Added ability to adjust stored IP address precision

Included tests to cover.

For #3560

app/Actions/ActivityLogger.php

@@ -40,12 +40,10 @@ class ActivityLogger
      */
     protected function newActivityForUser(string $type): Activity
     {
-        $ip = request()->ip() ?? '';
-
         return (new Activity())->forceFill([
             'type'     => strtolower($type),
             'user_id'  => user()->id,
-            'ip'       => config('app.env') === 'demo' ? '127.0.0.1' : $ip,
+            'ip'       => IpFormatter::fromCurrentRequest()->format(),
         ]);
     }
 

app/Actions/IpFormatter.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace BookStack\Actions;
+
+class IpFormatter
+{
+    protected string $ip;
+    protected int $precision;
+
+    public function __construct(string $ip, int $precision)
+    {
+        $this->ip = trim($ip);
+        $this->precision = max(0, min($precision, 4));
+    }
+
+    public function format(): string
+    {
+        if (empty($this->ip) || $this->precision === 4) {
+            return $this->ip;
+        }
+
+        return $this->isIpv6() ? $this->maskIpv6() : $this->maskIpv4();
+    }
+
+    protected function maskIpv4(): string
+    {
+        $exploded = $this->explodeAndExpandIp('.', 4);
+        $maskGroupCount = min( 4 - $this->precision, count($exploded));
+
+        for ($i = 0; $i < $maskGroupCount; $i++) {
+            $exploded[3 - $i] = 'x';
+        }
+
+        return implode('.', $exploded);
+    }
+
+    protected function maskIpv6(): string
+    {
+        $exploded = $this->explodeAndExpandIp(':', 8);
+        $maskGroupCount = min(8 - ($this->precision * 2), count($exploded));
+
+        for ($i = 0; $i < $maskGroupCount; $i++) {
+            $exploded[7 - $i] = 'x';
+        }
+
+        return implode(':', $exploded);
+    }
+
+    protected function isIpv6(): bool
+    {
+        return strpos($this->ip, ':') !== false;
+    }
+
+    protected function explodeAndExpandIp(string $separator, int $targetLength): array
+    {
+        $exploded = explode($separator, $this->ip);
+
+        while (count($exploded) < $targetLength) {
+            $emptyIndex = array_search('', $exploded) ?: count($exploded) - 1;
+            array_splice($exploded, $emptyIndex, 0, '0');
+        }
+
+        $emptyIndex = array_search('', $exploded);
+        if ($emptyIndex !== false) {
+            $exploded[$emptyIndex] = '0';
+        }
+
+        return $exploded;
+    }
+
+    public static function fromCurrentRequest(): self
+    {
+        $ip = request()->ip() ?? '';
+
+        if (config('app.env') === 'demo') {
+            $ip = '127.0.0.1';
+        }
+
+        return new self($ip, config('app.ip_address_precision'));
+    }
+}