[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

4 files changed, 176 insertions, 0 deletions

diff --git a/internal/processing/account/account.go b/internal/processing/account/account.go
index aca46394a..b18e705ca 100644
--- a/internal/processing/account/account.go
+++ b/internal/processing/account/account.go
@@ -21,6 +21,7 @@ package account
 import (
 	"context"
 	"mime/multipart"
+	"time"
 
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
 	"github.com/superseriousbusiness/gotosocial/internal/concurrency"
@@ -53,6 +54,8 @@ type Processor interface {
 	GetLocalByUsername(ctx context.Context, requestingAccount *gtsmodel.Account, username string) (*apimodel.Account, gtserror.WithCode)
 	// GetCustomCSSForUsername returns custom css for the given local username.
 	GetCustomCSSForUsername(ctx context.Context, username string) (string, gtserror.WithCode)
+	// GetRSSFeedForUsername returns RSS feed for the given local username.
+	GetRSSFeedForUsername(ctx context.Context, username string) (func() (string, gtserror.WithCode), time.Time, gtserror.WithCode)
 	// Update processes the update of an account with the given form
 	Update(ctx context.Context, account *gtsmodel.Account, form *apimodel.UpdateCredentialsRequest) (*apimodel.Account, gtserror.WithCode)
 	// StatusesGet fetches a number of statuses (in time descending order) from the given account, filtered by visibility for
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
+}
diff --git a/internal/processing/account/getrss_test.go b/internal/processing/account/getrss_test.go
new file mode 100644
index 000000000..dc81434a0
--- /dev/null
+++ b/internal/processing/account/getrss_test.go
@@ -0,0 +1,61 @@
+/*
+   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_test
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type GetRSSTestSuite struct {
+	AccountStandardTestSuite
+}
+
+func (suite *GetRSSTestSuite) TestGetAccountRSSAdmin() {
+	getFeed, lastModified, err := suite.accountProcessor.GetRSSFeedForUsername(context.Background(), "admin")
+	suite.NoError(err)
+	suite.EqualValues(1634733405, lastModified.Unix())
+
+	feed, err := getFeed()
+	suite.NoError(err)
+
+	fmt.Println(feed)
+
+	suite.Equal("<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss version=\"2.0\" xmlns:content=\"http://purl.org/rss/1.0/modules/content/\">\n  <channel>\n    <title>Posts from @admin@localhost:8080</title>\n    <link>http://localhost:8080/@admin</link>\n    <description>Posts from @admin@localhost:8080</description>\n    <pubDate>Wed, 20 Oct 2021 12:36:45 +0000</pubDate>\n    <lastBuildDate>Wed, 20 Oct 2021 12:36:45 +0000</lastBuildDate>\n    <item>\n      <title>open to see some puppies</title>\n      <link>http://localhost:8080/@admin/statuses/01F8MHAAY43M6RJ473VQFCVH37</link>\n      <description>@admin@localhost:8080 made a new post: &#34;🐕🐕🐕🐕🐕&#34;</description>\n      <content:encoded><![CDATA[🐕🐕🐕🐕🐕]]></content:encoded>\n      <author>@admin@localhost:8080</author>\n      <guid>http://localhost:8080/@admin/statuses/01F8MHAAY43M6RJ473VQFCVH37</guid>\n      <pubDate>Wed, 20 Oct 2021 12:36:45 +0000</pubDate>\n      <source>http://localhost:8080/@admin/feed.rss</source>\n    </item>\n    <item>\n      <title>hello world! #welcome ! first post on the instance :rainbow: !