fetchUtxos returns flow

- Switched fetchUtxos() to return Flow of Service.GetAddressUtxosReply
- Internally it calls getAddressUtxosStream() instead of getAddressUtxos() from GRPC layer

lightwallet-client-lib/src/main/java/co/electriccoin/lightwallet/client/CoroutineLightWalletClient.kt

@@ -27,18 +27,18 @@ interface CoroutineLightWalletClient {
      * @param tAddress the transparent address to use.
      * @param startHeight the starting height to use.
      *
-     * @return the UTXOs for the given address from the [startHeight].
+     * @return a flow of UTXOs for the given address from the [startHeight].
      */
     suspend fun fetchUtxos(
         tAddress: String,
         startHeight: BlockHeightUnsafe
-    ): List<Service.GetAddressUtxosReply>
+    ): Flow<Service.GetAddressUtxosReply>
 
     /**
      * @param heightRange the inclusive range to fetch. For instance if 1..5 is given, then every
      * block in that range will be fetched, including 1 and 5.
      *
-     * @return a list of compact blocks for the given range
+     * @return a flow of compact blocks for the given range
      *
      */
     fun getBlockRange(heightRange: ClosedRange<BlockHeightUnsafe>): Flow<CompactFormats.CompactBlock>
@@ -58,7 +58,7 @@ interface CoroutineLightWalletClient {
      * effectively the same as an RPC call to a node that's running an insight server. The data is
      * indexed and responses are fairly quick.
      *
-     * @return a list of transactions that correspond to the given address for the given range.
+     * @return a flow of transactions that correspond to the given address for the given range.
      */
     fun getTAddressTransactions(
         tAddress: String,

lightwallet-client-lib/src/main/java/co/electriccoin/lightwallet/client/internal/CoroutineLightWalletClientImpl.kt

@@ -126,20 +126,23 @@ internal class CoroutineLightWalletClientImpl private constructor(
     override suspend fun fetchUtxos(
         tAddress: String,
         startHeight: BlockHeightUnsafe
-    ): List<Service.GetAddressUtxosReply> {
+    ): Flow<Service.GetAddressUtxosReply> {
-        val result = requireChannel().createStub().getAddressUtxos(
+        if (tAddress.isBlank()) {
+            return emptyFlow()
+        }
+        return requireChannel().createStub().getAddressUtxosStream(
             Service.GetAddressUtxosArg.newBuilder().setAddress(tAddress)
                 .setStartHeight(startHeight.value).build()
         )
-        return result.addressUtxosList
     }
 
     override fun getTAddressTransactions(
         tAddress: String,
         blockHeightRange: ClosedRange<BlockHeightUnsafe>
     ): Flow<Service.RawTransaction> {
-        if (blockHeightRange.isEmpty() || tAddress.isBlank()) return emptyFlow()
+        if (blockHeightRange.isEmpty() || tAddress.isBlank()) {
-
+            return emptyFlow()
+        }
         return requireChannel().createStub().getTaddressTxids(
             Service.TransparentAddressBlockFilter.newBuilder().setAddress(tAddress)
                 .setRange(blockHeightRange.toBlockRange()).build()