1 files changed, 69 insertions, 0 deletions
diff --git a/internal/federation/finger.go b/internal/federation/finger.go
new file mode 100644
index 000000000..9afe83edf
--- /dev/null
+++ b/internal/federation/finger.go
@@ -0,0 +1,69 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 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 federation
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+)
+
+func (f *federator) FingerRemoteAccount(requestingUsername string, targetUsername string, targetDomain string) (*url.URL, error) {
+
+	t, err := f.GetTransportForUser(requestingUsername)
+	if err != nil {
+		return nil, fmt.Errorf("FingerRemoteAccount: error getting transport for username %s while dereferencing @%s@%s: %s", requestingUsername, targetUsername, targetDomain, err)
+	}
+
+	b, err := t.Finger(context.Background(), targetUsername, targetDomain)
+	if err != nil {
+		return nil, fmt.Errorf("FingerRemoteAccount: error doing request on behalf of username %s while dereferencing @%s@%s: %s", requestingUsername, targetUsername, targetDomain, err)
+	}
+
+	resp := &apimodel.WebfingerAccountResponse{}
+	if err := json.Unmarshal(b, resp); err != nil {
+		return nil, fmt.Errorf("FingerRemoteAccount: could not unmarshal server response as WebfingerAccountResponse on behalf of username %s while dereferencing @%s@%s: %s", requestingUsername, targetUsername, targetDomain, err)
+	}
+
+	if len(resp.Links) == 0 {
+		return nil, fmt.Errorf("FingerRemoteAccount: no links found in webfinger response %s", string(b))
+	}
+
+	// look through the links for the first one that matches "application/activity+json", this is what we need
+	for _, l := range resp.Links {
+		if strings.EqualFold(l.Type, "application/activity+json") {
+			if l.Href == "" || l.Rel != "self" {
+				continue
+			}
+			accountURI, err := url.Parse(l.Href)
+			if err != nil {
+				return nil, fmt.Errorf("FingerRemoteAccount: couldn't parse url %s: %s", l.Href, err)
+			}
+			// found it!
+			return accountURI, nil
+		}
+	}
+
+	return nil, errors.New("FingerRemoteAccount: no match found in webfinger response")
+}