优化结构

internal/platform/database/pagination/pagination.go

@@ -0,0 +1,37 @@
+// Package pagination contains GORM pagination helpers shared by repository
+// implementations in the data layer.
+package pagination
+
+import "gorm.io/gorm"
+
+// LimitOffset normalizes a page request and applies the optional maximum page
+// size. A non-positive size means that no limit should be applied.
+func LimitOffset(page, size, maxSize int) (limit, offset int) {
+	limit = size
+	if maxSize > 0 && size > maxSize {
+		limit = maxSize
+	}
+	if limit <= 0 {
+		return 0, 0
+	}
+	if page <= 0 {
+		page = 1
+	}
+	return limit, (page - 1) * limit
+}
+
+// Apply applies pagination only when the caller supplied a positive size.
+func Apply(db *gorm.DB, page, size, maxSize int) *gorm.DB {
+	limit, offset := LimitOffset(page, size, maxSize)
+	if limit == 0 {
+		return db
+	}
+	return db.Offset(offset).Limit(limit)
+}
+
+// ApplyRequired always applies LIMIT/OFFSET, including LIMIT 0. This keeps
+// the existing repository contract for APIs whose page size is mandatory.
+func ApplyRequired(db *gorm.DB, page, size, maxSize int) *gorm.DB {
+	limit, offset := LimitOffset(page, size, maxSize)
+	return db.Offset(offset).Limit(limit)
+}