feat: queue cached link previews for drafts

app/Actions/CreateCommit.php

@@ -11,7 +11,6 @@
 use App\Jobs\EmbedCommit;
 use App\Jobs\ModerateCommit;
 use App\Jobs\ReplyAsTom;
-use App\Jobs\UnfurlLink;
 use App\Models\Commit;
 use App\Models\LinkPreview;
 use App\Models\User;
@@ -31,6 +30,7 @@ public function __construct(
         private CreateMentionNotifications $createMentionNotifications,
         private CreateCommitImages $createCommitImages,
         private CreateWorldReply $createWorldReply,
+        private CreateLinkPreviewJob $createLinkPreviewJob,
         private UpdateCommitHotScores $updateCommitHotScores,
         private TheAlgorithm $theAlgorithm,
         private EmojiShortcodes $emojiShortcodes,
@@ -42,8 +42,6 @@ public function __construct(
     }
 
     /**
-     * The link preview is of the first URL in the body when true, of the given URL when a string, or none when false.
-     *
      * @param  list<UploadedFile>  $images
      * @param  array<int, string|null>  $imageDescriptions
      */
@@ -86,8 +84,10 @@ public function handle(User $user, string $body, ?Commit $parent = null, ?Commit
             $this->createQuoteNotifications->handle($commit);
             $this->createMentionNotifications->handle($commit);
 
-            if ($linkPreview instanceof LinkPreview && $linkPreview->fetched_at === null) {
-                dispatch(new UnfurlLink($linkPreview));
+            if ($linkPreview instanceof LinkPreview && $linkPreview->prepareUnfurlForPublication()) {
+                DB::afterCommit(function () use ($linkPreview): void {
+                    $this->createLinkPreviewJob->handle($linkPreview);
+                });
             }
 
             $this->createWorldReply->handle($commit);
@@ -118,9 +118,6 @@ public function handle(User $user, string $body, ?Commit $parent = null, ?Commit
         });
     }
 
-    /**
-     * A poll opens with its commit's approval, so polls of pending commits wait for moderation.
-     */
     private function createPoll(Commit $commit, NewPoll $newPoll): void
     {
         $poll = $commit->poll()->create([
@@ -135,9 +132,6 @@ private function createPoll(Commit $commit, NewPoll $newPoll): void
         ));
     }
 
-    /**
-     * Commits that link to the same URL share one preview, so a page is fetched once however often it is linked.
-     */
     private function linkPreviewFor(?string $url): ?LinkPreview
     {
         if ($url === null) {

app/Actions/CreateLinkPreviewJob.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Actions;
+
+use App\Jobs\UnfurlLink;
+use App\Models\LinkPreview;
+use Throwable;
+
+final readonly class CreateLinkPreviewJob
+{
+    public function handle(LinkPreview $linkPreview): void
+    {
+        $preview = $linkPreview->fresh();
+
+        if (! $preview instanceof LinkPreview || $preview->fetched_at !== null) {
+            return;
+        }
+
+        $job = new UnfurlLink($preview);
+
+        try {
+            dispatch($job)->afterCommit();
+        } catch (Throwable $throwable) {
+            $job->failed();
+
+            throw $throwable;
+        }
+    }
+}

app/Actions/CreateMessage.php

@@ -6,7 +6,6 @@
 
 use App\Enums\RemoteStatus;
 use App\Jobs\SendRemotePush;
-use App\Jobs\UnfurlLink;
 use App\Models\Conversation;
 use App\Models\ConversationParticipant;
 use App\Models\LinkPreview;
@@ -28,13 +27,11 @@ public function __construct(
         private CreateMessageVoiceFile $createMessageVoiceFile,
         private MentionedUsersQuery $mentionedUsers,
         private Urls $urls,
+        private CreateLinkPreviewJob $createLinkPreviewJob,
     ) {
         //
     }
 
