Identification middleware & tests

src/Middleware/InitializeTenancyBySubdomain.php

@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Stancl\Tenancy\Middleware;
+
+use Closure;
+use Illuminate\Http\Response;
+use Stancl\Tenancy\Exceptions\NotASubdomainException;
+
+class InitializeTenancyBySubdomain extends InitializeTenancyByDomain
+{
+    /** @var callable|null */
+    public static $onInvalidSubdomain;
+
+    /**
+     * The index of the subdomain fragment in the hostname
+     * split by `.`. 0 for first fragment, 1 if you prefix
+     * your subdomain fragments with `www`.
+     *
+     * @var int
+     */
+    public static $subdomainIndex = 0;
+
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @return mixed
+     */
+    public function handle($request, Closure $next)
+    {
+        $subdomain = $this->makeSubdomain($request->getHost());
+
+        // If a non-string, like a Response instance was returned
+        // from makeSubdomain() - due to NotASubDomainException
+        // being thrown, we abort by returning the value now.
+        if (! is_string($subdomain)) {
+            return $subdomain;
+        }
+
+        return $this->initializeTenancy(
+            $request, $next, $subdomain
+        );
+    }
+
+    /** @return string|Response|mixed */
+    protected function makeSubdomain(string $hostname)
+    {
+        $parts = explode('.', $hostname);
+
+        // If we're on localhost or an IP address, then we're not visiting a subdomain.
+        if (in_array(count($parts), [1, 4])) {
+            $handle = static::$onInvalidSubdomain ?? function ($e) {
+                throw $e;
+            };
+
+            return $handle(new NotASubdomainException($hostname));
+        }
+
+        // todo should we verify that the subdomain belongs to one of our central domains?
+        // if yes, then write a test for it.
+
+        return $parts[static::$subdomainIndex];
+    }
+}