Implemented /metrics endpoint and reimplemented /stats

closes #418 (/metrics endpoint)

Usage:
```yaml
scrape_configs:
  - job_name: 'engelsystem'
    static_configs:
    - targets: ['engelsystem.example.com:80']
```

3 files changed, 308 insertions, 0 deletions

diff --git a/tests/Unit/Controllers/Metrics/ControllerTest.php b/tests/Unit/Controllers/Metrics/ControllerTest.php
new file mode 100644
index 00000000..013a3352
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/ControllerTest.php
@@ -0,0 +1,165 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Config\Config;
+use Engelsystem\Controllers\Metrics\Controller;
+use Engelsystem\Controllers\Metrics\MetricsEngine;
+use Engelsystem\Controllers\Metrics\Stats;
+use Engelsystem\Http\Exceptions\HttpForbidden;
+use Engelsystem\Http\Request;
+use Engelsystem\Http\Response;
+use Engelsystem\Test\Unit\TestCase;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\HttpFoundation\ServerBag;
+
+class ControllerTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::__construct
+     * @covers \Engelsystem\Controllers\Metrics\Controller::metrics
+     */
+    public function testMetrics()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $request->server = new ServerBag();
+        $request->server->set('REQUEST_TIME_FLOAT', 0.0123456789);
+
+        $engine->expects($this->once())
+            ->method('get')
+            ->willReturnCallback(function ($path, $data) use ($response) {
+                $this->assertEquals('/metrics', $path);
+                $this->assertArrayHasKey('users', $data);
+                $this->assertArrayHasKey('users_working', $data);
+                $this->assertArrayHasKey('work_seconds', $data);
+                $this->assertArrayHasKey('registration_enabled', $data);
+                $this->assertArrayHasKey('scrape_duration_seconds', $data);
+
+                return 'metrics return';
+            });
+
+        $response->expects($this->once())
+            ->method('withHeader')
+            ->with('Content-Type', 'text/plain; version=0.0.4')
+            ->willReturn($response);
+        $response->expects($this->once())
+            ->method('withContent')
+            ->with('metrics return')
+            ->willReturn($response);
+
+        $stats->expects($this->exactly(2))
+            ->method('arrivedUsers')
+            ->withConsecutive([false], [true])
+            ->willReturnOnConsecutiveCalls(7, 43);
+        $stats->expects($this->exactly(2))
+            ->method('currentlyWorkingUsers')
+            ->withConsecutive([false], [true])
+            ->willReturnOnConsecutiveCalls(10, 1);
+        $stats->expects($this->exactly(3))
+            ->method('workSeconds')
+            ->withConsecutive([true, false], [false, false], [null, true])
+            ->willReturnOnConsecutiveCalls(60 * 37, 60 * 251, 60 * 3);
+        $this->setExpects($stats, 'newUsers', null, 9);
+
+        $config->set('registration_enabled', 1);
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+        $controller->metrics();
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::stats
+     * @covers \Engelsystem\Controllers\Metrics\Controller::checkAuth
+     */
+    public function testStats()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $response->expects($this->once())
+            ->method('withHeader')
+            ->with('Content-Type', 'application/json')
+            ->willReturn($response);
+        $response->expects($this->once())
+            ->method('withContent')
+            ->with(json_encode([
+                'user_count'         => 13,
+                'arrived_user_count' => 10,
+                'done_work_hours'    => 99,
+                'users_in_action'    => 5
+            ]))
+            ->willReturn($response);
+
+        $request->expects($this->once())
+            ->method('get')
+            ->with('api_key')
+            ->willReturn('ApiKey987');
+
+        $config->set('api_key', 'ApiKey987');
+
+        $stats->expects($this->once())
+            ->method('workSeconds')
+            ->with(true)
+            ->willReturn(60 * 60 * 99.47);
+        $this->setExpects($stats, 'newUsers', null, 3);
+        $this->setExpects($stats, 'arrivedUsers', null, 10, $this->exactly(2));
+        $this->setExpects($stats, 'currentlyWorkingUsers', null, 5);
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+        $controller->stats();
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::checkAuth
+     */
+    public function testCheckAuth()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $request->expects($this->once())
+            ->method('get')
+            ->with('api_key')
+            ->willReturn('LoremIpsum!');
+
+        $config->set('api_key', 'fooBar!');
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+
+        $this->expectException(HttpForbidden::class);
+        $this->expectExceptionMessage(json_encode(['error' => 'The api_key is invalid']));
+        $controller->stats();
+    }
+
+    /**
+     * @return array
+     */
+    protected function getMocks(): array
+    {
+        /** @var Response|MockObject $response */
+        $response = $this->createMock(Response::class);