-    /**
-     * Makes the message the conversation's latest, for every member's inbox.
-     */
     public static function advance(Conversation $conversation, Message $message, bool $unstash): void
     {
         Conversation::query()
@@ -48,10 +45,6 @@ public static function advance(Conversation $conversation, Message $message, boo
     }
 
     /**
-     * Sending the same client id again, as a retry does, returns the message it already created, without storing its
-     * images or voice note twice. A new message brings the conversation back out of the stash for everyone in it. The link card is
-     * of the first link in the body when true, of the given link when a string, or none when false.
-     *
      * @param  list<UploadedFile>  $images
      * @param  array<int, string|null>  $imageDescriptions
      * @param  list<int>  $voiceWaveform
@@ -108,8 +101,10 @@ public function handle(User $sender, Conversation $conversation, string $body, s
                 ->where('read_through_id', '<', $message->id)
                 ->update(['read_through_id' => $message->id, 'read_at' => now()]);
 
-            if ($linkPreview instanceof LinkPreview && $linkPreview->fetched_at === null) {
-                dispatch(new UnfurlLink($linkPreview))->afterCommit();
+            if ($linkPreview instanceof LinkPreview && $linkPreview->prepareUnfurlForPublication()) {
+                DB::afterCommit(function () use ($linkPreview): void {
+                    $this->createLinkPreviewJob->handle($linkPreview);
+                });
             }
 
             return $message;

app/Actions/UpdateLinkPreview.php

@@ -38,7 +38,7 @@ public function handle(LinkPreview $linkPreview): void
     {
         $metadata = $this->fetchMetadata($linkPreview->url);
 
-        $linkPreview->update([...$metadata->toArray(), 'fetched_at' => now()]);
+        $linkPreview->completeUnfurl($metadata->toArray());
     }
 
     private function fetchMetadata(string $url): LinkPreviewMetadata

app/Http/Controllers/DraftLinkPreviewController.php

@@ -0,0 +1,104 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers;
+
+use App\Actions\CreateLinkPreviewJob;
+use App\Dto\LinkPreviewMetadata;
+use App\Enums\EmbedKind;
+use App\Http\Requests\ShowDraftLinkPreviewRequest;
+use App\Models\LinkPreview;
+use App\Models\User;
+use App\Services\Embeds;
+use Carbon\CarbonInterface;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Log;
+use Illuminate\Support\Facades\RateLimiter;
+use Symfony\Component\HttpKernel\Exception\TooManyRequestsHttpException;
+use Uri\WhatWg\Url;
+
+final readonly class DraftLinkPreviewController
+{
+    public const int READS_PER_MINUTE = 120;
+
+    private const int UNFURLS_PER_MINUTE = 10;
+
+    public function __construct(private CreateLinkPreviewJob $createLinkPreviewJob)
+    {
+        //
+    }
+
+    public function show(ShowDraftLinkPreviewRequest $request, Embeds $embeds): JsonResponse
+    {
+        $user = $request->user();
+        assert($user instanceof User);
+
+        $url = $request->string('url')->value();
+
+        Log::info('Draft link preview requested', [
+            'user_id' => $user->id,
+            'host' => Url::parse($url)?->getAsciiHost(),
+        ]);
+
+        if ($embeds->for($url)?->kind === EmbedKind::Gif) {
+            return $this->response($this->preview($url, new LinkPreviewMetadata));
+        }
+
+        $key = "draft-link-unfurls:{$user->id}";
+
+        return $this->response($this->cachedPreview($url, $key));
+    }
+
+    private function cachedPreview(string $url, string $key): LinkPreview
+    {
+        $cached = LinkPreview::query()->where('url_hash', hash('sha256', $url))->first();
+
+        if ($cached instanceof LinkPreview) {
+            return $cached;
+        }
+
+        if (RateLimiter::tooManyAttempts($key, self::UNFURLS_PER_MINUTE)) {
+            throw new TooManyRequestsHttpException(RateLimiter::availableIn($key));
+        }
+
+        RateLimiter::increment($key, CarbonInterface::SECONDS_PER_MINUTE);
+
+        return $this->createPreview($url);
+    }
+
+    private function createPreview(string $url): LinkPreview
+    {
+        return DB::transaction(function () use ($url): LinkPreview {
+            $preview = LinkPreview::query()->firstOrCreate(
+                ['url_hash' => hash('sha256', $url)],
+                ['url' => $url, ...(new LinkPreviewMetadata)->toArray()],
+            );
+
+            if ($preview->wasRecentlyCreated) {
+                DB::afterCommit(function () use ($preview): void {
+                    $this->createLinkPreviewJob->handle($preview);
+                });
+            }
+
+            return $preview;
+        });
+    }
+
+    private function response(LinkPreview $preview): JsonResponse
+    {
+        return response()->json([
+            'link_preview' => $preview,
+        ])->header('Cache-Control', 'private, no-store');
+    }
+
+    private function preview(string $url, LinkPreviewMetadata $metadata): LinkPreview
+    {
+        return new LinkPreview([
+            'url' => $url,
+            ...$metadata->toArray(),
+            'fetched_at' => now(),
+        ]);
+    }
+}

