Add sum() Flux function + docs

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

docs/04-functions.md

@@ -16,6 +16,7 @@ or [fromBucket()](functions/fromBucket.md)
 * [addRangeStart()](functions/addRangeStart.md)
 or [addRangeInBetween()](functions/addRangeInBetween.md)
 * [addReduce()](functions/addReduce.md)
+* [addSum()](functions/addSum.md)
 
 Anything missing here? You can use this method to add anything to the query:
 * [addRawFunction()](functions/addRawFunction.md)

docs/functions/addSum.md

@@ -0,0 +1,39 @@
+# Flux Query Builder Docs
+
+## Functions » addSum()
+
+### Parameters:
+
+<table>
+  <tbody>
+    <tr>
+      <th>Name</th>
+      <th>Required</th>
+      <th>Data type</th>
+      <th>Description</th>
+    </tr>
+    <tr>
+      <td>column</td>
+      <td>Yes</td>
+      <td>string</td>
+      <td>Column to operate on. Default is "_value".</td>
+    </tr>
+  </tbody>
+</table>
+
+
+### Example
+
+```php
+->addSum('_value')
+```
+
+This will result in the following Flux function part:
+
+```
+|> sum(column: "_value")
+```
+
+### Extra resources
+
+* [Flux documentation](https://docs.influxdata.com/flux/v0.x/stdlib/universe/sum/)

src/Builder/Universe.php

@@ -12,6 +12,7 @@ use Arendsen\FluxQueryBuilder\Functions\Group;
 use Arendsen\FluxQueryBuilder\Functions\Limit;
 use Arendsen\FluxQueryBuilder\Functions\Mean;
 use Arendsen\FluxQueryBuilder\Functions\Window;
+use Arendsen\FluxQueryBuilder\Functions\Sum;
 
 trait Universe
 {
@@ -94,4 +95,12 @@ trait Universe
         );
         return $this;
     }
+
+    public function addSum(string $column): QueryBuilderInterface
+    {
+        $this->addToQuery(
+            new Sum($column)
+        );
+        return $this;
+    }
 }

src/Functions/Sum.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Arendsen\FluxQueryBuilder\Functions;
+
+class Sum extends Base
+{
+    /**
+     * @var string $column
+     */
+    private $column;
+
+    public function __construct(string $column)
+    {
+        $this->column = $column;
+    }
+
+    public function __toString()
+    {
+        return '|> sum(column: "' . (string)$this->column . '") ';
+    }
+}

tests/Functions/SumFunctionTest.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Functions;
+
+use Arendsen\FluxQueryBuilder\Functions\Sum;
+use PHPUnit\Framework\TestCase;
+
+final class SumFunctionTest extends TestCase
+{
+    public function testSimpleSum()
+    {
+        $expression = new Sum('_value');
+
+        $query = '|> sum(column: "_value") ';
+
+        $this->assertEquals($query, $expression->__toString());
+    }
+}

tests/QueryBuilderTest.php

@@ -188,4 +188,22 @@ final class QueryBuilderTest extends TestCase
 
         $this->assertEquals($expectedQuery, $queryBuilder->build());
     }
+
+    public function testQueryWithSum()
+    {
+        $queryBuilder = new QueryBuilder();
+        $queryBuilder->fromBucket('test_bucket')
+            ->addRangeStart(new DateTime('2022-08-12 17:31:00'))
+            ->fromMeasurement('test_measurement')
+            ->addKeyFilter(KeyFilter::setGreaterOrEqualTo('count', 1)->andGreaterOrEqualTo('count2', 2))
+            ->addSum('_value')
+            ->addFieldFilter(['username', 'ip']);
+
+        $expectedQuery = 'from(bucket: "test_bucket") |> range(start: time(v: 2022-08-12T17:31:00Z)) ' .
+            '|> filter(fn: (r) => r._measurement == "test_measurement") ' .
+            '|> filter(fn: (r) => r.count >= 1 and r.count2 >= 2) |> sum(column: "_value") ' .
+            '|> filter(fn: (r) => r._field == "username" or r._field == "ip") ';
+
+        $this->assertEquals($expectedQuery, $queryBuilder->build());
+    }
 }