For individuals and small teams"},
		{"code": "pro", "name": "Pro", "description": "For growing businesses"},
		{"code": "business", "name": "Business", "description": "For multi-location operations"},
	}

	// Check which plans are configured
	configured := make(map[string]bool)
	for planCode, priceID := range h.cfg.StripePriceIDs {
		if priceID != "" {
			configured[planCode] = true
		}
	}

	for i, plan := range plans {
		code := plan["code"].(string)
		plan["czkConfigured"] = configured[code+":czk"] || configured[code]
		plan["usdConfigured"] = configured[code+":usd"] || configured[code]
		plans[i] = plan
	}

	c.JSON(http.StatusOK, gin.H{
		"plans":             plans,
		"stripeConfigured":  h.cfg.StripeCheckoutReady(),
		"secretConfigured":  h.cfg.StripeSecretConfigured(),
		"webhookConfigured": h.cfg.StripeWebhookConfigured(),
		"pricesConfigured":  h.cfg.StripeHasAnyPriceConfigured(),
		"checkoutReady":     h.cfg.StripeCheckoutReady(),
		"currencies":        []string{"czk", "usd"},
	})
}

func (h *Handler) StripeWebhook(c *gin.Context) {
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 1<<20)
	payload, err := io.ReadAll(c.Request.Body)
	if err != nil {
		c.JSON(http.StatusRequestEntityTooLarge, gin.H{"error": "Webhook payload is too large"})
		return
	}

	if err := h.billingSvc.HandleWebhook(c.Request.Context(), c.GetHeader("Stripe-Signature"), payload); err != nil {
		switch {
		case errors.Is(err, billing.ErrStripeWebhookMissing), errors.Is(err, billing.ErrStripeSignatureMissing):
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		default:
			c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid Stripe webhook"})
		}
		return
	}

	c.JSON(http.StatusOK, gin.H{"received": true})
}

func (h *Handler) RequireAuth() gin.HandlerFunc {
	return func(c *gin.Context) {
		authHeader := c.GetHeader("Authorization")
		tokenString := ""

		if strings.HasPrefix(authHeader, "Bearer ") {
			tokenString = strings.TrimPrefix(authHeader, "Bearer ")
		}

		if tokenString == "" {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "Missing token"})
			c.Abort()
			return
		}

		claims, err := h.verifyBearerToken(tokenString)
		if err != nil {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid token"})
			c.Abort()
			return
		}

		c.Set("claims", claims)
		c.Next()
	}
}

func (h *Handler) verifyBearerToken(tokenString string) (*auth.Claims, error) {
	if h.neon != nil && h.neon.Enabled() {
		return h.neon.Verify(tokenString)
	}
	if h.cfg.AppEnv == "development" {
		return h.authSvc.VerifyToken(tokenString)
	}
	return nil, errors.New("neon auth is not configured")
}

func (h *Handler) claimsFromContext(c *gin.Context) (*auth.Claims, bool) {
	claims, exists := c.Get("claims")
	if !exists {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "claims not found"})
		return nil, false
	}

	userClaims, ok := claims.(*auth.Claims)
	if !ok {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "invalid claims"})
		return nil, false
	}

	return userClaims, true
}

func generateState() string {
	buffer := make([]byte, 24)
	if _, err := rand.Read(buffer); err != nil {
		return "state_" + time.Now().Format("20060102150405")
	}
	return "state_" + strings.TrimRight(base64.URLEncoding.EncodeToString(buffer), "=")
}

func oauthCookieSecure(c *gin.Context, cfg *config.Config) bool {
	if c.Request.TLS != nil {
		return true
	}
	if strings.EqualFold(c.GetHeader("X-Forwarded-Proto"), "https") {
		return true
	}
	return strings.HasPrefix(strings.ToLower(strings.TrimSpace(cfg.FrontendURL)), "https://")
}

func timeoutMiddleware(duration time.Duration) gin.HandlerFunc {
	return func(c *gin.Context) {
		ctx, cancel := context.WithTimeout(c.Request.Context(), duration)
		defer cancel()
		c.Request = c.Request.WithContext(ctx)
		c.Next()
	}
}