Dereference remote replies (#132)

* decided where to put reply dereferencing

* fiddling with dereferencing threads

* further adventures

* tidy up some stuff

* move dereferencing functionality

* a bunch of refactoring

* go fmt

* more refactoring

* bleep bloop

* docs and linting

* start implementing replies collection on gts side

* fiddling around

* allow dereferencing our replies

* lint, fmt

internal/federation/dereferencing/handshake.go

@@ -0,0 +1,98 @@
+/*
+   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 dereferencing
+
+import "net/url"
+
+func (d *deref) Handshaking(username string, remoteAccountID *url.URL) bool {
+	d.handshakeSync.Lock()
+	defer d.handshakeSync.Unlock()
+
+	if d.handshakes == nil {
+		// handshakes isn't even initialized yet so we can't be handshaking with anyone
+		return false
+	}
+
+	remoteIDs, ok := d.handshakes[username]
+	if !ok {
+		// user isn't handshaking with anyone, bail
+		return false
+	}
+
+	for _, id := range remoteIDs {
+		if id.String() == remoteAccountID.String() {
+			// we are currently handshaking with the remote account, yep
+			return true
+		}
+	}
+
+	// didn't find it which means we're not handshaking
+	return false
+}
+
+func (d *deref) startHandshake(username string, remoteAccountID *url.URL) {
+	d.handshakeSync.Lock()
+	defer d.handshakeSync.Unlock()
+
+	// lazily initialize handshakes
+	if d.handshakes == nil {
+		d.handshakes = make(map[string][]*url.URL)
+	}
+
+	remoteIDs, ok := d.handshakes[username]
+	if !ok {
+		// there was nothing in there yet, so just add this entry and return
+		d.handshakes[username] = []*url.URL{remoteAccountID}
+		return
+	}
+
+	// add the remote ID to the slice
+	remoteIDs = append(remoteIDs, remoteAccountID)
+	d.handshakes[username] = remoteIDs
+}
+
+func (d *deref) stopHandshake(username string, remoteAccountID *url.URL) {
+	d.handshakeSync.Lock()
+	defer d.handshakeSync.Unlock()
+
+	if d.handshakes == nil {
+		return
+	}
+
+	remoteIDs, ok := d.handshakes[username]
+	if !ok {
+		// there was nothing in there yet anyway so just bail
+		return
+	}
+
+	newRemoteIDs := []*url.URL{}
+	for _, id := range remoteIDs {
+		if id.String() != remoteAccountID.String() {
+			newRemoteIDs = append(newRemoteIDs, id)
+		}
+	}
+
+	if len(newRemoteIDs) == 0 {
+		// there are no handshakes so just remove this user entry from the map and save a few bytes
+		delete(d.handshakes, username)
+	} else {
+		// there are still other handshakes ongoing
+		d.handshakes[username] = newRemoteIDs
+	}
+}