</title>\n      <link>http://localhost:8080/@admin/statuses/01F8MH75CBF9JFX4ZAD54N0W0R</link>\n      <description>@admin@localhost:8080 posted 1 attachment: &#34;hello world! #welcome ! first post on the instance :rainbow: !&#34;</description>\n      <content:encoded><![CDATA[hello world! #welcome ! first post on the instance <img src=\"http://localhost:8080/fileserver/01F8MH17FWEB39HZJ76B6VXSKF/emoji/original/01F8MH9H8E4VG3KDYJR9EGPXCQ.png\" title=\":rainbow:\" alt=\":rainbow:\" class=\"emoji\"/> !]]></content:encoded>\n      <author>@admin@localhost:8080</author>\n      <enclosure url=\"http://localhost:8080/fileserver/01F8MH17FWEB39HZJ76B6VXSKF/attachment/original/01F8MH6NEM8D7527KZAECTCR76.jpeg\" length=\"62529\" type=\"image/jpeg\"></enclosure>\n      <guid>http://localhost:8080/@admin/statuses/01F8MH75CBF9JFX4ZAD54N0W0R</guid>\n      <pubDate>Wed, 20 Oct 2021 11:36:45 +0000</pubDate>\n      <source>http://localhost:8080/@admin/feed.rss</source>\n    </item>\n  </channel>\n</rss>", feed)
+}
+
+func (suite *GetRSSTestSuite) TestGetAccountRSSZork() {
+	getFeed, lastModified, err := suite.accountProcessor.GetRSSFeedForUsername(context.Background(), "the_mighty_zork")
+	suite.NoError(err)
+	suite.EqualValues(1634726437, lastModified.Unix())
+
+	feed, err := getFeed()
+	suite.NoError(err)
+
+	fmt.Println(feed)
+
+	suite.Equal("<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss version=\"2.0\" xmlns:content=\"http://purl.org/rss/1.0/modules/content/\">\n  <channel>\n    <title>Posts from @the_mighty_zork@localhost:8080</title>\n    <link>http://localhost:8080/@the_mighty_zork</link>\n    <description>Posts from @the_mighty_zork@localhost:8080</description>\n    <pubDate>Wed, 20 Oct 2021 10:40:37 +0000</pubDate>\n    <lastBuildDate>Wed, 20 Oct 2021 10:40:37 +0000</lastBuildDate>\n    <image>\n      <url>http://localhost:8080/fileserver/01F8MH1H7YV1Z7D2C8K2730QBF/avatar/small/01F8MH58A357CV5K7R7TJMSH6S.jpeg</url>\n      <title>Avatar for @the_mighty_zork@localhost:8080</title>\n      <link>http://localhost:8080/@the_mighty_zork</link>\n    </image>\n    <item>\n      <title>introduction post</title>\n      <link>http://localhost:8080/@the_mighty_zork/statuses/01F8MHAMCHF6Y650WCRSCP4WMY</link>\n      <description>@the_mighty_zork@localhost:8080 made a new post: &#34;hello everyone!&#34;</description>\n      <content:encoded><![CDATA[hello everyone!]]></content:encoded>\n      <author>@the_mighty_zork@localhost:8080</author>\n      <guid>http://localhost:8080/@the_mighty_zork/statuses/01F8MHAMCHF6Y650WCRSCP4WMY</guid>\n      <pubDate>Wed, 20 Oct 2021 10:40:37 +0000</pubDate>\n      <source>http://localhost:8080/@the_mighty_zork/feed.rss</source>\n    </item>\n  </channel>\n</rss>", feed)
+}
+
+func TestGetRSSTestSuite(t *testing.T) {
+	suite.Run(t, new(GetRSSTestSuite))
+}
diff --git a/internal/processing/account/update.go b/internal/processing/account/update.go
index 94e91ca4c..f39361c06 100644
--- a/internal/processing/account/update.go
+++ b/internal/processing/account/update.go
@@ -160,6 +160,10 @@ func (p *processor) Update(ctx context.Context, account *gtsmodel.Account, form
 		account.CustomCSS = text.SanitizePlaintext(customCSS)
 	}
 
+	if form.EnableRSS != nil {
+		account.EnableRSS = form.EnableRSS
+	}
+
 	updatedAccount, err := p.db.UpdateAccount(ctx, account)
 	if err != nil {
 		return nil, gtserror.NewErrorInternalError(fmt.Errorf("could not update account %s: %s", account.ID, err))