Add Map expression

Signed-off-by: davidarendsen <davidarendsen@hey.com>

tests/Expression/KeyFilterTest.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Expression;
+
+use Exception;
+use Arendsen\FluxQueryBuilder\Expression\KeyFilter;
+use PHPUnit\Framework\TestCase;
+
+final class KeyFilterExpressionTest extends TestCase
+{
+    public function testSimpleKeyvalue()
+    {
+        $keyFilter = KeyFilter::setEqualTo('_measurement', 'test_measurement')
+            ->andEqualTo('_field', 'user')
+            ->or('count', '>=', '1')
+            ->and('user', KeyFilter::EQUAL_TO, 'my_username')
+            ->orNotEqualTo('test', 'world');
+
+        $query = 'r._measurement == "test_measurement" and r._field == "user" or ' .
+            'r.count >= "1" and r.user == "my_username" or r.test != "world"';
+
+        $this->assertEquals($keyFilter->__toString(), $query);
+    }
+
+    public function testInvalidOperator()
+    {
+        $this->expectException(Exception::class);
+
+        KeyFilter::set('_measurement', '9dkda9e', 'test_measurement')
+            ->andEqualTo('_field', 'user')
+            ->or('_field', '==', 'field2')
+            ->andEqualTo('user', 'my_username');
+    }
+}