Introduce MediaWikiHostResolver (#989)

* Introduce MediaWikiHostResolver

Co-authored-by: Ollie <oliver.hyde@wikimedia.de>
Bug: T409085
Bug: T408624

* run pint

* revert Wiki.php changes

* throw if DB version isn't known

* Update app/Services/MediaWikiHostResolver.php

Co-authored-by: Dat WMDE <dat.nguyen@wikimedia.de>

* Update app/Services/MediaWikiHostResolver.php

Co-authored-by: Dat WMDE <dat.nguyen@wikimedia.de>

* use relations and accessors

* fix indent

* Update app/Services/MediaWikiHostResolver.php

Co-authored-by: Dat WMDE <dat.nguyen@wikimedia.de>

* Update app/Services/MediaWikiHostResolver.php

Co-authored-by: Dat WMDE <dat.nguyen@wikimedia.de>

* move exception above class

---------

Co-authored-by: Ollie <oliver.hyde@wikimedia.de>
Co-authored-by: Dat WMDE <dat.nguyen@wikimedia.de>

Author: 3 people

app/Services/MediaWikiHostResolver.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace App\Services;
+
+use App\Wiki;
+use Exception;
+
+/**
+ * Exception thrown when a database version is not recognized in MediaWikiHostResolver.
+ */
+class UnknownDBVersionException extends Exception {}
+
+class MediaWikiHostResolver {
+    // TODO: Move this mapping to a config file so that MW updates do not require code changes here.
+    /** @var array<string, string> Map of DB version strings to MediaWiki backend version strings */
+    private const DB_VERSION_TO_MW_VERSION = [
+        'mw1.39-wbs1' => '139-app',
+        'mw1.43-wbs1' => '143-app',
+    ];
+
+    // This service could have other methods in future, e.g. getBackendHostForWiki()
+    // public function getBackendHostForWiki(Wiki $wiki): string {
+    //     return $this->getBackendHostForDomain($wiki->domain);
+    // }
+
+    public function getBackendHostForDomain(string $domain): string {
+        // TODO: Move 'backend.default.svc.cluster.local' to an env variable (e.g. PLATFORM_MW_BACKEND_HOST_SUFFIX) for flexibility.
+        return sprintf('mediawiki-%s-backend.default.svc.cluster.local', $this->getMwVersionForDomain($domain));
+    }
+
+    public function getMwVersionForDomain(string $domain): string {
+        $dbVersion = Wiki::where('domain', $domain)
+            ->first()
+            ->wikiDb
+            ->version;
+
+        if (array_key_exists($dbVersion, self::DB_VERSION_TO_MW_VERSION)) {
+            return self::DB_VERSION_TO_MW_VERSION[$dbVersion];
+        }
+        throw new UnknownDBVersionException("Unknown DB version '{$dbVersion}' for domain '{$domain}'.");
+    }
+}

tests/Services/MediaWikiHostResolverTest.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Tests;
+
+use App\Services\MediaWikiHostResolver;
+use App\Services\UnknownDBVersionException;
+use App\Wiki;
+use App\WikiDb;
+use Faker\Factory;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+class MediaWikiHostResolverTest extends TestCase {
+    use RefreshDatabase;
+
+    public function testResolverRoutesToCorrectHost(): void {
+        $domain = (new Factory)->create()->unique()->text(30);
+        $this->createWiki($domain, 'mw1.39-wbs1');
+        $resolver = new MediaWikiHostResolver;
+        $this->assertEquals(
+            'mediawiki-139-app-backend.default.svc.cluster.local',
+            $resolver->getBackendHostForDomain($domain)
+        );
+    }
+
+    private function createWiki(string $domain, string $version) {
+        $wiki = Wiki::factory()->create(['domain' => $domain]);
+        WikiDb::create([
+            'name' => $domain,
+            'user' => 'someUser',
+            'password' => 'somePassword',
+            'version' => $version,
+            'prefix' => 'somePrefix',
+            'wiki_id' => $wiki->id,
+        ]);
+    }
+
+    public function testResolverThrowsIfUnableToFindHostInMap(): void {
+        $domain = (new Factory)->create()->unique()->text(30);
+        $this->createWiki($domain, 'mw1.39-unmapped');
+        $resolver = new MediaWikiHostResolver;
+        $this->assertThrows(
+            fn () => $resolver->getBackendHostForDomain($domain),
+            UnknownDBVersionException::class
+        );
+    }
+}