[#1485] Handle several Rust API calls errors

Closes #1485
Filed a follow-up issue #1484

backend-lib/src/main/java/cash/z/ecc/android/sdk/internal/Backend.kt

@@ -78,6 +78,7 @@ interface Backend {
 
     fun isValidUnifiedAddr(addr: String): Boolean
 
+    @Throws(RuntimeException::class)
     suspend fun getCurrentAddress(account: Int): String
 
     fun getTransparentReceiver(ua: String): String?
@@ -132,6 +133,7 @@ interface Backend {
      * @return The height to which the wallet has been fully scanned, or Null if no blocks have been scanned.
      * @throws RuntimeException as a common indicator of the operation failure
      */
+    @Throws(RuntimeException::class)
     suspend fun getFullyScannedHeight(): Long?
 
     /**
@@ -144,6 +146,7 @@ interface Backend {
      * @return The maximum height that the wallet has scanned, or Null if no blocks have been scanned.
      * @throws RuntimeException as a common indicator of the operation failure
      */
+    @Throws(RuntimeException::class)
     suspend fun getMaxScannedHeight(): Long?
 
     /**

sdk-lib/src/main/java/cash/z/ecc/android/sdk/SdkSynchronizer.kt

@@ -198,7 +198,13 @@ class SdkSynchronizer private constructor(
     override val transactions
         get() =
             combine(processor.networkHeight, storage.allTransactions) { networkHeight, allTransactions ->
-                val latestBlockHeight = networkHeight ?: backend.getMaxScannedHeight()
+                val latestBlockHeight =
+                    networkHeight ?: runCatching {
+                        backend.getMaxScannedHeight()
+                    }.onFailure {
+                        Twig.error(it) { "Failed to get max scanned height" }
+                    }.getOrNull()
+
                 allTransactions.map { TransactionOverview.new(it, latestBlockHeight) }
             }
 

sdk-lib/src/main/java/cash/z/ecc/android/sdk/exception/Exceptions.kt

@@ -10,21 +10,35 @@ import cash.z.ecc.android.sdk.model.FirstClassByteArray
 import cash.z.ecc.android.sdk.model.ZcashNetwork
 import co.electriccoin.lightwallet.client.model.BlockHeightUnsafe
 
+// TODO [#1484]: Validate and standardize SDK exceptions
+// TODO [#1484]: https://github.com/Electric-Coin-Company/zcash-android-wallet-sdk/issues/1484
+
 /**
  * Marker for all custom exceptions from the SDK. Making it an interface would result in more typing
  * so it's a supertype, instead.
  */
 open class SdkException(message: String, cause: Throwable?) : RuntimeException(message, cause)
 
 /**
- * Exceptions thrown in the Rust layer of the SDK. We may not always be able to surface details about this
- * exception so it's important for the SDK to provide helpful messages whenever these errors are encountered.
+ * Exceptions thrown in the Rust layer as [RuntimeException] that the Kotlin layer translates to a more detailed ones.
+ * It's important for the SDK to provide helpful messages whenever these errors are encountered.
  */
 sealed class RustLayerException(message: String, cause: Throwable? = null) : SdkException(message, cause) {
-    class BalanceException(cause: Throwable) : RustLayerException(
-        "Error while requesting the current balance over " +
-            "JNI. This might mean that the database has been corrupted and needs to be rebuilt. Verify that " +
-            "blocks are not missing or have not been scanned out of order.",
+    class GetCurrentAddressException(cause: Throwable) : RustLayerException(
+        "Error while requesting the current address from the Rust layer over JNI. This might mean that the SDK is " +
+            "not yet correctly set up.",
+        cause
+    )
+
+    class GetFullyScannedHeight(cause: Throwable) : RustLayerException(
+        "Error while requesting the fully scanned height from the Rust layer over JNI. This might mean that the SDK " +
+            "is not yet correctly set up.",
+        cause
+    )
+
+    class GetMaxScannedHeight(cause: Throwable) : RustLayerException(
+        "Error while requesting the max scanned height from the Rust layer over JNI. This might mean that the SDK " +
+            "is not yet correctly set up.",
         cause
     )
 }

sdk-lib/src/main/java/cash/z/ecc/android/sdk/internal/TypesafeBackend.kt

@@ -1,6 +1,7 @@
 package cash.z.ecc.android.sdk.internal
 
 import cash.z.ecc.android.sdk.exception.InitializeException
+import cash.z.ecc.android.sdk.exception.RustLayerException
 import cash.z.ecc.android.sdk.internal.model.JniBlockMeta
 import cash.z.ecc.android.sdk.internal.model.ScanRange
 import cash.z.ecc.android.sdk.internal.model.ScanSummary
@@ -46,6 +47,7 @@ internal interface TypesafeBackend {
         usk: UnifiedSpendingKey
     ): List<FirstClassByteArray>
 
