Reset observed WiFi session when client disappears

public/api.php

@@ -1464,18 +1464,48 @@ function wifi_connected_time_missing(mixed $value): bool
     return $text === '' || $text === 'N/A' || $text === '-';
 }
 
+function wifi_valid_mac(string $mac): bool
+{
+    return preg_match('/^[0-9a-f]{2}(?::[0-9a-f]{2}){5}$/', strtolower($mac)) === 1;
+}
+
+function prune_observed_wifi_sessions(PDO $pdo, array $visibleMacs): void
+{
+    $visibleMacs = array_values(array_unique(array_filter(
+        array_map(static fn($mac) => strtolower((string)$mac), $visibleMacs),
+        static fn($mac) => wifi_valid_mac($mac)
+    )));
+
+    if ($visibleMacs === []) {
+        $pdo->exec("DELETE FROM wifi_observed_sessions WHERE band = '5G'");
+        return;
+    }
+
+    $placeholders = implode(',', array_fill(0, count($visibleMacs), '?'));
+    $stmt = $pdo->prepare("
+        DELETE FROM wifi_observed_sessions
+        WHERE band = '5G'
+          AND mac NOT IN ($placeholders)
+    ");
+    $stmt->execute($visibleMacs);
+}
+
 function observed_wifi_duration_seconds(array $clients): array
 {
     $targets = [];
+    $visible5gMacs = [];
 
     foreach ($clients as $client) {
         $band = (string)($client['band'] ?? '');
         $mac = strtolower((string)($client['mac'] ?? ''));
 
-        if ($band !== '5G'
-            || !wifi_connected_time_missing($client['connected_time'] ?? null)
-            || !preg_match('/^[0-9a-f]{2}(?::[0-9a-f]{2}){5}$/', $mac)
-        ) {
+        if ($band !== '5G' || !wifi_valid_mac($mac)) {
+            continue;
+        }
+
+        $visible5gMacs[] = $mac;
+
+        if (!wifi_connected_time_missing($client['connected_time'] ?? null)) {
             continue;
         }
 
@@ -1488,18 +1518,15 @@ function observed_wifi_duration_seconds(array $clients): array
         ];
     }
 
-    if ($targets === []) {
-        try {
-            db()->exec("DELETE FROM wifi_observed_sessions WHERE last_seen_at < DATE_SUB(NOW(3), INTERVAL 2 MINUTE)");
-        } catch (Throwable) {
-        }
-
-        return [];
-    }
-
     try {
         $pdo = db();
         $pdo->beginTransaction();
+        prune_observed_wifi_sessions($pdo, $visible5gMacs);
+
+        if ($targets === []) {
+            $pdo->commit();
+            return [];
+        }
 
         $upsert = $pdo->prepare("
             INSERT INTO wifi_observed_sessions
@@ -1524,8 +1551,6 @@ function observed_wifi_duration_seconds(array $clients): array
             ]);
         }
 
-        $pdo->exec("DELETE FROM wifi_observed_sessions WHERE last_seen_at < DATE_SUB(NOW(3), INTERVAL 2 MINUTE)");
-
         $placeholders = implode(',', array_fill(0, count($targets), '?'));
         $stmt = $pdo->prepare("
             SELECT