From fce46f5124688806bde6a3181773310c2a092385 Mon Sep 17 00:00:00 2001
From: Michael <heluecht@pirati.ca>
Date: Wed, 30 Jan 2019 16:30:01 +0000
Subject: [PATCH] AP: Follow a note to receive all upcoming activities

---
 src/Protocol/ActivityPub/Receiver.php    |  6 +++-
 src/Protocol/ActivityPub/Transmitter.php | 36 ++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/Protocol/ActivityPub/Receiver.php b/src/Protocol/ActivityPub/Receiver.php
index 0ab2619412..e0ee1f0f90 100644
--- a/src/Protocol/ActivityPub/Receiver.php
+++ b/src/Protocol/ActivityPub/Receiver.php
@@ -208,7 +208,8 @@ class Receiver
 			}
 			// We had been able to retrieve the object data - so we can trust the source
 			$trust_source = true;
-		} elseif (in_array($type, ['as:Like', 'as:Dislike'])) {
+		} elseif (in_array($type, ['as:Like', 'as:Dislike']) ||
+			(($type == 'as:Follow') && in_array($object_type, self::CONTENT_TYPES))) {
 			// Create a mostly empty array out of the activity data (instead of the object).
 			// This way we later don't have to check for the existence of ech individual array element.
 			$object_data = self::processObject($activity);
@@ -394,6 +395,9 @@ class Receiver
 			case 'as:Follow':
 				if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 					ActivityPub\Processor::followUser($object_data);
+				} elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+					$object_data['reply-to-id'] = $object_data['object_id'];
+					ActivityPub\Processor::createActivity($object_data, ACTIVITY_FOLLOW);
 				}
 				break;
 
diff --git a/src/Protocol/ActivityPub/Transmitter.php b/src/Protocol/ActivityPub/Transmitter.php
index 7481db9e74..fa8bdc0439 100644
--- a/src/Protocol/ActivityPub/Transmitter.php
+++ b/src/Protocol/ActivityPub/Transmitter.php
@@ -601,6 +601,8 @@ class Transmitter
 			$type = 'Reject';
 		} elseif ($item['verb'] == ACTIVITY_ATTENDMAYBE) {
 			$type = 'TentativeAccept';
+		} elseif ($item['verb'] == ACTIVITY_FOLLOW) {
+			$type = 'Follow';
 		} else {
 			$type = '';
 		}
@@ -701,6 +703,8 @@ class Transmitter
 			$data['object'] = self::createNote($item);
 		} elseif ($data['type'] == 'Announce') {
 			$data = self::createAnnounce($item, $data);
+		} elseif ($data['type'] == 'Follow') {
+			$data['object'] = $item['parent-uri'];
 		} elseif ($data['type'] == 'Undo') {
 			$data['object'] = self::createActivityFromItem($item_id, true);
 		} else {
@@ -1275,6 +1279,38 @@ class Transmitter
 		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
+	/**
+	 * Transmits a "follow object" activity to a target
+	 * This is a preparation for sending automated "follow" requests when receiving "Announce" messages
+	 *
+	 * @param string  $object Object URL
+	 * @param string  $target Target profile
+	 * @param integer $uid    User ID
+	 * @return bool
+	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+	 * @throws \ImagickException
+	 * @throws \Exception
+	 */
+	public static function sendFollowObject($object, $target, $uid)
+	{
+		$profile = APContact::getByURL($target);
+
+		$owner = User::getOwnerDataById($uid);
+
+		$data = ['@context' => ActivityPub::CONTEXT,
+			'id' => System::baseUrl() . '/activity/' . System::createGUID(),
+			'type' => 'Follow',
+			'actor' => $owner['url'],
+			'object' => $object,
+			'instrument' => ['type' => 'Service', 'name' => BaseObject::getApp()->getUserAgent()],
+			'to' => [$profile['url']]];
+
+		Logger::log('Sending follow ' . $object . ' to ' . $target . ' for user ' . $uid, Logger::DEBUG);
+
+		$signed = LDSignature::sign($data, $owner);
+		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
+	}
+
 	/**
 	 * Transmit a message that the contact request had been accepted
 	 *
-- 
2.39.5