package templates

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"unicode"
)

// SafeDisplayNameToPathSegment converts a user-provided title to a safe
// filesystem path segment. It preserves human readability (Cyrillic, spaces)
// but removes or replaces characters illegal in filenames.
//
// If the resulting path would collide with an existing entry, callers should
// append a numeric suffix like " (2)".
func SafeDisplayNameToPathSegment(title string) string {
	title = strings.TrimSpace(title)
	if title == "" {
		return "Без названия"
	}

	var result strings.Builder
	for _, r := range title {
		switch {
		case r == '/' || r == '\\':
			result.WriteRune('_')
		case r == ':' || r == '*' || r == '?' || r == '"' || r == '<' || r == '>' || r == '|':
			result.WriteRune(' ')
		case unicode.IsControl(r):
		case r == '.' && result.Len() == 0:
			result.WriteRune('_')
		default:
			result.WriteRune(r)
		}
	}

	seg := strings.TrimSpace(result.String())
	if seg == "" {
		seg = "Без названия"
	}
	if len(seg) > 200 {
		seg = seg[:200]
	}
	return seg
}

// UniquePath returns a unique path by appending a numeric suffix if needed.
func UniquePath(basePath string) string {
	if _, err := os.Stat(basePath); os.IsNotExist(err) {
		return basePath
	}
	ext := filepath.Ext(basePath)
	stem := strings.TrimSuffix(basePath, ext)
	for i := 2; i < 1000; i++ {
		candidate := fmt.Sprintf("%s (%d)%s", stem, i, ext)
		if _, err := os.Stat(candidate); os.IsNotExist(err) {
			return candidate
		}
	}
	return fmt.Sprintf("%s_%d%s", stem, 1000, ext)
}