From d31ab23adaed62a6f2f4450e9c5b4509e16c5de1 Mon Sep 17 00:00:00 2001
From: Jesus Hernandez <jesushdez@protonmail.com>
Date: Fri, 20 Sep 2024 09:24:17 +0000
Subject: [PATCH] feat: Add spider RequestDeduplicationMiddleware

---
 .../RequestDeduplicationMiddleware.php        | 107 ++++++++++++++++++
 .../RequestDeduplicationMiddlewareTest.php    |  80 +++++++++++++
 2 files changed, 187 insertions(+)
 create mode 100644 src/Spider/Middleware/RequestDeduplicationMiddleware.php
 create mode 100644 tests/Spider/Middleware/RequestDeduplicationMiddlewareTest.php

diff --git a/src/Spider/Middleware/RequestDeduplicationMiddleware.php b/src/Spider/Middleware/RequestDeduplicationMiddleware.php
new file mode 100644
index 0000000..6eacd43
--- /dev/null
+++ b/src/Spider/Middleware/RequestDeduplicationMiddleware.php
@@ -0,0 +1,107 @@
+<?php
+
+namespace RoachPHP\Spider\Middleware;
+
+use Psr\Log\LoggerInterface;
+use RoachPHP\Http\Request;
+use RoachPHP\Http\Response;
+use RoachPHP\Support\Configurable;
+
+/**
+ * Drop duplicate requests to avoid unnecessary work.
+ *
+ * This middleware is optimized for reducing memory usage as it drops duplicate
+ * requests early in the request processing pipeline, and it uses a limited-size
+ * cache to store seen URIs.
+ */
+class RequestDeduplicationMiddleware implements RequestMiddlewareInterface
+{
+    use Configurable;
+
+    private array $seenUriHashesHits = [];
+    private int $requestCount = 0;
+    private int $requestDroppedCount = 0;
+
+    public function __construct(private LoggerInterface $logger)
+    {
+    }
+
+    private function defaultOptions(): array
+    {
+        return [
+            'ignore_url_fragments' => false,
+            'ignore_trailing_slashes' => true,
+            'ignore_query_string' => false,
+            'seen_uris_cache_size' => 10000,
+        ];
+    }
+
+    public function handleRequest(Request $request, Response $response): Request
+    {
+        $uri = $request->getUri();
+
+        if ($this->isDuplicatedUri($uri)) {
+            $this->logger->info(
+                '[RequestDeduplicationMiddleware] Dropping duplicate request',
+                ['uri' => $uri],
+            );
+
+            return $request->drop('Duplicate request');
+        }
+
+        return $request;
+    }
+
+    private function isDuplicatedUri(string $uri): bool
+    {
+        $uriHash = $this->hashUri($uri);
+
+        if (isset($this->seenUriHashesHits[$uriHash])) {
+            $this->seenUriHashesHits[$uriHash] += 1;
+            return true;
+        }
+
+        $this->seenUriHashesHits[$uriHash] = 1;
+        $this->cacheEviction();
+        return false;
+    }
+
+    private function hashUri(string $uri): string
+    {
+        $replaceFlags = HTTP_URL_REPLACE;
+        $parts = parse_url($uri);
+
+        if ($this->option('ignore_url_fragments')) {
+            $replaceFlags |= HTTP_URL_STRIP_FRAGMENT;
+        }
+
+        if ($this->option('ignore_trailing_slashes') && isset($parts['path'])) {
+            $parts['path'] = rtrim($parts['path'], '/');
+        }
+
+        if ($this->option('ignore_query_string')) {
+            $replaceFlags |= HTTP_URL_STRIP_QUERY;
+        }
+
+        $uri = http_build_url($uri, $parts, $replaceFlags);
+        return md5($uri); // Why md5? Because it's fast and short.
+    }
+
+    private function cacheEviction(): void
+    {
+        if (count($this->seenUriHashesHits) <= $this->option('seen_uris_cache_size')) {
+            return;
+        }
+
+        $averageHitCount = array_sum($this->seenUriHashesHits) / count($this->seenUriHashesHits);
+        $this->seenUriHashesHits = array_filter($this->seenUriHashesHits, fn($hitCount) => $hitCount > $averageHitCount);
+
+        $this->logger->info(
+            '[RequestDeduplicationMiddleware] Cache eviction',
+            [
+                'average_hit_count' => $averageHitCount,
+                'remaining_cache_size' => count($this->seenUriHashesHits),
+            ],
+        );
+    }
+}
diff --git a/tests/Spider/Middleware/RequestDeduplicationMiddlewareTest.php b/tests/Spider/Middleware/RequestDeduplicationMiddlewareTest.php
new file mode 100644
index 0000000..7dcc6c5
--- /dev/null
+++ b/tests/Spider/Middleware/RequestDeduplicationMiddlewareTest.php
@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+namespace RoachPHP\Tests\Spider\Middleware;
+
+use PHPUnit\Framework\TestCase;
+use RoachPHP\Spider\Middleware\RequestDeduplicationMiddleware;
+use RoachPHP\Testing\Concerns\InteractsWithRequestsAndResponses;
+use RoachPHP\Testing\FakeLogger;
+
+/**
+ * @internal
+ */
+final class RequestDeduplicationMiddlewareTest extends TestCase
+{
+    use InteractsWithRequestsAndResponses;
+
+    public function testDropDuplicatedRequest(): void
+    {
+        $uri = 'http://localhost/';
+        $middleware = $this
+            ->createMiddleware();
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri), $this->makeResponse());
+        self::assertSame(false, $processedRequest->wasDropped());
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri), $this->makeResponse());
+        self::assertSame(true, $processedRequest->wasDropped());
+    }
+
+    public function testCacheEviction(): void
+    {
+        $uri_a = 'http://localhost/a';
+        $uri_b = 'http://localhost/b';
+        $uri_c = 'http://localhost/c';
+        $middleware = $this
+            ->createMiddleware(2);
+
+        foreach(range(1, 3) as $index) {
+            $processedRequest = $middleware
+                ->handleRequest($this->makeRequest($uri_a), $this->makeResponse());
+        }
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_b), $this->makeResponse());
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_a), $this->makeResponse());
+        self::assertSame(true, $processedRequest->wasDropped());
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_b), $this->makeResponse());
+        self::assertSame(true, $processedRequest->wasDropped());
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_c), $this->makeResponse());
+        self::assertSame(false, $processedRequest->wasDropped()); // It needs the list of accessed URIs delete some entries.
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_b), $this->makeResponse());
+        self::assertSame(false, $processedRequest->wasDropped()); // B was removed from list of duplicated requests.
+
+        $processedRequest = $middleware
+            ->handleRequest($this->makeRequest($uri_a), $this->makeResponse());
+        self::assertSame(true, $processedRequest->wasDropped()); // A was not removed as it was requested more times than the others.
+    }
+
+    private function createMiddleware(?int $cacheSize = null): RequestDeduplicationMiddleware
+    {
+        $middleware = new RequestDeduplicationMiddleware(new FakeLogger());
+
+        if (null !== $cacheSize) {
+            $middleware->configure(['seen_uris_cache_size' => $cacheSize]);
+        }
+
+        return $middleware;
+    }
+}