From 96abdd985227307d4db5fbd666504db86d27556b Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Mon, 19 Jun 2023 01:13:31 -0500
Subject: [PATCH] Added code to check if the user is within the radius for the
 GLink

---
 checkloc.php | 60 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/checkloc.php b/checkloc.php
index 440259f..9ab84c1 100644
--- a/checkloc.php
+++ b/checkloc.php
@@ -1,9 +1,63 @@
 <?php
-	$latitude = $_GET["latitude"];
-	$longitude = $_GET["longitude"];
+
+	// FUNCTION TO CALCULATE HAVERSINE DISTANCE GIVEN COORDINATES OF
+	// TWO POINTS, AND RADIUS (IN KM)
+	function haversine_distance($lat1, $long1, $lat2, $long2, $radius) {
+		$term_1 = $lat2 - $lat1;
+		$term_1 = $term_1 / 2;
+		$term_1 = sin($term_1);
+		$term_1 = pow($term_1, 2);
+
+		$term_2 = $long2 - $long1;
+		$term_2 = $term_2 / 2;
+		$term_2 = sin($term_2);
+		$term_2 = pow($term_2, 2);
+		$term_2 = $term_2 * cos($lat1);
+		$term_2 = $term_2 * cos($lat2);
+
+		$distance = $term_1 + $term_2;
+		$distance = sqrt($distance);
+		$distance = asin($distance);
+		$distance = $distance * 2;
+		$distance = $distance * $radius;
+
+		return $distance;
+	}
+
+
+	function km_to_miles($distance) {
+		return $distance * 0.62137119;
+	}
+
+
+	$user_lat = $_GET["latitude"];
+	$user_lat = $user_lat * (M_PI / 180);
+	$user_long = $_GET["longitude"];
+	$user_long = $user_long * (M_PI / 180);
 	$glink = $_GET["glink"];
 
-	printf("Lat is %s, Long is %s, and glink is %s",$latitude,$longitude,$glink);
+	$cluster = Cassandra::cluster()->withPersistentSessions(true)->build();
+	$keyspace = 'glink';
+	$session = $cluster->connect($keyspace);
+	$statement = $session->prepare('SELECT latitude,longitude,radius,url FROM data WHERE shortlink=? ALLOW FILTERING;');
+	$result = $session->execute($statement,array('arguments' => array($glink)));
+
+	$link_lat = floatval($result[0]['latitude']);
+	$link_lat = $link_lat * (M_PI / 180);
+	$link_long = floatval($result[0]['longitude']);
+	$link_long = $link_long * (M_PI / 180);
+	$target_radius = intval($result[0]['radius']);
+
+	$url = $result[0]['url'];
+
+	$distance = haversine_distance($link_lat, $link_long, $user_lat, $user_long, 6371.009);
+	$distance = km_to_miles($distance);
+
+	if ($distance <= $target_radius) {
+		printf("%s",$url);
+	} else {
+		printf("B");
+	}
 
 	// Check the database to see if user is allowed to access the URL. If they are, respond 'Yes' (for the time being), if they are not, respond 'No' (for the time being).