Add preview card support

internal/processing/status/preview_card.go

@@ -0,0 +1,111 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// 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 status
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"regexp"
+
+	"github.com/PuerkitoBio/goquery"
+
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+)
+
+var urlRegex = regexp.MustCompile(`https?://[a-zA-Z0-9./?=_-]+`)
+
+func extractLastURL(text string) string {
+	matches := urlRegex.FindAllString(text, -1)
+	if len(matches) == 0 {
+		return ""
+	}
+	return matches[len(matches)-1]
+}
+
+// FetchPreview retrieves OpenGraph metadata from a URL.
+func FetchPreview(text string) (*gtsmodel.Card, gtserror.WithCode) {
+	link := extractLastURL(text)
+	if link == "" {
+		return nil, nil
+	}
+
+	parsed, err := url.ParseRequestURI(link)
+	if err != nil {
+		return nil, gtserror.NewErrorInternalError(err, "invalid URL")
+	}
+
+	if parsed.Scheme != "http" && parsed.Scheme != "https" {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("unsupported scheme: %s", parsed.Scheme))
+	}
+
+	resp, err := http.Get(link)
+	if err != nil {
+		return nil, gtserror.NewErrorInternalError(err, "request failed")
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("unexpected status: %s", resp.Status))
+	}
+
+	doc, err := goquery.NewDocumentFromReader(resp.Body)
+	if err != nil {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("failed to parse HTML: %w", err))
+	}
+
+	card := &gtsmodel.Card{
+		URL: link,
+	}
+
+	doc.Find("meta").Each(func(i int, s *goquery.Selection) {
+		property, _ := s.Attr("property")
+		content, _ := s.Attr("content")
+
+		switch property {
+		case "og:title":
+			card.Title = content
+		case "og:description":
+			card.Description = content
+		case "og:type":
+			card.Type = content
+		case "og:image":
+			card.Image = content
+		case "og:url":
+			if content != "" {
+				card.URL = content
+			}
+		case "og:site_name":
+			card.ProviderName = content
+		}
+	})
+
+	if card.Title == "" {
+		card.Title = doc.Find("title").Text()
+	}
+
+	if card.Description == "" {
+		desc, exists := doc.Find("meta[name='description']").Attr("content")
+		if exists {
+			card.Description = desc
+		}
+	}
+
+	return card, nil
+}