package utils

import (
	"html"
	"regexp"
	"strings"
	"unicode/utf8"
)

// Sanitizer provides input sanitization utilities
type Sanitizer struct {
	// Max lengths for common fields
	MaxNameLength        int
	MaxDescriptionLength int
	MaxEmailLength       int
}

// DefaultSanitizer returns a sanitizer with default settings
func DefaultSanitizer() *Sanitizer {
	return &Sanitizer{
		MaxNameLength:        255,
		MaxDescriptionLength: 10000,
		MaxEmailLength:       320,
	}
}

// SanitizeString escapes HTML and trims whitespace
func (s *Sanitizer) SanitizeString(input string) string {
	if input == "" {
		return ""
	}
	// Trim whitespace
	result := strings.TrimSpace(input)
	// Escape HTML entities to prevent XSS
	result = html.EscapeString(result)
	return result
}

// SanitizeName sanitizes a name field
func (s *Sanitizer) SanitizeName(input string) string {
	sanitized := s.SanitizeString(input)
	if utf8.RuneCountInString(sanitized) > s.MaxNameLength {
		runes := []rune(sanitized)
		sanitized = string(runes[:s.MaxNameLength])
	}
	return sanitized
}

// SanitizeEmail sanitizes and validates email format
func (s *Sanitizer) SanitizeEmail(input string) string {
	sanitized := strings.TrimSpace(strings.ToLower(input))
	if utf8.RuneCountInString(sanitized) > s.MaxEmailLength {
		return ""
	}
	return sanitized
}

// SanitizeDescription sanitizes long text fields
func (s *Sanitizer) SanitizeDescription(input string) string {
	sanitized := s.SanitizeString(input)
	if utf8.RuneCountInString(sanitized) > s.MaxDescriptionLength {
		runes := []rune(sanitized)
		sanitized = string(runes[:s.MaxDescriptionLength])
	}
	return sanitized
}

// SanitizeSlug creates a URL-safe slug
func (s *Sanitizer) SanitizeSlug(input string) string {
	// Convert to lowercase
	result := strings.ToLower(strings.TrimSpace(input))
	// Replace spaces with hyphens
	result = strings.ReplaceAll(result, " ", "-")
	// Remove non-alphanumeric characters except hyphens
	reg := regexp.MustCompile(`[^a-z0-9-]`)
	result = reg.ReplaceAllString(result, "")
	// Remove multiple consecutive hyphens
	reg = regexp.MustCompile(`-+`)
	result = reg.ReplaceAllString(result, "-")
	// Trim hyphens from ends
	result = strings.Trim(result, "-")
	return result
}

// StripHTML removes all HTML tags from input
func StripHTML(input string) string {
	reg := regexp.MustCompile(`<[^>]*>`)
	return reg.ReplaceAllString(input, "")
}

// SanitizePhone cleans a phone number, keeping only digits and an optional
// leading '+' (international dialing prefix). Removes all formatting characters
// such as spaces, dashes, parentheses, and dots.
//
// Examples:
//
//	"+55 (11) 99999-8888" → "+5511999998888"
//	"(11) 99999-8888"     → "11999998888"
//	"+1-800-555-0100"     → "+18005550100"
func SanitizePhone(phone string) string {
	phone = strings.TrimSpace(phone)
	if phone == "" {
		return ""
	}
	hasPlus := strings.HasPrefix(phone, "+")
	digitsOnly := regexp.MustCompile(`\D`).ReplaceAllString(phone, "")
	if hasPlus {
		return "+" + digitsOnly
	}
	return digitsOnly
}