# Flat File Listings

## Usage

To convert a `POST_FLAT_FILE_LISTINGS_DATA` feed to the newer `JSON_LISTINGS_FEED` format:

```php
use SellingPartnerApi\FeedTransformer\Transformer;
use SellingPartnerApi\FeedTransformer\FeedTypes\Listings;

$feedFile = 'path/to/your/feed.tab';
$json = Transformer::fromFile(
    Listings::$feedType,
    $feedFile,
    'ATVPDKIKX0DER'
);

$jsonFeedPath = 'path/to/new/feed.json';
file_put_contents($jsonFeedPath, json_encode($json));
```

***The first time using this feed transformer with a particular product type, we strongly recommend running the converted data through*** [***our validators***](https://docs.highsidelabs.co/feed-transformer/validation) ***before putting it into production.*** That way, you can ensure you know if certain elements of your feed aren't able to be mapped to the new format.

### Parameters <a href="#parameters" id="parameters"></a>

### `merchantId`

{% hint style="danger" %}
**Required**
{% endhint %}

There is documentation on how to retrieve your `merchantId`  in the [#common-required-parameters](https://docs.highsidelabs.co/feed-transformer/feed-types/tab/..#common-required-parameters "mention")section of the [](https://docs.highsidelabs.co/feed-transformer/feed-types/tab "mention") page.

### `shippingGroupMap` <a href="#shippinggroupmap" id="shippinggroupmap"></a>

{% hint style="warning" %}
Required if the `merchant_shipping_group_name` column is present in the feed file being converted.
{% endhint %}

This is a mapping of your account's shipping group names to their internal Amazon identifiers. Instructions on how to generate this mapping are here: [shippingGroupMap](https://docs.highsidelabs.co/feed-transformer/feed-types/tab/invloader#shippinggroupmap)

### `onUnsupportedField` <a href="#onunsupportedfield" id="onunsupportedfield"></a>

{% hint style="info" %}
Optional. Default `fail`.
{% endhint %}

This option controls what happens when the feed transformer encounters an XML tag that has no direct equivalent in the new JSON format. There are two accepted values:

* `ignore`: Silently move past un-mappable XML tags.
* `callback`: Pass un-mappable XML fields (by [xpath](https://developer.mozilla.org/en-US/docs/Web/XPath)) to a user-defined callback. See [callback](https://docs.highsidelabs.co/feed-transformer/feed-types/xml/product#callback)
* `fail`: The first time an un-mappable XML tag is encountered, throw an `InvalidFeedException`. This is the default.

### `callback` <a href="#callback" id="callback"></a>

{% hint style="info" %}
Conditionally required if `onSupportedField` is set to `callback` .
{% endhint %}

This option is the callback to be called if `onSupportedField` is set to `callback` and an un-mappable XML field is encountered while processing the input data. The callback's signature is `fn (string): void`. For example:

```php
$options = [
    'onUnsupportedField' => 'callback',
    'callback' => function ($field) {
        echo "Unsupported field: $field";
        // -> Unsupported field: unsupported_field_name
    },
    // ...
];
```