From 615fcb2e4518724c6e4585d1608fe0b145872881 Mon Sep 17 00:00:00 2001
From: Jeremy Dormitzer <jeremy.dormitzer@gmail.com>
Date: Sun, 28 Apr 2019 16:08:22 -0400
Subject: [PATCH] [WIP] Begin implementing CachingDereferencer

---
 composer.json                                 |  11 +-
 .../Dereferencer/CachingDereferencer.php      | 160 ++++++++++++++++++
 test/JsonLd/JsonLdNodeTest.php                |  23 ++-
 3 files changed, 184 insertions(+), 10 deletions(-)
 create mode 100644 src/JsonLd/Dereferencer/CachingDereferencer.php

diff --git a/composer.json b/composer.json
index 341fa30..87933b6 100644
--- a/composer.json
+++ b/composer.json
@@ -15,21 +15,17 @@
     "test-debug": "XDEBUG_CONFIG='idekey=ap_session' php ./vendor/bin/phpunit test",
     "docs": "phpdoc -d ./src -t ./docs"
   },
-  "repositories": [
-    {
-      "type": "vcs",
-      "url": "https://git.friendi.ca/friendica/php-json-ld"
-    }
-  ],
   "require": {
     "ext-json": "*",
+    "cache/apc-adapter": "0.3.2",
+    "cache/apcu-adapter": "0.2.2",
+    "cache/filesystem-adapter": "0.3.3",
     "doctrine/annotations": "1.2.7",
     "doctrine/cache": "1.6.2",
     "doctrine/collections": "1.3.0",
     "doctrine/common": "2.6.2",
     "doctrine/instantiator": "1.0.5",
     "doctrine/orm": "2.5.14",
-    "friendica/json-ld": "^1.1",
     "guzzlehttp/guzzle": "^6.3",
     "ml/json-ld": "1.1.0",
     "monolog/monolog": "^1.0",
@@ -44,6 +40,7 @@
   },
   "require-dev": {
     "ext-pdo": "*",
+    "cache/array-adapter": "0.4.2",
     "phpunit/dbunit": "^2.0",
     "phpunit/phpunit": "^4.0"
   },
diff --git a/src/JsonLd/Dereferencer/CachingDereferencer.php b/src/JsonLd/Dereferencer/CachingDereferencer.php
new file mode 100644
index 0000000..b6e1933
--- /dev/null
+++ b/src/JsonLd/Dereferencer/CachingDereferencer.php
@@ -0,0 +1,160 @@
+<?php
+
+namespace ActivityPub\JsonLd\Dereferencer;
+
+use ActivityPub\Crypto\HttpSignatureService;
+use ActivityPub\JsonLd\Exceptions\NodeNotFoundException;
+use ActivityPub\Utils\Util;
+use DateTime;
+use DateTimeZone;
+use GuzzleHttp\Client;
+use GuzzleHttp\Psr7\Request;
+use Psr\Cache\CacheItemPoolInterface;
+use Psr\Log\LoggerInterface;
+use stdClass;
+
+/**
+ * A dereferencer that caches its results by id. Signs outgoing requests if provided with a keyId and a privateKey.
+ * Class CachingDereferencer
+ * @package ActivityPub\JsonLd\Dereferencer
+ */
+class CachingDereferencer implements DereferencerInterface
+{
+    const DEFAULT_CACHE_TTL = 3600;
+
+    /**
+     * @var LoggerInterface
+     */
+    private $logger;
+
+    /**
+     * The cache.
+     * @var CacheItemPoolInterface
+     */
+    private $cache;
+
+    /**
+     * The HTTP client.
+     * @var Client
+     */
+    private $httpClient;
+
+    /**
+     * @var HttpSignatureService
+     */
+    private $httpSignatureService;
+
+    /**
+     * The keyId for signing requests, if there is one.
+     * @var null|string
+     */
+    private $keyId;
+
+    /**
+     * The private key for signing requests, if there is one.
+     * @var null|string
+     */
+    private $privateKey;
+
+    /**
+     * CachingDereferencer constructor.
+     * @param CacheItemPoolInterface $cache
+     * @param Client $httpClient
+     * @param HttpSignatureService $httpSignatureService
+     * @param null|string $keyId
+     * @param null|string $privateKey
+     */
+    public function __construct( LoggerInterface $logger,
+                                 CacheItemPoolInterface $cache,
+                                 Client $httpClient,
+                                 HttpSignatureService $httpSignatureService,
+                                 $keyId = null,
+                                 $privateKey = null )
+    {
+        $this->logger = $logger;
+        $this->cache = $cache;
+        $this->httpClient = $httpClient;
+        $this->httpSignatureService = $httpSignatureService;
+        $this->keyId = $keyId;
+        $this->privateKey = $privateKey;
+    }
+
+    public function setKeyId( $keyId )
+    {
+        $this->keyId = $keyId;
+    }
+
+    public function setPrivateKey( $privateKey )
+    {
+        $this->privateKey = $privateKey;
+    }
+
+    /**
+     * @param string $iri The IRI to dereference.
