From 08a5050b7c327f4833ea1a64f9c6b027ed6211a1 Mon Sep 17 00:00:00 2001
From: tuffnerdstuff <tuffnerdstuff@gmail.com>
Date: Tue, 30 Mar 2021 00:01:28 +0200
Subject: [PATCH] Implemented incremental fetch

---
 backend-php/api/fetch.php   |  6 ++++--
 backend-php/include/inc.php | 20 +++++++++++++++++---
 frontend/main.js            | 18 +++++++++++++++++-
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/backend-php/api/fetch.php b/backend-php/api/fetch.php
index d4e7c2f..166f3e6 100644
--- a/backend-php/api/fetch.php
+++ b/backend-php/api/fetch.php
@@ -20,6 +20,8 @@ if (!$share->exists()) {
 } else {
     header("Content-Type: text/json");
 
+    $sinceTime=$_GET["since"] ?? null;
+
     // Solo and group shares have different internal structures. Figure out the
     // correct type so that it can be output.
     switch ($share->getType()) {
@@ -34,7 +36,7 @@ if (!$share->exists()) {
                 "expire" => $share->getExpirationTime(),
                 "serverTime" => microtime(true),
                 "interval" => $session->getInterval(),
-                "points" => $session->getPoints(),
+                "points" => $session->getPoints($sinceTime),
                 "encrypted" => $session->isEncrypted(),
                 "salt" => $session->getEncryptionSalt()
             ));
@@ -46,7 +48,7 @@ if (!$share->exists()) {
                 "expire" => $share->getExpirationTime(),
                 "serverTime" => microtime(true),
                 "interval" => $share->getAutoInterval(),
-                "points" => $share->getAllPoints()
+                "points" => $share->getAllPoints($sinceTime)
             ));
             break;
     }
diff --git a/backend-php/include/inc.php b/backend-php/include/inc.php
index 366a7c2..64b6d16 100644
--- a/backend-php/include/inc.php
+++ b/backend-php/include/inc.php
@@ -565,12 +565,12 @@ class GroupShare extends Share {
     }
 
     // Returns a map of nicknames and the users' corresponding coordinates.
-    public function getAllPoints() {
+    public function getAllPoints($sinceTime) {
         $points = array();
         $hosts = $this->getHosts();
         foreach ($hosts as $nick => $host) {
             if ($host->exists()) {
-                $points[$nick] = $host->getPoints();
+                $points[$nick] = $host->getPoints($sinceTime);
             }
         }
         return $points;
@@ -758,8 +758,22 @@ class Client {
     }
 
     // Returns a list of all point arrays for this session.
-    public function getPoints() {
+    public function getPoints($sinceTime) {
+        if (is_null($sinceTime)) {
+            // return all memcached points
         return $this->sessionData["points"];
+        } else {
+            $newPoints = [];
+            // FIXME: use map instead of indices
+            $timeIndex = $this->isEncrypted() ? 3 : 2;
+            // only return points which are more recent than $oldestPointTime
+            foreach ($this->sessionData["points"] as $point) {
+                if (floatval($point[$timeIndex]) > $sinceTime) {
+                    array_push($newPoints, $point);
+                }
+            }
+            return $newPoints;
+        }
     }
 
     // Generates a random session ID for new sessions.
diff --git a/frontend/main.js b/frontend/main.js
index 3bbda17..14581d2 100644
--- a/frontend/main.js
+++ b/frontend/main.js
@@ -437,7 +437,8 @@ function setNewInterval(expire, interval, serverTime) {
             showMessage(LANG["dialog_expired_head"], LANG["dialog_expired_body"]);
         }
 
-        getJSON("./api/fetch.php?id=" + id, function(data) {
+        // Start incremental fetch
+        getJSON("./api/fetch.php?id=" + id + "&since=" + getOldestPointTime(), function(data) {
             // Recreate the interval timers if the interval or expiration
             // change.
             if (data.expire != expire || data.interval != interval) {
@@ -456,6 +457,21 @@ function setNewInterval(expire, interval, serverTime) {
     }, interval * 1000);
 }
 
+// Scans across all most recent points and returns the time of the oldest one
+function getOldestPointTime() {
+    var oldestTime = Number.MAX_VALUE;
+    var foundTime = false;
+    for (var share in shares) {
+        var points = shares[share].points
+        if (points && points.length > 0 ) {
+            var mostRecentTime = points[ points.length-1 ].time
+            oldestTime = mostRecentTime < oldestTime ? mostRecentTime : oldestTime;
+            foundTime = true;
+        }
+    }
+    return foundTime ? oldestTime : 0;
+}
+
 var noGPS = document.getElementById("searching");
 
 // Whether or not an initial location has been received.