Add FPM proxy script.

fpm/measurement.php

@@ -1,21 +1,15 @@
-<?php // phpcs:disable Squiz.Commenting.FileComment.SpacingAfterOpen ?>
-<?php // phpcs:disable Squiz.Commenting.InlineComment.InvalidEndChar ?>
 <?php
-
 /**
  * FirstPartyServing redirect file
  *
  * @package   Google\FirstPartyLibrary
  * @copyright 2024 Google LLC
  * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ *
+ * NOTICE: This file has been modified from its original version in accordance with the Apache License, Version 2.0.
  */
 
-// This file should run in isolation from any other PHP file. This means using
-// minimal to no external dependencies, which leads us to supressing the
-// following linting rules:
-//
-// phpcs:disable PSR1.Files.SideEffects.FoundWithSymbols
-// phpcs:disable PSR1.Classes.ClassDeclaration.MultipleClasses
+namespace Google\FirstPartyLibrary;
 
 /**
  * This is a stub for the measurement.php file which is used to proxy requests to the FPFE service.
@@ -28,3 +22,149 @@
 	echo 'ok';
 	exit;
 }
+
+/** Core measurement.php logic. */
+final class Measurement {
+
+	private const TAG_ID_QUERY        = '?id=';
+	private const REDIRECTOR_ID_QUERY = '.php' . self::TAG_ID_QUERY;
+	private const PATH_QUERY          = '&s=';
+	private const FPS_PATH            = 'PHP_FPM_REPLACE_PATH';
+
+	/** @var RequestHelper */
+	private $helper;
+
+	/**
+	 * Create the measurement request handler.
+	 *
+	 * @param RequestHelper $helper
+	 */
+	public function __construct( $helper ) {
+		$this->helper = $helper;
+	}
+
+	/** Run the measurement logic. */
+	public function run() {
+		$requestString = $_SERVER['REQUEST_URI'];
+		$documentRoot  = $_SERVER['DOCUMENT_ROOT'];
+
+		if ( empty( $documentRoot ) || empty( $requestString ) ) {
+			$this->helper->invalidRequest( 500 );
+			return '';
+		}
+
+		$redirectorFile = explode( $documentRoot, __FILE__ )[1];
+		if ( empty( $redirectorFile ) ) {
+			$this->helper->invalidRequest( 500 );
+			return '';
+		}
+
+		$parameters = self::extractParameters( $requestString );
+		if ( empty( $parameters ) ) {
+			$this->helper->invalidRequest( 400 );
+			return '';
+		}
+
+		$tagId = $parameters['tag_id'];
+		$path  = $parameters['path'];
+
+		if ( strlen( $tagId ) === 0 || strlen( $path ) === 0 ) {
+			http_response_code( 400 );
+			return '';
+		}
+
+		$fpsUrl = 'https://' . $tagId . '.fps.goog/' . self::FPS_PATH . $path;
+
+		if ( self::isScriptRequest( $path ) ) {
+			$response = $this->helper->sendRequest( $fpsUrl );
+			return str_replace(
+				'/' . self::FPS_PATH . '/',
+				$redirectorFile . self::TAG_ID_QUERY . $tagId . self::PATH_QUERY,
+				$response
+			);
+		} else {
+			return $this->helper->sendRequest( $fpsUrl );
+		}
+	}
+
+	private static function isScriptRequest( $requestPath ) {
+		return substr( $requestPath, 0, 7 ) === '/gtm.js'
+		|| substr( $requestPath, 0, 8 ) === '/gtag.js'
+		|| substr( $requestPath, 0, 8 ) === '/gtag/js';
+	}
+
+
+	private static function extractParameters( $requestString ) {
+		$tagIdPosition = strpos( $requestString, self::REDIRECTOR_ID_QUERY );
+		if ( $tagIdPosition === false ) {
+			return null;
+		}
+
+		$tagIdStart = $tagIdPosition + strlen( self::REDIRECTOR_ID_QUERY );
+		$tagIdEnd   = strpos( $requestString, self::PATH_QUERY, $tagIdStart );
+		if ( $tagIdEnd === false ) {
+			return null;
+		}
+
+		$tagId = substr( $requestString, $tagIdStart, $tagIdEnd - $tagIdStart );
+		$path  = substr( $requestString, $tagIdEnd + strlen( self::PATH_QUERY ) );
+
+		return array(
+			'tag_id' => $tagId,
+			'path'   => $path,
+		);
+	}
+}
+
+/**
+ * Isolates network requests and other methods like exit to inject into the
+ * Measurement class
+ */
+class RequestHelper {
+
+	/**
+	 * Helper method to exit the script early and send back a status code.
+	 *
+	 * @param int $statusCode
+	 */
+	public function invalidRequest( $statsCode ) {
+		http_response_code( $statsCode );
+		exit();
+	}
+
+	/**
+	 * Helper method to send requests depending on the PHP environment.
+	 *
+	 * @param string $url
+	 */
+	public function sendRequest( $url ) {
+		if ( $this->isCurlInstalled() ) {
+			$response = $this->sendCurlRequest( $url );
+		} else {
+			$response = $this->sendFileGetContents( $url );
+		}
+		return $response;
+	}
+
+	protected function sendCurlRequest( $url ) {
+		$ch = curl_init();
+		curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
+		curl_setopt( $ch, CURLOPT_URL, $url );
+		$result = curl_exec( $ch );
+		curl_close( $ch );
+		return $result;
+	}
+
+	protected function sendFileGetContents( $url ) {
+		return file_get_contents( $url );
+	}
+
+	protected function isCurlInstalled() {
+		return extension_loaded( 'curl' );
+	}
+}
+
+// Skip initial run for testing
+if ( ! defined( 'IS_FIRST_PARTY_MODE_TEST' ) ) {
+	echo ( new Measurement( new RequestHelper() ) )->run();
+}

phpcs.xml

@@ -100,6 +100,7 @@
 	<exclude-pattern>packages/apiclient-services-subscribewithgoogle/*</exclude-pattern>
 	<exclude-pattern>third-party/*</exclude-pattern>
 	<exclude-pattern>*/vendor/*</exclude-pattern>
+	<exclude-pattern>fpm/measurement.php</exclude-pattern>
 
 	<!-- Check for cross-version support for PHP 7.4 and higher. -->
 	<config name="testVersion" value="7.4-"/>