implement follow relationships (untested)

does NOT implement the actual behaviour behind follows (receiving posts and such)

10 files changed, 229 insertions, 17 deletions

diff --git a/Digitigrade/Model.php b/Digitigrade/Model.php
index 80a6d91..0db27ef 100644
--- a/Digitigrade/Model.php
+++ b/Digitigrade/Model.php
@@ -10,8 +10,8 @@ abstract class Model {
     }
 
     /**
-     * @return ?string a condition for a WHERE clause if this object already
-     *                 exists in the database, or null otherwise
+     * @return ?string a condition for a WHERE clause that uniquely identifies
+     * this object if it already exists in the database, or null if not
      */
     protected function getUpdateWhereClause(\PDO $db): ?string {
         if (isset($this->id) && static::find($this->{'id'}) != null) {
@@ -241,4 +241,21 @@ abstract class Model {
 
         $this->saved = true;
     }
+
+    /**
+     * Removes this record from the database.
+     * @return void
+     */
+    public function remove() {
+        $db = Db::getInstance()->getPdo();
+        $where = $this->getUpdateWhereClause($db);
+        if ($where == null) {
+            throw new \RuntimeException("object doesn't seem to exist in the database so i can't delete it");
+        }
+        $classNameParts = explode('\\', static::class);
+        $className = $classNameParts[count($classNameParts) - 1];
+        $tableName = self::mangleName($className);
+
+        $db->exec("DELETE FROM $tableName WHERE $where");
+    }
 }
\ No newline at end of file
diff --git a/Digitigrade/Model/Actor.php b/Digitigrade/Model/Actor.php
index 4f3aab2..fa08463 100644
--- a/Digitigrade/Model/Actor.php
+++ b/Digitigrade/Model/Actor.php
@@ -1,7 +1,10 @@
 <?php
 namespace Digitigrade\Model;
 
-class Actor extends PushableModel {
+use Digitigrade\RpcException;
+use Digitigrade\RpcReceiver;
+
+class Actor extends PushableModel implements RpcReceiver {
     public ?int $id;
     public string $uri;
     public bool $isLocal = false;
@@ -83,6 +86,64 @@ class Actor extends PushableModel {
         return ActorWebfinger::findByAcct($acct, $autoSave, $forceRefetch)->actor;
     }
 
+    public static function findByRequestHeaders(): ?self {
+        $instance = Instance::findByRequestHeaders();
+        if ($instance == null || !isset($_SERVER['HTTP_X_PAWPUB_ACTOR']))
+            return null;
+        $uri = $_SERVER['HTTP_X_PAWPUB_ACTOR'];
+        if (hostname_from_uri($uri) != $instance->domain)
+            return null;
+        return self::findByUri($uri);
+    }
+
+    protected function rpcCall(string $method, array $args) {
+        switch ($method) {
+            case 'follow': // $this is the target, $args[0] is the initiator
+                $status = $this->requestToFollow ? FollowRelationStatus::PENDING : FollowRelationStatus::ACTIVE;
+                if (!$this->isLocal) {
+                    $endpoint = $this->endpoints->follow ?? null;
+                    if (!isset($endpoint, $this->endpoints->unfollow)) {
+                        throw new RpcException("Actor `$this->uri` has no (un)follow endpoint");
+                    }
+                    $result = send_request_authenticated($endpoint, method: 'POST', actingAs: $args[0]);
+                    if (!str_contains($result->headers[0], ' 20')) {
+                        throw new RpcException('remote call did not indicate success: ' . $result->headers[0]);
+                    }
+                }
+                FollowRelation::create($args[0], $this, $status);
+                return $status;
+
+            case 'unfollow':
+                if (!$this->isLocal) {
+                    $endpoint = $this->endpoints->unfollow ?? null;
+                    if (!isset($endpoint, $this->endpoints->follow)) {
+                        throw new RpcException("Actor `$this->uri` has no (un)follow endpoint");
+                    }
+                    $result = send_request_authenticated($endpoint, method: 'POST', actingAs: $args[0]);
+                    if (!str_contains($result->headers[0], ' 20')) {
+                        throw new RpcException('remote call did not indicate success: ' . $result->headers[0]);
+                    }
+                }
+                FollowRelation::findByActors($args[0], $this)->remove();
+
+            default:
+                throw new \RuntimeException("Actor rpc method $method not (yet?) implemented");
+        }
+    }
+
+    /**
+     * Tries to follow (or send a follow request to) another actor
+     * @param Actor $target the actor to follow
+     * @return FollowRelationStatus PENDING if a request was sent or ACTIVE if the follow went through immediately
+     */
+    public function follow(self $target): FollowRelationStatus {
+        return $target->rpcCall('follow', [$this]);
+    }
+
+    public function unfollow(self $target) {
+        $target->rpcCall('unfollow', [$this]);
+    }
+
     public function jsonSerialize(): array {
         return [
             'type' => 'actor',
@@ -97,7 +158,9 @@ class Actor extends PushableModel {
             'automated' => $this->automated,
             'endpoints' => [
                 'basicFeed' => path_to_uri("/user/$this->handle/basicFeed"),
-                'fullFeed' => path_to_uri("/user/$this->handle/fullFeed")
+                'fullFeed' => path_to_uri("/user/$this->handle/fullFeed"),
+                'follow' => path_to_uri("/user/$this->handle/follow"),
+                'unfollow' => path_to_uri("/user/$this->handle/unfollow"),
             ]
         ];
     }
diff --git a/Digitigrade/Model/FetchableModel.php b/Digitigrade/Model/FetchableModel.php
index 1120823..5e4d1e8 100644
--- a/Digitigrade/Model/FetchableModel.php
+++ b/Digitigrade/Model/FetchableModel.php
@@ -55,10 +55,10 @@ abstract class FetchableModel extends Model implements RemoteFetchable {
     protected static function fetchFromRemote(string $uri, bool $autoSave): ?static {
         // fetch the object
         // janky hack: if this is an Instance then avoid recursively fetching itself
-        $data = @get_remote_object_authenticated($uri, static::class == Instance::class);
-        if ($data === false)
+        $result = @send_request_authenticated($uri, static::class == Instance::class);
+        if (!str_contains($result->headers[0], '200'))
             return null;
-        $data = json_decode($data);
+        $data = json_decode($result->body);
         if ($data === null)
             return null;
 
