From cf2dad3ab8872d3ff50a702a8bfaa93cc3ff794d Mon Sep 17 00:00:00 2001
From: Matt DeMoss <demoss.matt@gmail.com>
Date: Tue, 29 Mar 2022 19:50:07 -0400
Subject: [PATCH] Reducer (retrying after failed tests) (#2273)

---
 bridges/FeedReducerBridge.php | 60 +++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 bridges/FeedReducerBridge.php

diff --git a/bridges/FeedReducerBridge.php b/bridges/FeedReducerBridge.php
new file mode 100644
index 00000000..1963b53b
--- /dev/null
+++ b/bridges/FeedReducerBridge.php
@@ -0,0 +1,60 @@
+<?php
+class FeedReducerBridge extends FeedExpander {
+
+	const MAINTAINER = 'mdemoss';
+	const NAME = 'Feed Reducer';
+	const URI = 'http://github.com/RSS-Bridge/rss-bridge/';
+	const DESCRIPTION = 'Choose a percentage of a feed you want to see.';
+	const PARAMETERS = array( array(
+		'url' => array(
+			'name' => 'Feed URI',
+			'exampleValue' => 'https://lorem-rss.herokuapp.com/feed?length=42',
+			'required' => true
+		),
+		'percentage' => array(
+			'name' => 'percentage',
+			'type' => 'number',
+			'exampleValue' => 50,
+			'required' => true
+		)
+	));
+	const CACHE_TIMEOUT = 3600;
+
+	public function collectData(){
+		if(preg_match('#^http(s?)://#i', $this->getInput('url'))) {
+			$this->collectExpandableDatas($this->getInput('url'));
+		} else {
+			throw new Exception('URI must begin with http(s)://');
+		}
+	}
+
+	public function getItems(){
+		$filteredItems = array();
+		$intPercentage = (int)preg_replace('/[^0-9]/', '', $this->getInput('percentage'));
+
+		foreach ($this->items as $thisItem) {
+			// The URL is included in the hash:
+			//  - so you can change the output by adding a local-part to the URL
+			//  - so items with the same URI in different feeds won't be correlated
+
+			// $pseudoRandomInteger will be a 16 bit unsigned int mod 100.
+			// This won't be uniformly distributed 1-100, but should be close enough.
+
+			$pseudoRandomInteger = unpack(
+				'S', // unsigned 16-bit int
+				hash( 'sha256', $thisItem['uri'] . '::' . $this->getInput('url'), true )
+			)[1] % 100;
+
+			if ($pseudoRandomInteger < $intPercentage) {
+				$filteredItems[] = $thisItem;
+			}
+		}
+
+		return $filteredItems;
+	}
+
+	public function getName(){
+		$trimmedPercentage = preg_replace('/[^0-9]/', '', $this->getInput('percentage'));
+		return parent::getName() . ' [' . $trimmedPercentage . '%]';
+	}
+}