package security

import (
	"regexp"
	"strings"
	"unicode"
)

const (
	// MaxCampaignPromptRunes caps custom campaign / brand AI prompts (prompt-injection surface).
	MaxCampaignPromptRunes = 8000
	// MaxBrandFieldRunes caps individual brand kit text fields.
	MaxBrandFieldRunes = 2000
	// MaxBrandListItems caps dos/donts/preferred_terms entries.
	MaxBrandListItems = 40
	// MaxBrandListItemRunes caps each list entry.
	MaxBrandListItemRunes = 200
)

var injectPhrase = regexp.MustCompile(`(?i)(ignore\s+previous|system\s*:|assistant\s*:|<\s*/?\s*script)`)

// SanitizePrompt strips controls, soft-filters injection phrases, and truncates by runes.
func SanitizePrompt(s string, maxRunes int) string {
	if maxRunes <= 0 {
		maxRunes = MaxCampaignPromptRunes
	}
	s = stripControls(strings.TrimSpace(s))
	s = injectPhrase.ReplaceAllString(s, "[filtered]")
	return TruncateRunes(s, maxRunes)
}

// CapPromptLength reports whether s exceeds max (rune count).
func CapPromptLength(s string, maxRunes int) bool {
	if maxRunes <= 0 {
		maxRunes = MaxCampaignPromptRunes
	}
	n := 0
	for range s {
		n++
		if n > maxRunes {
			return true
		}
	}
	return false
}

// SanitizeBrandList cleans and bounds a brand kit string list.
func SanitizeBrandList(in []string) []string {
	if len(in) == 0 {
		return []string{}
	}
	out := make([]string, 0, len(in))
	seen := map[string]struct{}{}
	for _, s := range in {
		s = SanitizePrompt(s, MaxBrandListItemRunes)
		if s == "" {
			continue
		}
		key := strings.ToLower(s)
		if _, ok := seen[key]; ok {
			continue
		}
		seen[key] = struct{}{}
		out = append(out, s)
		if len(out) >= MaxBrandListItems {
			break
		}
	}
	return out
}

func stripControls(s string) string {
	if s == "" {
		return ""
	}
	var b strings.Builder
	b.Grow(len(s))
	for _, r := range s {
		if r == '\n' || r == '\t' || unicode.IsPrint(r) {
			b.WriteRune(r)
		}
	}
	return b.String()
}

// TruncateRunes truncates s to at most max runes.
func TruncateRunes(s string, max int) string {
	if max <= 0 {
		return ""
	}
	n := 0
	for i := range s {
		if n == max {
			return s[:i]
		}
		n++
	}
	return s
}