+     * @return stdClass|array The dereferenced node.
+     * @throws NodeNotFoundException If a node with the IRI could not be found.
+     */
+    public function dereference( $iri )
+    {
+        $key = $this->makeCacheKey( $iri );
+        $cacheItem = $this->cache->getItem( $key );
+        if ( $cacheItem->isHit() ) {
+            return $cacheItem->get();
+        } else {
+            if ( Util::isLocalUri( $iri ) ) {
+                // TODO fetch object from persistence backend
+            }
+            $headers = array(
+                'Accept' => 'application/ld+json',
+                'Date' => $this->getNowRFC1123(),
+            );
+            $request = new Request( 'GET', $iri, $headers );
+            if ( $this->shouldSign() ) {
+                $signature = $this->httpSignatureService->sign( $request, $this->privateKey, $this->keyId );
+                $request = $request->withHeader( 'Signature', $signature );
+            }
+            $response = $this->httpClient->send( $request );
+            if ( $response->getStatusCode() >= 400 ) {
+                $statusCode = $response->getStatusCode();
+                $this->logger->error(
+                    "[ActivityPub-PHP] Received response with status $statusCode from $iri",
+                    array( 'request' => $request, 'response' => $response )
+                );
+            } else {
+                $body = json_decode( $response->getBody() );
+                if ( ! $body ) {
+                    throw new NodeNotFoundException( $iri );
+                }
+                $cacheItem->set( $body );
+                $cacheItem->expiresAfter( self::DEFAULT_CACHE_TTL );
+                $this->cache->save( $cacheItem );
+                return $body;
+            }
+        }
+    }
+
+    /**
+     * Generates a valid cache key for $id.
+     * @param string $id
+     * @return string
+     */
+    private function makeCacheKey( $id )
+    {
+        return str_replace( array( '{', '}', '(', ')', '/', '\\', '@', ':' ), '_', $id );
+    }
+
+    /**
+     * True if the dereferencer should sign outgoing requests.
+     * @return bool
+     */
+    private function shouldSign()
+    {
+        return $this->keyId && $this->privateKey;
+    }
+
+    private function getNowRFC1123()
+    {
+        $now = new DateTime( 'now', new DateTimeZone( 'GMT' ) );
+        return $now->format( 'D, d M Y H:i:s T' );
+    }
+}
\ No newline at end of file
diff --git a/test/JsonLd/JsonLdNodeTest.php b/test/JsonLd/JsonLdNodeTest.php
index d872904..30183b0 100644
--- a/test/JsonLd/JsonLdNodeTest.php
+++ b/test/JsonLd/JsonLdNodeTest.php
@@ -441,6 +441,21 @@ class JsonLdNodeTest extends APTestCase
                     'id' => 'https://example.org/articles/1',
                     'type' => 'Article',
                 )
+            ),
+            array(
+                new stdClass(),
+                $this->asContext,
+                'to',
+                array(
+                    (object) array(
+                        'id' => 'https://example.org/sally',
+                        'type' => 'Person',
+                    ),
+                    (object) array(
+                        'id' => 'https://example.org/bob',
+                        'type' => 'Person',
+                    )
+                ),
             )
         );
     }
@@ -452,9 +467,11 @@ class JsonLdNodeTest extends APTestCase
     {
         $parentNode = $this->makeJsonLdNode( $inputObj, $context );
         $parentNode->set( $newPropertyName, $newNodeValue );
-        $childNode = $parentNode->get( $newPropertyName );
-        $this->assertInstanceOf( JsonLdNode::class, $childNode );
-        $this->assertEquals( $childNode->getBackReferences( $newPropertyName ), array( $parentNode ) );
+        $childNodes = $parentNode->getMany( $newPropertyName );
+        foreach ( $childNodes as $childNode ) {
+            $this->assertInstanceOf( JsonLdNode::class, $childNode );
+            $this->assertEquals( $childNode->getBackReferences( $newPropertyName ), array( $parentNode ) );
+        }
     }
 
     private function makeJsonLdNode( $inputObj, $context, $nodeGraph = array() )