> For the complete documentation index, see [llms.txt](https://docs.caf.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.caf.io/caf-sdk/react-native/standalone-modules/cafsmartauth/expo-modules/native-module-android.md).

# Native Module Android

## How to Create a Native Module in Android

This detailed guide explains how to create a expo module for the Android platform within a Expo application. The process follows the step-by-step instructions from the [official documentation](https://docs.expo.dev/modules/native-module-tutorial/#android-native-module).

### 1. Open the Android Project in Android Studio

You can include this in your package.json under the scripts section:

```json
"scripts": {
    "open:android": "open -a \"Android Studio\" android"
},
```

This script ensures that the Expo module opens correctly in Android Studio.

### 2. Create the Native Module

Create a file named `CafSmartAuthBridgeModule.kt` in the directory `modules/caf-smart-auth-react-native/android/app/src/main/java/com/your-app-name/`. This file will contain the class that implements the native module.

#### Key Functions of the `CafSmartAuthBridgeModule` Class

* **`build`**: The `build` function is responsible for configuring and instantiating the `CafSmartAuth` object using the provided parameters. This function applies various settings, such as defining stages and facial authentication, to prepare the SDK for use.
* **`setupListener`**: Sets up a listener to monitor the status of verification operations, such as success, pending, error, cancellation, and others.
* **`requestPermission`**: Requests the necessary permissions, such as location permissions, for the proper functioning of the SDK.
* **`startSmartAuth`**: Exposed to JavaScript, this function starts the smart authentication process using the received parameters.
* **`requestLocationPermissions`**: Exposed to JavaScript, allows the application to request location permissions from the user.

