feat: SEO backend data (1/4)

internal/infrastructure/persistence/database/articleSlugBackfill.go

@@ -0,0 +1,87 @@
+package database
+
+import (
+	"RenewCMS/internal/domain/article"
+	entity "RenewCMS/internal/infrastructure/persistence/models"
+
+	"gorm.io/gorm"
+)
+
+const (
+	articleSlugIndexName      = "idx_articles_site_slug"
+	articleSlugIndexStatement = "CREATE UNIQUE INDEX " + articleSlugIndexName + " ON articles (site_id, slug)"
+)
+
+type slugOwner struct {
+	siteID uint32
+	slug   string
+}
+
+type slugAssignment struct {
+	id   uint32
+	slug string
+}
+
+func BackfillArticleSlugs(db *gorm.DB) error {
+	return db.Transaction(func(tx *gorm.DB) error {
+		var rows []entity.Article
+		if err := tx.Unscoped().Select("id", "site_id", "title", "slug", "deleted_at").Order("id ASC").Find(&rows).Error; err != nil {
+			return err
+		}
+		assignments := planSlugAssignments(rows)
+		for _, assignment := range assignments {
+			if err := tx.Unscoped().Model(&entity.Article{}).Where("id = ?", assignment.id).UpdateColumn("slug", assignment.slug).Error; err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}
+
+func planSlugAssignments(rows []entity.Article) []slugAssignment {
+	assignments := []slugAssignment{}
+	claimed := map[slugOwner]bool{}
+	pending := []entity.Article{}
+	for _, row := range rows {
+		if row.DeletedAt.Valid {
+			if tombstone := article.Tombstone(row.ID); row.Slug != tombstone {
+				assignments = append(assignments, slugAssignment{row.ID, tombstone})
+			}
+			continue
+		}
+		owner := slugOwner{row.SiteID, row.Slug}
+		if row.Slug == "" || claimed[owner] {
+			pending = append(pending, row)
+			continue
+		}
+		claimed[owner] = true
+	}
+	for _, row := range pending {
+		base := row.Slug
+		attempt := 2
+		if base == "" {
+			base = snapshotSlug(row.Title)
+			attempt = 1
+		}
+		slug := firstFreeSnapshotSlug(claimed, row.SiteID, base, attempt)
+		claimed[slugOwner{row.SiteID, slug}] = true
+		assignments = append(assignments, slugAssignment{row.ID, slug})
+	}
+	return assignments
+}
+
+func firstFreeSnapshotSlug(claimed map[slugOwner]bool, siteID uint32, base string, attempt int) string {
+	for ; ; attempt++ {
+		candidate := snapshotSlugWithSuffix(base, attempt)
+		if !claimed[slugOwner{siteID, candidate}] {
+			return candidate
+		}
+	}
+}
+
+func ensureArticleSlugIndex(db *gorm.DB) error {
+	if db.Migrator().HasIndex(&entity.Article{}, articleSlugIndexName) {
+		return nil
+	}
+	return db.Exec(articleSlugIndexStatement).Error
+}