[feature] Add opt-in RSS feed for account's latest Public posts (#897)

* start adding rss functionality

* add gorilla/feeds dependency

* first bash at building rss feed
still needs work, this is an interim commit

* tidy up a bit

* add publicOnly option to GetAccountLastPosted

* implement rss endpoint

* fix test

* add initial user docs for rss

* update rss logo

* docs update

* add rssFeed to frontend

* feed -> feed.rss

* enableRSS

* increase rss logo size a lil bit

* add rss toggle

* move emojify to text package

* fiddle with rss feed formatting

* add Text field to test statuses

* move status to rss item to typeconverter

* update bun schema for enablerss

* simplify 304 checking

* assume account not rss

* update tests

* update swagger docs

* allow more characters in title, trim nicer

* update last posted to be more consistent

1 files changed, 108 insertions, 0 deletions

diff --git a/internal/processing/account/getrss.go b/internal/processing/account/getrss.go
new file mode 100644
index 000000000..f07204b56
--- /dev/null
+++ b/internal/processing/account/getrss.go
@@ -0,0 +1,108 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package account
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/gorilla/feeds"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+const rssFeedLength = 20
+
+func (p *processor) GetRSSFeedForUsername(ctx context.Context, username string) (func() (string, gtserror.WithCode), time.Time, gtserror.WithCode) {
+	account, err := p.db.GetAccountByUsernameDomain(ctx, username, "")
+	if err != nil {
+		if err == db.ErrNoEntries {
+			return nil, time.Time{}, gtserror.NewErrorNotFound(errors.New("GetRSSFeedForUsername: account not found"))
+		}
+		return nil, time.Time{}, gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: db error: %s", err))
+	}
+
+	if !*account.EnableRSS {
+		return nil, time.Time{}, gtserror.NewErrorNotFound(errors.New("GetRSSFeedForUsername: account RSS feed not enabled"))
+	}
+
+	lastModified, err := p.db.GetAccountLastPosted(ctx, account.ID, true)
+	if err != nil {
+		return nil, time.Time{}, gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: db error: %s", err))
+	}
+
+	return func() (string, gtserror.WithCode) {
+		statuses, err := p.db.GetAccountWebStatuses(ctx, account.ID, rssFeedLength, "")
+		if err != nil && err != db.ErrNoEntries {
+			return "", gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: db error: %s", err))
+		}
+
+		author := "@" + account.Username + "@" + config.GetAccountDomain()
+		title := "Posts from " + author
+		description := "Posts from " + author
+		link := &feeds.Link{Href: account.URL}
+
+		var image *feeds.Image
+		if account.AvatarMediaAttachmentID != "" {
+			if account.AvatarMediaAttachment == nil {
+				avatar, err := p.db.GetAttachmentByID(ctx, account.AvatarMediaAttachmentID)
+				if err != nil {
+					return "", gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: db error fetching avatar attachment: %s", err))
+				}
+				account.AvatarMediaAttachment = avatar
+			}
+			image = &feeds.Image{
+				Url:   account.AvatarMediaAttachment.Thumbnail.URL,
+				Title: "Avatar for " + author,
+				Link:  account.URL,
+			}
+		}
+
+		feed := &feeds.Feed{
+			Title:       title,
+			Description: description,
+			Link:        link,
+			Image:       image,
+		}
+
+		for i, s := range statuses {
+			// take the date of the first (ie., latest) status as feed updated value
+			if i == 0 {
+				feed.Updated = s.UpdatedAt
+			}
+
+			item, err := p.tc.StatusToRSSItem(ctx, s)
+			if err != nil {
+				return "", gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: error converting status to feed item: %s", err))
+			}
+
+			feed.Add(item)
+		}
+
+		rss, err := feed.ToRss()
+		if err != nil {
+			return "", gtserror.NewErrorInternalError(fmt.Errorf("GetRSSFeedForUsername: error converting feed to rss string: %s", err))
+		}
+
+		return rss, nil
+	}, lastModified, nil
+}