app/Http/Requests/ShowDraftLinkPreviewRequest.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Requests;
+
+use App\Services\Urls;
+use Illuminate\Foundation\Http\FormRequest;
+
+final class ShowDraftLinkPreviewRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /**
+     * @return array<string, list<string>>
+     */
+    public function rules(): array
+    {
+        return [
+            'url' => ['required', 'string', 'url:http,https', 'max:'.Urls::MAX_LENGTH],
+        ];
+    }
+}

app/Jobs/UnfurlLink.php

@@ -6,41 +6,59 @@
 
 use App\Actions\UpdateLinkPreview;
 use App\Models\LinkPreview;
+use Illuminate\Contracts\Queue\ShouldBeUnique;
 use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Foundation\Queue\Queueable;
 use Illuminate\Queue\Attributes\Backoff;
 use Illuminate\Queue\Attributes\DeleteWhenMissingModels;
 use Illuminate\Queue\Attributes\Tries;
+use Illuminate\Support\Facades\DB;
 
 #[Backoff([60, 600])]
 #[Tries(3)]
 #[DeleteWhenMissingModels]
-final class UnfurlLink implements ShouldQueue
+final class UnfurlLink implements ShouldBeUnique, ShouldQueue
 {
     use Queueable;
 
+    // Allow foreign-key references while serializing workers.
+    private const string METADATA_LOCK = 'for no key update';
+
+    // Default supports older queued payloads.
+    public int $publicationUnfurlRetries = 0;
+
     public function __construct(public readonly LinkPreview $linkPreview)
     {
-        //
+        if ($linkPreview->publication_unfurl_retries === 0) {
+            return;
+        }
+
+        $this->publicationUnfurlRetries = $linkPreview->publication_unfurl_retries;
+    }
+
+    public function uniqueId(): string
+    {
+        return $this->linkPreview->id;
     }
 
-    /**
-     * Commits that share a link may each queue this job before the first one runs, so only the first one fetches.
-     */
     public function handle(UpdateLinkPreview $action): void
     {
-        if ($this->linkPreview->fetched_at !== null) {
-            return;
-        }
+        DB::transaction(function () use ($action): void {
+            $linkPreview = LinkPreview::query()->lock(self::METADATA_LOCK)->find($this->linkPreview->id);
+
+            if (! $linkPreview instanceof LinkPreview
+                || $linkPreview->fetched_at !== null
+                || $linkPreview->publication_unfurl_retries !== $this->publicationUnfurlRetries
+            ) {
+                return;
+            }
 
-        $action->handle($this->linkPreview);
+            $action->handle($linkPreview);
+        });
     }
 
-    /**
-     * Once every attempt has failed, the link preview is marked as fetched without metadata, so it is not tried again.
-     */
     public function failed(): void
     {
-        $this->linkPreview->update(['fetched_at' => now()]);
+        $this->linkPreview->markUnfurlAsTransientFailure($this->publicationUnfurlRetries);
     }
 }