+    @Throws(RustLayerException.GetCurrentAddressException::class)
     suspend fun getCurrentAddress(account: Account): String
 
     suspend fun listTransparentReceivers(account: Account): List<String>
@@ -107,8 +109,9 @@ internal interface TypesafeBackend {
      * preceding blocks above the wallet's birthday height.
      *
      * @return The height to which the wallet has been fully scanned, or Null if no blocks have been scanned.
-     * @throws RuntimeException as a common indicator of the operation failure
+     * @throws RustLayerException.GetFullyScannedHeight as a common indicator of the operation failure
      */
+    @Throws(RustLayerException.GetFullyScannedHeight::class)
     suspend fun getFullyScannedHeight(): BlockHeight?
 
     /**
@@ -119,8 +122,9 @@ internal interface TypesafeBackend {
      * height due to the fact that out-of-order scanning can leave gaps.
      *
      * @return The maximum height that the wallet has scanned, or Null if no blocks have been scanned.
-     * @throws RuntimeException as a common indicator of the operation failure
+     * @throws RustLayerException.GetMaxScannedHeight as a common indicator of the operation failure
      */
+    @Throws(RustLayerException.GetMaxScannedHeight::class)
     suspend fun getMaxScannedHeight(): BlockHeight?
 
     /**

sdk-lib/src/main/java/cash/z/ecc/android/sdk/internal/TypesafeBackendImpl.kt

@@ -1,6 +1,7 @@
 package cash.z.ecc.android.sdk.internal
 
 import cash.z.ecc.android.sdk.exception.InitializeException
+import cash.z.ecc.android.sdk.exception.RustLayerException
 import cash.z.ecc.android.sdk.internal.model.JniBlockMeta
 import cash.z.ecc.android.sdk.internal.model.JniSubtreeRoot
 import cash.z.ecc.android.sdk.internal.model.ScanRange
@@ -80,7 +81,11 @@ internal class TypesafeBackendImpl(private val backend: Backend) : TypesafeBacke
         ).map { FirstClassByteArray(it) }
 
     override suspend fun getCurrentAddress(account: Account): String {
-        return backend.getCurrentAddress(account.value)
+        return runCatching {
+            backend.getCurrentAddress(account.value)
+        }.onFailure {
+            Twig.error(it) { "Failed to get current address" }
+        }.getOrElse { throw RustLayerException.GetCurrentAddressException(it) }
     }
 
     override suspend fun listTransparentReceivers(account: Account): List<String> {
@@ -195,21 +200,29 @@ internal class TypesafeBackendImpl(private val backend: Backend) : TypesafeBacke
     override suspend fun updateChainTip(height: BlockHeight) = backend.updateChainTip(height.value)
 
     override suspend fun getFullyScannedHeight(): BlockHeight? {
-        return backend.getFullyScannedHeight()?.let {
-            BlockHeight.new(
-                ZcashNetwork.from(backend.networkId),
-                it
-            )
-        }
+        return runCatching {
+            backend.getFullyScannedHeight()?.let {
+                BlockHeight.new(
+                    ZcashNetwork.from(backend.networkId),
+                    it
+                )
+            }
+        }.onFailure {
+            Twig.error(it) { "Failed to get fully scanned height" }
+        }.getOrElse { throw RustLayerException.GetFullyScannedHeight(it) }
     }
 
     override suspend fun getMaxScannedHeight(): BlockHeight? {
-        return backend.getMaxScannedHeight()?.let {
-            BlockHeight.new(
-                ZcashNetwork.from(backend.networkId),
-                it
-            )
-        }
+        return runCatching {
+            backend.getMaxScannedHeight()?.let {
+                BlockHeight.new(
+                    ZcashNetwork.from(backend.networkId),
+                    it
+                )
+            }
+        }.onFailure {
+            Twig.error(it) { "Failed to get max scanned height" }
+        }.getOrElse { throw RustLayerException.GetMaxScannedHeight(it) }
     }
 
     override suspend fun scanBlocks(