diff --git a/Digitigrade/Model/FollowRelation.php b/Digitigrade/Model/FollowRelation.php
new file mode 100644
index 0000000..fc43a6f
--- /dev/null
+++ b/Digitigrade/Model/FollowRelation.php
@@ -0,0 +1,37 @@
+<?php
+namespace Digitigrade\Model;
+
+use Digitigrade\Model;
+
+class FollowRelation extends Model {
+    public Actor $subject;
+    public Actor $object;
+    public FollowRelationStatus $status;
+
+    /**
+     * Creates and saves a new follower/following relationship
+     * @param Actor $subject the follower
+     * @param Actor $object the followee
+     * @param FollowRelationStatus $status whether the relationship is pending or active
+     * @return FollowRelation
+     */
+    public static function create(Actor $subject, Actor $object, FollowRelationStatus $status): self {
+        $rel = new self();
+        $rel->subject = $subject;
+        $rel->object = $object;
+        $rel->status = $status;
+        $rel->save();
+        return $rel;
+    }
+
+    protected function getUpdateWhereClause(\PDO $db): ?string {
+        if (self::findWhere('subject = ? and object = ?', [$this->subject->id, $this->object->id]) != null) {
+            return 'subject = ' . $this->subject->id . ' and object = ' . $this->object->id;
+        }
+        return null;
+    }
+
+    public static function findByActors(Actor $subject, Actor $object): ?self {
+        return self::findWhere('subject = ? and object = ?', [$subject->id, $object->id]);
+    }
+}
\ No newline at end of file
diff --git a/Digitigrade/Model/FollowRelationStatus.php b/Digitigrade/Model/FollowRelationStatus.php
new file mode 100644
index 0000000..24ba34b
--- /dev/null
+++ b/Digitigrade/Model/FollowRelationStatus.php
@@ -0,0 +1,7 @@
+<?php
+namespace Digitigrade\Model;
+
+enum FollowRelationStatus: string {
+    case PENDING = 'pending';
+    case ACTIVE = 'active';
+}
\ No newline at end of file
diff --git a/Digitigrade/RpcException.php b/Digitigrade/RpcException.php
new file mode 100644
index 0000000..f2d4775
--- /dev/null
+++ b/Digitigrade/RpcException.php
@@ -0,0 +1,6 @@
+<?php
+namespace Digitigrade;
+
+class RpcException extends \Exception {
+
+}
\ No newline at end of file
diff --git a/Digitigrade/RpcReceiver.php b/Digitigrade/RpcReceiver.php
new file mode 100644
index 0000000..f776bf2
--- /dev/null
+++ b/Digitigrade/RpcReceiver.php
@@ -0,0 +1,22 @@
+<?php
+namespace Digitigrade;
+
+/**
+ * Describes an object that can be acted on via an abstract RPC interface.
+ * 
+ * If the object comes from a remote server, it will be contacted to complete the call,
+ * whereas if it is a local object, the call may be completed using regular function calls.
+ */
+interface RpcReceiver {
+    /**
+     * Makes a remote or local method call on this object.
+     * 
+     * Implementors should not expose this method publicly, but should instead create wrapper
+     * methods with a nicer interface.
+     * @param string $method the name of the remote method to call
+     * @param array $args any arguments
+     * @return mixed results of the call
+     * @throws RpcException if there was an error contacting the other server
+     */
+    protected function rpcCall(string $method, array $args);
+}
\ No newline at end of file
diff --git a/migrations/20241219_181401_create_follow_relation.php b/migrations/20241219_181401_create_follow_relation.php
new file mode 100644
index 0000000..e5e5e73
--- /dev/null
+++ b/migrations/20241219_181401_create_follow_relation.php
@@ -0,0 +1,19 @@
+<?php
+
+use \Digitigrade\Db\Migrator;
+
+Migrator::getInstance()->register(20241219_181401, function (PDO $db) {
+    $db->beginTransaction();
+    $db->exec(<<<END
+    CREATE TYPE follow_relation_status AS ENUM (
+        'pending', 'active'
+    );
+    CREATE TABLE follow_relation (
+        subject bigint not null references actor,
+        object bigint not null references actor,
+        status follow_relation_status not null,
+        unique(subject, object)
+    );
+    END);
+    $db->commit();
+});
diff --git a/misc/get_remote_object_authenticated.php b/misc/send_request_authenticated.php
index 9f2db43..9019da8 100644
--- a/misc/get_remote_object_authenticated.php
+++ b/misc/send_request_authenticated.php
@@ -1,6 +1,7 @@
 <?php
 