+        /** @var Request|MockObject $request */
+        $request = $this->createMock(Request::class);
+        /** @var MetricsEngine|MockObject $engine */
+        $engine = $this->createMock(MetricsEngine::class);
+        /** @var Stats|MockObject $stats */
+        $stats = $this->createMock(Stats::class);
+        $config = new Config();
+
+        return array($response, $request, $engine, $stats, $config);
+    }
+}
diff --git a/tests/Unit/Controllers/Metrics/MetricsEngineTest.php b/tests/Unit/Controllers/Metrics/MetricsEngineTest.php
new file mode 100644
index 00000000..b810b10a
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/MetricsEngineTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Controllers\Metrics\MetricsEngine;
+use Engelsystem\Test\Unit\TestCase;
+
+class MetricsEngineTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::get
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::formatData
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::renderLabels
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::renderValue
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::formatValue
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::escape
+     */
+    public function testGet()
+    {
+        $engine = new MetricsEngine();
+
+        $this->assertEquals('', $engine->get('/metrics'));
+
+        $this->assertEquals('engelsystem_users 13', $engine->get('/metrics', ['users' => 13]));
+
+        $this->assertEquals('engelsystem_bool_val 0', $engine->get('/metrics', ['bool_val' => false]));
+
+        $this->assertEquals('# Lorem \n Ipsum', $engine->get('/metrics', ["Lorem \n Ipsum"]));
+
+        $this->assertEquals(
+            'engelsystem_foo{lorem="ip\\\\sum"} \\"lorem\\n\\\\ipsum\\"',
+            $engine->get('/metrics', [
+                'foo' => ['labels' => ['lorem' => 'ip\\sum'], 'value' => "\"lorem\n\\ipsum\""]
+            ])
+        );
+
+        $this->assertEquals(
+            'engelsystem_foo_count{bar="14"} 42',
+            $engine->get('/metrics', ['foo_count' => ['labels' => ['bar' => 14], 'value' => 42],])
+        );
+
+        $this->assertEquals(
+            'engelsystem_lorem{test="123"} NaN' . "\n" . 'engelsystem_lorem{test="456"} 999.99',
+            $engine->get('/metrics', [
+                'lorem' => [
+                    ['labels' => ['test' => 123], 'value' => 'NaN'],
+                    ['labels' => ['test' => 456], 'value' => 999.99],
+                ],
+            ])
+        );
+
+        $this->assertEquals(
+            "# HELP engelsystem_test Some help\\n  text\n# TYPE engelsystem_test counter\nengelsystem_test 99",
+            $engine->get('/metrics', ['test' => ['help' => "Some help\n  text", 'type' => 'counter', 'value' => 99]])
+        );
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::canRender
+     */
+    public function testCanRender()
+    {
+        $engine = new MetricsEngine();
+
+        $this->assertFalse($engine->canRender('/'));
+        $this->assertFalse($engine->canRender('/metrics.foo'));
+        $this->assertTrue($engine->canRender('/metrics'));
+    }
+}
diff --git a/tests/Unit/Controllers/Metrics/StatsTest.php b/tests/Unit/Controllers/Metrics/StatsTest.php
new file mode 100644
index 00000000..1618b99b
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/StatsTest.php
@@ -0,0 +1,74 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Controllers\Metrics\Stats;
+use Engelsystem\Models\User\State;
+use Engelsystem\Models\User\User;
+use Engelsystem\Test\Unit\HasDatabase;
+use Engelsystem\Test\Unit\TestCase;
+use Illuminate\Support\Str;
+
+class StatsTest extends TestCase
+{
+    use HasDatabase;
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Stats::newUsers
+     * @covers \Engelsystem\Controllers\Metrics\Stats::getQuery
+     * @covers \Engelsystem\Controllers\Metrics\Stats::__construct
+     */
+    public function testNewUsers()
+    {
+        $this->initDatabase();
+        $this->addUsers();
+
+        $stats = new Stats($this->database);
+        $this->assertEquals(2, $stats->newUsers());
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Stats::arrivedUsers
+     */
+    public function testArrivedUsers()
+    {
+        $this->initDatabase();
+        $this->addUsers();
+
+        $stats = new Stats($this->database);
+        $this->assertEquals(3, $stats->arrivedUsers());
+    }
+
+    /**
+     * Add some example users
+     */
+    protected function addUsers()
+    {
+        $this->addUser();
+        $this->addUser();
+        $this->addUser(['arrived' => 1]);
+        $this->addUser(['arrived' => 1, 'active' => 1]);
+        $this->addUser(['arrived' => 1, 'active' => 1]);
+    }
+
+    /**
+     * @param array $state
+     */
+    protected function addUser(array $state = [])
+    {
+        $name = 'user_' . Str::random(5);
+
+        $user = new User([
+            'name'     => $name,
+            'password' => '',
+            'email'    => $name . '@engel.example.com',
+            'api_key'  => '',
+        ]);
+        $user->save();
+
+        $state = new State($state);
+        $state->user()
+            ->associate($user)
+            ->save();
+    }
+}