Add sitemap support (#18407)

modules/sitemap/sitemap.go

@@ -0,0 +1,69 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package sitemap
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"time"
+)
+
+// sitemapFileLimit contains the maximum size of a sitemap file
+const sitemapFileLimit = 50 * 1024 * 1024
+
+// Url represents a single sitemap entry
+type URL struct {
+	URL     string     `xml:"loc"`
+	LastMod *time.Time `xml:"lastmod,omitempty"`
+}
+
+// SitemapUrl represents a sitemap
+type Sitemap struct {
+	XMLName   xml.Name
+	Namespace string `xml:"xmlns,attr"`
+
+	URLs []URL `xml:"url"`
+}
+
+// NewSitemap creates a sitemap
+func NewSitemap() *Sitemap {
+	return &Sitemap{
+		XMLName:   xml.Name{Local: "urlset"},
+		Namespace: "http://www.sitemaps.org/schemas/sitemap/0.9",
+	}
+}
+
+// NewSitemap creates a sitemap index.
+func NewSitemapIndex() *Sitemap {
+	return &Sitemap{
+		XMLName:   xml.Name{Local: "sitemapindex"},
+		Namespace: "http://www.sitemaps.org/schemas/sitemap/0.9",
+	}
+}
+
+// Add adds a URL to the sitemap
+func (s *Sitemap) Add(u URL) {
+	s.URLs = append(s.URLs, u)
+}
+
+// Write writes the sitemap to a response
+func (s *Sitemap) WriteTo(w io.Writer) (int64, error) {
+	if len(s.URLs) > 50000 {
+		return 0, fmt.Errorf("The sitemap contains too many URLs: %d", len(s.URLs))
+	}
+	buf := bytes.NewBufferString(xml.Header)
+	if err := xml.NewEncoder(buf).Encode(s); err != nil {
+		return 0, err
+	}
+	if err := buf.WriteByte('\n'); err != nil {
+		return 0, err
+	}
+	if buf.Len() > sitemapFileLimit {
+		return 0, fmt.Errorf("The sitemap is too big: %d", buf.Len())
+	}
+	return buf.WriteTo(w)
+}