Add json encode transformer

docs/transformers.md

@@ -32,3 +32,29 @@ $options = [
 
 $job->transform('trim', $options);
 ```
+
+## Json Encode
+### Syntax
+```php
+$job->transform('JsonEncode', $options);
+```
+### Options
+| Name | Type   | Default | Description |
+| ---- | ------ |-------- | ----------- |
+| columns | array | null | Columns that will be transformed. |
+| options | int | 0 | Bitmask consisting of JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS, JSON_NUMERIC_CHECK, JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, JSON_FORCE_OBJECT, JSON_PRESERVE_ZERO_FRACTION, JSON_UNESCAPED_UNICODE, JSON_PARTIAL_OUTPUT_ON_ERROR. The behaviour of these constants is described on the [JSON constants](http://php.net/manual/en/json.constants.php) page.  |
+| depth | int | 512 | The maximum depth. Must be greater than zero. |
+
+### Examples
+Convert all columns to JSON:
+```php
+$job->transform('JsonEncode');
+```
+Convert specific columns to JSON:
+```php
+$options = [
+    'columns' => ['data'],
+];
+
+$job->transform('JsonEncode', $options);
+```

src/Transformers/JsonEncode.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Marquine\Etl\Transformers;
+
+class JsonEncode implements TransformerInterface
+{
+    /**
+     * Transformer columns.
+     *
+     * @var array
+     */
+     public $columns;
+
+    /**
+     * Options.
+     *
+     * @var int
+     */
+    public $options = 0;
+
+    /**
+     * Maximum depth.
+     *
+     * @var string
+     */
+    public $depth = 512;
+
+    /**
+     * Execute a transformation.
+     *
+     * @param array $items
+     * @return array
+     */
+    public function transform($items)
+    {
+        return array_map(function($row) {
+            if ($this->columns) {
+                foreach ($this->columns as $column) {
+                    $row[$column] = json_encode($row[$column], $this->options, $this->depth);
+                }
+            } else {
+                foreach ($row as $column => $value) {
+                    $row[$column] = json_encode($value, $this->options, $this->depth);
+                }
+            }
+
+            return $row;
+        }, $items);
+    }
+}

tests/Transformers/JsonEncodeTest.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace Tests\Transformers;
+
+use Tests\TestCase;
+use Marquine\Etl\Transformers\JsonEncode;
+
+class JsonEncodeTest extends TestCase
+{
+    /** @test */
+    function convert_all_columns_to_json()
+    {
+        $items = [
+            ['id' => '1', 'data' => ['name' => 'John Doe', 'email' => 'johndoe@email.com']],
+            ['id' => '2', 'data' => ['name' => 'Jane Doe', 'email' => 'janedoe@email.com']],
+        ];
+
+        $transformer = new JsonEncode;
+
+        $results = $transformer->transform($items);
+
+        $expected = [
+            ['id' => '"1"', 'data' => '{"name":"John Doe","email":"johndoe@email.com"}'],
+            ['id' => '"2"', 'data' => '{"name":"Jane Doe","email":"janedoe@email.com"}'],
+        ];
+
+        $this->assertEquals($expected, $results);
+    }
+
+    /** @test */
+    function convert_specific_columns_to_json()
+    {
+        $items = [
+            ['id' => '1', 'data' => ['name' => 'John Doe', 'email' => 'johndoe@email.com']],
+            ['id' => '2', 'data' => ['name' => 'Jane Doe', 'email' => 'janedoe@email.com']],
+        ];
+
+        $transformer = new JsonEncode;
+
+        $transformer->columns = ['data'];
+
+        $results = $transformer->transform($items);
+
+        $expected = [
+            ['id' => '1', 'data' => '{"name":"John Doe","email":"johndoe@email.com"}'],
+            ['id' => '2', 'data' => '{"name":"Jane Doe","email":"janedoe@email.com"}'],
+        ];
+
+        $this->assertEquals($expected, $results);
+    }
+}