#### Example Implementation of the `CafSmartAuthBridgeModule.kt` File

```kotlin
class CafSmartAuthBridgeModule : Module() {
    private val context
        get() = requireNotNull(appContext.reactContext)
    private val activity
        get() = requireNotNull(appContext.currentActivity)

    // Each module class must implement the definition function. The definition consists of components
    // that describes the module's functionality and behavior.
    // See https://docs.expo.dev/modules/module-api for more details about available components.
    override fun definition() = ModuleDefinition {
        // Sets the name of the module that JavaScript code will use to refer to the module. Takes a string as an argument.
        // Can be inferred from module's class name, but it's recommended to set it explicitly for clarity.
        // The module will be accessible from `requireNativeModule('CafSmartAuthBridgeModule')` in JavaScript.
        Name(CAF_SMART_AUTH_MODULE_NAME)

        // Defines event names that the module can send to JavaScript.
        Events(
            CAF_SMART_AUTH_SUCCESS_EVENT,
            CAF_SMART_AUTH_PENDING_EVENT,
            CAF_SMART_AUTH_ERROR_EVENT,
            CAF_SMART_AUTH_CANCEL_EVENT,
            CAF_SMART_AUTH_LOADING_EVENT,
            CAF_SMART_AUTH_LOADED_EVENT
        )

        // Defines a JavaScript synchronous function that runs the native code on the JavaScript thread.
        Function(CAF_SMART_AUTH_FUNCTION_START_SMART_AUTH) { mfaToken: String, faceAuthToken: String, personId: String, policyId: String, jsonString: String ->
            Handler(Looper.getMainLooper()).post {
                val smartAuth = build(
                    mfaToken = mfaToken,
                    faceAuthToken = faceAuthToken,
                    settings = jsonString
                )

                smartAuth.verifyPolicy(personId, policyId, setupListener())
            }
        }

        // Defines a JavaScript asynchronous function that runs the native code on the JavaScript thread.
        AsyncFunction(CAF_SMART_AUTH_FUNCTION_REQUEST_LOCATION_PERMISSIONS) {
            Handler(Looper.getMainLooper()).post {
                try {
                    requestPermission(
                        permission = Manifest.permission.ACCESS_FINE_LOCATION,
                        activity = activity
                    )
                    requestPermission(
                        permission = Manifest.permission.ACCESS_COARSE_LOCATION,
                        activity = activity
                    )
                } catch (e: Exception) {
                    throw IllegalStateException("$PERMISSION_ERROR_DESCRIPTION ${e.message}")
                }
            }
        }
    }

    private fun build(mfaToken: String, faceAuthToken: String, settings: String): CafSmartAuth {
        val smartAuthSettings = CafSmartAuthBridgeSettings(settings = settings)

        return CafSmartAuth.CafBuilder(mfaToken, context).apply {
            setSdkPlatform(CafSdkPlatform.REACT_NATIVE)
            smartAuthSettings.cafStage?.let { setStage(it) }
            smartAuthSettings.emailUrl?.let { setEmailUrl(it) }
            smartAuthSettings.phoneUrl?.let { setPhoneUrl(it) }
            setFaceAuthenticatorSettings(
                CafFaceAuthenticatorSettings(
                    faceAuthToken,
                    smartAuthSettings.faceAuthenticatorSettings?.loadingScreen,
                    smartAuthSettings.faceAuthenticatorSettings?.enableScreenCapture,
                    smartAuthSettings.faceAuthenticatorSettings?.filter
                )
            )
            setThemeConfigurator(
                CafThemeConfigurator(
                    lightTheme = smartAuthSettings.theme?.lightTheme ?: CafTheme(),
                    darkTheme = smartAuthSettings.theme?.darkTheme ?: CafTheme()
                )
            )
        }.build()
    }

    private fun setupListener() = object : CafVerifyPolicyListener {
        override fun onSuccess(
            isAuthorized: Boolean,
            attemptId: String?,
            attestation: String?
        ) {
            sendEvent(CAF_SMART_AUTH_SUCCESS_EVENT, mapOf(
                CAF_MAP_KEY_IS_AUTHORIZED to isAuthorized,
                CAF_MAP_KEY_ATTEMPT_ID to (attemptId ?: ""),
                CAF_MAP_KEY_ATTESTATION to (attestation ?: "")
            ))
        }

        override fun onPending(isAuthorized: Boolean, attestation: String?) {
            sendEvent(CAF_SMART_AUTH_PENDING_EVENT, mapOf(
                CAF_MAP_KEY_IS_AUTHORIZED to isAuthorized,
                CAF_MAP_KEY_ATTESTATION to (attestation ?: "")
            ))
        }

        override fun onError(failure: CafFailure, message: String?) {
            sendEvent(CAF_SMART_AUTH_ERROR_EVENT, mapOf(
                CAF_MAP_KEY_ERROR_MESSAGE to failure.message
            ))
        }

        override fun onCancel() {
            sendEvent(CAF_SMART_AUTH_CANCEL_EVENT, mapOf(CAF_MAP_KEY_IS_CANCELLED to true))
        }

        override fun onLoading() {
            sendEvent(CAF_SMART_AUTH_LOADING_EVENT, mapOf(CAF_MAP_KEY_IS_LOADING to true))
        }

        override fun onLoaded() {
            sendEvent(CAF_SMART_AUTH_LOADED_EVENT, mapOf(CAF_MAP_KEY_IS_LOADED to true))
        }
    }

    private fun requestPermission(permission: String, activity: Activity) {
        if (ContextCompat.checkSelfPermission(
                context,
                permission
            ) != PackageManager.PERMISSION_GRANTED
        ) {
            ActivityCompat.requestPermissions(activity, arrayOf(permission), REQUEST_CODE)
        }
    }

    companion object {
        private const val REQUEST_CODE = 1234

        private const val CAF_SMART_AUTH_MODULE_NAME = "CafSmartAuthBridgeModule"
        private const val CAF_SMART_AUTH_FUNCTION_START_SMART_AUTH = "startSmartAuth"
        private const val CAF_SMART_AUTH_FUNCTION_REQUEST_LOCATION_PERMISSIONS = "requestLocationPermissions"

        private const val CAF_SMART_AUTH_SUCCESS_EVENT = "CafSmartAuth_Success"
        private const val CAF_SMART_AUTH_PENDING_EVENT = "CafSmartAuth_Pending"
        private const val CAF_SMART_AUTH_ERROR_EVENT = "CafSmartAuth_Error"
        private const val CAF_SMART_AUTH_CANCEL_EVENT = "CafSmartAuth_Cancel"
        private const val CAF_SMART_AUTH_LOADING_EVENT = "CafSmartAuth_Loading"
        private const val CAF_SMART_AUTH_LOADED_EVENT = "CafSmartAuth_Loaded"

        private const val CAF_MAP_KEY_IS_AUTHORIZED = "isAuthorized"
        private const val CAF_MAP_KEY_ATTEMPT_ID = "attemptId"
        private const val CAF_MAP_KEY_ATTESTATION = "attestation"
        private const val CAF_MAP_KEY_ERROR_MESSAGE = "errorMessage"
        private const val CAF_MAP_KEY_IS_CANCELLED = "isCancelled"
        private const val CAF_MAP_KEY_IS_LOADING = "isLoading"
        private const val CAF_MAP_KEY_IS_LOADED = "isLoaded"

        private const val PERMISSION_ERROR_DESCRIPTION = "Error checking location permissions:"
    }
}
```

