package validation

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

// ValidateCommentContent checks if comment content meets requirements
func ValidateCommentContent(content string) error {
	c := strings.TrimSpace(content)
	if c == "" {
		return errors.New("comment cannot be empty")
	}
	length := utf8.RuneCountInString(c)
	if length < 6 {
		return errors.New("comment too short (minimum 6 characters)")
	}
	if length > 2000 {
		return errors.New("comment too long (maximum 2000 characters)")
	}
	// Check for excessive caps (anti-spam)
	if isExcessiveCaps(c) {
		return errors.New("too many capital letters detected")
	}
	// Check for excessive repetition
	if hasExcessiveRepetition(c) {
		return errors.New("excessive character repetition detected")
	}
	return nil
}

// ValidateCommentTargetType checks if target type is allowed
func ValidateCommentTargetType(targetType string) error {
	allowed := map[string]bool{
		"article":       true,
		"event":         true,
		"gallery_album": true,
		"youtube_video": true,
	}
	if !allowed[targetType] {
		return errors.New("invalid target type")
	}
	return nil
}

// ValidateCommentStatus checks if status is valid
func ValidateCommentStatus(status string) error {
	if status != "visible" && status != "hidden" {
		return errors.New("status must be 'visible' or 'hidden'")
	}
	return nil
}

// ValidateBanReason checks ban reason
func ValidateBanReason(reason string) error {
	r := strings.TrimSpace(reason)
	if r == "" {
		return errors.New("ban reason cannot be empty")
	}
	if len(r) > 500 {
		return errors.New("ban reason too long (max 500 characters)")
	}
	return nil
}

// ValidateBanDuration checks ban duration in hours
func ValidateBanDuration(hours int) error {
	if hours < 0 {
		return errors.New("ban duration cannot be negative (use 0 for permanent)")
	}
	if hours > 8760 { // More than 1 year
		return errors.New("ban duration too long (max 1 year = 8760 hours)")
	}
	return nil
}

// Helper: check if more than 50% of letters are uppercase
func isExcessiveCaps(text string) bool {
	if len(text) < 20 {
		return false // Allow caps in short messages
	}
	var upper, lower int
	for _, r := range text {
		if r >= 'A' && r <= 'Z' {
			upper++
		} else if r >= 'a' && r <= 'z' {
			lower++
		}
	}
	total := upper + lower
	if total == 0 {
		return false
	}
	return float64(upper)/float64(total) > 0.5
}

// Helper: detect excessive character repetition (e.g., "aaaaaa", "!!!!!!")
func hasExcessiveRepetition(text string) bool {
	// Check for 5+ consecutive identical characters without using backreferences (unsupported in Go regex)
	run := 1
	var prev rune
	first := true
	for _, r := range text {
		if first {
			prev = r
			first = false
			continue
		}
		if r == prev {
			run++
			if run >= 5 {
				return true
			}
		} else {
			prev = r
			run = 1
		}
	}
	return false
}

// SanitizeCommentContent removes dangerous HTML but preserves basic formatting
func SanitizeCommentContent(content string) string {
	// Remove script tags and their content
	re := regexp.MustCompile(`(?i)<script[^>]*>.*?</script>`)
	content = re.ReplaceAllString(content, "")

	// Remove iframe tags
	re = regexp.MustCompile(`(?i)<iframe[^>]*>.*?</iframe>`)
	content = re.ReplaceAllString(content, "")

	// Remove on* event handlers
	re = regexp.MustCompile(`(?i)\s*on\w+\s*=\s*["'][^"']*["']`)
	content = re.ReplaceAllString(content, "")

	return strings.TrimSpace(content)
}

// ValidateReportReason checks report reason
func ValidateReportReason(reason string) error {
	r := strings.TrimSpace(reason)
	if len(r) > 255 {
		return errors.New("report reason too long (max 255 characters)")
	}
	return nil
}

// ValidateReactionType checks if reaction type is valid
func ValidateReactionType(reactionType string) error {
	allowed := map[string]bool{
		"like":        true,
		"heart":       true,
		"smile":       true,
		"laugh":       true,
		"surprised":   true,
		"thumbs_up":   true,
		"thumbs_down": true,
		"sad":         true,
		"angry":       true,
	}
	if !allowed[reactionType] {
		return errors.New("invalid reaction type")
	}
	return nil
}