# Validation and Errors Handling

## VGSTextInput Input Validation

VGS Collect SDK provides built-in validation for data intput. Validation is based on defined validation rules set for each specific `VGSTextInput`. These rule sets are defined by default for each VGSTextInput based on it's `type` value, but you still have possibility to customize them.

`VGSTextInput` execute validation after each it's input editing event. You can check validation results through VGSTextInput's state callback: `.onStateChange()`.

### Default Validation

Default validation for specific input `type`:

| **VGSInputType**    | **Validation Details**                                                                                                                                                                                                                                                             |
| ------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **.text**           | Any input will be valid if no other validation rules will be applied                                                                                                                                                                                                               |
| **.card**           | Card number validation with checkSum algorithm(Luhn algorithm), available card lengths for defined card types                                                                                                                                                                      |
| **.expDate**        | Any date starting from current month. By default valid expiration date should be in short year format - `mm/yy`                                                                                                                                                                    |
| **.cardHolderName** | Name, should be 2 or more symbols, valid characters shold match pattern: `[a-zA-Z0-9]`                                                                                                                                                                                             |
| **.cvc**            | Card cvc number, should be 3-4 digits. If in same `VGSCollect` instance there is associated `.cardNumer` field, **cvc** validation will be dynamic. It depends on input Card Brand type. For example: for **AMEX** valid cvc only with 4 digits, while for **Visa** 3 digits only. |
| **.ssn**            | US social security number, should be 9 digits, don't start with \[000,666,9] or contain sequences of the same digits. Ignores some SSNs used in advertising                                                                                                                        |

If you didn't find specific `type` for your use case, you can always configure `VGSTextInput` with `text` type. Then assign any specific rule set to the field and use other configuration attributes. Check more on our code examples below.

### Validation Rules

VGS Collect SDK provides pre-build validation rules that you can apply to `VGSTextInput` object through it's `type` configuration.

Here are some examples of the available rules:

| **VGSValidationRule** | **Description**                                                                                                                                                                               |
| --------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| PatternRule           | Validates input in scope of matching the regex `pattern`                                                                                                                                      |
| CardExpDateRule       | Validats input in scope of matching card expiration date format and time range. Supports `VGSCardExpDateFormat` date formats validation                                                       |
| PaymentCardRule       | Validates input in scope of matching supported card brands, available lengths and checkSum algorithms. Support optional validation of cards that are not defined in SDK - `CardBrand.unknown` |
| LuhnCheckRule         | Validates input in scope of matching Luhn algorithm                                                                                                                                           |
| LengthRule            | Validates input in scope of `min` & `max` lengths                                                                                                                                             |
| LengthMatchRule       | Validates input in scope of exact length                                                                                                                                                      |
| NotEmptyRule          | Validates input is not empty                                                                                                                                                                  |
| ABARoutingNumberRule  | Validate input against ABA (American Bankers Association) routing number requirements                                                                                                         |

### How to customize VGSTextInput Validation?

Check examples below on how to create your own validation rules or edit exiting rules that will validate input in `VGSTextInput`.

Set custom validation rules:

```javascript
import { NotEmptyRule, LengthRule, PatternRule } from '@vgs/collect-react-native';

<VGSTextInput
  //... other props
  validationRules={[
    new NotEmptyRule('This field is required'),
    new LengthRule(5, 10, 'Length must be between 5 and 10 characters'),
    new PatternRule('/^[a-zA-Z]+$/', 'Only letters are allowed'),
  ]}
/>
```

Use only Luhn validation for card number field:

```javascript
<VGSCardInput
  //... other props
  validationRules={[
    new LuhnCheckRule('Card not valid'),
  ]}
```

Ignore all default validations:

```javascript
<VGSCardInput
  //... other props
  validationRules={[]}
```

## Errors Handling

This guide covers error handling features which will help you to make your App more reliable and recover from errors produced by `VGSCollectSDK`.

### VGSError

An object the SDK uses to produce errors inside the SDK.

#### Declaration

```javascript
class VGSError extends Error
```

Some of `VGSError` provide detailes of error reason in `error.details` prop.

#### Error codes

List of Error codes produced by VGS Collect iOS SDK locally.

| **Code** | **Key**                        | **Description**                                        |
| -------- | ------------------------------ | ------------------------------------------------------ |
| 1001     | `InputDataIsNotValid`          | When input data is not valid, but required to be valid |
| 1101     | `InputFileNotFound`            | When can't find file on device                         |
| 1102     | `InputFileTypeIsNotSupported`  | When selected file type not supported                  |
| 1103     | `InputFileSizeExceedsTheLimit` | When file size is larger then allowed limit            |
| 1150     | `SourceNotAvailable`           | When can't get access to file source                   |
| 1400     | `unexpectedResponseType`       | When response type is not supported                    |
| 1470     | `InvalidVaultConfiguration`    | When VGSCollect init parameters not valid              |
| 1480     | `invalidConfigurationURL`      | When VGS configuration URL is not valid                |
| 1300     | `invalidAccessToken`           | When access token is nil or empty                      |

#### Code example

```javascript
// Add import
import { VGSError, VGSErrorCode } from '@vgs/collect-react-native';
// Other code here...

const handleSubmit = async () => {
    try {
      const { status, response } = await collector.submit('/post', 'POST')
    } catch (error) {
      if (error instanceof VGSError) {
        switch (error.code) {
          case VGSErrorCode.InputDataIsNotValid:
            for (const fieldName in error.details) {
              console.error(
                `Not valid fieldName: ${fieldName}: ${error.details[fieldName].join(', ')}`
              );
            }
            break;
          default:
            console.error('VGSError:', error.code, error.message);
        }
      } else {
        console.error('Network or unexpected error:', error);
      }
    }
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.verygoodsecurity.com/vault/developer-tools/vgs-collect/react-native-sdk/error-handling.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.