 use Digitigrade\GlobalConfig;
+use Digitigrade\Model\Actor;
 use Digitigrade\Model\Instance;
 
 /**
@@ -8,16 +9,22 @@ use Digitigrade\Model\Instance;
  * @param string $uri
  * @param bool $dontLookUpInstance if true, will skip looking up the Instance, and consequently the auth token
  * @param string $method HTTP verb
- * @return false|string the response data, or false if it failed
+ * @param ?Actor $actingAs if specified, the local actor to send the request on behalf of
+ * @return stdClass object with fields `body` and `headers`
  */
-function get_remote_object_authenticated(string $uri, bool $dontLookUpInstance = false, string $method = 'GET'): false|string {
-    if (!str_starts_with($uri, 'https://'))
-        return false;
+function send_request_authenticated(
+    string $uri,
+    bool $dontLookUpInstance = false,
+    string $method = 'GET',
+    ?Actor $actingAs = null
+) {
+    if (!str_starts_with($uri, 'https://')) {
+        throw new RuntimeException('refusing to fetch a non-https uri');
+    }
 
     $remoteHost = hostname_from_uri($uri);
     if ($remoteHost == GlobalConfig::getInstance()->getCanonicalHost()) {
-        // refuse to fetch objects from ourself. that's silly
-        return false;
+        throw new RuntimeException('refusing to fetch content from myself');
     }
 
     $instance = null;
@@ -37,14 +44,23 @@ function get_remote_object_authenticated(string $uri, bool $dontLookUpInstance =
             // so i'm choosing to begin the auth process now and return false in the hopes that
             // this request will be retried later
             $instance?->beginOutboundAuth();
-            return false;
         }
-        return $resp;
+        $result = new stdClass();
+        $result->body = $resp;
+        $result->headers = $http_response_header;
+        return $result;
     }
 
+    $header = 'Authorization: Bearer ' . $instance->auth->outboundToken;
+    if ($actingAs != null) {
+        $header .= "\nX-PawPub-Actor: $actingAs->uri";
+    }
     $context = stream_context_create(['http' => [
         'method' => $method,
-        'header' => 'Authorization: Bearer ' . $instance->auth->outboundToken
+        'header' => $header
     ]]);
-    return file_get_contents($uri, context: $context);
+    $result = new stdClass();
+    $result->body = file_get_contents($uri, context: $context);
+    $result->headers = $http_response_header;
+    return $result;
 }
\ No newline at end of file
diff --git a/routes/actor.php b/routes/actor.php
index 51c0e1a..30b28c5 100644
--- a/routes/actor.php
+++ b/routes/actor.php
@@ -2,6 +2,7 @@
 
 use Digitigrade\HttpResponseStatus\NotFound;
 use Digitigrade\HttpResponseStatus\TemporaryRedirect;
+use Digitigrade\HttpResponseStatus\Unauthorized;
 use Digitigrade\Model\Actor;
 use Digitigrade\Model\Note;
 use Digitigrade\Router;
@@ -43,4 +44,28 @@ Router::getInstance()->mount('/user/:handle/fullFeed', function (array $args) {
         'previousPage' => null,
         'items' => $notes
     ]);
+});
+
+Router::getInstance()->mount('/user/:handle/follow', function (array $args) {
+    $target = Actor::findLocalByHandle($args['handle']);
+    if ($target == null) {
+        throw new NotFound();
+    }
+    $initiator = Actor::findByRequestHeaders();
+    if ($initiator == null) {
+        throw new Unauthorized('please authenticate yourself on behalf of the initiating actor');
+    }
+    $initiator->follow($target);
+});
+
+Router::getInstance()->mount('/user/:handle/unfollow', function (array $args) {
+    $target = Actor::findLocalByHandle($args['handle']);
+    if ($target == null) {
+        throw new NotFound();
+    }
+    $initiator = Actor::findByRequestHeaders();
+    if ($initiator == null) {
+        throw new Unauthorized('please authenticate yourself on behalf of the initiating actor');
+    }
+    $initiator->unfollow($target);
 });
\ No newline at end of file