0904

internal/dbutil/pagination.go

@@ -0,0 +1,46 @@
+// Copyright 2022 E99p1ant. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package dbutil
+
+var (
+	DefaultPageSize    = 20
+	MaxDefaultPageSize = 100
+)
+
+type Pagination struct {
+	Page     int
+	PageSize int
+}
+
+// LimitOffset returns LIMIT and OFFSET parameter for SQL.
+// The first page is page 0.
+func (p Pagination) LimitOffset() (limit, offset int) {
+	page := p.Page
+	pageSize := p.PageSize
+
+	if page <= 0 {
+		page = 1
+	}
+	if pageSize < 1 {
+		pageSize = DefaultPageSize
+	}
+	return pageSize, (page - 1) * pageSize
+}
+
+type Cursor struct {
+	Value    interface{}
+	PageSize int
+}
+
+func (p Cursor) Limit() int {
+	pageSize := p.PageSize
+	if pageSize < 1 {
+		pageSize = DefaultPageSize
+	}
+	if pageSize > MaxDefaultPageSize {
+		pageSize = MaxDefaultPageSize
+	}
+	return pageSize
+}