feat: SEO backend data (1/4)

internal/infrastructure/useCases/articleSlug.go

@@ -0,0 +1,39 @@
+package useCases
+
+import (
+	"RenewCMS/internal/domain/article"
+	"errors"
+)
+
+const (
+	firstSlugAttempt      = 1
+	firstSuggestedAttempt = 2
+	maxCreateSlugAttempts = 5
+	maxFreeSlugAttempts   = 100
+)
+
+func freeSlug(articles article.Repository, siteID uint32, base string, exceptID uint32, firstAttempt int) (string, error) {
+	for attempt := firstAttempt; attempt <= maxFreeSlugAttempts; attempt++ {
+		candidate := article.SlugWithSuffix(base, attempt)
+		taken, err := articles.SlugTaken(siteID, candidate, exceptID)
+		if err != nil {
+			return "", err
+		}
+		if !taken {
+			return candidate, nil
+		}
+	}
+	return "", article.ErrSlugTaken
+}
+
+func slugConflict(articles article.Repository, siteID uint32, slug string, exceptID uint32) error {
+	suggestion, err := freeSlug(articles, siteID, slug, exceptID, firstSuggestedAttempt)
+	if err != nil {
+		return err
+	}
+	return &article.SlugTakenError{Suggestion: suggestion}
+}
+
+func isSlugTakenError(err error) bool {
+	return errors.Is(err, article.ErrSlugTaken)
+}