Merge pull request #678 from braintree/kotlin_authorization_loader

Refactor `AuthorizationLoader` to Kotlin

BraintreeCore/src/main/java/com/braintreepayments/api/AuthorizationCallback.kt

@@ -1,12 +1,11 @@
 package com.braintreepayments.api
 
 import androidx.annotation.RestrictTo
-import java.lang.Exception
 
 /**
  * @suppress
  */
 @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
-interface AuthorizationCallback {
+fun interface AuthorizationCallback {
     fun onAuthorizationResult(authorization: Authorization?, error: Exception?)
 }

BraintreeCore/src/main/java/com/braintreepayments/api/AuthorizationLoader.kt

@@ -0,0 +1,41 @@
+package com.braintreepayments.api
+
+import androidx.annotation.VisibleForTesting
+
+internal class AuthorizationLoader(
+    initialAuthString: String?,
+    private val clientTokenProvider: ClientTokenProvider?
+) {
+    // cache initial auth if available
+    @VisibleForTesting
+    var authorizationFromCache = initialAuthString?.let { Authorization.fromString(it) }
+
+    fun loadAuthorization(callback: AuthorizationCallback) {
+        if (authorizationFromCache != null) {
+            callback.onAuthorizationResult(authorizationFromCache, null)
+        } else if (clientTokenProvider != null) {
+            clientTokenProvider.getClientToken(object : ClientTokenCallback {
+                override fun onSuccess(clientToken: String) {
+                    authorizationFromCache = Authorization.fromString(clientToken)
+                    callback.onAuthorizationResult(authorizationFromCache, null)
+                }
+
+                override fun onFailure(error: Exception) {
+                    callback.onAuthorizationResult(null, error)
+                }
+            })
+        } else {
+            val clientSDKSetupURL =
+                "https://developer.paypal.com/braintree/docs/guides/client-sdk/setup/android/v4#initialization"
+            val message = "Authorization required. See $clientSDKSetupURL for more info."
+            callback.onAuthorizationResult(null, BraintreeException(message))
+        }
+    }
+
+    fun invalidateClientToken() {
+        // only invalidate client token cache if we can fetch a new one with a client token provider
+        if (clientTokenProvider != null) {
+            authorizationFromCache = null
+        }
+    }
+}