package middleware

import (
	"net/http"
	"regexp"
	"strings"
	"time"

	"golang.org/x/time/rate"
)

// ── Input Validation ───────────────────────────────────────────────────────

var (
	emailRegex    = regexp.MustCompile(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`)
	uuidRegex     = regexp.MustCompile(`^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$`)
	phoneRegex    = regexp.MustCompile(`^[+0-9\s()-]{8,20}$`)
	orgNumRegex   = regexp.MustCompile(`^\d{6}-\d{4}$`)
)

// ValidateEmail kontrollerar email-format
func ValidateEmail(email string) bool {
	return emailRegex.MatchString(email)
}

// ValidateUUID kontrollerar UUID-format
func ValidateUUID(id string) bool {
	return uuidRegex.MatchString(id)
}

// ValidatePhone kontrollerar telefonnummer
func ValidatePhone(phone string) bool {
	return phoneRegex.MatchString(phone)
}

// ValidateOrgNumber kontrollerar svenskt orgnummer
func ValidateOrgNumber(org string) bool {
	return orgNumRegex.MatchString(org)
}

// SanitizeString rensar input från farliga tecken
func SanitizeString(s string) string {
	s = strings.TrimSpace(s)
	// Ta bort potentiellt farliga tecken
	s = strings.ReplaceAll(s, "<", "&lt;")
	s = strings.ReplaceAll(s, ">", "&gt;")
	s = strings.ReplaceAll(s, "\"", "&quot;")
	return s
}

// ── RBAC (Role Based Access Control) ──────────────────────────────────────

type Permission string

const (
	PermRead   Permission = "read"
	PermWrite  Permission = "write"
	PermDelete Permission = "delete"
	PermAdmin  Permission = "admin"
)

type Resource string

const (
	ResCustomers  Resource = "customers"
	ResEmployees  Resource = "employees"
	ResFinance    Resource = "finance"
	ResLegal      Resource = "legal"
	ResHR         Resource = "hr"
	ResSettings   Resource = "settings"
	ResAudit      Resource = "audit"
)

// RolePermissions definierar vilka permissions varje roll har
var RolePermissions = map[string]map[Resource][]Permission{
	"admin": {
		ResCustomers: {PermRead, PermWrite, PermDelete},
		ResEmployees: {PermRead, PermWrite, PermDelete},
		ResFinance:   {PermRead, PermWrite, PermDelete},
		ResLegal:     {PermRead, PermWrite, PermDelete},
		ResHR:        {PermRead, PermWrite, PermDelete},
		ResSettings:  {PermRead, PermWrite, PermDelete},
		ResAudit:     {PermRead, PermWrite, PermDelete},
	},
	"manager": {
		ResCustomers: {PermRead, PermWrite},
		ResEmployees: {PermRead, PermWrite},
		ResFinance:   {PermRead},
		ResLegal:     {PermRead},
		ResHR:        {PermRead, PermWrite},
	},
	"user": {
		ResCustomers: {PermRead},
		ResEmployees: {PermRead},
		ResFinance:   {PermRead},
	},
	"viewer": {
		ResCustomers: {PermRead},
		ResEmployees: {PermRead},
	},
}

// HasPermission kontrollerar om en roll har en specifik permission
func HasPermission(role string, resource Resource, permission Permission) bool {
	perms, ok := RolePermissions[role]
	if !ok {
		return false
	}
	
	resourcePerms, ok := perms[resource]
	if !ok {
		return false
	}
	
	for _, p := range resourcePerms {
		if p == permission || p == PermAdmin {
			return true
		}
	}
	return false
}

// RBACMiddleware kontrollerar behörigheter
func RBACMiddleware(resource Resource, permission Permission) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			// Hämta roll från context (satt av auth middleware)
			role, ok := r.Context().Value("role").(string)
			if !ok {
				http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
				return
			}
			
			if !HasPermission(role, resource, permission) {
				http.Error(w, `{"error":"forbidden"}`, http.StatusForbidden)
				return
			}
			
			next.ServeHTTP(w, r)
		})
	}
}

// ── Rate Limiting ─────────────────────────────────────────────────────────

type RateLimiter struct {
	limiters map[string]*rate.Limiter
}

func NewRateLimiter() *RateLimiter {
	return &RateLimiter{
		limiters: make(map[string]*rate.Limiter),
	}
}

func (rl *RateLimiter) GetLimiter(key string) *rate.Limiter {
	limiter, ok := rl.limiters[key]
	if !ok {
		limiter = rate.NewLimiter(rate.Every(time.Second), 10) // 10 req/s
		rl.limiters[key] = limiter
	}
	return limiter
}

// RateLimit middleware
func RateLimit(rl *RateLimiter) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			key := r.RemoteAddr
			if !rl.GetLimiter(key).Allow() {
				http.Error(w, `{"error":"rate limit exceeded"}`, http.StatusTooManyRequests)
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}

// ── Audit Log ─────────────────────────────────────────────────────────────

type AuditEvent struct {
	Timestamp   time.Time `json:"timestamp"`
	UserID      string    `json:"user_id"`
	Action      string    `json:"action"`
	Resource    string    `json:"resource"`
	ResourceID  string    `json:"resource_id,omitempty"`
	IP          string    `json:"ip"`
	UserAgent   string    `json:"user_agent"`
	Success     bool      `json:"success"`
	Details     string    `json:"details,omitempty"`
}

// AuditLog middleware loggar alla requests
func AuditLog(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		
		// Wrap response writer för att fånga status code
		wrapped := &responseRecorder{ResponseWriter: w, statusCode: http.StatusOK}
		
		next.ServeHTTP(wrapped, r)
		
		// Logga audit event
		event := AuditEvent{
			Timestamp:  start,
			Action:     r.Method,
			Resource:   r.URL.Path,
			IP:         r.RemoteAddr,
			UserAgent:  r.UserAgent(),
			Success:    wrapped.statusCode < 400,
		}
		
		// Hämta user ID från context om finns
		if userID, ok := r.Context().Value("user_id").(string); ok {
			event.UserID = userID
		}
		
		// TODO: Spara till databas eller skicka till Kafka
		_ = event
	})
}

type responseRecorder struct {
	http.ResponseWriter
	statusCode int
}

func (rr *responseRecorder) WriteHeader(code int) {
	rr.statusCode = code
	rr.ResponseWriter.WriteHeader(code)
}

// ── Security Headers ──────────────────────────────────────────────────────

func SecurityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("X-XSS-Protection", "1; mode=block")
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
		w.Header().Set("Content-Security-Policy", "default-src 'self'")
		next.ServeHTTP(w, r)
	})
}