### 3. Create the `CafSmartAuthBridgeSettings.kt` File

This file will handle the interpretation of data sent from React Native to the native module.

#### Example Implementation:

```kotlin
internal data class CafFaceAuthenticationSettingsModel(
    val loadingScreen: Boolean?,
    val enableScreenCapture: Boolean?,
    val filter: CafFilterStyle?
)

internal data class CafSmartAuthBridgeTheme(
    val lightTheme: CafTheme,
    val darkTheme: CafTheme
)

internal class CafSmartAuthBridgeSettings(settings: String) : Serializable {
    val cafStage: CafStage?
    val emailUrl: String?
    val phoneUrl: String?
    val faceAuthenticatorSettings: CafFaceAuthenticationSettingsModel?
    val theme: CafSmartAuthBridgeTheme?

    init {
        val jsonObject = JSONObject(settings)

        cafStage = jsonObject.takeIf {
            it.has(STAGE)
        }?.let {
            CafStage.values()[it.getInt(STAGE)]
        }

        emailUrl = jsonObject.takeIf {
            it.has(EMAIL)
        }?.getString(EMAIL)

        phoneUrl = jsonObject.takeIf {
            it.has(PHONE)
        }?.getString(PHONE)

        faceAuthenticatorSettings = jsonObject.takeIf {
            it.has(FACE_AUTHENTICATION_SETTINGS)
        }?.let {
            val faceAuthenticatorSettings = it.getJSONObject(FACE_AUTHENTICATION_SETTINGS)

            val filterStyle = faceAuthenticatorSettings.takeIf { settings ->
                settings.has(FILTER)
            }?.let {
                CafFilterStyle.values()[faceAuthenticatorSettings.getInt(FILTER)]
            }

            CafFaceAuthenticationSettingsModel(
                faceAuthenticatorSettings.getBoolean(LOADING_SCREEN),
                faceAuthenticatorSettings.optBoolean(ENABLE_SCREEN_CAPTURE),
                filterStyle ?: CafFilterStyle.LINE_DRAWING
            )
        }

        theme = jsonObject.takeIf {
            it.has(THEME)
        }?.let {
            val theme = it.getJSONObject(THEME)

            val lightTheme = theme.optJSONObject(LIGHT_THEME)
            val darkTheme = theme.optJSONObject(DARK_THEME)

            CafSmartAuthBridgeTheme(
                lightTheme = parseTheme(lightTheme),
                darkTheme = parseTheme(darkTheme)
            )
        }
    }

    private companion object {
        const val STAGE = "stage"
        const val EMAIL = "emailUrl"
        const val PHONE = "phoneUrl"
        const val FACE_AUTHENTICATION_SETTINGS = "faceAuthenticationSettings"
        const val LOADING_SCREEN = "loadingScreen"
        const val ENABLE_SCREEN_CAPTURE = "enableScreenCapture"
        const val FILTER = "filter"
        const val THEME = "theme"
        const val LIGHT_THEME = "lightTheme"
        const val DARK_THEME = "darkTheme"
        const val BACKGROUND_COLOR = "backgroundColor"
        const val TEXT_COLOR = "textColor"
        const val PROGRESS_COLOR = "progressColor"
        const val LINK_COLOR = "linkColor"
        const val BOX_BACKGROUND_COLOR = "boxBackgroundColor"
        const val BOX_BORDER_COLOR = "boxBorderColor"
        const val BOX_TEXT_COLOR = "boxTextColor"

        const val BACKGROUND_COLOR_HEX = "#FFFFFF"
        const val TEXT_COLOR_HEX = "#FF000000"
        const val PRIMARY_COLOR_HEX = "#004AF7"
        const val BOX_BACKGROUND_COLOR_HEX = "#0A004AF7"
    }
}
```

With this, your native module is configured and ready to be used in React Native.


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