Add RSS/Atom feed support for user actions (#16002)

Return rss/atom feed for user based on rss url suffix or Content-Type header.

vendor/github.com/gorilla/feeds/feed.go

@@ -0,0 +1,145 @@
+package feeds
+
+import (
+	"encoding/json"
+	"encoding/xml"
+	"io"
+	"sort"
+	"time"
+)
+
+type Link struct {
+	Href, Rel, Type, Length string
+}
+
+type Author struct {
+	Name, Email string
+}
+
+type Image struct {
+	Url, Title, Link string
+	Width, Height    int
+}
+
+type Enclosure struct {
+	Url, Length, Type string
+}
+
+type Item struct {
+	Title       string
+	Link        *Link
+	Source      *Link
+	Author      *Author
+	Description string // used as description in rss, summary in atom
+	Id          string // used as guid in rss, id in atom
+	Updated     time.Time
+	Created     time.Time
+	Enclosure   *Enclosure
+	Content     string
+}
+
+type Feed struct {
+	Title       string
+	Link        *Link
+	Description string
+	Author      *Author
+	Updated     time.Time
+	Created     time.Time
+	Id          string
+	Subtitle    string
+	Items       []*Item
+	Copyright   string
+	Image       *Image
+}
+
+// add a new Item to a Feed
+func (f *Feed) Add(item *Item) {
+	f.Items = append(f.Items, item)
+}
+
+// returns the first non-zero time formatted as a string or ""
+func anyTimeFormat(format string, times ...time.Time) string {
+	for _, t := range times {
+		if !t.IsZero() {
+			return t.Format(format)
+		}
+	}
+	return ""
+}
+
+// interface used by ToXML to get a object suitable for exporting XML.
+type XmlFeed interface {
+	FeedXml() interface{}
+}
+
+// turn a feed object (either a Feed, AtomFeed, or RssFeed) into xml
+// returns an error if xml marshaling fails
+func ToXML(feed XmlFeed) (string, error) {
+	x := feed.FeedXml()
+	data, err := xml.MarshalIndent(x, "", "  ")
+	if err != nil {
+		return "", err
+	}
+	// strip empty line from default xml header
+	s := xml.Header[:len(xml.Header)-1] + string(data)
+	return s, nil
+}
+
+// WriteXML writes a feed object (either a Feed, AtomFeed, or RssFeed) as XML into
+// the writer. Returns an error if XML marshaling fails.
+func WriteXML(feed XmlFeed, w io.Writer) error {
+	x := feed.FeedXml()
+	// write default xml header, without the newline
+	if _, err := w.Write([]byte(xml.Header[:len(xml.Header)-1])); err != nil {
+		return err
+	}
+	e := xml.NewEncoder(w)
+	e.Indent("", "  ")
+	return e.Encode(x)
+}
+
+// creates an Atom representation of this feed
+func (f *Feed) ToAtom() (string, error) {
+	a := &Atom{f}
+	return ToXML(a)
+}
+
+// WriteAtom writes an Atom representation of this feed to the writer.
+func (f *Feed) WriteAtom(w io.Writer) error {
+	return WriteXML(&Atom{f}, w)
+}
+
+// creates an Rss representation of this feed
+func (f *Feed) ToRss() (string, error) {
+	r := &Rss{f}
+	return ToXML(r)
+}
+
+// WriteRss writes an RSS representation of this feed to the writer.
+func (f *Feed) WriteRss(w io.Writer) error {
+	return WriteXML(&Rss{f}, w)
+}
+
+// ToJSON creates a JSON Feed representation of this feed
+func (f *Feed) ToJSON() (string, error) {
+	j := &JSON{f}
+	return j.ToJSON()
+}
+
+// WriteJSON writes an JSON representation of this feed to the writer.
+func (f *Feed) WriteJSON(w io.Writer) error {
+	j := &JSON{f}
+	feed := j.JSONFeed()
+
+	e := json.NewEncoder(w)
+	e.SetIndent("", "  ")
+	return e.Encode(feed)
+}
+
+// Sort sorts the Items in the feed with the given less function.
+func (f *Feed) Sort(less func(a, b *Item) bool) {
+	lessFunc := func(i, j int) bool {
+		return less(f.Items[i], f.Items[j])
+	}
+	sort.SliceStable(f.Items, lessFunc)
+}