refactor: convert java to kotlin and add support for kotlin

android/build.gradle

@@ -1,4 +1,6 @@
 buildscript {
+  // Buildscript is evaluated before everything else so we can't use safeExtGet
+  def kotlin_version = rootProject.ext.has('kotlinVersion') ? rootProject.ext.get('kotlinVersion') : "1.8.0"
   repositories {
     maven {
       url "https://plugins.gradle.org/m2/"
@@ -7,7 +9,8 @@ buildscript {
     google()
   }
   dependencies {
-    classpath("com.android.tools.build:gradle:8.3.1")
+    classpath "com.android.tools.build:gradle:8.3.1"
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
   }
 }
 
@@ -23,6 +26,7 @@ if (isNewArchitectureEnabled()) {
   apply plugin: "com.facebook.react"
 }
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
 
 repositories {
   google()
@@ -34,13 +38,13 @@ android {
   if (project.android.hasProperty("namespace")) {
     namespace = "com.oblador.keychain"
   }
-  compileSdkVersion safeExtGet('compileSdkVersion', 33)
+  compileSdkVersion safeExtGet('compileSdkVersion', 34)
   buildToolsVersion safeExtGet('buildToolsVersion', '33.0.0')
 
   defaultConfig {
     minSdkVersion safeExtGet('minSdkVersion', 23)
-    compileSdkVersion safeExtGet('compileSdkVersion', 33)
-    targetSdkVersion safeExtGet('targetSdkVersion', 33)
+    compileSdkVersion safeExtGet('compileSdkVersion', 34)
+    targetSdkVersion safeExtGet('targetSdkVersion', 34)
     buildConfigField "boolean", "IS_NEW_ARCHITECTURE_ENABLED", isNewArchitectureEnabled().toString()
   }
 
@@ -57,24 +61,20 @@ android {
     disable "GradleCompatible"
     abortOnError false
   }
-
-  testOptions {
-    unitTests {
-      includeAndroidResources = true
-    }
-  }
 }
 
 repositories {
   mavenCentral()
 }
 
+def kotlin_version = safeExtGet('kotlinVersion', '1.8.0')
+
 dependencies {
   //noinspection GradleDynamicVersion
   implementation "com.facebook.react:react-android:+"
-
   implementation 'androidx.appcompat:appcompat:1.6.1'
   implementation 'androidx.legacy:legacy-support-v4:1.0.0'
+  implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
 
   // https://mvnrepository.com/artifact/androidx.biometric/biometric
   implementation 'androidx.biometric:biometric:1.1.0@aar'

android/src/main/java/com/oblador/keychain/DeviceAvailability.kt

@@ -0,0 +1,54 @@
+package com.oblador.keychain
+
+import android.Manifest
+import android.app.KeyguardManager
+import android.content.Context
+import android.content.pm.PackageManager
+import android.os.Build
+import androidx.biometric.BiometricManager
+
+/**
+ * @see
+ *   [Biometric hardware](https://stackoverflow.com/questions/50968732/determine-if-biometric-hardware-is-present-and-the-user-has-enrolled-biometrics)
+ */
+@Suppress("deprecation")
+object DeviceAvailability {
+  fun isStrongBiometricAuthAvailable(context: Context): Boolean {
+    return BiometricManager.from(context)
+        .canAuthenticate(BiometricManager.Authenticators.BIOMETRIC_STRONG) ==
+        BiometricManager.BIOMETRIC_SUCCESS
+  }
+
+  fun isFingerprintAuthAvailable(context: Context): Boolean {
+    return context.packageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT)
+  }
+
+  fun isFaceAuthAvailable(context: Context): Boolean {
+    return context.packageManager.hasSystemFeature(PackageManager.FEATURE_FACE)
+  }
+
+  fun isIrisAuthAvailable(context: Context): Boolean {
+    return context.packageManager.hasSystemFeature(PackageManager.FEATURE_IRIS)
+  }
+
+  /** Check is permissions granted for biometric things. */
+  @JvmStatic
+  fun isPermissionsGranted(context: Context): Boolean {
+    // before api23 no permissions for biometric, no hardware == no permissions
+    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
+      return false
+    }
+    val km = context.getSystemService(Context.KEYGUARD_SERVICE) as KeyguardManager
+    if (!km.isKeyguardSecure) return false
+
+    // api28+
+    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+      context.checkSelfPermission(Manifest.permission.USE_BIOMETRIC) ==
+          PackageManager.PERMISSION_GRANTED
+    } else
+        context.checkSelfPermission(Manifest.permission.USE_FINGERPRINT) ==
+            PackageManager.PERMISSION_GRANTED
+
+    // before api28
+  }
+}